An experimental investigation of elastic-plastic behavior of a fibrous boron-aluminum composite: I. matrix-dominated mode

Abstract

Initial and subsequent yield surfaces, and plastic strains in a unidirectionally reinforced boron-6061-O aluminum composite were found experimentally for various monotonic and cyclic loading sequences in plane stress. An axially reinforced thin-walled tube was instrumented and loaded in an MTS servo hydraulic testing machine under incrementally applied monotonic and cyclic stress paths. The results confirm the connections previously established between matrix and composite hardening. Kinematic translation of the composite yield surfaces and bimodal plasticity dominate the behavior. Changes in the size of the overall yield surface were also found; these are believed to be caused,in part, by age hardening of the aluminum matrix. New results are reported for plastic strain magnitudes and directions in several loading sequences, at different loading rates. The measurements indicate that the direction of the plastic strain vector is not normal to the experimentally detected yield surface. However, related modeling in an earlier paper showed that the plastic strain vectors are contained within the cone of normals at each loading point. The effect of loading rate appears to be significant only at very low rates.