CHARACTERISTIC PROPERTY OF IMPACT FRACTURE-TOUGHNESS

Impact fracture experiments were performed using three CT type specime ns made of PMMA with the size ratio 1:2:3 with analogous geometry. A p recrack was introduced artificially in each specimen, which was subjec ted to impact by a wedge bar. The flyer was accelerated by a gas gun t o impose an impact force to the wedge bar, and the fracture behavior w as measured by a strain gage cemented at the crack tip of each specime n. Based on the diagram of the dynamic strain history, the impact frac ture toughness K(I,IC) was evaluated. The results showed that K(I,IC) of a small specimen was lower than that of a large one, and that it de creased with increasing impact velocity. When the specimen was partial ly supported by a notched wall, K(I,IC) increased, except for the S-ty pe specimen. At low temperature, K(I,IC) increased for all specimens. A dense distribution of parabola patterns was observed on the fracture d surface of L-type specimens.