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1
Ekh, Johan. "Multi-fastener single-lap joints in composite structures." Doctoral thesis, Stockholm : Royal Institute of Technology, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4006.
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Chazerain, Aurélie. "Characterization of resistance-welded thermoplastic composite double-lap joints." Thesis, McGill University, 2009. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=67019.
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An investigation of resistance welding of thermoplastic composite double-lap shear joints is presented. Double-lap shear specimens consisting of carbon fibre/poly-etherether-ketone (PEEK/CF), carbon fibre/poly-etherketone-ketone (PEKK/CF), carbon fibre/poly-ether-imide (PEI/CF) and glassfibre/poly-ether-imide (PEI/GF) were resistance-welded using a stainless steel mesh heating element. The objective of this work was to study the mechanical performances of the double lap shear resistance-welded joints and to compare them with the single lap shear resistance-welded joints. The welded specimens were analyzed using static and dynamic lap shear tests and optical and scanning electron microscopy. Lap shear strengths of 53 MPa, 49 MPa, 45 MPa and an extrapolated value of 34 MPa were obtained for PEEK/CF, PEKK/CF, PEI/CF and PEI/GF double-lap joints, respectively. Infinite fatigue lives were obtained at 30% for PEEK/CF and PEKK/CF, 25% for PEI/CF and 20% for PEI/GF. Resistance-welded double-lap joints were found to have equivalent static and fatigue mechanical properties compared with single-lap joints, for all materials tested.Ce travail présente une étude des joints à recouvrement double de matériaux composites à matrice thermoplastique assemblés par soudage par résistance. Des échantillons de joints à recouvrement double constitués de fibre de carbone/polyéther éther cétone (PEEK/CF), fibre de carbone/polyéther cétone cétone (PEKK/CF), fibre de carbone/polyéther imide (PEI/CF) et fibre de verre/polyéther imide (PEI/CF), ont été assemblés pas soudage par résistance à l'aide d'un élément chauffant en acier inoxydable. L'objectif de ce travail est d'étudier les performances mécaniques des joints à recouvrement double soudés pas résistance et de les comparer avec celles des joints à recouvrement simple. Les échantillons soudés ont été analysés à l'aide de tests de chargement statiques et dynamiques, ainsi que pas microscopie optique et par microscopie électronique à balayage. Une résistance au cisaillement de 53 MPa, 49 MPa, 45M Pa, et une valeur extrapolée de 34 MPa ont été obtenues pour les joints à recouvrement double de PEEK/CF, PEKK/CF, PEI/CF et PEI/GF, respectivement. Une durée de vie indéterminée en fatigue de 30% du chargement statique pour les joints de PEEK/CF et PEKK/CF, de 25% pour les joints de PEI/CF, et de 20% pour les joints de PEI/GF ont été obtenues. Pour chacun des matériaux testés, les joints à recouvrement double soudés par résistance ont donné lieu à des propriétés mécaniques en statique et en fatigue équivalentes à celles des joints à recouvrement simple.
3
Doering, Kenneth Thomas Nathaniel. "Fatigue of friction stir welded lap joints with sealants." Diss., Rolla, Mo. : Missouri University of Science and Technology, 2009. http://scholarsmine.mst.edu/thesis/pdf/Doering_09007dcc80627994.pdf.
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Thesis (M.S.)--Missouri University of Science and Technology, 2009.Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed April 9, 2009) Includes bibliographical references (p. 118-127).
4
Dinsley, Christopher Paul. "Fatigue properties of dissimilar metal laser welded lap joints." Thesis, Sheffield Hallam University, 2004. http://shura.shu.ac.uk/19561/.
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This work involves laser welding austenitic and duplex stainless steel to zinc-coated mild steel, more specifically 1.2mm V1437, which is a Volvo Truck Coiporation rephosphorised mild steel. The work investigates both tensile and lap shear properties of similar and dissimilar metal laser welded butt and lap joints, with the majority of the investigation concentrating on the fatigue properties of dissimilar metal laser welded lap joints. The problems encountered when laser welding zinc-coated steel are addressed and overcome with regard to dissimilar metal lap joints with stainless steel. The result being the production of a set of guidelines for laser welding stainless steel to zinc-coated mild steel. The stages of laser welded lap joint fatigue life are defined and the factors affecting dissimilar metal laser welded lap joint fatigue properties are analysed and determined; the findings suggesting that dissimilar metal lap joint fatigue properties are primarily controlled by the local stress at the internal lap face and the early crack growth rate of the material at the internal lap face. The lap joint rotation, in turn, is controlled by sheet thickness, weld width and interfacial gap. Laser welded lap joint fatigue properties are found to be independent of base material properties, allowing dissimilar metal lap joints to be produced without fatigue failure occurring preferentially in the weaker parent material, irrespective of large base material property differences. The effects of Marangoni flow on the compositions of the laser weld beads are experimentally characterised. The results providing definite proof of the stirring mechanism within the weld pool through the use of speeds maps for chromium and nickel. Keywords: Laser welding, dissimilar metal, Zinc-coated mild steel, Austenitic stainless steel, Duplex stainless steel, Fatigue, Lap joint rotation, Automotive.
5
Curnutt, Austin. "Research on the mechanics of CFRP composite lap joints." Thesis, Kansas State University, 2017. http://hdl.handle.net/2097/38191.
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Master of ScienceDepartment of Architectural Engineering
Donald J. Phillippi
For this thesis, research was performed on CFRP bonded composite lap-joints with one and two continuous laminas through the lap. Composite wraps used to retrofit existing structures use lap joints to maintain their integrity. The use of composites for retrofitting structures has many advantages over traditional methods, such as steel jacketing, and is becoming more widely accepted in the structural engineering industry. While much literature exists documenting the performance of composite wraps as a whole when applied to concrete columns, less information is available on the behavior of the lap-joint of the wrap. Developing a better understanding of how the lap-joint behaves will help researchers further understand composite column wraps. This research sought to determine what affect continuous middle laminas may have on the stiffness of lap joints and whether or not stress concentrations exist in the lap-joint due to a change in stiffness.
6
Scott, Jason P. "Corrosion and multiple site damage in riveted fuselage lap joints." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp04/mq22127.pdf.
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Li, Gang. "Deformation of balanced and unbalanced adhesively bonded single-lap joints." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape4/PQDD_0030/NQ65464.pdf.
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Scott, Jason P. (Jason Philip) Carleton University Dissertation Engineering Mechanical and Aerospace. "Corrosion and multiple site damage in riveted fuselage lap joints." Ottawa, 1997.
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Karachalios, E. F. "Stress and failure analysis of adhesively bonded single lap joints." Thesis, University of Bristol, 1999. http://hdl.handle.net/1983/72fde066-0a88-4b2b-83ea-c2c08f0ce0fc.
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Coates, Cameron Wayne. "New concepts for strength enhancement of co-cured composite single lap joints." Diss., Georgia Institute of Technology, 2001. http://hdl.handle.net/1853/12937.
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Kratochvil, Jan. "Asymptotic Analysis of the Load Transfer on Double-Lap Bolted Joints." Phd thesis, Techn. Univ., Studienbereich Mechanik, 2012. https://tuprints.ulb.tu-darmstadt.de/2997/1/Diss_Kratochvil.pdf.
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In this thesis, the complex potential method along with the method of compound asymptotic expansions is applied to the analysis of selected problems of plane elasticity related to double-lap bolted joints. The contribution to the thesis lies in the construction of several closed-form approximations of solutions to the considered problems.
After a brief introduction of the basic theoretical concepts in Chapter 2, a mathematical model of a double-lap bolted joint is presented in Chapter 3. A very simple model is chosen in order to make an analytical treatment possible. This model assumes the (generalised) state of plane stress in each of the plates and a simple sinusoidal distribution of contact pressure in the bolt-to-hole contact and leads mathematically to the first fundamental problem of the plane theory of elasticity.
In Chapter 4, a formal asymptotic solution of the first fundamental problem for an infinite plane or half-plane weakened by a finite number or an infinite symmetric array of small holes is derived. The relative hole radius plays the role of the small parameter. Three different governing partial differential equations are considered, namely the Laplace equation, the bipotential equation and a more general linear elliptic fourth-order partial differential equation with constant coefficients. An asymptotic expansion of the complex potentials is derived for each equation. It is uniformly valid in the whole domain, i.e. in the vicinity of each of the holes as well as in the far-field. The solution is summarised in form of algorithms for a computer algebra system and implemented in Mathematica. Furthermore, a fully parametrised finite element model of the considered problem has been created using the commercial FE Software Abaqus and its Python programming interface in order to verify the results in an independent way.
This general solution is in Chapter 5 applied to three types of problems. The first one is the problem of stress concentration on unloaded holes. Its purpose is to evaluate the capability of the method by means of simple examples where a sufficiently high number of terms of the asymptotic series can be generated. The second type of problems involves the compliance of an infinite row of pin-loaded holes. A closed-form approximate formula for the compliance of an infinite row of pin-loaded holes in an infinite isotropic plane and a half-plane is derived. This formula, as opposed to semi-empirical formulae commonly used in the industrial environment, correctly takes into account the contributions of the plane deformation of the plates to the overall compliance of the joint. Finally, the third type deals with the determination of the load distribution on both finite number of bolts as well as infinite rows of bolts. Closed-form approximations of the load distribution factor for these configurations are presented.
A certain problem related to the nature of the proposed solution is the convergence of the asymptotic series. As expected from the nature of the asymptotic solution, the discrepancy between the asymptotic solution and a reference numerical one is the smallest for small radii and with increasing radii, it generally increases. However, results with the presented order of approximation are sufficiently accurate in the technically relevant domain.
In the case of anisotropic material behaviour, the formulae describing the dependence on the material parameters are too complex for practical use even in the simplest situations such as stress concentration on a single hole in a half-plane. A certain simplification can be achieved by assuming strong orthotropy and performing a Taylor expansion in terms of the corresponding small parameter. It appears that such an expansion exhibits good convergence and can be therefore used also for moderately orthotropic materials. Unfortunately, it was not possible to obtain analytical results for infinite rows of holes in anisotropic plates because the proposed algorithm leads to infinite sums that cannot be be evaluated analytically.
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Atre, Amarendra. "A Finite Element and Experimental Investigation on the Fatigue of Riveted Lap Joints in Aircraft Applications." Diss., Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/10494.
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Aircraft fuselage skin panels are joined together by rivets. The initiation and propagation
of fatigue cracks in aircraft structures at and around the rivet/skin interface is directly related to residual stress field induced during the riveting process and subsequent service loads. Variations in the manufacturing process, such as applied loading and presence of sealant can influence the induced residual stress field. In previous research, the riveting process has been simulated by a 2D axisymmetric force-controlled analysis. The 2D analysis cannot capture the unsymmetrical residual stress state resulting from process variations. Experimental work has also been limited to observing effects of squeeze force on fatigue crack initiation in the riveted lap joint. In this work, a 3D finite element model of the riveting process that incorporates plasticity and contact between the various surfaces is simulated using ABAQUS finite element code to capture the residual stress state at the rivet/skin interface. The finite element model is implemented to observe the effects of interference, sealant and hole quality on the residual stress state using Implicit and Explicit solvers. Effects of subsequent load transfer are also analyzed with the developed model. A set of controlled lap joint fatigue experiments for the different conditions provides validation to the model.
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Kradinov, Vladimir Y. "Optimum design of bolted composite lap joints under mechanical and thermal loading." Diss., The University of Arizona, 2003. http://hdl.handle.net/10150/280296.
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A new approach is developed for the analysis and design of mechanically fastened composite lap joints under mechanical and thermal loading. Based on the combined complex potential and variational formulation, the solution method satisfies the equilibrium equations exactly while the boundary conditions are satisfied by minimizing the total potential. This approach is capable of modeling finite laminate planform dimensions, uniform and variable laminate thickness, laminate lay-up, interaction among bolts, bolt torque, bolt flexibility, bolt size, bolt-hole clearance and interference, insert dimensions and insert material properties. Comparing to the finite element analysis, the robustness of the method does not decrease when modeling the interaction of many bolts; also, the method is more suitable for parametric study and design optimization. The Genetic Algorithm (GA), a powerful optimization technique for multiple extrema functions in multiple dimensions search spaces, is applied in conjunction with the complex potential and variational formulation to achieve optimum designs of bolted composite lap joints. The objective of the optimization is to acquire such a design that ensures the highest strength of the joint. The fitness function for the GA optimization is based on the average stress failure criterion predicting net-section, shear-out, and bearing failure modes in bolted lap joints. The criterion accounts for the stress distribution in the thickness direction at the bolt location by applying an approach utilizing a beam on an elastic foundation formulation.
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Jolly, Prateek. "Lamb wave based active damage identification in adhesively bonded composite lap joints." Thesis, Mississippi State University, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10100288.
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Bonding composite structures using adhesives offers several advantages over mechanical fastening such as better flow stress, weight saving, improved fatigue resistance and the ability to join dissimilar structures. The hesitation to adopt adhesively bonded composite joints stems from the lack of knowledge regarding damage initiation and propagation mechanisms within the joint. A means of overcoming this hesitation is to continuously monitor damage in the joint. This study proposes a methodology to conduct structural health monitoring (SHM) of an adhesively bonded composite lap joint using acoustic, guided Lamb waves by detecting, locating and predicting the size of damage. Finite element modeling of a joint in both 2D and 3D is used to test the feasibility of the proposed damage triangulation technique. Experimental validation of the methodology is conducted by detecting the presence, location and size of inflicted damage with the use of tuned guided Lamb waves.
15
Towse, Adam. "The use of Weibull statistics for predicting cohesive failure in double lap joints." Thesis, University of Bristol, 1999. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.297803.
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Stocchi, Cesare. "Investigation on the mechanical behaviour of single-lap composite joints with countersunk bolts." Thesis, Imperial College London, 2013. http://hdl.handle.net/10044/1/24134.
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In this thesis, the mechanical behaviour of 2-bolt single-lap CFRP joints with countersunk bolts is investigated, both numerically and experimentally. A detailed 3D non-linear FE model of composite bolted joints has been developed. The model replicates with good agreement the experimental tensile tests up to the point where bearing damage occurs and reproduces the joint behaviour correctly. Five stages are identified in the joint behaviour. The evolution of contact during the test is studied showing a correlation with the joint stiffness. Parametric studies investigate the influence of bolt clamping force, coefficient of friction and bolt-hole clearance on the joint behaviour. Using the developed FE model, the distribution of the six stress components around the holes of the composite joints is studied together with the effects of head height, shank-hole clearance and position of bolts. The stress along the fibres is identified as the critical stress component and the compressive fibre failure of the 0° oriented plies as the start of the bearing damage. The 0° oriented plies in the cylindrical part of the hole are found to be the plies carrying the bearing load. Increasing clearance reduces the extent of the bolt shank-hole contact and leads to higher stresses and lower joint stiffness. The 45° and -45° oriented plies are found to have a key role in the joint bearing strength and shear-out failure. Fatigue tests are run with the introduction of a novel method to monitor the loss of clamping force and detect crack initiation in the fasteners during the test itself, using strain gauges and a real-time algorithm. The clamping force is found to remain constant until crack initiation and progressively drop until final failure. Load transfer and interaction between the bolts is observed during the fast but stable fatigue crack propagation. The fatigue tests are conducted on joints with differing plate thicknesses and countersunk head geometries to assess the influence of these on the number of cycles to crack initiation and to final failure. A link between fatigue and static test results is highlighted and, in addition, a fatigue failure mechanism of the joint is proposed.
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Samadi, Reza. "Compaction, flow and mechanical properties in lap joints for large multilayer VARTM preforms." Thesis, University of Ottawa (Canada), 2007. http://hdl.handle.net/10393/27554.
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Reinforcement preforms for the vacuum assisted resin transfer moulding (VARTM) manufacturing of large composite parts are made from different layers where presence of double curvature and varying fibre orientation imposes the use of superimposed lap joints. A series of tests were conducted to investigate the compaction of jointed preforms, flow through jointed preforms and the structural behaviour of composite parts featuring superimposed lap joints.
A variety of lap joint configurations was investigated, characterized by specific values of overlap length, OL, horizontal distance between joints, HD, and number of immediately superimposed joints, NS, for a random matt and a woven reinforcement.
The compaction of reinforcements was evaluated using a novel thickness measurement system for preforms. The thickness measurement system utilizes Hall effect sensors. The local fibre volume fraction, vf, was derived from the readings of Hall effect sensors positioned at selected locations above the jointed preforms. Different vf values were observed around joints; consequently, simulations of the manufacturing and performance of jointed composite parts must feature variable vf at the joints.
The effective permeability to resin of jointed preforms parallel to the joints was investigated. The flow of resin in the preform was different from that in un-cut preforms. Specimens cut from cured panels were tested in four-point bending tests based on ASTM standard D790-03. The structural stiffness, maximum flexural stress and failure mode of specimens, were investigated. The structural stiffness and failure mode followed clear trends, while the maximum flexural stress was affected by local stress concentration at the joints.
It is concluded that the presence of lap joints in VARTM preforms changes the behaviour during manufacturing and in service. This should be considered in design of parts and simulation of VARTM manufacturing.
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Katepalli, Nagababu Lankarani Hamid M. "Parametric study of stress concentration in bolted lap joints between particulate metal matrix composite materials." Diss., A link to this thesis in SOAR, 2006. http://soar.wichita.edu/dspace/handle/10057/660.
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Thesis (M.S.)--Wichita State University, College of Engineering, Dept. of Mechanical Engineering."December 2006. Title from PDF title page (viewed on August 17, 2007). Thesis adviser: H.M. Lankarani. Includes bibliographic references (leaves 84-86).
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Faishal, Kazi Aman Ullah M. Cheraghi S. Hossein. "Impact of riveting sequence, pitch and gap between sheets on quality of riveted lap joints." Diss., A link to full text of this thesis in SOAR, 2006. http://soar.wichita.edu/dspace/handle/10057/645.
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Thesis (M.S.)--Wichita State University, College of Engineering, Dept. of Industrial and Manufacturing Engineering."December 2006." Title from PDF title page (viewed on Oct 31, 2007). Thesis adviser: S. Hossein Cheraghi. Includes bibliographic references (leaves 63-64).
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Ganji, Nagesh Lankaranu Hamid M. "Parametric study of load transfer in two-bolted single lap hybrid (bonded/bolted) shear joints." Diss., A link to full text of this thesis in SOAR, 2007. http://soar.wichita.edu/dspace/handle/10057/1133.
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Thesis (M.S.)--Wichita State University, College of Engineering, Dept. of Mechanical Engineering."May 2007." Title from PDF title page (viewed on Dec. 20, 2007). Thesis adviser: Hamid M. Lankarani. Includes bibliographic references (leaves 62-64).
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Davies, Richard G. H. "Analysis of the influence of temperature on the performance of adhesively bonded single lap joints." Thesis, London South Bank University, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.367906.
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Chiu, Jack. "The Effect of Ballistic Impact on Adhesively-Bonded Single Lap Joints in the Shear Mode." Thesis, The City College of New York, 2018. http://pqdtopen.proquest.com/#viewpdf?dispub=10743329.
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Adhesive bonding is a common, robust, and inexpensive method of joining materials. Of particular interest is the behavior under shear loading, where adhesive bonding excels compared to alternative joining methods. However, while the quasi-static response of these joints is well understood, the dynamic behavior is largely unknown.
To this end, a series of experiments were devised and performed where two bars are adhesively bonded using a simple lap joint and subjected to a high-speed impact from a steel slug. These tests were configured to, as much as possible, isolate the type of wave that generates adhesive shear and minimize the effect of reflected and induced waves. While keeping the overall geometry constant, the adhesive material, substrate material, and projectile velocity were varied.
The wave behavior was recorded using surface-mounted strain gages. Also, digital image correlation techniques were developed to analyze high-speed video of the impact event. From these experiments, a number of useful measures can be extracted, including the critical input (projectile) kinetic energy and the specific energy absorbed by the adhesive.
The techniques developed in this thesis allow for the suitability of different substrate/adhesive combinations under ballistic shear impact to be quantitatively evaluated.
Additionally, dynamic plate theory is used to derive an analytical model of the substrate/adhesive system. Several solutions to this model which were solved using a Finite Difference approach are included. These solutions were then compared to the strain histories recorded in the physical experiments.
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He, Yuchuan. "Bearing behaviour of lap joints to thin-walled steel plates at ambient and elevated temperatures." Thesis, University of Manchester, 2012. https://www.research.manchester.ac.uk/portal/en/theses/bearing-behaviour-of-lap-joints-to-thinwalled-steel-plates-at-ambient-and-elevated-temperatures(a2dcf328-3435-4fbf-86b8-e3aff0ad998f).html.
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This thesis presents the results of a comprehensive research study of the bearing behaviour of single or multiple bolted plates in bolt shear at ambient and elevated temperatures. A total of 18 tests were carried out to provide detailed experimental information on bearing behaviour of plates with single bolt. A series of parametric studies using the commercial finite element package ABAQUS were conducted to investigate the effects of different design parameters on the connected plate bearing behaviour, including initial stiffness, ultimate resistance and deformation at the ultimate resistance. The finite element models were verified by comparing the simulated results against the author’s tests conducted as part of this research and other researchers’ test results. Based on the parametric study results, an analytical model was proposed to predict the bearing load-deformation relationship of bolted plate in bolt shear. It was found that the stiffness and ultimate resistance could be predicted accurately by using existing methods. The main contribution of the analytical study was the development of a simple method to calculate the maximum plate deformation (bolt-hole elongation) at the ultimate resistance, based on proposed strain distributions according to different failure modes. This method has been verified against the parametric study results and has been found to be suitable for ambient and elevated temperature applications.
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Skoorka, Michelle E. "The effect of humidity on composite lap joints and an electrochemical study on coatings and galvanic systems /." View online ; access limited to URI, 2004. http://0-wwwlib.umi.com.helin.uri.edu/dissertations/dlnow/3135915.
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Miller, Jodi R. "Temperature profiles and thermal strain analysis in multi-fastener carbon fibre reinforced plastic-aluminium lap joints." Thesis, University of Bristol, 2004. http://hdl.handle.net/1983/ea15b2b3-beac-4a0f-8953-4bc66e512c97.
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Temperature profiles of and combined thermal-mechanical induced strains for Carbon Fibre Reinforced Plastic (CFRP)-Aluminium multi-fastener double lap joints in a wingbox structure are examined. Two dimensional (2D) FE analyses for cases of full, empty, and half-full fuel tank scenarios are used to develop temperature profiles. The influence of conduction, convection, and radiation on temperature profiles is examined. Results show that the empty tank scenario produces the highest temperatures, with the joint region having the peak temperatures, and that convection and radiation must both be modelled in order to accurately estimate wingbox temperatures for the empty, and halffull tank scenarios. Analytical temperature prediction models, both at and away from the joint region, are developed for combined convection and radiation boundary conditions at both external surfaces of this unique finite geometry. For transient analyses, single and multiple layer models are designed using integral transforms and separation of variables, respectively. To show the joint region is critical in terms of induced strains, sequentially coupled thermal-stress analysis is performed using the resulting temperature profiles. Based on these results, and on the results of the temperature profiling, an experimental model is designed to study the effects of thermal and mechanical 1 oading on a threefastener double lap joint with CFRP'skin and aluminium laps. To fully explore the joint region, three dimensional (3D) FE results are compared with experimental data. Mechanical tensile stress in the elastic range is applied at room temperature (295K) and at an elevated temperature (373K). Increasing temperature alters the strain patterns among the fasteners and generally decreases' the peak radial strains at individual fasteners, but increases tangential strains. The effect of torque on the strain distribution in these multi-fastener double lap joints is examined by comparing finger-tight and operationally-tight (35Nm) torques at both temperatures. Increasing torque significantly reduces peak strains on individual fasteners and evens the strain distribution across the joint
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Poudel, Anish. "BOND STRENGTH EVALUATION IN ADHESIVE JOINTS USING NDE AND DIC METHODS." OpenSIUC, 2015. https://opensiuc.lib.siu.edu/dissertations/1010.
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Adhesive bonding of graphite epoxy composite laminates to itself or traditional metal alloys in modern aerospace and aircraft structural applications offers an excellent opportunity to use the most efficient and intelligent combination of materials available thus providing an attractive package for efficient structural designs. However, one of the major issues of adhesive bonding is the occasional formation of interfacial defects such as kissing or weak bonds in the bondline interface. Also, there are shortcomings of existing non-destructive evaluation (NDE) methods to non-destructively detect/characterize these interfacial defects and reliably predicting the bond shear strength. As a result, adhesive bonding technology is still not solely implemented in primary structures of an aircraft. Therefore, there is a greater demand for a novel NDE tool that can meet the existing aerospace requirement for adhesive bondline characterization. This research implemented a novel Acoustography ultrasonic imaging and digital image correlation (DIC) technique to detect and characterize interfacial defects in the bondline and determine bond shear strength in adhesively bonded composite-metal joints. Adhesively bonded Carbon Fiber Reinforced Plastic (CFRP) laminate and 2024-T3 Aluminum single lap shear panels subjected to various implanted kissing/weak bond defects were the primary focus of this study. Kissing/weak bonds were prepared by controlled surface contamination in the composite bonding surface and also by improperly mixing the adhesive constituent. SEM analyses were also conducted to understand the surface morphology of substrates and their interaction with the contaminants. Morphological changes were observed in the microscopic scale and the chemical analysis confirmed the stability of the contaminant at or very close to the interface. In addition, it was also demonstrated that contaminants migrated during the curing of the adhesive from CFRP substrate which caused a decrease of bond shear strength in single lap shear test samples. Through-transmission ultrasonics (TTU) Acoustography at 3.8 MHz showed promising results on the detectability of bondline defects in adhesively bonded CFRP-Al lap shear test samples. A correlation between Acoustography ultrasonic attenuation and average bond shear strength in CFRP-Al lap shear panels demonstrated that differential attenuation increased with the reduction of the bond shear strength. Similarly, optical DIC tests were conducted to identify and quantify kissing bond defects in CFRP-Al single lap shear joints. DIC results demonstrated changes in the normal strain (εyy) contour map of the contaminated specimens at relatively lower load levels (15% ~ 30% of failure loads). Kissing bond regions were characterized by negative strains, and these were attributed to high compressive bending strains and the localized disbonding taking placed at the bondline interface as a result of the load application. It was also observed that contaminated samples suffered from more compressive strains (εyy) compared to the baseline sample along the loading direction and they suffered from less compressive strains (εxx) compared to the baseline sample perpendicular to the loading direction. This demonstrated the adverse effect of the kissing bond on the adhesive joint integrity. This was a very significant finding for the reason that hybrid ultrasonic DIC is being developed as a faster, more efficient, and more reliable NDE technique for determining bond quality and predicting bond shear strength in adhesively bonded structures.
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Kecelioglu, Galip. "Stress And Fracture Analysis Of Riveted Joints." Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/12610132/index.pdf.
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The objective of this study is to model and analyze a three dimensional single riveted lap joint (with and without a crack). By using finite element method, stress and fracture analyses are carried out under both the residual stress field and external tensile loading. Using a two step simulation, riveting process and subsequent tensile loading of the lap joint are simulated to determine the residual and overall stress state. Residual stress state due to riveting is obtained by interference and clamping misfit method. By employing different interference and clamping misfit values, the effects of riveting process parameters on stress state are examined. Two cracks namely the semi elliptical surface crack at faying surfaces of plates and the quarter elliptical corner crack at rivet hole are the most widely observed crack types in riveted joints. Fracture analysis of cracked riveted joints is carried out by introducing these two crack types to the outer plate at a plane perpendicular to the loading. The mixed mode stress intensity factors (SIFs) and energy release rates (G) around the crack front are obtained by using displacement correlation technique (DCT). Effects riveting process parameters (interference and clamping ratios) and geometrical parameters (crack shape and size) on fracture parameters are studied. The stress intensity factor solutions presented herein could be useful for correlating fatigue crack growth rates, fracture toughness computation, and multiple site damage (MSD) analysis in aircraft bodies.
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McGee, Caleb. "NUMERICAL EVALUATION OF ADHESIVE JOINTS IN COMPOSITE STRUCTURES USING FEA." OpenSIUC, 2015. https://opensiuc.lib.siu.edu/theses/1743.
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The increasing use of composite materials in many industries such as aerospace, automotive, and civil industries has increased the need for the development of effective techniques to detect defects in the bondlines of adhesive joints in composite structures. Currently, composite structures used in commercial applications such as modern aircraft use mechanical fasteners in redundancy to adhesive bonds to ensure structural integrity due to a lack of methods to reliably detect defects in the bondline of composite structure. As such, this thesis facilitates the development of nondestructive evaluation techniques for detecting bondline defects by using finite element (FE) modeling to simulate the effects of disbond defects caused by contamination of the bondline. These models were developed for single-lap joint specimens made of metal, composite, and dissimilar materials (metal bonded with composite) with contamination induced disbonds. The created FE models were used to generate whole-field strain data for single-lap joints under tensile loading. This generated strain data was then used to provide a model for evaluating and interpreting experimental strain measurements captured by digital image correlation (DIC). Finally, conclusions were drawn outlining the observed capability of strain measurement in the evaluation of bondline contamination in single-lap joints.
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Vinnakota, Lakshman. "Parametric study of stress concentration of single and double bolted lap joints between adhesive bonded aluminum laminates." Thesis, Wichita State University, 2011. http://hdl.handle.net/10057/5026.
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In the distant past, adhesive materials were considered to be a kind of mere glue. But today adhesive materials are used extensively in the field of manufacturing because of the good properties they exhibit. Adhesive bonded aluminum laminates are well known materials that belong to the family of metal laminates. Adhesive bonded aluminum laminates are made by joining several thin sheets of aluminum. These sheets are bonded by an adhesive material in between. The adhesive bonded aluminum laminates when compared to the monolithic aluminum plates, exhibit very good mechanical and chemical properties. They also exhibit some useful properties such as weight reduction, capability of withstanding high loads, thermal resistance, etc. Because of this, they are widely used in aerospace, marine and automobile fields, particularly in manufacturing of doublers plates.
Optimizing the design of structural joint will definitely improve the load carrying capability of the structural joint. Identifying the significant factors that affect the structural joint is one way to avoid failure at the joints. The main purpose of this study is to predict the stress concentration around the hole in single and double lap joints of adhesive bonded aluminum laminate. A three dimensional finite element model is developed in ABAQUS to know the effect of stress concentration and is validated by comparing the results of the finite element model with the results obtained from theoretical closed form solution. The present study shows the relationship between the stress concentration around the hole and the Young‟s modulus of the adhesive material, Radius of the fastener holes, Distance between the fastener holes, position of the adhesive layer and number of the adhesive layers. The results obtained from this parametric study are analyzed in a design of experiments software to determine the significance of each parameter.Thesis (M.S.)--Wichita State University, College of Engineering, Dept. of Mechanical Engineering.
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Arbex, Alexandra Alvim. "Análise estrutural e de fadiga de juntas rebitadas de uso aeronaútico utilizando o método dos elementos finitos /." Guaratinguetá : [s.n.], 2011. http://hdl.handle.net/11449/97053.
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Orientador: Fernando de Azevedo SilvaBanca: José Elias Tomazini
Banca: Silvana Aparecida Barbosa
Resumo: Juntas rebitadas sobrepostas representam elementos críticos na construção de estruturas aeronáuticas quando projetadas à fadiga. Por serem elementos de fixação largamente utilizados na indústria aeronáutica, o estudo de suas propriedades e variáveis à fadiga tem sido cada vez mais amplo. A variável que tem mostrado possuir alta influência na resistência à fadiga de juntas rebitadas é a força de aperto aplicada no processo de rebitagem. A vida da peça tende a ser maior quando o valor dessa força é aumentado. O método dos elementos finitos, que é uma ferramenta de cálculo aplicada nos mais diversos campos de atuação e tem se tornado parte indispensável de projetos mecânicos, é utilizado nesta dissertação para a análise de uma junta rebitada sobreposta de uso aeronáutico. A junta é simulada levando em conta as etapas do processo de fabricação e aplicação, a fim de realizar a análise de seu comportamento mecânico e calcular sua vida em fadiga. Através de um teste experimental de tração monotônica foram obtidos valores de deformação com extensômetros, e é feita a correlação desses dados com o modelo numérico a fim de validar a modelagem. Em seguida são feitas mais duas análises com diferentes forças de aperto, com o objetivo de verificar a influência dessa variação na vida em fadiga da peça.
Abstract: Riveted lap joints represent a critical element in metallic airframe construction when designing against fatigue. These elements are widely used in the aerospace industry, so the study of the fatigue's properties and variables has been increasingly broad. The variable that has shown to have a high influence on the fatigue strength of riveted joints is the clamping force applied to the riveting process. The life of the part tends to be higher when the clamping force applied is increased. The finite element method, which is a calculation tool applied in various fields of activity and has become an indispensable step of mechanical design, is used in this dissertation for the analysis of a riveted lap joint of aeronautic use. The joint is simulated considering the stages of the manufacturing process and application, in order to perform analysis of mechanical behavior and calculate the fatigue life. Through an experimental test of monotonic tensile, strain values were obtained with strain-gauges, and is made the correlation of these data with the numerical model to validate the modeling. Finally two more tests are made with different clamping forces, in order to check the influence of this variation in fatigue life of the joint.
Mestre
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Kratochvíl, Jan [Verfasser], Wilfried [Akademischer Betreuer] Becker, and Holm [Akademischer Betreuer] Altenbach. "Asymptotic Analysis of the Load Transfer on Double-Lap Bolted Joints / Jan Kratochvil. Betreuer: Wilfried Becker ; Holm Altenbach." Darmstadt : Universitäts- und Landesbibliothek Darmstadt, 2012. http://d-nb.info/1106115805/34.
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Zeeshan, Muhammad. "Tensile Strength of Bonded Lap-mitered Butt-Joints between Layered CFRP Bands : -In collaboration with RUAG Space AB." Thesis, KTH, Lättkonstruktioner, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-172209.
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Joints in structures always cause strength reduction. The percentage of strength reduction depends upon the selection of several factors such as: type of joint (i.e. adhesive or mechanical), technique of joint (i.e. lap joint, butt joint etc.), geometry of joint, mode of load application etc. Here in this research, the strength of adhesively bonded butt joints with several geometries, later referred as joint angles, is investigated under uniaxial tension loading. Adhesively bonded simple butt joints, where joints are placed perpendicular to the loading direction are in common practice mainly because of ease in manufacturing process. But when the joint is fabricated with an angle respective to the loading direction, the geometry of the joint itself affects the strength of the joint significantly. Without going too deep into other factors that affects the joint strength such as manufacturing techniques, manufacturing defects, material behavior etc. only the geometry of the joint is considered and it is evaluated whether it is worth to change the joint geometry or not. The significant issue in adhesive joint technology is the prediction of joint strength. However, an approach similar to plastic yield criterion later referred as elastic limit offset method (attempted for 0.025% offset) is considered to estimate the linear elastic limit. Since RUAG Space AB (the industry for which this project is performed) is only interested in the linear elastic regime of the stress-strain curve, therefore the elastic limit offset method is considered to be the suitable one. The present work is concerned with the study of adhesively bonded angled butt joint vs. strength behavior. The strength of adhesively bonded butt joints is examined for several butt joint angles under uniaxial tensile loading. The employed butt joint angles are: 0°, 30°, 45°, 60° and 75°. The main objective of the current investigation is to find the joint angle that has the highest strength or the highest capability of load transfer. In addition to the above, the influence of the joint on the stress field, joint strength and type of failure is also evaluated using DSP (Digital Speckle Photography) technique and simulated using well known finite element tool, ABAQUS. It is observed that specific strength of the joint is greatly influenced with joint angle. The 45° joint showed the highest elasticity and failed like ductile behavior whereas 75° joint showed the lowest elasticity and failure was purely brittle. Moreover, post-failure inspection of fractured surfaces showed cohesive failure (failure within adhesive layers) for 0°, 30°, 45° and 60°whereas 75° showed composite or adherend failure. The simulation is performed for each joint angle. However to validate the model only 45° and 75° joints results are compared with experimental results and plotted in the report. The simulation results of these angles showed good agreement with the experimental ones. Moreover, the stress fields for each joint angle are captured (from ABAQUS), showing that all joints are susceptible to inter-laminar shear. Besides, the relative slip between the top and middle adherends is also calculated, the results show that, the 45° joint has higher tendency of relative slip than others.
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Sahellie, Samer Verfasser], and Hartmut [Akademischer Betreuer] [Pasternak. "Study on the temperature effect on lap shear adhesive joints in lightweight steel construction / Samer Sahellie ; Betreuer: Hartmut Pasternak." Cottbus : BTU Cottbus - Senftenberg, 2015. http://d-nb.info/1114283789/34.
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WAGH, VIJAY HEMANT. "VAPOR PHASE SILANATION OF PLASMA-POLYMERIZED SILICA-LIKE FILMS BY 3-AMINOPROPYLTRIETHOXYSILANE." University of Cincinnati / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1121884987.
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Madureira, Fernando. "Fabricação e controle de espessura de juntas coladas single lap joint: caracterização mecânica dos aderentes e do adesivo." Universidade de São Paulo, 2018. http://www.teses.usp.br/teses/disponiveis/18/18148/tde-10122018-205044/.
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Devido a suas vantagens comparadas aos métodos tradicionais de união mecânica, a utilização de juntas coladas estruturais só tende a crescer, entretanto, devido suas propriedades e modos de falha dependerem de diversos parâmetros (tratamento superficial, geometria, material, condições de tralho, etc.) uma utilização mais ampla desta técnica ainda é restrita pela ausência de modelos de falhas confiáveis. O presente trabalho consiste na apresentação de métodos para fabricação de juntas coladas em material compósito e verificação da influência da espessura da camada adesiva na resistência de juntas simples coladas (single lap joints) submetidas à tração. São também apresentados métodos para fabricação dos aderentes, corpos de prova de adesivo puro para ensaios de caracterização e realização de ensaios mecânicos para obtenção das propriedades mecânicas tanto dos aderentes quanto do adesivo. As propriedades mecânicas dos aderentes e do adesivo foram obtidas através de ensaios realizados em uma máquina de tração universal com o auxílio da técnica de correlação digital de imagem, e a obtenção das energias críticas de resistência à fratura (GIc,GIIc) da camada adesiva foram calculadas através de ensaios Double Cantilever Beam (DCB) e End Notched Flexure (ENF). Foram estudados métodos para gerar falha coesiva nas juntas adesivas, sendo que o melhor método encontrado foi o de tratamento superficial dos aderentes com jateamento abrasivo seguido pela limpeza superficial com acetona. O controle preciso da espessura da camada adesiva foi alcançado através do desenvolvimento de um dispositivo de fácil construção, compostos por suportes de madeira, hastes e linhas de nylon. Nos ensaios em juntas coladas foi constatado uma relação inversamente proporcional entre a espessura da camada adesiva e a resistência máxima suportada pela junta, ou seja, quanto maior a espessura do adesivo menor sua resistência. Os métodos aqui apresentados foram os resultados de vários meses de estudo e compreensão das normas e técnicas disponíveis na literatura, o aprimoramento das técnicas foram frutos de um ciclo compostos por fabricação, testes e análise de resultados.Amongst the joining techniques, adhesively bonding joints are one of the most commonly applied nowadays. However, a lack of reliable failure criteria still exists, limiting in this way a more widespread application of adhesively bonded joints in principal load-bearing structural applications. An accurate strength prediction of the adhesively bonded joints is essential to decrease the amount of expensive testing at the design stage. This work consists to show methods for manufacturing single lap joints and to verify the adhesive thickness influence on the joint resistance. The manufacturing process of the composite adherends and adhesives for bulk tests was also covered. The mechanical properties of the adherends and bulk adhesive were performed on a universal testing machine with assistance of a digital image correlation (DIC) technique. The fracture toughness energy release rates (GIc,GIIc) of the adhesive layer were obtained respectively through Double Cantilever Beam (DCB) and End Notched Flexure (ENF) tests. Cohesive failure was achieved by grit blasting the adherents followed by cleaning with acetone. A constant adhesive thickness was guaranteed by placing nylon fishing lines between the adherents. Single lap joints tests showed that the joint resistance decrease with increasing adhesive thickness.
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Arbex, Alexandra Alvim [UNESP]. "Análise estrutural e de fadiga de juntas rebitadas de uso aeronaútico utilizando o método dos elementos finitos." Universidade Estadual Paulista (UNESP), 2011. http://hdl.handle.net/11449/97053.
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Juntas rebitadas sobrepostas representam elementos críticos na construção de estruturas aeronáuticas quando projetadas à fadiga. Por serem elementos de fixação largamente utilizados na indústria aeronáutica, o estudo de suas propriedades e variáveis à fadiga tem sido cada vez mais amplo. A variável que tem mostrado possuir alta influência na resistência à fadiga de juntas rebitadas é a força de aperto aplicada no processo de rebitagem. A vida da peça tende a ser maior quando o valor dessa força é aumentado. O método dos elementos finitos, que é uma ferramenta de cálculo aplicada nos mais diversos campos de atuação e tem se tornado parte indispensável de projetos mecânicos, é utilizado nesta dissertação para a análise de uma junta rebitada sobreposta de uso aeronáutico. A junta é simulada levando em conta as etapas do processo de fabricação e aplicação, a fim de realizar a análise de seu comportamento mecânico e calcular sua vida em fadiga. Através de um teste experimental de tração monotônica foram obtidos valores de deformação com extensômetros, e é feita a correlação desses dados com o modelo numérico a fim de validar a modelagem. Em seguida são feitas mais duas análises com diferentes forças de aperto, com o objetivo de verificar a influência dessa variação na vida em fadiga da peça.
Riveted lap joints represent a critical element in metallic airframe construction when designing against fatigue. These elements are widely used in the aerospace industry, so the study of the fatigue’s properties and variables has been increasingly broad. The variable that has shown to have a high influence on the fatigue strength of riveted joints is the clamping force applied to the riveting process. The life of the part tends to be higher when the clamping force applied is increased. The finite element method, which is a calculation tool applied in various fields of activity and has become an indispensable step of mechanical design, is used in this dissertation for the analysis of a riveted lap joint of aeronautic use. The joint is simulated considering the stages of the manufacturing process and application, in order to perform analysis of mechanical behavior and calculate the fatigue life. Through an experimental test of monotonic tensile, strain values were obtained with strain-gauges, and is made the correlation of these data with the numerical model to validate the modeling. Finally two more tests are made with different clamping forces, in order to check the influence of this variation in fatigue life of the joint.
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Bandi, Raghava. "Effect of Surface Treatment on the Performance of CARALL, Carbon Fiber Reinforced Aluminum Dissimilar Material Joints." Thesis, University of North Texas, 2017. https://digital.library.unt.edu/ark:/67531/metadc1011869/.
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Fiber-metal laminates (FML) are the advanced materials that are developed to improve the high performance of lightweight structures that are rapidly becoming a superior substitute for metal structures. The reasons behind their emerging usage are the mechanical properties without a compromise in weight other than the traditional metals. The bond remains a concern. This thesis reviews the effect of pre-treatments, say heat, P2 etch and laser treatments on the substrate which modifies the surface composition/roughness to impact the bond strength. The constituents that make up the FMLs in our present study are the Aluminum 2024 alloy as the substrate and the carbon fiber prepregs are the fibers. These composite samples are manufactured in a compression molding process after each pre-treatment and are then subjected to different tests to investigate its properties in tension, compression, flexural and lap shear strength. The results indicate that heat treatment adversely affects properties of the metal and the joint while laser treatments provide the best bond and joint strength.
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Chang, Paul, and mrpc@tpg com au. "The Mechanical Properties and Failure Mechanisms of Z-Pinned Composites." RMIT University. Aerospace, Mechanical and Manufacturing Engineering, 2006. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20070111.145714.
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Z-pinning is a through-thickness reinforcement technology for polymer composite materials that has been developed and commercialised over the past fifteen years. The through-thickness reinforcement of composites with thin metallic or fibrous pins aids in suppressing delamination, improving impact damage tolerance and increasing joint strength. Z-pins are applied to the composite part during its manufacture. Pins are embedded within sheets of foam and placed over the unconsolidated part. Subsequently, the foam is compacted and the pins transferred into the part, which is usually an uncured prepreg. In this manner, large numbers of pins can be inserted quickly and easily. The pinned composite is then cured using conventional processes. The use of z-pins is currently limited to several high performance composite structures, most notably Formula One racing cars and F/A-18 E/F (Superhornet) fighter aircraft, although the technology has potential applications in a d iverse variety of aerospace and non-aerospace composite structures. A limited understanding of the mechanical performance of z-pinned parts under high load and fatigue loading conditions currently hinders the application of z-pinned composites. The aim of this PhD project is to investigate the mechanical properties, strengthening mechanics and failure mechanisms of z-pinned carbon/epoxy laminates and joints. The effect of z-pin reinforcement on the tensile and flexural properties of laminates under monotonic and fatigue loading is studied. The sensitivity of these properties to the volume content and diameter of the z-pins is systematically studied by experimentation and analytical modelling. This PhD also evaluates the efficacy of z-pins in improving the load-bearing properties of carbon/epoxy lap joints. Improvements to the room temperature and elevated temperature properties of z-pinned lap joints under monotonic and fatigue tensile loading were determined. The effect of strain rate on the load-bearing properties of z-pinned lap joints was also evaluated. A further aim of the PhD project was to assess the z-pin manufacturing process and the microstructural damage caused by that process. The outcome of this study augments the analysis of the me chanical properties of z-pinned laminates and joints.
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Dhamari, Ruby Dharma Adji Aerospace Civil & Mechanical Engineering Australian Defence Force Academy UNSW. "The effects of water displacing corrosion preventatives on the fatigue behaviour of mechanically fastened aluminium joints." Awarded by:University of New South Wales - Australian Defence Force Academy. School of Aerospace, Civil and Mechanical Engineering, 2005. http://handle.unsw.edu.au/1959.4/38668.
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Two failure mechanisms in a double lap joint are investigated. Analytical models of net-section and gross-section failure modes are proposed to describe these mechanisms. The effects of lamping force, interference fit, maximum axial load and WDCP on fatigue performance of the joint are included in the models. The effect of WDCP is assumed to give a reduction in friction coefficient. Three types of stress reduction factors are proposed in the net-section failure model to account for these parameters. The stress reduction factors modify stress range that is used in crack growth calculation. If there are no effects of these parameters, the stress reduction factors are equal to one. Two types of fretting stress are introduced in gross-section failure model to describe either sliding contact or incipient sliding contact on faying surface. The fretting stress is combined with body stress to modify stress range. The net-section failure model predicts that fatigue life is increasing as interference fit, clamping force and friction coefficient increase. The gross-section failure model predicts that fatigue life is decreasing as clamping force and friction coefficient increase. Both models predict that fatigue life is decreasing as maximum axial load increases. Transition of the failure mode occurs earlier as friction coefficient and interference fit increase, while it is delayed as maximum axial load increases. A transition parameter is proposed to establish a relationship between the four main parameters. The transition parameter is expressed in a polynomial equation. It gives an optimum combination of the four main parameters in order to achieve relatively higher fatigue life by having gross-section failure mode. Finite element analysis and fatigue testing are performed to validate the models. The finite element and the analytical models show that stress concentration factor at the edge of the hole is decreasing as clamping force increases. The rate of decrease of stress concentration factor is increasing as friction coefficient increases. While stress concentration factor on the faying surface is increasing as clamping force and friction coefficient increase. Fatigue testing reveals that the fatigue life of the joint is in good agreement with the predicted fatigue life of the proposed models.
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Islam, Mohammad Majharul. "Global-local Finite Element Fracture Analysis of Curvilinearly Stiffened Panels and Adhesive Joints." Diss., Virginia Tech, 2012. http://hdl.handle.net/10919/38687.
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Global-local finite element analyses were used to study the damage tolerance of curvilinearly stiffened panels; fabricated using the modern additive manufacturing process, the so-called unitized structures, and that of adhesive joints. A damage tolerance study of the unitized structures requires cracks to be defined in the vicinity of the critical stress zone. With the damage tolerance study of unitized structures as the focus, responses of curvilinearly stiffened panels to the combined shear and compression loadings were studied for different stiffenersâ height. It was observed that the magnitude of the minimum principal stress in the panel was larger than the magnitudes of the maximum principal and von Mises stresses. It was also observed that the critical buckling load factor increased significantly with the increase of stiffenersâ height.
To study the damage tolerance of curvilinearly stiffened panels, in the first step, buckling analysis of panels was performed to determine whether panels satisfied the buckling constraint. In the second step, stress distributions of the panel were analyzed to determine the location of the critical stress under the combined shear and compression loadings. Then, the fracture analysis of the curvilinearly stiffened panel with a crack of size 1.45 mm defined at the location of the critical stress, which was the common location with the maximum magnitude of the principal stresses and von Mises stress, was performed under combined shear and tensile loadings. This crack size was used because of the requirement of a sufficiently small crack, if the crack is in the vicinity of any stress raiser. A mesh sensitivity analysis was performed to validate the choice of the mesh density near the crack tip. All analyses were performed using global-local finite element method using MSC. Marc, and global finite element methods using MSC. Marc and ABAQUS. Negligible difference in results and 94% saving in the CPU time was achieved using the global-local finite element method over the global finite element method by using a mesh density of 8.4 element/mm ahead of the crack tip. To study the influence of different loads on basic modes of fracture, the shear and normal (tensile) loads were varied differently. It was observed that the case with the fixed shear load but variable normal loads and the case with the fixed normal load but variable shear loads were Mode-I. Under the maximum combined loading condition, the largest effective stress intensity factor was very smaller than the critical stress intensity factor. Therefore, considering the critical stress intensity factor of the panel with the crack of size 1.45 mm, the design of the stiffened panel was an optimum design satisfying damage tolerance constraints.
To acquire the trends in stress intensity factors for different crack lengths under different loadings, fracture analyses of curvilinearly stiffened panels with different crack lengths were performed by using a global-local finite element method under three different load cases: a) a shear load, b) a normal load, and c) a combined shear and normal loads. It was observed that 85% data storage space and the same amount in CPU time requirement could be saved using global-local finite element method compared to the standard global finite element analysis. It was also observed that the fracture mode in panels with different crack lengths was essentially Mode-I under the normal load case; Mode-II under the shear load case; and again Mode-I under the combined load case. Under the combined loading condition, the largest effective stress intensity factor of the panel with a crack of recommended size, if the crack is not in the vicinity of any stress raiser, was very smaller than the critical stress intensity factor.
This work also includes the performance evaluation of adhesive joints of two different materials. This research was motivated by our experience of an adhesive joint failure on a test-fixture that we used to experimentally validate the design of stiffened panels under a compression-shear load. In the test-fixture, steel tabs were adhesively bonded to an aluminum panel and this adhesive joint debonded before design loads on the test panel were fully applied. Therefore, the requirement of studying behavior of adhesive joints for assembling dissimilar materials was found to be necessary. To determine the failure load responsible for debonding of adhesive joints of two dissimilar materials, stress distributions in adhesive joints of the nonlinear finite element model of the test-fixture were studied under a gradually increasing compression-shear load. Since the design of the combined load test fixture was for transferring the in-plane shear and compression loads to the panel, in-plane loads might have been responsible for the debonding of the steel tabs, which was similar to the results obtained from the nonlinear finite element analysis of the combined load test fixture.
Then, fundamental studies were performed on the three-dimensional finite element models of adhesive lap joints and the Asymmetric Double Cantilever Beam (ADCB) joints for shear and peel deformations subjected to a loading similar to the in-plane loading conditions in the test-fixtures. The analysis was performed using ABAQUS, and the cohesive zone modeling was used to study the debonding growth. It was observed that the stronger adhesive joints could be obtained using the tougher adhesive and thicker adherends. The effect of end constraints on the fracture resistance of the ADCB specimen under compression was also investigated. The numerical observations showed that the delamination for the fixed end ADCB joints was more gradual than for the free end ADCB joints.
Finally, both the crack propagation and the characteristics of adhesive joints were studied using a global-local finite element method. Three cases were studied using the proposed global-local finite element method: a) adhesively bonded Double Cantilever Beam (DCB), b) an adhesive lap joint, and c) a three-point bending test specimen. Using global-local methods, in a crack propagation problem of an adhesively bonded DCB, more than 80% data storage space and more than 65% CPU time requirement could be saved. In the adhesive lap joints, around 70% data storage space and 70% CPU time requirement could be saved using the global-local method. For the three-point bending test specimen case, more than 90% for both data storage space and CPU time requirement could be saved using the global-local method.Ph. D.
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Ghafoori, Roozbahany Ehsan. "Fracture testing and evaluation of asphalt pavement joints in quasi static tension mode." Thesis, KTH, Väg- och banteknik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-96672.
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Asphalt joints are inevitable parts of every pavement. They are constructed for different reasons. Although much attention is dedicated to the construction joints (hot with hot pavement), a scientific approach for cold joints (cold with hot pavement) with respect to large patch constructions is still missing. This report tries to evaluate existing construction techniques and to suggest new testing methods of tests. Although, indirect tensile tests IDT and direct tension tests DTT are familiar in the field of asphalt pavement characterization, they have not been used for the assessment of joint quality so far. In this report, these two test types are evaluated and the results are analyzed using finite element software ABAQUS. The results of the comparison of joint compaction techniques on a laboratory scale suggest that joints with angles seem to show more promising behavior than vertical joints. Also, starting compaction from the hot side generally produces better results than compaction starting from cold side.
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WINTER, MATTHEW CHARLES. "A STUDY OF THE LAP-JOINT IN ARCHITECTURE." University of Cincinnati / OhioLINK, 2003. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1053380315.
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Wu, Tsun-Yen. "Prediction and experimental validation of weld dimensions in thin plates using superimposed laser sources technique." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/41106.
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The objective of this research is to develop a method to evaluate important weld dimensions in thin plates by using laser generated ultrasounds and EMAT receiver. The superimposed laser sources (SLS) technique is developed to generate narrowband Lamb waves with fixed wavelengths in thin plates. The method permits the flexibility of selecting desired wavelength. The signal processing procedure that combines wavenumber-frequency (k-w) domain filtering and synthetic phase tuning (SPT) is used to further reduce the complexity of Lamb waves. The k-w domain filtering technique helps to filter out the unwanted wave components traveling at the direction that is not of interest to us and the SPT technique is applied to amplify and isolate a particular Lamb wave mode. The signal processing procedure facilitates the calculation of reflection coefficients of Lamb waves that result from the presence of weld joints. The SLS and signal processing procedure are then applied to measure reflection coefficients in butt welds and lap welds. Two methods, the direct method and indirect method, are used to develop models that use reflection coefficients as predictors to predict these weld dimensions. The models developed in this research are shown to accurately predict weld dimensions in thin plates.
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Bhamare, Vinay Vasant Lankarani Hamid M. "Transverse impact characteristics of adhesively bonded composite single lap joint." Diss., Click here for available full-text of this thesis, 2006. http://library.wichita.edu/digitallibrary/etd/2006/t080.pdf.
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Thesis (M.S.)--Wichita State University, College of Engineering."May 2006." Title from PDF title page (viewed on October 29, 2006). Thesis adviser: Hamid M. Lankarani. Includes bibliographic references (leaves 62-64).
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Winter, Matthew C. "A study of the lap-joint in architecture an investigtion /." Cincinnati, Ohio : University of Cincinnati, 2003. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=ucin1053380315.
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Bean, Gerard M. D. "Fiduciary relationships, fiduciary duties and joint ventures : the joint operating agreement." Thesis, University of Cambridge, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.334089.
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He, Xiaocong. "Static and dynamic analysis of single lap-jointed cantilevered beams." Thesis, University of Manchester, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.627916.
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The work presented in this thesis is concerned with the static and dynamic analyses of single lap-jointed cantilevered beams. An analytical model is presented for predicting the stress distribution within a single lap-jointed beam under tension. With suitable boundary conditions, the stress distribution of the adhesive at the longitudinal direction is determined. However, the simplifying assumptions of the analytical model are too restrictive. Consequently, all analysis carried out are based on the finite element method. The stress distribution of a single-lap jointed cantilevered beam under tension has been investigated using the three dimensional FEA method. The results show that there is considerable variation in the stress distribution across the width, and that the highest stress concentrations occur in the portions of the adhesive layer closest to the clamped end of the bonded beam. Four finite element models to analyse the behaviour of adhesively bonded joints are described. Comparisons are performed between models with different modelling approaches as well as different types of element combinations in order to find a suitable model to predict the mechanical behaviour of adhesively bonded joints. The effects of typical boundary conditions and of adhesive properties were also investigated. The results indicate that the stress distributions of a single-lap jointed cantilevered beam are strongly affected by the boundary conditions of the beam and by the elastic properties of the adhesive.
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Zhang, Yuan. "Investigation of Magnetic Pulse Welding on Lap Joint of Similar and Dissimilar Materials." The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1268135049.
Full text
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Guvendik, Ozen. ""." Master's thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/12605523/index.pdf.
Full textAbstract:
In this Thesis, the problems of the Free Flexural (or Bending) Vibrations of Composite, Orthotropic Plates and/or Panels with Various Bonded Joints are formulated and investigated in detail. The composite bonded plate system is composed of Plate Adherends adhesively bonded by relatively very thin adhesive layers. The general problem is considered in terms of the three Main PROBLEMS, namely Main PROBLEM I, Main PROBLEM II and Main PROBLEM III.
The theoretical formulation of the Main PROBLEMS is based on Mindlin Plate Theory which is a First Order Shear Deformation Plate Theory (FSDPT). Thus, the transverse shear deformations, the transverse and the rotary moments of inertia of the plates are included in the formulation. Very thin, elastic deformable adhesive layers are considered as continua with transverse normal and shear stresses. The
damping effects in the plates and the adhesive layers are neglected.
The entire composite bonded joint assembly is assumed to be simple supported along the two opposite edges, so that the Classical Levy’
s Solutions can be applied in this direction. The dynamic equations of the Bonded Joint System which combines together the Mindlin Plate dynamic equations with the adhesive layer equations are reduced to a system of First Order Ordinary Differential Equations in the state vector form. This special form of the Governing System of the First Order Ordinary Differential Equations are numerically integrated by means of the Modified Transfer Matrix Method which is a combination of the Classical Levy&
#8217
s Method, the Transfer Matrix Method and the Integrating Matrix Method (with Interpolation Polynomials and/or Chebyshev Polynomials). The Main PROBLEMS are investigated and presented in terms of the mode shapes and the corresponding natural frequencies for various sets of boundary conditions. The significant effects of the hard and the soft adhesive layer elastic constants on the mode shapes and on the natural frequencies are demonstrated. Some important parametric studies such as the influences of the Joint Length Ratio, the Joint Position Ratio, the Bending Stiffness Ratio, etc. on the natural frequencies are computed and plotted for the hard and soft adhesive cases for several support conditions.
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Margetts, Adam R. "Joint scale-lag diversity in mobile wideband communications." Connect to resource, 2005. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1123963618.
Full textAbstract:
Thesis (Ph. D.)--Ohio State University, 2005.Title from first page of PDF file. Document formatted into pages; contains xviii, 139 p.; also includes graphics (some col.). Includes bibliographical references (p. 130-139). Available online via OhioLINK's ETD Center