Shear response of carbon fiber composite pyramidal truss structures after high-temperature exposure

Shear behavior and residual strength at room temperature of carbon fiber composite sandwich panel with pyramidal truss cores exposed to different temperatures for different time were studied experimentally and analytically. Experimental results showed that the residual shear modulus and strength of composite sandwich panels decreased with increasing exposure temperature and time. The decreasing of shear modulus and strength after thermal exposure was mainly attributed to the degradation of the matrix property and fiber-matrix interface property. The effect of high-temperature exposure on failure mode was revealed as well. The failure was characterized by node rupture when sandwich panels were exposed to temperature in a range of 20-250 degrees C, while node rupture and face sheet delamination were observed when specimens were exposed to 280 degrees C. The analytical formulae were also presented to describe residual shear modulus and strength after thermal exposure.