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

LAURA A. FASCE; VALERIA PETTARIN; R. SELTZER; P. M. FRONTINI

POLYMER ENGINEERING AND SCIENCE

JOHN WILEY & SONS INC

Lugar: New York; Año: 2003 p. 1081 - 1095

0032-3888

The most commonly accepted method of determining impact fracture toughnessof polymeric materials that exhibit small scale yielding and negligible influence ofdynamic effects is given by the ISO/DIS 17281 Standard, which states that for brittlebehavior, basically a linear relationship exists between the fracture energy, U,and the energy calibration factor. +. This relationship allows calculation of the criticalstrain energy release rate, G,,, from the slope of the U vs. BW+ plot. This paperdescribes a simpler alternative methodology capable of evaluating impact fracturetoughness using the J, parameter. The J-integral is evaluated at the instability loadpoint. by calculating the fracture energy required to produce cleavage behavior of apre-cracked specimen. The methodology is limited to single edge notched threepoint-bending specimens with a crack to depth ratio equal to 0.5. Tests were carriedout on an instrumented falling weight impact testing machine on the followingmaterials: PP (polypropylene), HDPE (high-density polyethylene), MDPE (middensitypolyethylene) and RT-PMMA (rubber toughened polymethylmetacrylate).Results are in excellent agreement with the critical values determined by theISO/DIS 17281 Standard