Letteratura scientifica selezionata sul tema "Double Cantilever Beam (DCB) test"
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Articoli di riviste sul tema "Double Cantilever Beam (DCB) test"
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Sponseller, David L., e Thomas E. Sponseller. "The Double Cantilever Beam (DCB) Test at Forty". BHM Berg- und Hüttenmännische Monatshefte 161, n. 1 (gennaio 2016): 19–26. http://dx.doi.org/10.1007/s00501-016-0449-7.
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Alfred Franklin, V., T. Christopher e B. Nageswara Rao. "Influence of Root Rotation on Delamination Fracture Toughness of Composites". International Journal of Aerospace Engineering 2014 (2014): 1–12. http://dx.doi.org/10.1155/2014/829698.
Testo completoAbstract (sommario):
Large deviations have been observed while analysing composite double cantilever beam (DCB) specimens assuming each cracked half as a simple cantilever beam. This paper examines the effect of rotational spring stiffness(K)on the critical fracture energy(GIC)considering nonzero slope at the crack-tip of the DCB specimen by modelling each cracked half as the spring-hinged cantilever beam. The critical load estimates of DCB specimens fromGICare found to be in good agreement with in-house and existing test results of different composite material systems.
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Gourlie, A. D., G. N. Podolski e J. R. Fleet. "A Detailed Statistical Examination of the Double Cantilever Beam (DCB) Test". CORROSION 47, n. 9 (settembre 1991): 728–35. http://dx.doi.org/10.5006/1.3585859.
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LOO, SHANE ZHI YUAN, PUAY CHENG LEE, ZAN XUAN LIM, NATALIA YANTARA, TONG YAN TEE, CHER MING TAN e ZHONG CHEN. "INTERFACE FRACTURE TOUGHNESS ASSESSMENT OF SOLDER JOINTS USING DOUBLE CANTILEVER BEAM TEST". International Journal of Modern Physics B 24, n. 01n02 (20 gennaio 2010): 164–74. http://dx.doi.org/10.1142/s0217979210064095.
Testo completoAbstract (sommario):
In the current work, a test scheme to evaluate solder joint interface fracture toughness using double cantilever beam (DCB) test has been successfully demonstrated. The obtained results, in terms of critical energy release rate, predict the joint failure based on the principle of fracture mechanics. The results can be used as a materials property in the reliability design of various types of solder-ball joined packages. DCB specimens made of 99.9 wt% copper were selected in the current work. Eutectic Sn -37 Pb and lead-free Sn -3.5 Ag -0.5 Cu solders were used to join two pieces of the copper beams with controlled solder thickness. The test record showed steady propagation of the crack along the solder / copper interface, which verifies the viability of such a testing scheme. Interface fracture toughness for as-joined, extensively-reflowed and thermally aged samples has been measured. Both the reflow treatment and the thermal aging lead to degradation of the solder joint fracture resistance. Reflow treatment was more damaging as it induces much faster interface reaction. Fractographic analysis established that the fracture has a mixed micromechanism of dimple and cleavage. The dimples are formed as a result of the separation between the hard intermetallic compound (IMC) particles and the soft solder material, while the cleavage is formed by the brittle split of the IMCs. When the IMC thickness is increased due to extended interface reaction, the proportion of IMC cleavage failure increases, and this was reflected in the decrease of the critical energy release rate.
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de Morais, A. B. "A new fibre bridging based analysis of the Double Cantilever Beam (DCB) test". Composites Part A: Applied Science and Manufacturing 42, n. 10 (ottobre 2011): 1361–68. http://dx.doi.org/10.1016/j.compositesa.2011.05.019.
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Hlača, Ivan, Marin Grbac e Leo Škec. "Determining Fracture Resistance of Structural Adhesives in Mode-I Debonding Using Double Cantilever Beam Test". Zbornik radova 22, n. 1 (20 dicembre 2019): 59–74. http://dx.doi.org/10.32762/zr.22.1.4.
Testo completoAbstract (sommario):
Double cantilever beam (DCB) test is the most commonly used test for determining the fracture resistance of structural adhesive joints in mode-I debonding. Test specimens are composed of two equal plates that are glued together, and then exposed to the opening load causing crack propagation along the bonded surface. During the experiment, loadline displacement, applied force and crack length are measured continuously. Using these data, the fracture toughness of the adhesive can be computed by the procedure given in the relevant ISO standard (BS ISO 25217:2009). The calculations are based on simple beam theory and linear elastic fracture mechanics (LEFM) equations. In this paper, we will present the standard method for performing a DCB test and the method for data processing required to obtain the adhesive fracture toughness, i.e. the critical energy release rate. Experiments are performed for SikaPower® 4720 adhesive, applied with controlled thickness between the aluminium plates (adherends). After the curing period recommended by the adhesive manufacturer, DCB specimens with piano hinges are loaded by a tensile-testing machine. Loading is applied in the displacement-control mode because when the crack starts to propagate, the applied load drops. Using the optical measurement system GOM Aramis, complete displacement field is recorded during the experiment. Displacement field is then used to obtain the actual load-line displacement of the adherends (different than the one recorded on the tensile-testing machine grips) and the position of the crack tip. After syncing the measurements from different devices, fracture toughness for the adhesive is determined and a statistical analysis performed.
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Tawk, I., J. F. Ferrero, J. J. Barrau, E. Abdullah e M. Sudre. "Amultilayered Solid Element used to Model Composite Delamination". Advanced Composites Letters 19, n. 1 (gennaio 2010): 096369351001900. http://dx.doi.org/10.1177/096369351001900103.
Testo completoAbstract (sommario):
This paper focuses on the latest development of a solid hexahedron element for composite delamination analysis. The 8-node solid is derived from a 20-node hexahedron. It is transformed into two physical independent 4-node shell elements according to the propagation of delamination process within the element. This transformation is driven by a transfer and damage laws that are defined by calibrating the element with a FE modeling for a double cantilever beam (DCB) test. According to the position of the crack in the element, one parameter defines the degradation of the transverse properties at the Gauss point as well as the transfer of the volume element towards the bi-plate formulation. A sensitivity study of the element is presented. A global-local finite element approach coupled with the traditional virtual crack closure technique (VCCT) method allows to calculate the energy release rates and to control the propagation of cracking in the element. This method is validated by comparison between conventional FE models and experimental tests [DCB, and end load split (ELS)]. Experimental asymmetric double cantilever beam (ADCB) test is carried out and modelled using the developed element. The numerical simulation properly correlates with the experimental results.
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Shen, Yurong, Dongsheng Huang, Ying Hei Chui e Chunping Dai. "Fracture of Parallel Strand Bamboo Composite under Mode I Loading: DCB Test Investigation". Advances in Materials Science and Engineering 2019 (23 settembre 2019): 1–10. http://dx.doi.org/10.1155/2019/7657234.
Testo completoAbstract (sommario):
This paper describes the experimental studies on Mode I fracture of parallel strand bamboo (PSB) by the double cantilever beam (DCB) test. R-curves based on the elementary beam theory and specimen compliance are proposed in order to overcome the difficulties to monitor the crack propagation during experiments. The results demonstrate that the energy release rate (ERR) is influenced by the specimen geometry, i.e., the specimen width and initial crack length. The ERR at the plateau level is similar for the range of the analyzed widths (B = 20, 40, and 60 mm), while it decreases with width increasing up to 80 mm and 100 mm. The energy release rate for PSB specimens would verge to a stable value with the width increasing up to a specific value, while the value of the energy release rate will be influenced by the initial crack length. Consequently, the DCB tests also show that the obtained R-curve in this study is not a material property.
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Gliszczynski, A., S. Samborski, N. Wiacek e J. Rzeczkowski. "Mode I Interlaminar Fracture of Glass/Epoxy Unidirectional Laminates. Part II: Numerical Analysis". Materials 12, n. 10 (16 maggio 2019): 1604. http://dx.doi.org/10.3390/ma12101604.
Testo completoAbstract (sommario):
The paper deals with numerical analysis of double cantilever beam (DCB) predefined to Mode I Interlaminar Fracture Tests of GRFP unidirectional laminates. The numerical analyses were performed in the ANSYS® program based on the finite element. In geometrically nonlinear analysis, two algorithms, responsible for initiation and propagation of delamination front, were applied: Virtual Crack Closure Technique (VCCT) and Cohesive zone method (CZM). Due to the unidirectional arrangement of layers of the laminate, the problem of DCB test was solved with the use of one- and three-dimensional models with the implementation of linear interface element and contact element. The present study highlights the limitations of existing formulae used to reliably reflect the behavior of DCB. The use of three-dimensional models allowed confirming the curved shape of the delamination front observed in experimental studies. The application of the VCCT in the three-dimensional model led to an underestimation of the global response (force–opening displacement curve) recorded during numerical DCB test.
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Pavelko, Vitalijs. "Application of the Nonlinear Model of a Beam for Investigation of Interlaminar Fracture Toughness of Layered Composite". Key Engineering Materials 665 (settembre 2015): 273–76. http://dx.doi.org/10.4028/www.scientific.net/kem.665.273.
Testo completoAbstract (sommario):
Earlier presented the geometrically nonlinear model of a flexible beam (cylindrical bending of a plate) was used for analysis of post-buckling behavior of the layered composite with delamination at compression. In this paper the model is used for more details nonlinear analysis of double cantilever beam (DCB) that used in standard test for determination of the interlaminar fracture toughness composites with delamination-type damage. The main advantage of the model is a precise description of the curved axis of the beam (plate) without linearization or other higher order approximations. The exact solution of bending differential equation finally can be expressed in terms of the incomplete elliptic integrals of the first and second kind. The model describes only geometrically nonlinear effect of DCB arms bending (global effect) and should be combined with the procedure of effective delamination extension to correct DCB arms rotation at delamination front (local effect). First of all the nonlinear model can serve as a tool to estimate the possible error due the geometrical nonlinearity in comparison with linear solution. On the other hand, this model can be effectively used to determine interlaminar fracture toughness using DCB samples at large deflections. Validation of the model is made using data of standard tests of glass/epoxy DCB samples.
Tesi sul tema "Double Cantilever Beam (DCB) test"
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Majeed, Moiz, e Teja Geesala Rahitya Venkata. "Characterization of thin laminate interface by using Double Cantilever Beam and End Notched Flexure tests". Thesis, Blekinge Tekniska Högskola, Institutionen för maskinteknik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-20852.
Testo completoAbstract (sommario):
This thesis is intended to identify the mode I and mode II fracture toughness to characterize the thin laminate interface by using the Double Cantilever Beam test (DCB) and End Notched Flexure test (ENF). This study’s thin laminate was Polyethylene Terephthalate and Low-Density Polyethylene (PET-LDPE), which is mostly used by packaging industries in the manufacturing of packages to store liquid food. As PET-LDPE film is very flexible and difficult to handle, DCB and ENF tests cannot be performed directly so, sheet metal (Aluminium) was used as carrier material. PET-LDPE film is placed between two aluminum plates to reduce the flexibility and perform the tests. Therefore, the Aluminium plate was also studied to find the constitutive parameters (young’s modulus (E) and mixed hardening parameters (Plastic properties)) under the tensile test and three-point bending test. From the test response, energy release rate calculation has been done for different Pre-crack lengths to validate the DCB and ENF experimental setup, study the different Pre-crack lengths, and characterize the laminate interface. Finite Element simulation (FE simulation) for those tests were carried out in AbaqusTM2020. When needed, the force versus displacement response from FE simulation was optimized against experimental response to find the required constitutive parameters (Young’s modulus, Hardening parameters, and PET-LDPE material properties). Implementing of optimization algorithm and automated simulation has been done with the help of MATLAB code. In contrast, MATLAB works as a server, and Abaqus works as a client and connected two interfaces to run the optimization. The results obtained from experiments and FE simulations were compared to the results found in the literature.
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Peignon, Axel. "Contribution au développement de méthodes de caractérisation et de modélisation de LVL de peuplier en vue de leur usage dans la mobilité". Electronic Thesis or Diss., Université de Toulouse (2023-....), 2024. http://www.theses.fr/2024TLSEI017.
Testo completoAbstract (sommario):
Cette thèse s’inscrit dans le projet « BOOST » (acronyme de « le BOis pOur les STructures des véhicules ») financé par l’Agence Nationale de la Recherche (ANR). Il s’agit d’un Projet de Recherche Collaboratif entre l’ICA (Institut Clément Ader) à Toulouse et le LaBoMaP (LaBoratoire des Matériaux et Procédés) à Cluny.Le bois est une ressource locale, à très faible empreinte carbone et renouvelable. Largement utilisé dans l’aéronautique, mais aussi dans l’automobile en tant que structure travaillante dans le passé, son réemploi devient aujourd’hui un enjeu de la bioéconomie (Mair-Bauernfeind et al., 2020; Skullestad et al., 2016). Dans ce domaine, des travaux récents montrent que le bois est un matériau « crédible » pour la substitution de matériaux métalliques dans les structures de véhicules (Baumann et al., 2020).Les résultats antérieurs de l’Institut Clément Ader démontrent les très bonnes qualités mécaniques du bois, et notamment du contreplaqué associé à des peaux métalliques ou composites en statique, impact et crash (Guélou, 2021; Susainathan, 2017). Le LaBoMaP a pour sa part développé une méthode d’identification optique de l’orientation des fibres de chaque pli déroulé composant le contreplaqué (Duriot, 2021; Viguier et al., 2018). L’objectif scientifique de cette thèse est donc de :- Caractériser des LVL de peuplier, tout en caractérisant l’effet de la pente de fil, l’influence du nombre de plis et d’autres caractéristiques propres au LVL ;- Caractériser les interfaces collées dans le LVL en étudiant l’influence de l’orientation des plis à cette même interface ;- Étudier l’effet de la présence d’un trou sur le comportement mécanique des LVL, première étape pour définir une méthode de dimensionnement des jonctions dans les LVL.En effet, dans la perspective de démontrer l’intérêt des structures bois pour les moyens de transport, il n’est pas possible de se limiter à la caractérisation de matériaux élémentaires et à une stratégie de modélisation éprouvée au niveau du coupon seul. Comme pour la certification des structures aéronautiques, une démarche multiniveaux de type « pyramide des essais » semble pertinente. Aussi, il est primordial de caractériser au mieux le comportement du LVL. Les essais sur éprouvettes trouées ont été choisis, car ils sont utilisés dans de nombreux domaines et n’ont pratiquement pas été étudiés dans les contreplaqués. De plus, ils sont un premier pas vers la caractérisation de jonctions boulonnées et d’assemblages plus complexes. Au travers de ces essais, de nombreuses similitudes, mais aussi des différences significatives ont été observées entre le LVL et les matériaux composites synthétiques. Des modèles numériques élémentaires, s’inspirant de modèles de matériaux composites, ont aussi été proposés dans ces travaux pour appréhender le comportement mécanique spécifique du LVLThis thesis is part of the "BOOST" project (an acronym for "le BOis pOur les STructures des véhicules") funded by the French National Research Agency (ANR). This is a Collaborative Research Project between ICA (Institut Clément Ader) in Toulouse and LaBoMaP (LaBoratoire des Matériaux et Procédés) in Cluny.Wood is a local, renewable resource with a very low carbon footprint. Widely used in aeronautics but also in automobiles as a working structure in the past, its reuse today is becoming a challenge for the bioeconomy (Mair-Bauernfeind et al., 2020; Skullestad et al., 2016). In this field, recent work shows that wood is a "credible" material for the substitution of metallic materials in vehicle structures (Baumann et al., 2020).Previous results from the Institut Clément Ader demonstrate excellent mechanical qualities of wood, and in particular plywood combined with metal or composite skins in static, impact, and crash tests (Guélou, 2021; Susainathan, 2017). For its part, LaBoMaP has developed a method for optically identifying the fiber orientation of each peeled ply making up plywood (Duriot, 2021; Viguier et al., 2018). The scientific objective of this thesis is therefore to:- Characterize poplar LVLs, while characterizing the effect of yarn slopes, the influence of the number of plies, and other LVL-specific characteristics;- Characterize bonded interfaces in LVL, studying the influence of ply orientation at the same interface;- Study the effect of the presence of a hole in the mechanical behavior of LVLs, the first step towards defining a method for dimensioning junctions in LVLs.Indeed, to demonstrate the value of wood structures for the transport industry, it is not possible to limit ourselves to elementary material characterization and elementary modeling strategy. As with the certification of aeronautical structures, a multi-level "test pyramid" approach seems appropriate. It is therefore essential to characterize LVL behavior as accurately as possible. Testing on open-hole specimens was chosen because it is used in many fields and has hardly been studied in plywood or LVL. In addition, they are a first step towards characterizing bolted joints and more complex assemblies. Through these tests, many similarities and significant differences were observed between LVL and synthetic composite materials. Elementary numerical models, inspired by composite material models, were also proposed in this work to apprehend the specific mechanical behavior of LVL
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Verdade, João Filipe Silva. "Comportamento à fadiga em modo I usando o ensaio Double Cantilever Beam modificado". Master's thesis, Universidade de Aveiro, 2016. http://hdl.handle.net/10773/17446.
Testo completoAbstract (sommario):
Mestrado em Engenharia MecânicaA delaminagem é um dos modos de rutura mais frequentes dos laminados compósitos, e que é geralmente tratado no âmbito da Mecânica da Fratura. Tem havido recentemente interesse crescente na caraterização do comportamento à delaminagem sob fadiga. O primeiro objetivo deste trabalho foi adaptar a máquina de baixo custo desenvolvida no Departamento de Engenharia Mecânica da Universidade de Aveiro à realização de ensaios de delaminagem sob fadiga em modo I. O segundo objetivo foi realizar alguns ensaios de laminado carbono/epóxido iniciando assim um estudo mais alargado de longo prazo. Para isso recorreu-se a ensaios Double Cantilever Beam (DCB) modificados sob deslocamentos cíclicos impostos. Os resultados obtidos foram analisados no quadro da bem conhecida Lei de Paris, que relaciona a taxa de propagação da fenda com a variação da taxa de libertação de energia de deformação. Apesar de serem ainda escassos para tirar conclusões seguras, os resultados indicam um comportamento à fadiga complexo, muito influenciado pelo fenómeno da ponte de fibras.
Delamination is one of the most common damage modes of laminated composites. It is usually analyzed within the scope of Fracture Mechanics. Recently, there has been growing interest in the characterization of fatigue driven delamination. The main objective of the present work was to study the mode I delamination under fatigue of carbon/epoxy laminates through modified Double Cantilever Beam (DBC) tests under imposed cyclic displacements. The tests were conducted on a low cost machine developed at the Department of Mechanical Engineering of the University of Aveiro. The results proved to be consistent with well-known Paris law, which relates the crack propagation rate with the variation of the strain-energy release rate. Though scarce to draw definitive conclusions, the present results indicate a complex fatigue behavior, which is strongly influenced by fiber bridging.
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Liswell, Brian P. "Exploration of Wood DCB Specimens Using Southern Yellow Pine for Monotonic and Cyclic Loading". Thesis, Virginia Tech, 2004. http://hdl.handle.net/10919/9955.
Testo completoAbstract (sommario):
The primary direction of this thesis was towards exploring qualitative and quantitative characteristics necessary for refining and understanding the flat wood double cantilever beam (DCB) as a valid means for testing Mode I fracture energy in wood adhesive bonds. Southern yellow pine (SYP) adherends were used with epoxy and phenol formaldehyde (PF) impregnated films, providing two systems with different characteristics for investigation.
An adhesive penetration analysis was performed for both the epoxy and PF bonds. The PF penetration into the SYP was shown to be relatively shallow. The epoxy penetration was shown to be deeper. Epoxy-SYP DCBs were quasi-statically tested with varying widths (10 mm, 15 mm, and 20 mm), showing decreases in scatter of critical and arrest strain energy release rates, GIc and GIa, with increases in specimen width. Quasi-static fracture testing was also performed on PF SYP-DCBs, showing much higher critical and arrest fracture energy values than the epoxy-SYP DCBs, indicating that deep adhesive penetration is not necessarily a requisite for higher Mode I fracture energy values.
Grain distribution influences were computationally investigated because of the stiffness difference between latewood and earlywood growth and the grain angle along the length of the beams. The grain angle and the stiffness difference between latewood and earlywood growth caused the effective stiffness, (ExxI)eff, to vary along the length of the beam. The effective stiffness variation caused variations in the beam's ability to receive and store strain energy, complicating and confounding determination of experimental results.
Cyclic loading tests were performed on PF-SYP DCB's. The cycle frequency was 3Hz, with a valley to peak load ratio of R = 0.5. Specimen softening was observed with cycling, with re-stiffening occurring with crack growth. Contrary to expectations, specimen compliance occasionally decreased with small crack extensions. A toughening mechanism was frequently observed, whereby subsequent crack lengths required more cycles to failure than the previous crack length. Monotonically extending the crack length far from the fatigued region created a fresh crack that did not show the toughened behavior. But toughening did resume with subsequent crack lengths.Master of Science
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Budhe, Sandip Rudha. "Effect of pre-bond moisture on the static and fatigue behaviour of bonded joints between CFRP laminates for structural repairs". Doctoral thesis, Universitat de Girona, 2014. http://hdl.handle.net/10803/283567.
Testo completoAbstract (sommario):
In recent years, the use of composite materials in the aeronautic, automotive, marine construction, etc. has increased significantly. Hence, there is an increasing need for repair technologies on primary structural components, as replacing a damaged component by a new one is not cost effective in many cases. The composite structures experience damage in service that comes from accidental impacts, mechanical stresses, environmental factors (moisture and temperature), etc. Thus, maintenance and repair is the concern of the end users as well as of the manufacturers. Suitable material systems and controlled curing conditions are essential to fabricate reliable repairs. In this work, the effect of pre-bond moisture is analyzed for co-bonded adhesive joints subjected to static and fatigue loads. Specimens with three levels of pre-bond moisture (0%, 0.33% and 1.25%) and two different adhesive films (F1, F2) have been used in the analysisDurant els últims anys, la utilització de materials compòsits en la indústria aeronàutica, automoció, construcció marina, etc. ha tingut un gran creixement. Es per aquesta raó, que cada vegada té més importància el desenvolupament de mètodes per a la seva reparació, i especialment la definició mètodes de reparació en components que realitzen una funció estructural, doncs la substitució del component no és econòmicament viable en molts dels casos. És un fet conegut, que les estructures de material compòsit en condicions de servei pateixen danys provocats per impactes accidentals, tensions mecàniques, efectes ambientals (humitat i temperatura), etc. Per tant, el manteniment i la reparació d’aquestes estructures són considerats processos de vital importància per a l’usuari final i també per als fabricants. Una bona tria dels materials, així com un bon control dels processos de curat, tenen un gran efecte en l’obtenció de reparacions fiables. En aquest treball s’ha analitzat l’efecte la l’absorció de la humitat en el substrat abans del procés de curat en unions co-encolades sotmeses a càrregues estàtiques i de fatiga. L’anàlisi s’ha dut a terme amb provetes amb 3 nivells d’absorció d’humitat (0%, 0.33% y 1.25%) i dos tipus d’adhesius laminats (F1 i F2)
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Cámara, Vela Juan Antonio, e Molina Juan Manuel Sánchez. "Design of a Double Cantilever Beam Test Specimen and Fixture for Kink Band Formation in Unidirectional Fibre Reinforced Composites". Thesis, Högskolan i Skövde, Institutionen för ingenjörsvetenskap, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:his:diva-11218.
Testo completoAbstract (sommario):
Composite materials are widely used in demanding applications in aerospace and other industries. In order to understand the complex behaviour of the composite materials and their components, standardised test methods are used. One example is the double cantilever beam (DCB) test in which the test specimen is loaded in an opening, i.e., tensile mode. Failures in composite materials loaded compression are different from those in tension, for example, kink band or buckling-like failures can occur. In this project, several DCBs are designed and a new fixture which allows for compression testing of a DCB is developed for an existing Instron testing machine. The fixture overcomes a known problem of tensile peak causing the failure of the adhesive at the inner surfaces of the DBC by applying additional compressive loads along the outer surfaces of the DBC. The compressive forces can induce the desired kink band formation so that researchers can better study the failure mode. The conceptual development of the new DCBs and the new fixture are presented. Several prototypes of the specimens and the fixture are modelled using the three-dimensional (3D) computer-aided design software Creo Parametric 2.0. One of the fixtures is selected to further study. The different DCB specimens are studied in order to obtain information about the kink band using 3D finite element analysis with the software programme Abaqus CAE. The selected fixture is analysed to determine if there are any areas of concern. Finally, the behaviour of the compression stress along the DCB using two pairs of forces is studied. Unfortunately, it is determined that the tensile peak experienced by the adhesive cannot be eliminated by the application of two pairs of compressive loads, one at the free end and the other in the vicinity of the tensile peak. Several suggestions are made for future work which might serve to reduce the tensile peak; e.g., the movable force couple is applied as a surface load instead of a point load. For this, the fixture will have to be modified with a new geometry, although the DCB could be the same. This will allow further work to focus on the combined behaviour of the tensile peak and the fixture.
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Gozluklu, Burak. "Delamination Analysis By Using Cohesive Interface Elements In Laminated Composites". Master's thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/12611005/index.pdf.
Testo completoAbstract (sommario):
Finite element analysis using Cohesive Zone Method (CZM) is a commonly used method to investigate delamination in laminated composites. In this study, two plane strain, zero-thickness six-node quadratic (6-NQ) and four-node linear (4-NL) interface elements are developed to implement CZM. Two main approaches for CZM formulation are categorized as Unified Mode Approach (UMA) and Separated Mode Approach (SMA), and implemented into 6-NQ interface elements to model a double cantilever beam (DCB) test of a unidirectional laminated composite. The results of the approaches are nearly identical. However, it is theoretically shown that SMA spawns non-symmetric tangent stiffness matrices, which may lower convergence and/or overall performance, for mixed-mode loading cases. Next, a UMA constitutive relationship is rederived. The artificial modifications for improving convergence rates such as lowering penalty stiffness, weakening interfacial strength and using 6-NQ instead of 4-NL interface elements are investigated by using the derived UMA and the DCB test model. The modifications in interfacial strength and penalty stiffness indicate that the convergence may be improved by lowering either parameter. However, over-softening is found to occur if lowering is performed excessively. The morphological differences between the meshes of the models using 6-NQ and 4-NL interface elements are shown. As a consequence, it is highlighted that the impact to convergence performance and overall performance might be in opposite. Additionally, benefits of selecting CZM over other methods are discussed, in particular by theoretical comparisons with the popular Virtual Crack Closure Technique. Finally, the numerical solution scheme and the Arc-Length Method are discussed.
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Ranade, Shantanu Rajendra. "Performance Evaluation and Durability Studies of Adhesive Bonds". Diss., Virginia Tech, 2014. http://hdl.handle.net/10919/64990.
Testo completoAbstract (sommario):
In this dissertation, four test approaches were developed to characterize the adhesion performance and durability of adhesive bonds for specific applications in areas spanning from structural adhesive joints to popular confectionaries such as chewing gum. In the first chapter, a double cantilever beam (DCB) specimen geometry is proposed for combinatorial fracture studies of structural adhesive bonds. This specimen geometry enabled the characterization of fracture energy vs. bondline thickness trends through fewer tests than those required during a conventional "one at a time" characterization approach, potentially offering a significant reduction in characterization times. The second chapter investigates the adhesive fracture resistance and crack path selection in adhesive joints containing patterns of discreet localized weak interfaces created using physical vapor deposition of copper. In a DCB specimen tested under mode-I conditions, fracture energy within the patterned regions scaled according to a simple rule of mixture, while reverse R-curve and R-curve type trends were observed in the regions surrounding weak interface patterns. Under mixed mode conditions such that bonding surface with patterns is subjected to axial tension, fracture energy did not show R-curve type trends while it was observed that a crack could be made to avoid exceptionally weak interfaces when loaded such that bonding surface with defects is subjected to axial compression. In the third chapter, an adaptation of the probe tack test is proposed to characterize the adhesion behavior of gum cuds. This test method allowed the introduction of substrates with well-defined surface energies and topologies to study their effects on gum cud adhesion. This approach and reported insights could potentially be useful in developing chewing gum formulations that facilitate easy removal of improperly discarded gum cuds from adhering surfaces. In the fourth chapter we highlight a procedure to obtain insights into the long-term performance of silicone sealants designed for load-bearing applications such as solar panel support sealants. Using small strain constitutive tests and time-temperature-superposition principle, thermal shift factors were obtained and successfully used to characterize the creep rupture master curves for specific joint configurations, leading to insights into delayed failures corresponding to three years through experiments carried out in one month.Ph. D.
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Guan, Youliang. "Crack path selection and shear toughening effects due to mixed mode loading and varied surface properties in beam-like adhesively bonded joints". Diss., Virginia Tech, 2014. http://hdl.handle.net/10919/24905.
Testo completoAbstract (sommario):
Structural adhesives are widely used with great success, and yet occasional failures can occur, often resulting from improper bonding procedures or joint design, overload or other detrimental service situations, or in response to a variety of environmental challenges. In these situations, cracks can start within the adhesive layer or debonds can initiate near an interface. The paths taken by propagating cracks can affect the resistance to failure and the subsequent service lives of the bonded structures. The behavior of propagating cracks in adhesive joints remains of interest, including when some critical environments, complicated loading modes, or uncertainties in material/interfacial properties are involved. From a mechanics perspective, areas of current interest include understanding the growth of damage and cracks, loading rate dependency of crack propagation, and the effect of mixed mode fracture loading scenarios on crack path selection. This dissertation involves analytical, numerical, and experimental evaluations of crack propagation in several adhesive joint configurations. The main objective is an investigation of crack path selection in adhesively bonded joints, focusing on in-plane fracture behavior (mode I, mode II, and their combination) of bonded joints with uniform bonding, and those with locally weakened interfaces.
When removing cured components from molds, interfacial debonds can sometimes initiate and propagate along both mold surfaces, resulting in the molded product partially bridging between the two molds and potentially being damaged or torn. Debonds from both adherends can sometimes occur in weak adhesive bonds as well, potentially altering the apparent fracture behavior. To avoid or control these multiple interfacial debonding, more understanding of these processes is required. An analytical model of 2D parallel bridging was developed and the interactions of interfacial debonds were investigated using Euler-Bernoulli beam theory. The numerical solutions to the analytical results described the propagation processes with multiple debonds, and demonstrated some common phenomena in several different joints corresponding to double cantilever beam configurations. The analytical approach and results obtained could prove useful in extensions to understanding and controlling debonding in such situations and optimization of loading scenarios.
Numerical capabilities for predicting crack propagation, confirmed by experimental results, were initially evaluated for crack behavior in monolithic materials, which is also of interest in engineering design. Several test cases were devised for modified forms of monolithic compact tension specimens (CT) were developed. An asymmetric variant of the CT configuration, in which the initial crack was shifted to two thirds of the total height, was tested experimentally and numerically simulated in ABAQUS®, with good agreement. Similar studies of elongated CT specimens with different specimen lengths also revealed good agreement, using the same material properties and cohesive zone model (CZM) parameters. The critical specimen length when the crack propagation pattern abruptly switches was experimentally measured and accurately predicted, building confidence in the subsequent studies where the numerical method was applied to bonded joints.
In adhesively bonded joints, crack propagation and joint failure can potentially result from or involve interactions of a growing crack with a partially weakened interface, so numerical simulations were initiated to investigate such scenarios using ABAQUS®. Two different cohesive zone models (CZMs) are applied in these simulations: cohesive elements for strong and weak interfaces, and the extended finite element method (XFEM) for cracks propagating within the adhesive layer. When the main crack approaches a locally weakened interface, interfacial damage can occur, allowing for additional interfacial compliance and inducing shear stresses within the adhesive layer that direct the growing crack toward the weak interface. The maximum traction of the interfacial CZM appears to be the controlling parameter. Fracture energy of the weakened interface is shown to be of secondary importance, though can affect the results when particularly small (e.g. 1% that of the bulk adhesive). The length of the weakened interface also has some influence on the crack path. Under globally mixed mode loadings, the competition between the loading and the weakened interface affects the shear stress distribution and thus changes the crack path. Mixed mode loading in the opposite direction of the weakened interface is able to drive the crack away from the weakened interface, suggesting potential means to avoid failure within these regions or to design joints that fail in a particular manner.
In addition to the analytical and numerical studies of crack path selection in adhesively bonded joints, experimental investigations are also performed. A dual actuator load frame (DALF) is used to test beam-like bonded joints in various mode mixity angles. Constant mode mixity angle tracking, as well as other versatile loading functions, are developed in LabVIEW® for use with a new controller system. The DALF is calibrated to minimize errors when calculating the compliance of beam-like bonded joints. After the corrections, the resulting fracture energies ( ) values are considered to be more accurate in representing the energy released in the crack propagation processes. Double cantilever beam (DCB) bonded joints consisting of 6061-T6 aluminum adherends bonded with commercial epoxy adhesives (J-B Weld, or LORD 320/322) are tested on the DALF. Profiles of the values for different constant mode mixity angles, as well as for continuously increasing mode mixity angle, are plotted to illustrate the behavior of the crack in these bonded joints.
Finally, crack path selection in DCB specimens with one of the bonding surfaces weakened was studied experimentally, and rate-dependency of the crack path selection was found. Several contamination schemes are attempted, involving of graphite flakes, silicone tapes, or silane treatments on the aluminum oxide interfaces. In all these cases, tests involving more rapid crack propagation resulted in interfacial failures at the weakened areas, while slower tests showed cohesive failure throughout. One possible explanation of this phenomenon is presented using the rate-dependency of the yield stress (commonly considered to be corresponding to the maximum traction) of the epoxy adhesives. These experimental observations may have some potential applications tailoring adhesive joint configurations and interface variability to achieve or avoid particular failure modes.Ph. D.
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Xu, Shuangyan. "Evaluating Thermal and Mechanical Properties of Electrically Conductive Adhesives for Electronic Applications". Diss., Virginia Tech, 2002. http://hdl.handle.net/10919/27112.
Testo completoAbstract (sommario):
The objective of this study was to evaluate and gain a better understanding of the short-term impact performance and the long-term durability of electrically conductive adhesives for electronic interconnection applications. Three model conductive adhesives, designated as ECA1, ECA2 and ECA3, supplied by Emerson & Cuming, were investigated, in conjunction with printed circuit board (PCB) substrates with metallizations of Au/Ni/Cu and Cu, manufactured by Triad Circuit Inc.
Effects of environmental aging on the durability of conductive adhesives and their joints were evaluated. All the samples for both mechanical tests and thermal tests were aged at 85%, 100%RH for periods of up to 50 days. Studies of bulk conductive adhesives suggested that both plasticization, which is reversible and further crosslinking and thermal degradation, which are irreversible, might have occurred upon exposure of ECAs to the hot/wet environment. The durability of electrically conductive adhesive joints was then investigated utilizing the double cantilever beam (DCB) test. It was observed that the conductive adhesive joint was significantly weakened following hydrothermal aging, and there was a transition from cohesive failure to interfacial failure as aging continued. A comparative study of the durability of different conductive adhesive and substrate metallization combinations suggested that the resistance of the adhesive joints to moisture attack is related to the adhesive properties, as well as the substrate metallizations. It was noted that the gold/adhesive interface had better resistance to moisture attack than the copper/adhesive interface. A reasonable explanation of this phenomenon was given based upon the concept of surface free energy and interfacial free energy. XPS analysis was performed on the fractured surfaces of DCB samples. For adhesive joints with copper metallization, copper oxide was detected on the failed surfaces upon exposure of the conductive adhesive joints following aging. XPS analysis on the fractured surfaces of adhesive joints with Au metallization suggested that diffusion of Cu to the Au surface might have happened on the Au/Ni/Cu plated PCB substrates during aging.
The impact performance of conductive adhesives was quantitatively determined using a falling wedge test. This unique impact resistance testing method could serve as a useful tool to screen conductive adhesives at the materials level for bonding purpose. Moreover, this test could also provide some useful information for conductive adhesive development. This study revealed that the viscoelastic energy, which is a result of the internal friction created by chain motions within the adhesive material, played an important role in the impact fracture behavior of the conductive adhesives. This study also demonstrated that the loss factor, evaluated at the impact environment conditions, is a good indicator of a conductive adhesive's ability to withstand impact loading.Ph. D.
Libri sul tema "Double Cantilever Beam (DCB) test"
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Pavlovskis, Pēteris. Analysis of Two Actual Problems of Interlaminar Fracture Assessment of Layered Composite. RTU Press, 2022. http://dx.doi.org/10.7250/9789934228148.
Testo completoAbstract (sommario):
Two types of specimens were studied based on applying the nonlinear theory of flexible plates to obtain the interlaminar fracture toughness of layered composites. For a specimen of the thin sub-layer type, a theoretical solution was obtained in relation to the determination of the interlaminar fracture toughness for a mixed II/I mode. The fundamental possibility of using this solution in test practice was confirmed. The application of the nonlinear theory of flexible plates to the well-known standard specimen of the double-cantilever beam (DCB) was studied in more detail. A theoretical solution was obtained, an iterative algorithm for processing test results based on MATLAB code was developed, highly flexible glass fiber reinforced polymer (GFRP) specimens were tested and their comparison with the results of processing according to the ASTM D 5528-01 standard with correction of the linear solution was given.
Capitoli di libri sul tema "Double Cantilever Beam (DCB) test"
1
Carpinteri, A., B. Chiaia e P. Cornetti. "Double-Cantilever Beam Test in Brittle Materials". In Problems of Fracture Mechanics and Fatigue, 183–87. Dordrecht: Springer Netherlands, 2003. http://dx.doi.org/10.1007/978-94-017-2774-7_40.
Testo completo
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Liao, C. H., B. Watson, M. J. Worswick e D. S. Cronin. "Mode I Rigid Double Cantilever Beam Test and Analysis Applied to Structural Adhesives". In Dynamic Behavior of Materials, Volume 1, 73–81. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-62956-8_13.
Testo completo
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Sun, Chen, Minghua Dai, Liang Ying, Kai Du, Zhigang Chen e Ping Hu. "Experimental and Numerical Simulation on Formability and Failure Behavior of Thermoplastic Carbon Fiber/AL Composite Laminates". In Lecture Notes in Mechanical Engineering, 383–93. Cham: Springer International Publishing, 2024. http://dx.doi.org/10.1007/978-3-031-58006-2_30.
Testo completoAbstract (sommario):
AbstractCarbon fiber reinforced thermoplastic/aluminum alloy (CFRTP/AL) composite laminates have the advantages of low density, high specific strength, and good fatigue resistance, which is a new type of engineering composite material to realize lightweight vehicle body. Heterogeneous interface delamination failure occurs in the forming process of the fiber metal laminates (FMLs). It is necessary to establish an effective finite element simulation strategy to accurately predict the delamination failure behavior of FMLs. In this work, thermoplastic PA6 continuous carbon fiber/AL FMLs were taken as the research object, and the double cantilever beam (DCB) and the end-notched flexure (ENF) experiments were carried out to determine the basic mechanical parameters between the interlayer interfaces of CFRTP/AL. Furthermore, a numerical simulation model based on ABAQUS software was developed to describe the progressive damage failure behavior of the CRFTP/AL in the forming process by using the equivalent modeling strategy of discontinuous micro-shear, which realized the effective prediction of ply directional damage failure of FMLs on the basis of the S-beam model. The results show that the established damage constitutive model and numerical method coupled with cohesive zone model (CZM) can effectively predict the ply directional damage failure behavior of CFRTP/AL composites during the large deformation forming.
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Mansour, Rabih, Manigandan Kannan, Gregory N. Morscher, Frank Abdi, Cody Godines e Saber DorMohammadi. "The Wedge-Loaded Double Cantilever Beam Test: A Friction Based Method for Measuring Interlaminar Fracutre Properties in Ceramic Matrix Composites". In Ceramic Transactions Series, 273–82. Hoboken, NJ, USA: John Wiley & Sons, Inc., 2017. http://dx.doi.org/10.1002/9781119407270.ch27.
Testo completo
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Meltem Toygar, Evren, e Ahmet Gulakman. "Failure Modes in Fiber Reinforced Composites and Fracture Toughness Testing of FRP". In Advances in Fatigue and Fracture Testing and Modelling. IntechOpen, 2022. http://dx.doi.org/10.5772/intechopen.99268.
Testo completoAbstract (sommario):
In this paper, interlaminar fracture behavior of woven-fabric-reinforced glass/epoxy composites has been investigated experimentally and numerically. The mechanical properties of this composite were studied and Mode I (Tensile Opening) DCB (Double Cantilever Beam) tests were performed on Fiber Reinforced Composite (FRP) specimens to determine the delaminating resistance of composite laminates used for structural applications. Techniques for measuring the interlaminar fracture toughness, KIC data of woven-fabric-reinforced glass/epoxy composite materials, are highlighted under the consideration of ASTM Standard D5528–01 and test methods ISO 15024, DIN EN ISO 75-1 and DIN EN ISO 75-3. The obtained test results were apparently consistent with the assumptions of the CCM (Compliance Calibration Method) that was used to obtain the interlaminar critical SERR (strain energy release rate), GIC. Finite element analysis was conducted to validate the closed form solution. The use of obtained mechanical properties data in finite element analyses utilizing fracture mechanics are examined. Results show a good agreement between experimental and numerical solutions.
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Gaona-Tiburcio, Citlalli, Alejandro Lira-Martínez, Marianggy Gomez-Avila, Jesús M. Jaquez-Muñoz, Miguel Angel Baltazar-Zamora, Laura Landa-Ruiz, Demetrio Nieves-Mendoza, Francisco Estupiñan-López e Facundo Almeraya-Calderón. "Delamination and Tensile Effect of Fine z-Binder Reinforced on Fiberglass/Polyester Composite for Aerospace Applications". In Next Generation Fiber-Reinforced Composites - New Insights [Working Title]. IntechOpen, 2022. http://dx.doi.org/10.5772/intechopen.106927.
Testo completoAbstract (sommario):
Delamination propagation in laminated composite materials is a common issue that always concerns us when we consider composites for structural purpose. Many possible solutions have been studied; the most famous is the three-dimensional (3D) woven composites materials, which have promising interlaminar fracture resistance but at the cost of increasing density, which for aerospace industry is very important. In this chapter, mode 1 double cantilever beam (DCB) interlaminar fracture toughness tests according to the American Society for Testing and Materials (ASTM) D5528 standard were performed on composite specimens made of E-Glass Saertex 830 g/m2 Biaxial (+/−45°) with Sypol 8086 CCP polyester resin with orthogonal z-axis oriented yarn woven of 0.22 mm diameter nylon monofilament. Four specimens were made with a longitudinal distance between the warp binders of 0.5, 1, 1.5, and 2 cm, respectively. A tensile test according to the ASTM D3039 standard was performed to study how z-binder may affect tensile resistance. The results show a considerable increase in interlaminar fracture toughness, several stress concentrators have been created because of the new yarn and premature failure in the matrix.
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"Fracture properties of concrete as determined by means of wedge splitting tests and tapered double cantilever beam tests". In Fracture Mechanics Test Methods For Concrete, 99–140. CRC Press, 2004. http://dx.doi.org/10.1201/9781482267532-9.
Testo completoAtti di convegni sul tema "Double Cantilever Beam (DCB) test"
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XU, WU, e JIANCAN DING. "CLOSED-FORM J-INTEGRAL AND ITS APPLICATIONS FOR MEASUREMENT OF MODE I INTERLAMINAR FRACTURE TOUGHNESS OF COMPOSITES". In Thirty-sixth Technical Conference. Destech Publications, Inc., 2021. http://dx.doi.org/10.12783/asc36/35925.
Testo completoAbstract (sommario):
Due to the interlaminar properties of composites are low, delamination is one of the major failure modes. It threatens the safety of composite structure subjected to out-of-plane static and especially impact loadings. High interlaminar fracture toughness is demanded in the society where composite structures are widely used. However, for tough material, large deformation may occur in the determination of the interlaminar fracture toughness when using the double cantilever beam (DCB) test. Therefore, accurate determination of the fracture toughness of tough material and dynamic loading is very challenging under large deformation. J-integral is an important parameter in fracture mechanics. It’s equivalent to energy release rate under monotonic loading and widely used in the determination of interlaminar fracture toughness of composites. In this paper, it is used to determine the fracture toughness for composite DCB under large deformation and wedge-insert double cantilever beam (WDCB) test, which is widely used to determine the dynamic interlaminar fracture toughness. Exact and closed form nonlinear J-integrals are derived for the largely deformed DCB and WDCB. Compared with the alternative data reduction methods for determining interlaminar fracture toughness, the J- integral method is more accurate. In addition, the J-integral method is simple and promising, since it is unnecessary to measure the crack length in the tests.
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WEEKS, SHAWN, e MICHAEL CZABAJ. "STATIC AND FATIGUE CHARACTERIZATION OF MODE I FRACTURE IN ADHESIVELY BONDED COMPOSITES BASED ON THE J-INTEGRAL APPROACH". In Proceedings for the American Society for Composites-Thirty Eighth Technical Conference. Destech Publications, Inc., 2023. http://dx.doi.org/10.12783/asc38/36708.
Testo completoAbstract (sommario):
In this work, efforts are made to further develop tests for characterization of mode I quasi-static and fatigue fracture of adhesively bonded composites based on the J-integral approach using the double cantilever beam (DCB) test. This work will address the few remaining challenges that must be resolved before standardization of these test methods. Specifically presented are the attempts to: 1) establish a robust procedure for measuring JI using specimen arm rotation and the applied load, 2) determine specimen geometry that would enable accurate characterization of the traction separation law (TSL) during DCB testing, and 3) develop a protocol for J-controlled fatigue testing without explicit knowledge of crack extension.
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Kapania, Rakesh K., Dhaval P. Makhecha, Eric R. Johnson, Josh Simon e David A. Dillard. "Modeling Stable and Unstable Crack Growth Observed in Quasi-Static Adhesively Bonded Beam Tests". In ASME 2004 International Mechanical Engineering Congress and Exposition. ASMEDC, 2004. http://dx.doi.org/10.1115/imece2004-59765.
Testo completoAbstract (sommario):
An experimental and computational study of an adhesively bonded, double cantilevered beam (DCB) under quasi-static loading is presented. The polymeric adhesives are either an acrylic or an epoxy, and the adherends are 6061 aluminum alloy. DCB tests bonded with the acrylic exhibited stable crack growth, while the DCB tests bonded with the epoxy exhibited unstable crack growth. The responses of the DCB test speciments were modeled in the ABAQUS/Standard® software package. Interface finite elements were located between bulk elements to model crack initiation and crack growth in the adhesive. These interface elements are implemented as user-defined elements in ABAQUS®, and the material law relating the interfacial tractions to the separation displacements is based on a cohesive zone model (CZM). Using interface elements only to model the acrylic adhesive, the simulation correlates very well to the test. Good correlation between the simulation and the test for the epoxy adhesive is achieved if both bulk modeling of the adhesive and inertia of the specimen are included.
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Pal, Joydeep, Chandan Mukhopadhyay e Ajit K. Roy. "Cracking of Alloy C-276 in an Acidic Environment". In ASME 2007 Pressure Vessels and Piping Conference. ASMEDC, 2007. http://dx.doi.org/10.1115/pvp2007-26429.
Testo completoAbstract (sommario):
Austenitic Alloy C-276 has been identified as a structural material for application in hydrogen generation using nuclear heat. Fracture-mechanics-based pre-cracked and wedge-loaded double-cantilever-beam (DCB) specimens have been tested in an acidic solution at ambient temperature for 15 and 30 days. Three levels of initial stress intensity factors (K1) were used to determine crack propagation following exposure of the DCB specimens to the test environment. The results indicate that the magnitude of K1 was substantially reduced after testing, the extent of reduction being more pronounced with specimens tested for a longer duration. Three different types of failures namely, striations, cleavage and ductile, respectively were noted in the tested specimens, as determined by scanning electron microscopy.
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Mou, Shancong, Jialei Chen, Chuck Zhang e Ben Wang. "A Data Fusion Framework for Fracture Toughness Modeling Using Multiple Sources of Data". In 2020 International Symposium on Flexible Automation. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/isfa2020-9649.
Testo completoAbstract (sommario):
Abstract The adhesive bonding technology of composite material is widely used in the industry, and the double-cantilever beam (DCB) test is a standard test for measuring the bonding quality. However, adhesive bonding methods may compromise the bonding strength, leading to weak bonds or so-called kissing bonds. In this research, we present a data-driven method to model the relationship between the process parameters and the mode-I fracture toughness. Due to the limited size of the DCB training data, we propose a novel data fusion framework, also incorporating the historical single-lap joint (SLJ) dataset at hand. Though the SLJ test is a less effective method for measuring the fracture toughness, we show it can be used to improve the model performance. We then demonstrate the effectiveness of our data-driven framework in an airplane maintenance application, with two times better predictive performance obtained.
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Makhecha, Dhaval P., Rakesh K. Kapania, Eric R. Johnson, David A. Dillard, George C. Jacob e J. Michael Starbuck. "Rate-Dependent Cohesive Zone Modeling of Unstable Crack Growth in an Epoxy Adhesive". In ASME 2005 International Mechanical Engineering Congress and Exposition. ASMEDC, 2005. http://dx.doi.org/10.1115/imece2005-81317.
Testo completoAbstract (sommario):
This paper presents the development and numerical implementation of a rate dependent fracture model of an epoxy adhesive. Previous mode I fracture tests conducted under quasistatic, displacement controlled loading of an aluminum double cantilever beam (DCB) bonded with the epoxy exhibited unstable crack growth in the adhesive. Results from mode I fracture tests of compact tension specimens made from bulk adhesive at increasing cross head opening speeds are reported in this paper. The compact tension tests results showed a decreasing critical strain energy release rate with increasing cross head speed, with the critical energy release rate at 1 m/s cross head speed equal to about 20% of its quasi-static value. Two rate dependent cohesive zone models are formulated based on the compact tension test data. A cohesive de-cohesive relationship was postulated between the tractions acting across the crack faces and the opening displacement and opening velocity. These rate dependent cohesive zone models are implemented in a interface finite element to model discrete crack growth in the adhesive. The reaction force history from simulation of the DCB test is in good agreement with the test data using only the rate dependent interface element to model the adhesive.
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Jadhav, Vishwas S., e Ajit D. Kelkar. "Fabrication, Processing and Characterization of Carbon Fibre Reinforced Laminated Composite Embedded With Graphene Lattice Sheets". In ASME 2021 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2021. http://dx.doi.org/10.1115/imece2021-71191.
Testo completoAbstract (sommario):
Abstract This manuscript introduces the challenges in the fabrication of graphene sheet reinforced non-crimp fabric (NCF) composite laminates and their influence on the interlaminar strength of the composite laminates. In the current work, the laminates were fabricated using non-crimp carbon fabric prepreg along with 50,120 and 240 μm thick graphene sheets at the mid-plane. Double Cantilever Beam (DCB) tests are done as per ASTM 5528 using INSTRON electromechanical testing system. Modified Beam Theory method used to compute Mode I fracture toughness, using load, displacement, specimen dimension, and crack opening displacement. The graphene sheets are brittle; little bonding between the graphene and matrix observed during the fabrication process results in a fragile interface. To overcome this problem, graphene sheets were converted into a lattice structure. The lattice structure used in the present research had horizontal, vertical, and square grids. Effects of sheet thickness, grid pattern were evaluated by Mode I fracture toughness, with and without nanoengineered enhanced laminates. Axio Image upright microscope used to compare the bonding at the midplane after the DCB test. The results indicate that the composite laminates fabricated using lattice graphene structure had better interlaminar strength than the laminates fabricated with straight graphene sheets.
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Vishe, Nilesh J., Sankha S. Aditya, Sameer B. Mulani e Samit Roy. "Fatigue Delamination Damage Sensing and Self-Healing in Thermoset Composites Using Thermoplastic Healants". In ASME 2024 Aerospace Structures, Structural Dynamics, and Materials Conference. American Society of Mechanical Engineers, 2024. http://dx.doi.org/10.1115/ssdm2024-121605.
Testo completoAbstract (sommario):
Abstract In this study, fatigue testing under mode-I loading and damage (delamination) detection tests were carried out on double cantilever beam (DCB) specimens, and subsequent healing of the delamination was investigated. Due to the susceptibility of laminated composites to delamination, fatigue delamination is one of the critical damage modes in laminated composites and can lead to catastrophic failure if it is allowed to proceed unchecked. Hence, it is necessary to investigate and quantify the delamination crack growth behavior due to fatigue loading and to accurately predict the size of the delamination crack and then to heal it in situ in a repeatable manner. A DCB specimen with an array of 8 MFCs was used to detect damage with the actuation signal as anti-symmetric Lamb wave excitation. The signal difference coefficient (SDC) was used as a delamination detection metric and calculated for different actuator and sensor location combinations.
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Skec, Leo, e Giulio Alfano. "Characterisation of rate-dependent fracture in adhesive joints". In UK Association for Computational Mechanics Conference 2024. Durham University, 2024. http://dx.doi.org/10.62512/conf.ukacm2024.044.
Testo completoAbstract (sommario):
For adhesive joints, several authors questioned the applicability of LEFM when the combination between the ductility of the adhesive, the stiffness of the adherents and the fracture mode leads to a relatively large process zone during crack propagation. For such cases, nonlinear fracture mechanics (NLFM) and the use of the critical value, 𝐽𝑐, of the J integral have been recommended. This was until it was recently showed, at least for the case of mode-I crack propagation along a thin interface, that the difference between 𝐺𝑐 and 𝐽𝑐is found to be equal to the partial derivative with respect to the increase in crack length, 𝑎, of the energy dissipated in front of the crack tip. The fact that this difference is extremely small for double-cantilever-beam (DCB) specimens, together with a rigorous assessment of the accuracy entailed by the use of the equivalent-crack-length concept, were used to develop an accurate and practically effective experimental/numerical procedure to assess the rate dependence of fracture resistance in adhesive joints made of aluminium arms bonded with an epoxy adhesive. The effectiveness is the result of using simple DCB tests without the need to measure the crack length. Numerical simulations were conducted using a bespoke finite-element code tailored for DCB tests based on Timoshenko beam theory and a cohesive-zone model based on fractional viscoelasticity.
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Yekani Fard, Masoud, John M. Woodward, Siddhant Datta, Brian Raji e Aditi Chattopadhyay. "Characterization of Interlaminar Fracture Properties of Advanced Polymer Matrix Composites Interleaved With Buckypaper". In ASME 2016 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/imece2016-66943.
Testo completoAbstract (sommario):
Recently a novel high-speed/high-yield surfactant-free manufacturing method has been developed for manufacturing of large size buckypaper. In spite of this development, there is no data on the effects of microstructural characteristics on the structural properties of surfactant-free buckypaper based nanocomposites. This investigation examines the effects of the proposed manufacturing procedure on the resultant interlaminar fracture properties of buckypaper based nanocomposites. Buckypaper samples were fabricated using the novel surfactant-free technique. Buckypaper based nanocomposite samples were subjected to mode I, II, and I-II fracture testing in Double Cantilever Beam (DCB ), End Notched Flexure (ENF) and 4-point End Notched Flexure (4ENF), and Mixed Mode Bending (MMB) configurations, respectively. Analysis of the test specimens in terms of mode I energy release rates showed good agreement among Modified Beam Theory, Compliance Calibration, and Modified Compliance Calibration methods. ENF and 4ENF tests gave very consistent crack initiation and propagation results for mode II fracture. The fracture envelope function of the composite and the nanocomposites was developed as a design guideline for nanocomposite materials.
Rapporti di organizzazioni sul tema "Double Cantilever Beam (DCB) test"
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Stavig, Mark E., Rex Jaramillo, Elizabeth Larkin, Jason Wade Dugger e Reedy, Earl David ,. Asymmetric Double Cantilever Beam Test to Measure the Toughness of an Alumina/Epoxy Interface. Office of Scientific and Technical Information (OSTI), dicembre 2019. http://dx.doi.org/10.2172/1595916.
Testo completo