Qualitative separation of the effect of voids on the bending fatigue performance of hygrothermal conditioned carbon/epoxy composites

This study investigates the effect of voids on the static bending and bending fatigue properties of T300/914 composite laminates that are exposed to room temperature, hygrothermal and drying environment, respectively. Displacement-controlled three-point bending fatigue tests were conducted on specimens, while damage in the composite was continuously recorded with a metallurgical microscope. After 40,000 cycles the fatigue test was stopped and residual properties were measured on the tested specimens. Reduction in material strength was found to depend on the level of the specimen’s void content. The changes in weight and size gradually increased with an increase in porosity from 0.33% to 1.50% in the hygrothermal environment. It is found that the maximum rate of dimensional change occurred in the thickness direction. Both bending strength and fatigue performance were reduced with increasing porosity. The damage evaluation of aged specimens was more severe than non-aged and drying specimens.

► We investigate the effect of voids on the bending fatigue properties of laminates. ► Reduction in strength was found to depend on void content in different environment. ► Both bending strength and fatigue performance were reduced with increasing porosity. ► The damage evaluation of aged specimens was more severe than non-aged specimens. ► The damage evaluation of drying specimens is more severe than the non-aged specimens.