ESSENTIAL WORK OF FRACTURE CONCEPT IN POLYMERS

Abstract

Plane-stress fracture toughness of amorphous copolyester (COP) sheets of different composition and molecular mass characteristics was determined by the essential work of fracture (EWF) concept using tensile-loaded deeply double-edge notched (DDEN-T) specimens. It was determined that these COPs meet the basic requirement of the EWF concept since their yielding along the full ligament preceded crack growth. A drop in load in the corresponding load-displacement (F-x) curves indicated yielding and allowed us to split both the specific essential and non-essential work of fracture (w_e and w_p, respectively) into their contributing terms based on yielding (w_y) and necking including fracture (w_n). Development and size of the plastic zone were studied by light microscopy (LM) and infrared thermography (IT).