Evaluation of Impact Fracture Toughness of Polymeric Materials by Means of a Non-Linear Elastic Methodology

LAURA FASCE; VALERIA PETTARIN; ROCÍO SELTZER; PATRICIA FRONTINI

Cambridge, England

Conferencia; 12th International Conference on Deformation, Yield and Fracture of Polymers; 2003

The most commonly accepted method of determining impact fracture toughness of polymeric materials that exhibited small scale yielding and negligible influence of dynamic effects is given by the ISO/DIS 17281 Standard. The latter states that for brittle behavior, basically a linear relationship exists between the fracture energy, U, and the energy calibration factor, f. This relationship allows calculating the critical strain energy release rate, GIC, from the slope of the U vs. BWf plot. This paper describes a simpler alternative methodology capable of evaluating impact fracture toughness using the Jc parameter. The J- integral is evaluated at the instability load point, by calculating the fracture energy required to produce cleavage behavior of a pre-cracked specimen. The methodology is limited to single edge notched three point bending specimens with a crack to depth ratio equal to 0.5. Tests were carried out on an instrumented falling weight impact testing machine on various polymeric materials. Results are in excellent agreement with the critical values determined by the ISO/DIS 17281 Standard.