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Articoli di riviste sul tema "Composite materials Delamination":
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Ellison, Andrew, e Hyonny Kim. "Shadowed delamination area estimation in ultrasonic C-scans of impacted composites validated by X-ray CT". Journal of Composite Materials 54, n. 4 (27 luglio 2019): 549–61. http://dx.doi.org/10.1177/0021998319865311.
Although ultrasonic pulse-echo C-scanning is a mature non-destructive evaluation technique for imaging internal damage in composite structures, a major impediment of obtaining a full characterization of the internal damage state is delamination shadowing effects. Specifically, shadowing refers to regions of interest that are behind other delamination planes or discontinuities with respect to the scanning surface. The delamination planes block ultrasonic wave transmission and the regions of interest are thus hidden (i.e. shadowed) from the scan. A methodology has been developed to expand ultrasonic scan data of impacted composites by utilizing damage morphology information that is well established in the composite impact research community, such as matrix cracks bounding delaminations, to estimate shadowed delamination information and matrix cracking. First, impacted flat composite plates were C-scanned by pulse-echo ultrasonic and the results were segmented by depth of damage to establish interface-by-interface delamination information. These delaminations were then fit by bounding lines representing the fiber/matrix crack directions defined by the orientations of plies adjacent to each interface to estimate the shadowed portion of the delamination results. The area inside this boundary was added to the original ultrasonic delamination area to create an estimation of the full delamination state at each shadowed interface. Additionally, because this extension method is based on the interactions between delaminations and matrix cracking, this extension method provides an approximation of the matrix cracking of adjacent plies. Results were compared with X-ray computed tomography scans to assess the effectiveness of the extension method.
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Toscano, Cinzia, Aniello Riccio, FrancescoPaolo Camerlingo e Carosena Meola. "On the use of lock-in thermography to monitor delamination growth in composite panels under compression". Science and Engineering of Composite Materials 21, n. 4 (1 settembre 2014): 485–92. http://dx.doi.org/10.1515/secm-2013-0156.
AbstractThe success of composites in automotive, aerospace, and naval applications is mainly related to their aptitude to be tailored to obtain a final product that perfectly fulfills the design requirements. However, during both manufacturing processes and maintenance, some flaws, like delaminations (which may escape simple visual inspection), may be induced in composite structures. The presence of delaminations is of major concern for the load-carrying capability of carbon fiber-reinforced polymer panels. Indeed, delaminations can strongly affect the structural strength and may grow under in-service loads, leading sometimes to catastrophic failures. The aim of this work is to explore the use of lock-in thermography for the monitoring of delamination propagation in composite structures when subjected to generic multiaxial loading conditions. A stiffened composite panel with an embedded skin delamination subjected to compressive loading was taken as a benchmark to assess experimentally the effectiveness of lock-in thermography for monitoring the delamination propagation in situ during the compressive mechanical test. The delamination size as a function of the applied load, observed by lock-in thermography during the execution of the compressive test, was used to validate the results of preliminary numerical computations.
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Mahieddine, Ali, e Mohammed Ouali. "Analysis of Delaminated Composite Plates". Advanced Materials Research 686 (aprile 2013): 104–8. http://dx.doi.org/10.4028/www.scientific.net/amr.686.104.
A mathematical model for plates with partially delaminated layers is presented to investigate their behavior. In this formulation account is taken of lateral strains. The principal advantage of the element is that it allows the modeling of delamination anywhere in the structure. The region without delamination is modeled to carry constant peel and shear stresses; while the region with delamination is modeled by assuming that there is no peel and shear stress transfer between the top and bottom layers. Numerical results of the present model are presented and its performance is evaluated for static problems. Laminated beams and plates are often used as primary load-carrying structures. However, the mechanical properties of composite materials may degrade severely in the presence of damage. One of the common types of damage modes in laminated composites is delamination. The presence of delamination is one of the most prevalent life-limiting failure modes in laminated composite structures. Many researchers had been studying the effect of delamination. Wee and Boay [1] developed an analytical model to predict the critical load of a delaminated composite laminated beam. Lee et al. [2] investigated the buckling behavior of the beam plate with multiple delaminations under compression. Kapania and Wolfe [3] examined the buckling behavior of a beam plate with two delaminations of equal length. Wang et al. [4] improved the analytical solution by including the coupling between the flexural and axial vibrations of the delaminated sub-laminates. Lee et al. [5] studied a composite beam with arbitrary lateral and longitudinal multiple delamination. Finite-element methods have been developed using the layerwise theory by Kim et al. [6]. Tan and Tong [7] developed a dynamic analytical model for the identification of delamination embedded in a laminated composite beam. To investigate the effects of delamination of a plate layers, a finite-element model is developed. Both displacement continuity and force equilibrium conditions are imposed between the regions with and without delamination. The accuracy of the approach is verified by comparing results with previously published data.
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Hajikhani, Milad, Amir Refahi Oskouei, Mehdi Ahmadi Najaf Abadi, Amir Sharifi e Mohammad Heidari. "Progressive Fracture Evaluation in Composite Materials by Acoustic Emission Technique". Key Engineering Materials 465 (gennaio 2011): 535–38. http://dx.doi.org/10.4028/www.scientific.net/kem.465.535.
Glass/polyester and glass/epoxy laminated composites widely used in structures and have very near properties. These composite laminates have poor inter-laminar fracture resistance and suffer extensive damage by delamination cracking when subjected to out of plane loading and hence are vulnerable to delamination. The presence of delamination in the composite material may reduce the overall stiffness. Structural design and nondestructive test techniques have evolved as increased emphasis has been placed on the durability and damage tolerance of these materials. There are several methods used to investigate damages of composite materials. Acoustic emission is one of these. In this work the effect of delamination propagation on acoustic emission (AE) events in glass/polyester and glass/epoxy composites is obtained also Fracture surface examinations were conducted using a scanning electron microscope (SEM) and results in these two common composites compared. Consequently, revealed that the AE technique is a practicable and effective tool for identifying and separating kinds of cracks in these composites.
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Chang, Fu-Kuo, e Zafer Kutlu. "Delamination Effects on Composite Shells". Journal of Engineering Materials and Technology 112, n. 3 (1 luglio 1990): 336–40. http://dx.doi.org/10.1115/1.2903334.
An analytical investigation was performed to study the effect of delamination on the response of cylindrical composite shells subjected to external loadings. It was of particular interest to determine the buckling load and the post-buckling behavior of externally pressurized cylindrical composite shells containing delaminations. An analytical model was developed that consists of a structural analysis for calculating the global deformations of the structures and a fracture analysis for determining the delamination growth in the structures. A nonlinear finite element code based on the updated Lagrangian formulation was developed for the model. Based on the results of calculations, it was found that delamination can significantly affect the buckling load and response of cylindrical composite shells subjected to externally pressurized loadings, depending upon the initial length and location of the delamination, ply orientation and laminate curvature. The calculated strain energy release rate at the crack tips indicates that delamination growth occurs in the wake of buckling due to Mode II shear fracture.
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Brunner, Andreas J., René Alderliesten e John-Alan Pascoe. "In-Service Delaminations in FRP Structures under Operational Loading Conditions: Are Current Fracture Testing and Analysis on Coupons Sufficient for Capturing the Essential Effects for Reliable Predictions?" Materials 16, n. 1 (27 dicembre 2022): 248. http://dx.doi.org/10.3390/ma16010248.
Quasi-static or cyclic loading of an artificial starter crack in unidirectionally fibre-reinforced composite test coupons yields fracture mechanics data—the toughness or strain-energy release rate (labelled G)—for characterising delamination initiation and propagation. Thus far, the reproducibility of these tests is typically between 10 and 20%. However, differences in the size and possibly the shape, but also in the fibre lay-up, between test coupons and components or structures raise additional questions: Is G from a coupon test a suitable parameter for describing the behaviour of delaminations in composite structures? Can planar, two-dimensional, delamination propagation in composite plates or shells be properly predicted from essentially one-dimensional propagation in coupons? How does fibre bridging in unidirectionally reinforced test coupons relate to delamination propagation in multidirectional lay-ups of components and structures? How can multiple, localised delaminations—often created by impact in composite structures—and their interaction under service loads with constant or variable amplitudes be accounted for? Does planar delamination propagation depend on laminate thickness, thickness variation or the overall shape of the structure? How does exposure to different, variable service environments affect delamination initiation and propagation? Is the microscopic and mesoscopic morphology of FRP composite structures sufficiently understood for accurate predictive modelling and simulation of delamination behaviour? This contribution will examine selected issues and discuss the consequences for test development and analysis. The discussion indicates that current coupon testing and analysis are unlikely to provide the data for reliable long-term predictions of delamination behaviour in FRP composite structures. The attempts to make the building block design methodology for composite structures more efficient via combinations of experiments and related modelling look promising, but models require input data with low scatter and, even more importantly, insight into the physics of the microscopic damage processes yielding delamination initiation and propagation.
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Subba Rao, V. V., Godavarthi Yeswanth Kiran Kumar e Sansanka Pentapalli. "Reduction of AWJ Induced Delaminations by Impregnated Nanoclay GFRP Composites". Materials Science Forum 969 (agosto 2019): 284–90. http://dx.doi.org/10.4028/www.scientific.net/msf.969.284.
Composite materials are extensively used in various applications like space, aircraft, and automobile sector because of superior physical and mechanical properties even though they are costly. In recent technological innovations, using Montmorillonite (Nanoclay) to reinforce polymer-based composites has raised attention to academic and industrial sectors since small addition could enhance Mechanical properties thereby decreasing failures like delaminations. In present research work, the effect of AWJ machining parameters on delaminations of glass fibre reinforced epoxy composite is investigated. The Main objective is determining delamination factor and reduce delaminations which is major failure in laminates. This paper investigates on effects of impregnated Nanoclay epoxy in Bi-directional GFRP where previous research has been made only in changing the parameters for reduction of delaminations. The samples were machined using AWJ, delamination factors are measured using image-J software and SEM analysis for comparing micrographs. Finally with increase in nano clay weight fraction, delaminations are checked.
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Wei, Z., L. H. Yam e L. Cheng. "Delamination Assessment of Multilayer Composite Plates Using Model-based Neural Networks". Journal of Vibration and Control 11, n. 5 (maggio 2005): 607–25. http://dx.doi.org/10.1177/1077546305052317.
A procedure for damage detection in multilayer composites is described using model-based neural networks and vibration response measurement. The appropriate finite element model is established to generate the training data of neural networks. Internal delaminations with different sizes and locations are considered as the particular damage scenarios in multilayer composite plates. The damage-induced energy variation of response signal is investigated, and the mechanism of mode-dependent energy dissipation of composite plates due to delamination is revealed. In order to obtain the structural dynamic response of the samples, impulse forced vibration testing is conducted using a piezoelectric patch actuator and an accelerometer. To enhance the sensitivity of damage features in the vibrating plate, the damage-induced energy variation of the response signal decomposed by wavelet packets is used as the input data of backward propagation neural networks for the prediction of delamination size and location. The test results show that the proposed method is effective for the assessment of delamination status in composites.
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Marshall, I. H. "Delamination Buckling of Composite Materials". Composite Structures 13, n. 3 (gennaio 1989): 235–36. http://dx.doi.org/10.1016/0263-8223(89)90007-x.
Sreekanth, T. G., M. Senthilkumar e S. Manikanta Reddy. "Natural Frequency based delamination estimation in GFRP beams using RSM and ANN". Frattura ed Integrità Strutturale 16, n. 61 (19 giugno 2022): 487–95. http://dx.doi.org/10.3221/igf-esis.61.32.
The importance of delamination detection can be understood from aircraft components like Vertical Stabilizer, which is subjected to heavy vibration during the flight movement and it may lead to delamination and finally even flight crash can happen because of that. Any solid structure's vibration behaviour discloses specific dynamic characteristics and property parameters of that structure. This research investigates the detection of delamination in composites using a method based on vibration signals. The composite material's flexural stiffness and strength are reduced as a result of delaminations, and vibration properties such as natural frequency responses are altered. In inverse problems involving vibration response, the response signals such as natural frequencies are utilized to find the location and magnitude of delaminations. For different delaminated beams with varying position and size, inverse approaches such as Response Surface Methodology (RSM) and Artificial Neural Network (ANN) are utilized to address the inverse problem, which aids in the prediction of delamination size and location.
Whitcomb, J. D. "Instability-related delamination growth of embedded and edge delaminations". Diss., Virginia Polytechnic Institute and State University, 1988. http://hdl.handle.net/10919/77755.
Compressive loads can cause local buckling in composite laminates that have a near-surface delamination. This buckling causes load redistribution and secondary loads, which in turn cause interlaminer stresses and delamination growth. The goal of this research effort was to enhance the understanding of this instability-related delamination growth in laminates containing either an embedded or an edge delamination.
There were three primary tasks: 1) development of a geometrically nonlinear finite element analysis named NONLIN3D; 2) performance of a parametric analytical study to determine the effects of strain, delamination shape, and delamination size on the distribution of the strain energy release rate components along the delamination front; and 3) performance of a combined experimental and analytical study of instability-related delamination growth (IRDG). Two material systems (AS4/PEEK and IM7/8551-7) and two stacking sequences (0/90/90/0)₆ and (90/0/0/90)₆ were examined. The laminates were fabricated with Kapton inserts between the fourth and fifth plies from the top surface to give an initial delamination.
The analysis predicted a large variation of GI and GII along the delamination front. The GIII component was always small. The location of maximum GI and GII depended on the delamination shape and applied strain. In general, the strain-energy release rates were small except in a small region. Hence, delamination growth was expected to occur over only a small portion of the delamination front. Experiments corroborated this prediction. The laminate stacking sequence had a large effect on the shape of the deformed region, the direction of delamination growth, and the strain at which delamination growth occurred. These effects were predicted by the analysis. The GI component appeared to govern initial delamination growth in the IM7/8551-7 laminates. Matrix ply cracking generally accompanied delamination growth. In some cases fiber micro-buckling also occurred shortly after delamination growth occurred. Ph. D.
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Van, Hoof J. "Modelling of impact induced delamination in composite materials". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape4/PQDD_0028/NQ52335.pdf.
Van, Hoof Jack (Jacobus Franciscus Adrianus Maria) Carleton University Dissertation Engineering Mechanical and Aerospace. "Modelling of impact induced delamination in composite materials". Ottawa, 1999.
Malik, Basharat U. "Fatigue delamination growth under cyclic compression in unidirectional composites". Diss., Georgia Institute of Technology, 1995. http://hdl.handle.net/1853/12094.
Awal, Mohammad A. 1959. "Transient response of delamination, intersecting and transverse cracks in layered composite plates". Thesis, The University of Arizona, 1989. http://hdl.handle.net/10150/276955.
A numerical method is developed to determine the dynamic behavior of delamination and transverse cracks in multilayered plates. The plate is subjected to a time dependent antiplane shear stress field which is acting on the plate surfaces. The interaction of waves diffracted at the crack tip with those reflected at the plate boundaries and transmitted at the material interface makes the problem very complicated, so analytical study of this problem cannot be carried out with our present state of knowledge; hence the problem is solved numerically. The finite element equations are obtained by variational calculus applied in the frequency domain. Thus time intregration schemes are avoided, but time dependent response can still be obtained after inverting the frequency dependent response spectra numerically by Fast Fourier Transform (FFT) routine. Another advantage of the frequency domain analysis is that the resonance frequency can be easily detected from the sharp peaks of the response spectra. The numerical difficulty associated with the singular behavior of the stress field near the crack tip has been avoided by using quarter point elements. The numerical results obtained from this investigation are compared with analytical results to verify the accuracy of the method.
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Gambone, Livio R. "The effect of R-ratio on the mode II fatigue delamination growth of unidirectional carbon/epoxy composites". Thesis, University of British Columbia, 1991. http://hdl.handle.net/2429/29968.
An investigation of the effect of R-ratio on the mode II fatigue delamination of AS4/3501-6 carbon/epoxy composites has been undertaken. Experiments have been performed on end notched cantilever beam specimens over a wide range of R-ratios (-l ≤R ≤0.50). The measured delamination growth rate data have been correlated with the mode II values of strain energy release rate range ∆G[formula omitted]), maximum strain energy release rate (G[formula omitted]) and stress intensity factor range (∆K[formula omitted]). The growth rate is dependent on the R-ratio over the range tested. For a constant level of ∆G[formula omitted], the crack growth rate decreases with increasing R-ratio. A similar trend is observed when the data is plotted as a function of G[formula omitted]. The effect of plotting the growth rate as a function of ∆K[formula omitted] is to produce an R-ratio dependence opposite to that obtained by either the ∆G[formula omitted] or G[formula omitted] approach. For a constant level of ∆K[formula omitted], the crack growth rate increases with increasing R-ratio.
Master equations which completely characterize the fatigue behaviour as a function of ∆G[formula omitted] and ∆K[formula omitted] have been derived, based on the observation that the growth rate law exponent, n and constant, A are unique functions of R-ratio. Values for n are surprisingly large and increase with increasing R-ratio whereas values for A decrease with increasing R-ratio.
The effect of time-at-load has been considered in an attempt to explain the existence of the R-ratio dependence of the growth rate. The correct trend can be established for the exponent, n but not for the constant, A. Friction between the crack faces, particularly at higher R-ratios, is proposed as a possible explanation for the observed anomaly. Further evidence of a frictional mechanism operating at higher R-ratios has been discovered through a postmortem fracture surface examination.
Additional fractographic observations are presented over the entire range of R-ratios tested. In regions subjected to negative R-ratio cycling, there is no evidence of the characteristic mode II hackle features. Instead, loose rounded particles of matrix material are found. An extensive amount of hackling is observed in regions subjected to low positive R-ratio cycles. The extent of hackle damage visibly decreases in areas where higher levels of R-ratio are imposed. A correlation between the general fracture surface morphology and the fatigue data provides support for the hypothesis that energy for delamination is always available in sufficient quantity, and that growth is dependent on the stresses ahead of the crack tip being sufficiently high. Applied Science, Faculty of Materials Engineering, Department of Graduate
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Tenek, Lazarus H. "Delamination dynamics and vibrothermographic-thermoelastic evaluation of advanced composite materials". Thesis, This resource online, 1991. http://scholar.lib.vt.edu/theses/available/etd-10312009-020116/.
Lee, Jaehong. "Vibration, buckling and postbuckling of laminated composites with delaminations". Diss., This resource online, 1992. http://scholar.lib.vt.edu/theses/available/etd-06062008-170322/.
Chang, Cherng-Chi. "Finite element analysis of laminated composite free-edge delamination specimens /". The Ohio State University, 1987. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487584612162791.
Whitcomb, John David. Instability-related delamination growth of embedded and edge delaminations. Blacksburg, Va: Virginia Polytechnic Institute and State University, 1988.
United States. National Aeronautics and Space Administration. Scientific and Technical Information Division., a cura di. Delamination stresses in semicircular laminated composite bars. [Washington, DC]: National Aeronautics and Space Administration, Scientific and Technical Information Division, 1988.
United States. National Aeronautics and Space Administration. Scientific and Technical Information Division., a cura di. Delamination stresses in semicircular laminated composite bars. [Washington, DC]: National Aeronautics and Space Administration, Scientific and Technical Information Division, 1988.
Capitoli di libri sul tema "Composite materials Delamination":
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Davies, Peter, e Leif A. Carlsson. "Delamination of Composite Cylinders". In Major Accomplishments in Composite Materials and Sandwich Structures, 67–82. Dordrecht: Springer Netherlands, 2009. http://dx.doi.org/10.1007/978-90-481-3141-9_4.
Köllner, Anton, Fabian Forsbach e Christina Völlmecke. "Delamination Buckling in Composite Plates: an Analytical Approach to Predict Delamination Growth". In Advanced Structured Materials, 241–55. Cham: Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-030-13307-8_18.
Soutis, C., e S. H. Díaz Valdés. "Delamination Detection in Laminated Composites Using Lamb Waves". In Recent Advances in Composite Materials, 109–26. Dordrecht: Springer Netherlands, 2003. http://dx.doi.org/10.1007/978-94-017-2852-2_10.
Hirwani, Chetan K., Rishabh Pal, Mrinal Chaudhury, Subrata Kumar Panda e Nitin Sharma. "Dynamic Behavior of Laminated Composites with Internal Delamination". In Advanced Composite Materials and Structures, 277–94. Boca Raton: CRC Press, 2022. http://dx.doi.org/10.1201/9781003158813-16.
Banks-Sills, Leslie. "Testing–Delamination Between Two Dissimilar Plies". In Interface Fracture and Delaminations in Composite Materials, 77–89. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-60327-8_7.
Ladeveze, P., O. Allix e L. Daudeville. "Mesomodeling of Damage for Laminate Composites: Application to Delamination". In Inelastic Deformation of Composite Materials, 607–22. New York, NY: Springer New York, 1991. http://dx.doi.org/10.1007/978-1-4613-9109-8_29.
Steinmetz, G., F. J. Arendts e R. Nething. "Delamination Buckling of Laminated Plates". In Developments in the Science and Technology of Composite Materials, 495–502. Dordrecht: Springer Netherlands, 1990. http://dx.doi.org/10.1007/978-94-009-0787-4_68.
Mróz, Z., e S. Stupkiewicz. "Hysteretic Effects and Progressive Delamination at Composite Interfaces". In IUTAM Symposium on Microstructure-Property Interactions in Composite Materials, 247–64. Dordrecht: Springer Netherlands, 1995. http://dx.doi.org/10.1007/978-94-011-0059-5_21.
He, J., F. L. Cong, L. Lin e B. T. Wang. "Delamination failure analysis of aircraft composite material opening siding". In Advances in Materials Science and Engineering, 623–28. London: CRC Press, 2021. http://dx.doi.org/10.1201/9781003225850-93.
Pliusys, E., e P. T. Mativenga. "Reducing Delamination in Micro Drilling of Carbon Composite Materials". In Proceedings of the 38th International MATADOR Conference, 337–56. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-319-64943-6_24.
Atti di convegni sul tema "Composite materials Delamination":
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Johnson, Mark, e Srinivasan Sridharan. "Delamination in compressively loaded composite laminates". In 39th AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference and Exhibit. Reston, Virigina: American Institute of Aeronautics and Astronautics, 1998. http://dx.doi.org/10.2514/6.1998-2026.
Gu, Haozhong, e Aditi Chattopadhyay. "Delamination buckling and postbuckling of composite cylindrical shells". In 36th Structures, Structural Dynamics and Materials Conference. Reston, Virigina: American Institute of Aeronautics and Astronautics, 1995. http://dx.doi.org/10.2514/6.1995-1499.
Luo, H., e S. Hanagud. "Delamination detection using dynamic characteristics of composite plates". In 36th Structures, Structural Dynamics and Materials Conference. Reston, Virigina: American Institute of Aeronautics and Astronautics, 1995. http://dx.doi.org/10.2514/6.1995-1172.
Guruprasad, P. J., Ajay Kumar Tamrakar e Dineshkumar Harursampath. "Modeling of active fiber composite for delamination sensing". In Smart Materials, Nano- and Micro-Smart Systems, a cura di Nicolas H. Voelcker. SPIE, 2006. http://dx.doi.org/10.1117/12.695110.
Chernyakin, Sergey, Sergey Perov e Yurii Skvortsov. "Probabilistic approach at delamination propagation problem in composite materials". In ICNPAA 2018 WORLD CONGRESS: 12th International Conference on Mathematical Problems in Engineering, Aerospace and Sciences. Author(s), 2018. http://dx.doi.org/10.1063/1.5081536.
Glaessgen, E., I. Raju e C. Poe, Jr. "Delamination and stitch failure in stitched composite joints". In 40th Structures, Structural Dynamics, and Materials Conference and Exhibit. Reston, Virigina: American Institute of Aeronautics and Astronautics, 1999. http://dx.doi.org/10.2514/6.1999-1247.
Zhang, Zhifang, Obinna Kenneth Ihesiulor, Krishna Shankar e Tapabrata Ray. "Comparison of Inverse Algorithms for Delamination Detection in Composite Laminates". In ASME 2012 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/smasis2012-7904.
Delamination is a frequent and potentially serious damage that can occur in laminated polymer composites due to the poor inter-laminar fracture toughness of the matrix. Vibration based detection methods employ changes caused by loss of stiffness in dynamic parameters such as frequencies and mode shapes to detect and assess damage. Because it is a whole field method, and can be applied instantaneously and remotely, vibration monitoring using frequency measurements offers great potential for implementation in online structural health monitoring systems. However, one of the disadvantages of using frequency measurements is that while the presence of damage is easily identified through a shift in measured frequency, the determination of the location and the severity of the damage is not easy to accomplish. To determine the location and severity of damage from measured changes in frequency, it is necessary to solve the inverse problem, which requires the solution of a set of non-linear simultaneous equations. In this paper, we have compared the performance of three different inverse algorithms for delamination detection in the fibre-reinforced composite laminates: direct of solution using a graphical method, artificial neural network (ANN) and surrogate-based optimization. In particular, the graphical method which was earlier proposed for problems of two variables has been extended to solution of three variables, the interface, location along the beam length and size of delamination in laminated composite beams. The three inverse algorithms have been compared using numerical validation data generated from the theoretical model of delaminated beam with and without artificial errors. All three algorithms can predict the delamination parameters accurately using the validation data directly generated from theoretical model. However, if artificial errors are introduced in the numerical data to simulate uncertainties in measurement of frequencies, ANN does not fare as well as the the other two methods as it is more sensitive to the artificial discrepancies. Also, ANN requires the network to be retrained if the measured frequency modes do not match the input modes in the existing network. The graphical technique and the surrogate based optimization performed equally well in the validations. However, the graphical technique is only applicable to no more than three variables, while the surrogate-based optimization algorithm can be applied to inverse problems with several unknown parameters such as in the case of delaminations in composite plates.
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Tsao, Chungchen, e Keilin Kuo. "Theoretical Analysis of Thrust-Induced Delamination in Hemispherical Drilling Composite Materials". In ASME 2014 12th Biennial Conference on Engineering Systems Design and Analysis. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/esda2014-20633.
The theoretical analysis of thrust-induced delamination in hemispherical drilling composite materials was investigated in this study. The theoretical analysis indicated that the thrust force of hemispherical drill at drill and delamination ratio (s) about 0.8 has a significant effect on prevention of delamination damage in drilling composite materials. The maximum thrust force of hemispherical drill at α = 2, however, was about 36% of that of twist drill. In other words, hemispherical drill has a correspondence with lower bearing stresses on drilling-induced delamination, which is liable to cause separation of plies at the exit as the interlaminar bonding yields.
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Heidary, Hossein, Amir Refahi Oskouei, Milad Hajikhani, Behrooz Moosaloo e Mehdi Ahmadi Najafabadi. "Acoustic Emission Signal Analysis by Wavelet Method to Investigate Damage Mechanisms During Drilling of Composite Materials". In ASME 2010 10th Biennial Conference on Engineering Systems Design and Analysis. ASMEDC, 2010. http://dx.doi.org/10.1115/esda2010-24389.
Structural parts made of composites have frequently to be drilled in the industry. However, little is now about the interacting conditions between the drill tool and material, which may be multi-type and multi-size. Delamination free in drilling different fiber reinforced composites is the main objective of present paper. Therefore the influence of drilling and materials variables thrust force and delamination of GFRP composite was investigated experimentally. Drilling variables are cutting speed and feed; material variable is fiber orientation. Acoustic Emission sensing was employed for online detection of composite damage induced by drilling. This paper addresses an application of wavelet-based signal processing technique on a composite during drilling. The wavelet methodology is introduced and procedure of wavelet-based acoustic emission (AE) analysis methods is demonstrated. Result shows Acoustic Emission analysis by wavelet method can monitor damage mechanism in drilling of composites.
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Yin, Wan-Lee. "Thermal buckling of composite plates with a strip delamination". In 36th Structures, Structural Dynamics and Materials Conference. Reston, Virigina: American Institute of Aeronautics and Astronautics, 1995. http://dx.doi.org/10.2514/6.1995-1318.
Rapporti di organizzazioni sul tema "Composite materials Delamination":
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Bocchieri, Robert T., Douglas S. Dierdorf, Kristofor S. Cozart, Steven P. Wells, Steven W. Kirkpatrick, Robert A. MacNeill e John R. Hawk. Experimental Investigation of Widespread Delamination Damage to Composite Materials Caused by Radiant Heating. Fort Belvoir, VA: Defense Technical Information Center, giugno 2013. http://dx.doi.org/10.21236/ad1009242.
Lee, Wall e Burch. L52333 NDE and Inspection Techniques Applied to Composite Wrap Repairs. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), giugno 2012. http://dx.doi.org/10.55274/r0010468.
The objective includes: Assess commercially available inspection methods to validate integrity of composite repair systems. Identify applicability to inspect composite overwrap and parent metal for both onshore and sub-sea pipelines (where information is available). Identify sources of data to include other users of composite materials(aerospace/aircraft, naval/ship repairs). Identify procedures and technologies to assess inspection effectiveness and provide a gap analysis. Interface with other PRCI projects on long-term testing of composite repairs and other joint industry projects on composite repairs to improve our understanding of long term durability of repairs. Identify global experience with composite repairs; not just North America. For general wall loss, radiography or electromagnetic techniques appear to be the best candidates. Standard radiography techniques can detect changes in wall thickness over a large area. Saturated low frequency systems, e.g. SLOFEC are good for a quick rapid scan of the area of interest. Pulsed eddy current, e.g. PEC, is also available for a general survey of the underlying substrate. For pinhole leaks, the electromagnetic techniques do not have sufficient resolution to detect defects of order 20 mm (0.8 in.) diameter and less. Standard radiography techniques can detect pinhole leaks down to diameters of 3 mm (0.12 in.) or less. Tangential radiography techniques are generally good for defect sizing but there are practical limitations with chord length (i.e. beam path through the pipe wall). Ultrasonic techniques could offer a potential solution but is currently limited due to the high attenuation of the composite repair material where through the repair inspection could only detect large diameter defects greater than 25 mm (1 in.) diameter on thin repairs less than 5 mm (0.2 in.). Detecting pin hole defects by applying the ultrasound along the axial direction of the substrate, effectively skipping the ultrasound under the repair, showed more promise. For delamination or debonding of the interface between the composite laminate and the steel substrate, laser shearography and microwave inspection appear to offer the best solution. Currently there is no single inspection technique that can be applied with confidence to the inspection of interfacial delaminations. Further developments are on-going to provide a solution to this challenging inspection problem. Acoustic emission is able to give an overall picture of the damage within the composite under live loads. It can be used as a QA tool to test the integrity of the repair. However, it is difficult to interpret the signals to gain any quantitative information about a particular defect.
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Chin, Eric Brian, Shawn Allen English e Timothy Briggs. Criteria for initiation of delamination in quasi-static punch-shear tests of a carbon-fiber composite material. Office of Scientific and Technical Information (OSTI), settembre 2015. http://dx.doi.org/10.2172/1226924.
