Damage Models for Delamination and Transverse Fracture in Fibrous Composites.
Annual technical rept. 15 Feb 84-14 Feb 85,
TEXAS A AND M UNIV COLLEGE STATION MECHANICS AND MATERIALS RESEARCH CENTER
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Theoretical and experimental work on the deformation and fracture of fibrous composites with distributed damage is described. Emphasis is on establishing the existence of potentials analogous to strain energy and on using these so-called work potentials in fracture studies. The difference between loading and unloading behavior is accounted for by using one work potential for changing damage loading and another for constant damage unloading. First, using work potentials in a finite element representation, a new method for predicting crack growth is described which is believed to be applicable to many different materials. The results confirm the previously predicted path independence of the J integral for a crack in a continuum with distributed damage the damage is modelled in this initial study using deformation plasticity theory for loading and elasticity theory for unloading. Described next are investigations of flat rectangular bar specimens and thin-walled tubes under axial and torsional loading. The limited amount of experimental data presently available on angle-ply laminates confirms the existence of a potential even when there are large increases in microcracking. Author