Impact fracture toughness tests on polymers

Abstract

Abstract A series of impact tests are described in which the plane strain fracture toughness, K c 1 , of five different polymers is measured using a three point bend specimen at striker speeds up to 5m/s. At low speeds K c 1 is determined using the maximum load and a static analysis, but at speeds greater than 1 m/s the dynamic effects render the load signal unusable. For the higher speeds the fracture is timed using contact and crack propagation gages and the analysis is performed using the striker displacement at fracture. A dynamic analysis is used to convert this measurement to the true specimen displacement and K c 1 is determined from this. The apparent downward trends in the K c 1 results obtained, especially at speeds above 3m/s, are discussed.