Fatigue Crack Growth of Quenched Amorphous Polymers PC, PVC and PET
Masayoshi KITAGAWA and Daisuke NISHI
Abstract:The previous papers showed that the type of yielding at a constant strain rate shearing was quite different between as-received (AR) and quenched (Q) states of amorphous polymers. In AR samples, many slip lines and a couple of shear bands were nucleated, while in Q samples, vague shear bands appeared with no visible slip lines. The aim of this paper is to investigate the effect of this difference of yielding on fatigue crack growth in a serial research on the effect of quenching on the yielding of amorphous polymers. The tests were performed at tensile fatigue loading using single edge notched specimens of PC, PVC and PET. It was shown that (1) the plastic zone ahead of the crack tip was involved with slip lines for AR samples, but with craze like flaws for Q samples, (2) the fatigue crack growth rates were not so different between AR and Q samples at the same stress intensity factor ranges and (3) the striation geometry was more straight and sharper for Q samples than for AR ones. Key Words:Amorphous polymer, Fatigue crack growth, Quench, Yielding, Dugdale model