Toughness, fracture markings, and losses in bisphenol-A polycarbonate at high strainrate

Abstract

As-received and heat-treated specimens of bisphenol-A polycarbonate were impacted at temperatures ranging from −196 to +100° C. The critical stress intensity has been calculated for the as-received case from the impact energy data by making a strain-rate correction. To make this correction, the time-temperature superposition principle has been applied to existing dynamic mechanical measurements of the storage modulus and loss modulus (tan δ). Critical stress intensity values of 2.2 to 3.9 MPa m1/2 were found to be comparable with those obtained from instrumented impact and low strain-rate test techniques. Resulting fracture surfaces of the specimens were studied with the scanning electron microscope. Specifically, the morphology of the regions in which sharp striations were present was investigated and the width of the striations have been reported as a function of testing temperature for both as-received and heat-treated cases. There appears to be a direct correlation between the strain-energy release rate, the stress intensity, the striation spacing and the loss curve (tan δ) for the as-received case.