Prediction of Progressive Damage at the Fiber/Matrix Scale Using Cohesive Zone Elements
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abstract
2015, American Institute of Aeronautics and Astronautics Inc. All rights Reserved. Microscale failure analyses can predict failure properties to be used at larger scales and provide insight into the effect of microstructural variation. This is especially important in material design, since experimental measurement of failure properties for a wide variety composite materials can be expensive. This paper discusses the challenges of applying a cohesive zone model at the microscale and uses interfacial elements governed by a cohesive zone formulation in microscale analyses to predict cohesive zone properties for a graphite fiber-epoxy composite laminate under transverse tension. Current properties used in the literature lead to an oddity that the predicted strain at final failure can be more than 100%, which is not realistic. A discussion on material properties used at the microscale and this issue was given. Simple 1D cohesive zone models were used to provide insight into the causes of numerical instabilities in cohesive zone models, and some improved methods were proposed and tested. The convergence behavior for random fiber/matrix analyses was studied, exploring the performance of standard nonlinear methods, the effect of mesh refinement, and the effect of using a random distribution of properties. Multiple RVE sizes were used to predict cohesive zone properties for an IM7/5250-4 ply. The predicted transverse tensile strength of the composite was not very sensitive to the RVE size but was higher than an experimentally measured value. The predicted strain energy release rate was shown to strongly depend on the RVE size.
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56th AIAA/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference
