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Denys Gamby - One of the best experts on this subject based on the ideXlab platform.
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a decomposition of the strain energy release rate associated with the initiation of transverse cracking longitudinal cracking and delamination in cross ply Laminates
Composite Structures, 2008Co-Authors: Jean-luc Rebiere, Denys GambyAbstract:An energy criterion is proposed to study the damage evolution in a composite Cross-Ply Laminate. This criterion is based on the computation of the partial strain energy release rate associated with each damage mechanism (transverse cracking, longitudinal cracking and delamination) and mode (I, II or III). Several decompositions of the complementary strain energy are put forward. Each component part of this decomposition is related to a specific damage mechanism and loading mode. The related criterion can predict and describe the initiation and propagation of the different damage mechanisms.
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Analysis of damage mode transition in a Cross-Ply Laminate under uniaxial loading
Composite Structures, 2002Co-Authors: Jean-luc Rebiere, M.-n. Maâtallah, Denys GambyAbstract:The aim of this work is to study the transition from one damage mode to another. The three damage mechanisms usually observed in [0m/90n]s long fibre Cross-Ply Laminates with organic matrix are transverse cracking, which appears first, longitudinal cracking and/or delamination. The proposed analytical model is meant to describe the development of transverse cracks and to predict the order of initiation of subsequent damage modes; it relies on the strain energy release rate associated with each damage mechanism.
Jean-luc Rebiere - One of the best experts on this subject based on the ideXlab platform.
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a decomposition of the strain energy release rate associated with the initiation of transverse cracking longitudinal cracking and delamination in cross ply Laminates
Composite Structures, 2008Co-Authors: Jean-luc Rebiere, Denys GambyAbstract:An energy criterion is proposed to study the damage evolution in a composite Cross-Ply Laminate. This criterion is based on the computation of the partial strain energy release rate associated with each damage mechanism (transverse cracking, longitudinal cracking and delamination) and mode (I, II or III). Several decompositions of the complementary strain energy are put forward. Each component part of this decomposition is related to a specific damage mechanism and loading mode. The related criterion can predict and describe the initiation and propagation of the different damage mechanisms.
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Analysis of damage mode transition in a Cross-Ply Laminate under uniaxial loading
Composite Structures, 2002Co-Authors: Jean-luc Rebiere, M.-n. Maâtallah, Denys GambyAbstract:The aim of this work is to study the transition from one damage mode to another. The three damage mechanisms usually observed in [0m/90n]s long fibre Cross-Ply Laminates with organic matrix are transverse cracking, which appears first, longitudinal cracking and/or delamination. The proposed analytical model is meant to describe the development of transverse cracks and to predict the order of initiation of subsequent damage modes; it relies on the strain energy release rate associated with each damage mechanism.
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initiation and growth of transverse and longitudinal cracks in composite cross ply Laminates
Composite Structures, 2001Co-Authors: Jean-luc Rebiere, M.-n. Maâtallah, D. GambyAbstract:Abstract The aim of this study is to show the influence of transverse and longitudinal cracks on the distribution of the stress field and on the stiffness loss and Poisson ratio reduction of a Cross-Ply Laminate subjected to monotonic or fatigue tests. Two analytical models are proposed, which rely on different distributions of the stress field in the thickness direction of the Laminate. These models are based on a variational approach. A second type of approach is proposed, a three-dimensional finite element study. The three models are meant to predict the evolution of mechanical properties of [0m/90n]s Cross-Ply Laminates with (m+n=8) in order to better understand the damage evolution.
Chaeyoung Hong - One of the best experts on this subject based on the ideXlab platform.
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csai analysis of non crimp fabric cross ply Laminate manufactured through wet compression molding process
Composite Structures, 2021Co-Authors: Sooyoung Lee, Chaeyoung Hong, Taeseong Choi, Hyegyu Kim, Soochang Kang, Youngbin ParkAbstract:Abstract The main purpose of the present work is to demonstrate mechanical performance of a wet-compression-molding (WCM) composite product through conventional compressive-strength-after-impact (CSAI) analysis. Biaxial non-crimp fabric (NCF) is utilized to manufacture Laminated composite panels. Specimens are cut from the panels and tested to characterize fundamental mechanical properties of the NCF composite. The volume fractions of fibers and voids are also measured to evaluate the quality of the WCM product. Impact tests are carried out to examine impact resistance of the composite structure. Numerous impact characteristics at various energy levels are quantitatively measured. Internal failure patterns and damage extent are revealed via X-ray CT. Compression tests on the impacted plates are followed to evaluate structural integrity and damage tolerance (SIDT). 3D DIC technique is employed and distinct buckling responses dependent on impact energy levels are successfully visualized. Experimental results are showing a promising potential of the WCM process as one of the alternatives to the conventional autoclave-based fabrication method.
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complementary ex situ investigations of various fracture modes in a single edge notched symmetric cross ply Laminate subjected to tensile loading
Composites Communications, 2020Co-Authors: Chaeyoung HongAbstract:Abstract In situ experimentation using synchrotron radiation computed tomography (SRCT) is instrumental to observe subsurface mechanical behavior of composite materials in real time. However, the investigation areas of SRCT are often limited by its experimental configurations. In the present study, an ex situ observation is carried out to complement the in situ test results reported previously in the literature. Previous SRCT-based in situ experiment on the single-edge-notched symmetric Cross-Ply Laminate has visualized various failure modes at the notch, which are sequentially occurring inside the specimen. The tested specimen is further examined here using a laboratory-scale X-ray CT device with a dye penetrant. Delamination failures interacting with longitudinal and transverse cracks, which have not been detected by the in situ test, are found with other failure modes distributed over the entire specimen area. The ex situ and in situ experimental results are complementary and both of them are required to comprehensively understand the various and complex failure mechanisms of the composite.
Ji Wooseok - One of the best experts on this subject based on the ideXlab platform.
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Complementary ex situ investigations of various fracture modes in a single-edge-notched symmetric Cross-Ply Laminate subjected to tensile loading
Elsevier, 2020Co-Authors: Hong Chaeyoung, Ji WooseokAbstract:In situ experimentation using synchrotron radiation computed tomography (SRCT) is instrumental to observe subsurface mechanical behavior of composite materials in real time. However, the investigation areas of SRCT are often limited by its experimental configurations. In the present study, an ex situ observation is carried out to compliment the in situ test results reported previously in the literature. Previous SRCT-based in situ experiment on the single-edge-notched symmetric Cross-Ply Laminate has visualized various failure modes at the notch, which are sequentially occurring inside the specimen. The tested specimen is further examined here using a laboratory-scale X-ray CT device with a dye penetrant. Delamination failures interacting with longitudinal and transverse cracks, which are not detected by the in situ test, are found with other failure modes distributed over the entire specimen area. The ex situ and in situ experimental results are complementary and both of them are required to comprehensively understand the various and complex failure mechanisms of the composites
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In situ observation of interactive failure modes in a single-edge notched symmetric Cross-Ply Laminate using synchrotron X-ray tomography
Pergamon Press Ltd., 2020Co-Authors: Jo Eonyeon, Lee Sooyoung, Hong Chaeyoung, Ji WooseokAbstract:Interactive failure mechanisms of a single-edge notched (SEN) symmetric Cross-Ply Laminate subjected to tensile loading are studied in situ using synchrotron X-ray tomography and a DIC technique at the micro- and macro- scales. The SEN configuration guarantees the repeatability and consistency of the progressive and interactive failure behavior at the two different scales. The evolution of various fracture modes in different layers is observed through synchrotron radiation CT images. Due to the geometrically asymmetric configuration, all the initial cracks sequentially occurring near the notch tip can be captured in a narrow field of view. Stress relaxation due to the subsequent fracture initiations is indirectly captured by measuring the crack lengths and opening displacements from the 3D CT images at different loading steps. The stress relaxation is directly measured by DIC analysis using the macro-scale test data. DIC results show strains relaxed in the region between existing and emerging transverse cracks
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BVID analysis of non-crimp fabric Cross-Ply Laminate manufactured through wet compression molding process
'American Institute of Aeronautics and Astronautics (AIAA)', 2020Co-Authors: Lee Sooyoung, Hong Chaeyoung, Choi Taeseong, Kim Hye-gyu, Ji WooseokAbstract:The main purpose of the present work is to demonstrate the feasibility of the wet compression molding process for aerospace applications through the conventional BVID analysis. Non-crimp fabrics are utilized to manufacture Laminated composite panels with a Cross-Ply stacking sequence. Specimens are cut from the panels and tested to characterize various mechanical properties of the material. The volume fractions of fibers and voids are also measured to evaluate the quality of the WCM product. Impact tests per ASTM/D7131 are carried out to identify the BVID energy level for the composite structure. Failure patterns and damage extent at various energy levels are investigated. Experimental results are showing a promising potential of the WCM process as one of the alternatives to the conventional autoclave-based fabrication method
Janis Varna - One of the best experts on this subject based on the ideXlab platform.
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Effective stiffness concept in bending modeling of Laminates with damage in surface 90-layers
Composites Part A: Applied Science and Manufacturing, 2016Co-Authors: Andrejs Pupurs, Janis Varna, Mohamed Sahbi Loukil, H. Ben Kahla, David MattssonAbstract:Abstract Simple approach based on Classical Laminate Theory (CLT) and effective stiffness of damaged layer is suggested for bending stiffness determination of Laminate with intralaminar cracks in surface 90-layers and delaminations initiated from intralaminar cracks. The effective stiffness of a layer with damage is back-calculated comparing the in-plane stiffness of a symmetric reference Cross-Ply Laminate with and without damage. The in-plane stiffness of the damaged reference Cross-Ply Laminate was calculated in two ways: (1) using FEM model of representative volume element (RVE) and (2) using the analytical GLOB-LOC model. The obtained effective stiffness of a layer at varying crack density and delamination length was used to calculate the A, B and D matrices in the unsymmetrically damaged Laminate. The applicability of the effective stiffness in CLT to solve bending problems was validated analyzing bending of the damaged Laminate in 4-point bending test which was also simulated with 3-D FEM.
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crack opening displacement determination in damaged cross ply Laminate using electronic speckle pattern interferometry espi
Microelectronics Systems Education, 2012Co-Authors: Hana Zrida, Janis Varna, Mohamed Sahbi Loukil, Z AyadiAbstract:Composite Laminates during service undergo complex combinations of thermal and mechanical loading leading to microdamage accumulation in the plies. The most common damage mode and the one examined in this work is intralaminar cracking in layers. The crack opening displacement (COD) and the crack sliding displacement (CSD) during loading reduce the average stress in the damaged layer, thus reducing the Laminate stiffness. These parameters depend on material properties of the damaged layer and surrounding layers, on layer orientation and thickness. Previously these parameters have been calculated using finite element method (FEM) assuming linear elastic material with idealized geometry of cracks. To validate these assumptions experimentally the displacement field on the surface of a [90/0/90] carbon fiber/epoxy Laminate specimens with multiple intralaminar cracks in the surface layer is studied and the COD dependence on the applied mechanical load is measured. The specimen full-field displacement measurement is carried out using ESPI (Electronic Speckle Pattern Interferometry). The displacement jumps corresponding to cracks are clearly visible and can be used to determine the opening displacement along the cracks. The effect of crack interaction on the COD at high crack density is also investigated.
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analytical modeling of stiffness reduction in symmetric and balanced Laminates due to cracks in 90 layers
Composites Science and Technology, 1999Co-Authors: Roberts Joffe, Janis VarnaAbstract:Abstract Stiffness reduction in [S,90n]s symmetric Laminates, containing orthotropic sub-Laminates (S) and cracked 90° layer, is analyzed. Closed-form expressions relating stiffness changes to the transverse crack density are derived. They contain only material properties, Laminate geometry and a stress-perturbation function that is proportional to the normalized average crack-opening displacement. Stress-distribution models [shear lag, based on variational approach, and finite-element analysis (FEA)] are adopted for the [S,90n]s configurations and used to calculate the stress-perturbation function. Predictions are compared with experimental data for [θ, 904]s θ=0, 15, 30, 40 glass-fiber/epoxy-resin Laminates. Generally the FEA model slightly underestimates stiffness reduction whereas both of the variational models used lead to similar results, slightly lower than experimental. Even the shear-lag model may be successfully used if the shear-lag parameter is first obtained from fitting test results for Cross-Ply Laminate of the same material.
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transverse cracks in cross ply Laminates 2 stiffness degradation
Mechanics of Composite Materials, 1998Co-Authors: Janis Varna, Andrejs KrasnikovsAbstract:From the results of stress analysis between two transverse cracks in Cross-Ply Laminate [1], a model for the stiffness reduction based on generalized plane strain assumptions has been developed. Simple analytical expressions are obtained for the longitudinal modulus and the Poisson's ratio as a function of the transverse crack density. Apart from the crack density, these expressions depend only on the elastic and geometrical properties of constituent laminae and the average crack opening displacement (ACOD) normalized in the proper way. Calculations of the ACOD are performed and analyzed with the FEM and analytical models used for the stress analysis in [1]. The predicting capabilities of approximate models are discussed in comparison with experimental data and FEM results. In order to predict the stiffness degradation for a wide variety of Laminates, a simple procedure requiring only one FEM calculation for some “average Laminate” with “average crack spacing” is proposed and has been proved effective.
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crack opening geometry in cracked composite Laminates
International Journal of Damage Mechanics, 1997Co-Authors: Janis Varna, Lars Berglund, Andrejs Krasnikovs, A ChihalenkoAbstract:Talreja and coworkers have reported brittle and tough polymer matrix composites to show different Cross-Ply Laminate stiffness reductions due to transverse cracks, despite very similar elastic properties. Studies of crack opening displacement (COD) in [0,,,90,] Laminates may help in solution of this problem. Approximate analytical models based on the variational approach pioneered by Hashin were therefore applied in addition to FEM-calculations. Approximate models were concluded not to be reliable for future analyses of this problem. Experimental COD for brittle GF/EP Laminates at low crack densities was fairly well predicted by FEM-calculations. None of the models were able to predict experimental data at high crack densities. Residual plastic strains are suggested as an explanation and may also be responsible for reported matrix-related differences in stiffness reduction.