Ok. Muratoglu et al., MICROSTRUCTURAL FRACTURE PROCESSES ACCOMPANYING GROWING CRACKS IN TOUGH RUBBER-MODIFIED POLYAMIDES, Polymer, 36(25), 1995, pp. 4787-4795
The process of massive cavitational deformation in an ethylene-propyle
ne-diene grafted maleic-anhydride modified polyamide 66, initiated fro
m cavitating rubber particles and associated with stable crack propaga
tion in compact tension and Izod impact experiments, has been studied
in the region ahead of the crack front by scanning electron microscopy
. The very tough stable ductile tearing behaviour of the material was
manifested by steady-state crack opening angles of 60 degrees and larg
e stress-whitened zones. The process zone ahead of the advancing crack
comprised two regions with distinct morphologies: (a) within a radius
of 30 mu m in an 'intense' deformation zone in front of the crack. th
e cavities are elongated to large draw ratios (similar to 10); and (b)
in the remaining 'weak' zone cavities were found to be substantially
equiaxed. The material with the elongated cavities of the crack front
is parted by the propagating crack and immediately sheared by similar
to 60 degrees and left lying parallel to the crack flank surfaces. The
very tough behaviour of the material has been analysed by the well kn
own mechanics of fracture of tough structural materials, and the calcu
lated tearing moduli were found to be quite comparable with those of t
he toughest structural steels.