Determination of Fracture Toughness in Rubber Modified Glassy Polymers Under Impact Conditions

C. BERNAL; P. FRONTINI

POLYMER ENGINEERING AND SCIENCE

JOHN WILEY & SONS INC

Lugar: New York; Año: 1995 p. 1705 - 1712

0032-3888

This paper analyzes the applicability of simple indirect methods for determiningthe impact fracture toughness of ductile polymers. Commercial rubber-modifiedthermoplastics were assayed. Tests were camed out in a Charpy impact pendulumon sharp notched samples at room temperature and at 80°C. Specimens ofdifferent geometric relationship, were considered. Thickness, side grooving andspan effects were investigated. Results appear to be geometrically and strain rateindependent.ABS and high impact polystyrene samples exhibited a whitening effect due tocraze formation through the whole fracture surface, indicating that stable crackpropagation was occurring. Medium impact polystyrene, however, exhibited combinedstable and unstable crack propagation mode, displaying shiny and dullzones on the surfaces of the broken samples. Data were analyzed following thecorrected elastic and the J, methods. The fit quality was evaluated by statisticalanalysis. In addition, two new methods were tried: the methods proposed byVu-Khanh and De Charentenay for semiductile behavior and by Vu-Khanh forductile behavior. The equivalencies between the different critical parameters thatarose from the methods are compared and analyzed.