Temperature dependence of essential and non-essential work of fracture parameters for polycarbonate film

Abstract

Single edge and double edge notched polycarbonate specimens of thickness 0·;375 mm have been pulled to complete fracture at temperatures between 25 and 120°C. Within this temperature range specimens underwent full ligament yielding prior to final fracture, producing load–displacement curves at various ligament lengths that were geometrically similar to one another for a specific geometry. On the basis of these, the method of the essential work of fracture was used to study the effect of temperature on fracture toughness of polycarbonate film. Results showed that a linear relationship exists between specific total work of fracture wt and ligament length L over the entire temperature range under consideration. The slope of the line, which is referred to as the specific non-essential total work of fracture βwp , increased with increasing temperature. However, the interception at L = 0, which is referred to as the specific essential total work of fracture we , showed little variation with respect to temperature. Change of geometry affected both values, although the change in βwp was more significant than that of we , for which change of no more than 10%was attained. Based on the maximum load on the load–displacement curve, wt for double edge notched specimens was partitioned into the specific work of fracture for yielding wy and the specific work of fracture for yielding necking/tearing wnt . Linear relationships were found for both terms as a function of ligament length from which the essential (we,y , we,nt ) and non-essential (βy wp,y , βnt wp, nt ) related work terms were attained. Results showed that the yielding related work terms for polycarbonate decrease, while the necking/tearing related work terms increase, with increasing temperature.