The Use of Load Separation Criterion and Normalization Method in Ductile Fracture Characterization of Thermoplastic Polymers

C. BERNAL; P. MONTEMARTINI; P. FRONTINI

JOURNAL OF POLYMER SCIENCE PART B-POLYMER PHYSICS

JOHN WILEY & SONS INC

Lugar: New York; Año: 1996 p. 1869 - 1880

0887-6266

Load separation is the theoretical basis for the single-specimen J-integral experiment andthe incremental calculation of J-integral crack growth resistance (J-R) curves. This criterionhas been experimentally studied in nongrowing crack records in several materials, andmore recently a new method to extend the applicability to growing crack experiments hasbeen proposed in testing steel. This article examines the applicability of the load separationcriterion for evaluating ductile fracture mechanics parameters in rubber-modified polystyrenesand thermally treated polypropylene in the bending configuration. This criterionallows the load to be represented as the multiplication of two independent functions: amaterial deformation function and a crack geometry function. Its validity is evaluated withboth stationary and growing crack experiments. q-factor calculation for smooth and sidegroovedspecimens was also tried using the simple method of Sharobeam and Landes, inorder to identify material dependency. This article also investigates the applicability of thenormalization method, based on the load separation criterion for evaluating J-R curves onPP and PS. A simple approach which combines a blunt notched and a precracked specimenexperiment is proposed to determine the J-R curve of the materials studied. The resultingJ-R curves are compared with multiple specimen results available in the literature for thesematerials. A good agreement between the J-R curves obtained from this simple methodand from the multiple specimen technique was found