Ii and the total g associated with angleply matrix cracking and local del. We have implemented a principal stress model using a. Hajikazemi, mohammad, m homayoune sadr, and ramesh talreja. Variational analysis of cracked general crossply laminates under. A variational approach for predicting initiation of matrix cracking and. The effect of matrix cracking on mechanical properties in frp. Comparison to published experimental data demonstrates very good agreement between the prediction and the experimental measurements for the youngs modulus of glass. The effect of matrix cracking on mechanical properties in. Stress redistribution in angleply laminates due to formation of intralaminar matrix cracks depends on the crack spatial distribution. Analysis of local delaminations in composite laminates with. Research areas angleply laminate, inplane shear, stiffness reduction, transverse cracking, variational analysis.
Transverse cracking is probably the first and most dominant mode of damage in composite materials. If an angleply laminate has an even number of plies, then a16 a26 0. Mohammad hajikazemi, mohammad homayoune sadr lahidjani, ramesh talreja, variational analysis of cracked general cross ply laminates under bending and biaxial extension, international journal of damage mechanics, vol. Keywords transverse matrix crack, smooth planesurface crack, perfect meshing crack, angleply laminate, stiffness reduction, variational analysis references 1. Fatigue tests were conducted at a frequency of 5 hz and an rratio of 0. Pseudoductility of thin ply cfrp angleply laminates youtube. Jonathan fuller presented at visit to airbus, filton 19th may 2015. Variational analysis of cracked general crossply laminates under bending and biaxial extension mohammad hajikazemi, mohammad h sadr, and ramesh talreja international journal of damage mechanics 2014 24. Abstract multiple transverse cracking is one of the most common faiure modes in composite laminates. Cracks observation for cfrp laminates is done by using the xray technique, while for gfrp laminates a dslr camera is used. Most of the existing approaches for stress analysis of a cracked laminate are either limited to cross ply laminates or to symmetrical arrays of cracks. Vinogradov, v, hashin, z 2010 variational analysis of cracked angleply laminates. Therefore, these models do not have the capability of analyzing. The measured stiffness reduction as a function of the crack density is compared to an analytical prediction for cracked angleply laminates based on a variational stress analysis.
Variational analysis of cracked angle ply laminates. Understanding the behavior of damaged cross ply and simple angle ply laminates is of high importance for prediction of damage effects on. In this paper, transverse cracking of crossply 0290ns n 2,3,4 laminates under uniaxial tension load was studied by means of experimental and numerical methods. Dye penetrantenhanced xradiography was used to document the onset of matrix cracking in the central. Variational analysis of cracked angleply laminates sciencedirect.
The cracks parallel to the fiber direction are extended over the full thickness of transverse plies and often cross the entire test specimen width. Angleply laminate stiffness reduction fiber orientation abstract a stressbased variational model is developed to study stiffness reduction and stress distribution in angleply laminates. Variational analysis for angleply laminates with matrix cracks z. Quasistatic tension tests were conducted on as435016 graphite epoxy 0 2. Liewb a school of mechanical and electrical engineering, wuhan institute of technology, wuhan 430073, hubei, china bdepartment of civil and architectural engineering, city university of hong kong, tat chee avenue, hong kong article info. Variational analysis for angleply laminates with matrix cracks international journal of solids and structures, vol. Validating, using bem, a model for ply cracks in crossply laminates subject to combined inplane loading and.
Validation of the variational asymptotic beam sectional. This work was extended to investigate the effect of test specimen width, 3 100. The eightnode lagrange finiteelement technique is used for. Variational analysis of angleply laminates with parallel intralaminar cracks v vinogradov, n tyne 20th international conference on composite materials, iccm 2015, 1924, 2015. Deepdyve is the easiest way to get instant access to the academic journals you need. It also yields approximate values for stress perturbations pro duced by the cracks. Local delamination in laminates with angle ply matrix cracks.
Variational analysis of cracking in general composite laminates. In the field of matrix cracks analysis for symmetric laminates, the present. The variational analysis developed permits the evaluation of stiffness reduction of any. Constant amplitude tensiontension fatigue tests were conducted on as435016 graphite epoxy 0 2. Stiffness degradation resulting from 90 ply cracking in. Comparison to published experimental data demonstrates very good agreement between the prediction and the experimental measurements for the youngs modulus of glassepoxy 0 45 s laminate. Understanding the behavior of damaged crossply and simple angleply laminates is of high importance for prediction of damage effects on. Measurement of the mechanical properties of angle ply laminates doctor of phiiosophy 2000 jing wang department of chemical engineering and applied chemistry university of toronto abstract design of advanced fiber composite structures requires a knowledge of the strength and stiffness of laminates.
Variational definition of variational by the free dictionary. Variational analysis of angle ply laminates with arrays of parallel intralaminar and delamination cracks. Earlier finite element method analysis of laminates with cracked 90plies showed that the effective longitudinal modulus and poissons ratio of the ply do not change during cracking, whereas the transverse modulus reduction can be described by a simple crack density dependent function. Cracked laminates with imperfect interlaminar interface. Rao department ofmechanical engineering indian institute of technology, kharagpur721 302. Transverse cracking in laminated composites springerlink. Micromacro approach for prediction of matrix cracking evolution in laminated composites mohammadhossein ghayour, h hosseinitoudeshky, meisam jalalvand, and ever j barbero journal of composite materials 2015 50. Cfrp laminates is done by using the xray technique, while for gfrp laminates a dslr camera is used. Parameter analysis of damaged region for laminates with. Comparing laminates of glassepoxy and graphiteepoxy with the available finite element results shows that stress components are in very good accordance. Cracks observation for cfrp laminates is done by using the xray. A variational model for stress analysis in cracked laminates.
An accurate threedimensional stress analysis of angleply laminates with cracks andor holes, as opposed to the use of simpler classical laminates plate theories, is often times mandatory to understand 1 the complicated feature of the oftenobserved nonselfsimilar crack growth in symmetric angleply laminates. The work described in this report was conducted in the period july ii, 1977 to april ii, 1981. Mohammad hajikazemi, mohammad homayoune sadr lahidjani, ramesh talreja, variational analysis of cracked general crossply laminates under bending and biaxial extension, international journal of damage mechanics, vol. Assumed stress finite element analysis of throughcracks. Delaminations were modeled in the 08 interface, bounded by a matrix crack and the stress free edge. Pdf stress redistribution in angleply laminates due to formation of intralaminar matrix cracks depends on the crack spatial distribution.
Stress analysis of crossply composite laminates with. Staff profile engineering, school of newcastle university. Stiffness degradation in hygrothermal aged crossply. Variational analysis of angleply laminates with arrays of parallel intralaminar and delamination cracks. Hashin department of solid mechanics, materials and structures, tel aviv university, tel aviv, israel received 7 june 1985 crossply 0 90 laminates which contain distributions of intralaminar cracks within the 90ply are analyzed by variational methods for tensile and for shear. The shearlag model and variational approach were used to predict the effect of transverse cracks on the stiffness degradation of transient hygrothermal aged angleply. A thermal buckling analysis of symmetric and antisymmetric angleply laminated hybrid composite plates with an inclined crack subjected to a uniform temperature rise is presented in this paper. The admissible stress state of the cracked laminate was derived in each distribution pattern implementing ply refinement technique. Mechanics of materials 4 1985 1216 121 northholland analysis of cracked laminates. Analysis of local delaminations caused by angle ply matrix. Limits of the compliance elements and the stress distributions at the infinite crack density are compared to the results of the classical theory of laminates. Stiffness reduction resulting from matrix cracking in frp. Thin prepreg angleply laminates university of bristol.
Assumed stress finite element analysis of throughcracks in angle ply laminates 1125 t. A novel variational model is developed that can predict the stress transfer between plies in cracked general crossply laminates subject to general inplane nxx, nyy, nxy and outofplane. Variational analysis of cracked laminates with imperfect interlaminar interface is developed on the basis of a generalized extemum principle of thermoelastic complementary energy. Variational analysis of transverse cracking and local delamination in h m90 n s laminates. Micromacro approach for prediction of matrix cracking. Variational analysis for angleply laminates with matrix cracks article in international journal of solids and structures 512122 october 2014 with 29 reads how we measure reads. A simplified computational strategy focused on resin. During service loading of crossply laminates, transverse cracks occur in plies. It is widely recognized that the changes of laminate thermomechanical constants, caused by the transverse cracking of composite laminates, can be significant. Variational analysis of angle ply laminates with parallel intralaminar cracks v vinogradov, n tyne 20th international conference on composite materials, iccm 2015, 1924, 2015. Variational analysis of angleply laminates with parallel. Abstracta stressbased variational model is developed to study stiffness reduction and stress distribution in angleply laminates.
Varna, analysis of cracked general crossply laminates under general bending loads. Stiffness reduction of angleply laminates of the type. Assumed stress finite element analysis of throughcracks in. Manufacture, test and model angleply laminates in order to achieve ductility through fibre rotation and matched matrix response. Variational analysis of cracked angleply laminates.
The orientation of the ith layer is specified by the angle i i. All plausible matrix crack distribution patterns are considered and implementing the. Variational analysis of cracked general crossply laminates under bending and biaxial extension m hajikazemi, mh sadr, r talreja international journal of damage mechanics 24 4, 582624, 2015. Most of the existing approaches for stress analysis of a cracked laminate are either limited to crossply laminates or to symmetrical arrays of cracks. Atlurit center for advancement of computational mechanics, georgia institute of technology, atlanta, ga. Comparison of variational and generalized plane strain. Nonlinear static and stability analysis of composite beams by the variational asymptotic method international journal of engineering science, vol.
Effective shear modulus of a damaged ply in laminate. Analysis of initial accumulation of matrix cracks in angle ply laminates. Damage mode considered here includes intralaminar ply cracking that develops within the o. The measured stiffness reduction as a function of the crack density is compared to an analytical prediction for cracked angle ply laminates based on a variational stress analysis. Variational analysis of transverse cracking and local. Jan 28, 2009 a boundarydiscontinuous fourier expansion method to analyze the displacements and stresses in cross ply composite laminates with transverse cracks is presented. In this paper, local delaminations growing uniformly from the tips of angle ply matrix cracks in composite laminates loaded in tension are modelled theoretically.
Good agreement is obtained by comparing the prediction models and experimental data published by joffe et al. In this paper, transverse cracking of cross ply 0290ns n 2,3,4 laminates under uniaxial tension load was studied by means of experimental and numerical methods. Previous investigators proposed that the initiation and orientation of curved microcracks are controlled by local maxima and stress trajectories of the principal stresses. The experimental results for stiffness reduction agree well with the analytical results. The governing equations of the problem are derived on the basis of the generalized plane strain assumption and twodimensional equations of elasticity. A variational model for stress analysis in cracked laminates with. In the present paper an attempt to understand the e. Deepdyve is the largest online rental service for scholarly research with thousands of academic publications available at your fingertips. In this study, an analytical method is developed to exactly obtain the interlaminar stresses near the free edges of laminated composite plates under the bending moment based on the reduced form of elasticity displacement field for a long laminate.
A variational analysis of the stress state in microcracked crossply laminates has been used to investigate the phenomenon of curved microcracking in s90ns laminates. A variational method for analysis of laminates with. Stiffness degradation in hygrothermal aged crossply laminate. All models use the principle of minimum complementary energy for calculation of the stress state in a laminate element between two cracks, as was the case with the original model by hashin. Chandrashekhara and bangera investigated the free vibration of angle ply composite beams by a higherorder shear deformation theory using the shear flexible finite. Models based on variational analysis are compared with respect to the elastic properties of crossply laminates with transverse cracks. Composite angle ply laminates and netting analysis 01pa3253 stress. Natural boundary conditions are derived from the variational principle to overcome the limitations of the existing variational methods on the analysis of cracked general crossply laminates. However, the resulting strain would cause the reinforcement to rotate to a new angle. So, it can be concluded that design with angle ply laminates, based on the earlier theory, may be unduly conservative.
May 02, 2012 variational analysis for angle ply laminates with matrix cracks international journal of solids and structures, vol. Closed form results for effective youngs modulus, thermal expansion coefficient, shear modulus and internal stresses are developed for cracked crossply laminates. Geometry of a symmetric laminate containing cracks in. The obtained results show a good agreement comparing with experimental data 6 for different angleply laminate and without taking into. Micromechanics of cracked laminates under uniaxial load. In order to obtain higher crack densities in specimens, artificial cracks method was introduced in this study. A unit cell based method is developed based on variational principles to derive the stress state and effective mechanical properties of angleply laminates of type. Matrix microcracking damage mechanics of composite materials talreja, r.
Variational analysis for angleply laminates with matrix cracks. In the numerical simulations, a simplified computational strategy only focusing on the damage of the resin was proposed and the. Investigation of throughthickness stresses in composite. Prediction of poissons ratio degradation in hygrothermal. High strain rate properties of angleply composite laminates. Two different families of graphiteepoxy laminates with similar layups but different stacking sequences, 0e0s and 600s,were analyzed using threedimensional finite element analysis for 0 15 and 30 degrees. Variational analysis of cracked general crossply laminates under bending and biaxial extension. Delaminations were modeled in the 08 interface, bounded by a matrix crack. Prediction of poissons ratio degradation in hygrothermal aged and cracked. Variational analysis of angleply laminates article pdf available in composites science and technology 704. Stress redistribution in angle ply laminates due to formation of intralaminar matrix cracks depends on the crack spatial distribution. A stressbased variational model is developed to study stiffness reduction and stress distribution in angleply laminates. Pdf stress redistribution in angle ply laminates due to formation of intralaminar matrix cracks depends on the crack spatial distribution.
Analysis of cracked general crossply laminates under. Damage mechanisms and fatiguelife diagrams chapter 7. The stiffness degradation as a transverse crack extends in the width direction for glassepoxy angleply. A control volume having a single simulated transverse crack in 90 plyplies and intact. In the present paper a new assumed stress finite element method, based on a complementary energy method, is developed for the. A variational model for stress analysis in cracked. Analysis of initial accumulation of matrix cracks in angleply laminates. Liewb a school of mechanical and electrical engineering, wuhan institute of technology, wuhan 430073, hubei, china bdepartment of civil and architectural engineering, city university of hong kong, tat chee avenue, hong kong article info article history. Application of nonstraight or wavy fibres to provide deformation over a wider range of angles.
A 2d shear lag method is used to determine stresses in a laminate representative segment containing one crack and two crack tip delaminations. A variational model for stress analysis in cracked laminates with arbitrary. A simplified computational strategy focused on resin damage. A unitcell based stress analysis was developed upon variational principles to permit the evaluation of stiffness reduction of any. Variational analysis for angleply laminates with matrix. Thin prepreg angleply laminates project is part of the hiperduct programme grant key challenges. Thermal buckling behavior of hybridcomposite angleply.
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