An attempt has been made here to evaluate the effect of thermal exposure on the mechanical behavior and failure mechanisms of carbon fiber composite sandwich panel with pyramidal truss core under axial compression.Analytical formulae for the collapse strength of composite sandwich panel after thermal exposure were derived.Axial compression tests of composite laminates and sandwich panels after thermal exposure were conducted at room temperature to assess the degradation caused by the thermal exposure.Experimental results showed that the failure of sandwich panel are not only temperature dependent,but are time dependent as well.The decrease in residual compressive strength is mainly attributed to the degradation of the matrix and the degradation of fibere-matrix interface,as well as the formation of cracks and pores when specimens are exposed to high temperature.The measured failure loads obtained in the experiments showed reasonable agreement with the analytical predictions. An attempt has been made to to evaluate the effect of thermal exposure on the mechanical behavior and failure mechanisms of carbon fiber composite sandwich panel with pyramidal truss core under axial compression. An analytical formula for the collapse strength of composite sandwich panel after thermal exposure were derived. Axial compression tests of composite laminates and sandwich panels after thermal exposure were conducted at room temperature to assess the degradation caused by the thermal exposure. Experimental results showed that the failure of sandwich panels are not only temperature dependent, but are time dependent as well. decrease in residual compressive strength is mainly attributed to the degradation of the matrix and the degradation of fibere-matrix interface, as well as the formation of cracks and pores when specimens are exposed to high temperature. The measured failure loads obtained in the experiments showediably reasonable agreement with the analytical predictions