effects of thermal cycling on mechanical properties such as longitudinal tensile strength, interlaminar shear strength and work of fracture of carbon fiber/aluminum composites have been investigated. the composite specimens fabricated by a squeeze casting technique were thermally cycled in fluidized baths between room temperature and various temperatures (260, 300, and 350 degrees c) for up to 1000 cycles. the cross sections and fracture surfaces were examined to clarify the degradation mechanism. significant degradation of the mechanical properties by thermal cycling was observed in untreated carbon fiber/aluminum composites whereas much less degradation in surface treated carbon fiber/aluminium composites. microscopic observations and short beam shear tests have indicated that the degradation of mechanical properties is caused by debonding at the fiber/matrix interface. the fiber/matrix interface for surface treated fiber was more resistant to debonding. it is concluded that thermal cycling damage of carbon fiber/aluminium composites can be minimized by increasing their fiber/matrix bond strengths