Thermal cycling studies of a cross-plied P100 graphite fibre-reinforced 6061 aluminium composite laminate

Abstract

Response to thermal cycling of a 0/90 cross-plied P100 Gr-6061 aluminium composite laminate was studied between a minimum temperature (T min) of 25 ‡C and maximum temperatures (T max) of 100 and 540 ‡C. Strain hysteresis was observed between the heating and cooling half-cycles and was attributed to anelastic strains induced by matrix residual stresses. A residual plastic strain was also observed after the first cycle, and was seen to disappear after subsequent cycles. Alteration of the thermal residual stress state of the matrix via heat treatments was found to change significantly the magnitude of the plastic strain. These results were compared with those of studies on unidirectionally reinforced P100 Gr-6061 aluminium composites, and the differences were explained on the basis of the residual stresses resident in the matrix. Optical and electron microscopy were also utilized to observe thermal damage, which occurred predominantly along improperly bonded fibre-matrix interfaces.