Micromechanical Finite Element Modeling of Micro Punch Shear Experiments on Unidirectional Composites

Abstract

Punch shear penetration of unidirectional composite shows micromechanical damage mechanisms such as (i) mode II dominated fiber facture, (ii) fiber-matrix debonding, and (iii) large deformation and cracking of matrix. Prediction of non-linear progressive punch shear damage behavior is of interest in determining the properties and parameters of continuum damage model such as, MAT162 in LS-Dyna®. A 2D micromechanical finite element model of unidirectional composite is developed by defining (i) crack planes orthogonal to fiber axis at an interval of 5 micron, and (ii) fiber-matrix debonding planes between the fiber and matrix. Zero thickness cohesive elements are used to model fiber fracture and fiber-matrix debonding. Energy release rate and cohesive parameters for glass is obtained from the literature. The stochastic distribution of fiber tensile strength is taken from experimental data of S glass at sub-millimeter length scale. Tangential tractions are estimated using maximum strain energy theory. Validated cohesive laws for fiber-matrix debonding is obtained from computational simulations of micro-droplet experiments. Elatic-plastic properties of matrix resin is obtained from experimental measurements.