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A Comprehensive Study on Damage Tolerance Properties of Notched Composite Laminates.
Final technical rept. 30 Sep 84-31 Dec 87,
DREXEL INST OF TECH PHILADELPHIA PA DEPT OF MECHANICAL ENGINEERING
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This final report contains the results of an investigation on matrix-related damage mechanisms in notched composite laminates. The theoretical approach taken follows the principles of micromechanisms and the mechanics of brittle fracture at the descriptive level considered valid for the so-called ply-elasticity. Namely, the laminate is basically treated as a 3-dimensional elastic solid which is made of distinctly anisotropic layers. Brittle fracture can initiate and propagate within any layer having a weaker axis of material anisotropy, and within any one of the weaker layer interfaces due to the 3-dimensional interlaminar stresses. Owing to the particular microstructure of the laminate, growth of such sublaminate cracks constitutes a load- or time-dependent evolutionary process. A computer simulation methodology is developed to describe the modes and the extent of damage caused initially by the presence of the notch, and subsequently by the damages themselves. Experiment using a graphite-epoxy laminate is then conducted to validate the simulation results. Keywords Graphite epoxy laminates, Notches, Holes, Stress concentration, Matrix cracks, Mixed modes, Crack growth, Finite element fracture mechanics.
APPROVED FOR PUBLIC RELEASE