Failure Analysis of Cross-Ply Laminates

This thesis focuses on understanding the failure mechanism of fiber glass reinforced laminates loaded in transverse tension. Fiber-reinforced composites are widely used in engineering applications including aerospace, automotive and wind energy for their high specific properties. Cross-ply laminates are analyzed using Continuum Damage Mechanics (CDM) methods to predict crack formation, propagation and strength of in ‘in-situ’ 90-plies. The Crackband method proposed by Bazant and Oh, is implemented within the Finite Element Method (FEM) to preserve mesh objectivity in the failure simulations. Analysis are carried out in Abaqus/Standard and Abaqus/EXPLICIT supplemented by user-written subroutines. First, a homogenized model is built to determine the converged size of a Representative Volume Element (RVE) according to the shear lag theory. Then, a detailed model of the RVE that accounts for fibers in the in-situ ply is generated. The zero ply are modeled as homogenized material using Glass Fiber Reinforced Epoxy properties. The influence of the transverse ply thickness on the failure mechanism of the composite is investigated keeping the thickness of the zero plies constant to d=0.5 mm while the 90-ply thickness ranges from 0.1 mm (thin ply) to 2 mm (thick ply). Different failure criteria have been studied including the maximum principal stress and the Hashin’s Failure Criteria. Results are discussed in term of onset of the microcracking with respect to the in-situ ply thickness.