PLASTIC ZONE IN FRONT OF MODE-I CRACK IN PHENOLPHTHALEIN POLYETHER KETONE

The plastic zone size and crack opening displacement of phenolphthalei n polyether ketone (PEK-C) at various conditions were investigated. Bo th of them increase with increasing temperature (decreasing strain rat e), i.e. yield stress steadily falls. Thus, the mechanism increasing t he yield stress leads to increased constraint in the crack tip and a c orresponding reduction in the crack opening displacement and the plast ic deformation zone. The effect of the plastic deformation on the frac ture toughness is also discussed.