Glass fiber/epoxy composites were thermally conditioned at 50, 100, 150, 200, and 250 degrees C for different periods of time and then immediately quenched directly in ice-cold water from each stage of conditioning temperature. The polymerization or depolymerization by thermal conditioning and the debonding effect by concurrently following thermal shock in polymer composites are assessed in the present study. The short-beam shear tests were performed at room temperature on the quenched samples to evaluate the value of interlaminar shear strength of the composites. The short conditioning time followed by thermal shock resulted in reduction of shear strength of the composites. The strength started regaining its original value with Ion-er conditioning time. Conditioning at 250 degrees C and thereafter quenching yielded a sharp and continuous fall in the shear strength. (c) 2006 Wiley Periodicals, Inc.