Evaluation of Impact Fracture Toughness of Polymeric Materials by Means of the J-integral Approach

FASCE, LAURA A.; PETTARÍN, VALERIA; SELTZER, ROCÍO; FRONTINI, PATRICIA MARÍA

POLYMER ENGINEERING AND SCIENCE

Society of Plastics Engineers

Año: 2003 vol. 43 p. 1081 - 1095

0032-3888

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 the following materials: PP (polypropylene), HDPE (high density polyethylene), MDPE (mid-density polyethylene) and RT-PMMA (rubber toughened polymethylmetacrylate). Results are in excellent agreement with the critical values determined by the ISO/DIS 17281 Standard.