Determination of fracture toughness in rubber modified glassy polymers under impact conditions

Abstract

This paper analyzes the applicability of simple indirect methods for determining the impact fracture toughness of ductile polymers. Commercial rubber‐modified thermoplastics were assayed. Tests were carried out in a Charpy impact pendulum on sharp notched samples at room temperature and at 80°C. Specimens of different geometric relationship, were considered. Thickness, side grooving and span effects were investigated. Reslts appear to be geometrically and strain rate independent. ABS and high impact polystyrene samples exhibited a whitening effect due to craze formation through the whole fracture surface, indicating that stable crack propagation was occurring. Medium impact polystyrene, however, exhibited combined stable and unstable crack propagation mode, displaying shiny and dull zones on the surfaces of the broken samples. Data were analyzed following the corrected elastic and the Jc methods. The fit quality was evaluated by statistical analysis. In addition, two new methods were tried: the methods proposed by Vu‐Khanh and De Charentenay for semiductile behavior and by Vu‐Khanh for ductile behavior. The equivalencies between the different critical parameters that arose from the methods are compared and analyzed.

Impact-Specific Essential Fracture Work of Banana Fiber Reinforced Low-Density Polyethylene Composites

“…The cause of this difference has not been found. These results have not been reported by previous researchers [23,24,26] who has reported a negative value on the slope of the wf versus ligament length curve, also there is no reported the presence of stresswhitened zone.…”

Characterization of Specific Essential Work of Fracture for various Fracture Modes on Thermoplastic Materials

“…In terms of applying the EWF to impact loads, around the 1990s, there was a debate about the suitability of this method for application. This is due to the fact that the test shows a negative slope of the df versus ligament length curve [33,34]. There are two common problems [6], namely (i) the fracture behavior shifts to brittle to increase crack growth, and (ii) the effect of plastic hinges so that the ligaments are not fully fractured.…”

Links between surface morphology changes and damage in a toughened epoxy adhesive

“…Strain whitening then, can be considered as a manifestation of the damage mechanisms that are active in a polymeric material. Although strain whitening is generally associated with crazing [24,25], other phenomena such as cracks, particle debonding and cavitation [26,27] , and shear banding can cause light scattering and manifest as strain whitening.…”