Finite Element-Based Damage Tolerance Methods for Aircraft Composites

Solid finite element-based techniques that have been successfully used for simulation of the matrix-dominated failure modes in carbon-fiber and glass-fiber reinforced polymer-matrix composites are presented in this work. Such techniques do not require initial flaw assumptions for the damage prediction. The main objective of this work is to show the ability of solid finite element-based techniques to accurately predict the onset and progression of damage under quasi-static and fatigue loading. The specific objectives are: (a) to develop failure simulation models of multidirectional carbon/epoxy laminate articles in a finite element code; and (b) to correlate the failure predictions with test data. The test articles include 16-ply IM7/8552 tape open-hole tensile coupons, a hybrid Ti, carbon/epoxy and glass/epoxy laminate, and a hybrid carbon/epoxy and glass/epoxy lug laminate. Available stress-strain relations and failure criteria are built in ABAQUS models, and material fatigue curves are used to predict the number of cycles to fatigue damage onset and progression. Model predictions and subsequent test correlations are presented.