The objective of this study was to determine the effect of nonlinear material behavior on the
response and failure of unnotched and notched angle-ply laminates under uniaxial
compressive loading. The endochronic theory was chosen as the constitutive theory to model
the AS4/3502 graphite-epoxy material system.
Three-dimensional finite element analysis incorporating the endochronic theory was used to
determine the stresses and strains in the laminates. An incremental/iterative initial strain
algorithm was used in the finite element program. To increase computational efficiency, a
180° rotational symmetry relationship was utilized and the finite element program was
vectorized to run on a super computer.
Laminate response was compared to experiment revealing excellent agreement for both the
unnotched and notched angle-ply laminates. Predicted stresses in the region of the hole were
examined and are presented, comparing linear elastic analysis to the inelastic endochronic
theory analysis.
A failure analysis of the unnotched and notched laminates was performed using the quadratic
tensor polynomial. Predicted fracture loads compared well with experiment for the unnotched
laminates, but were very conservative in comparison with experiments for the notched laminates.
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