VOLUME STRAIN-MEASUREMENTS BY OPTICAL EXTENSOMETRY - APPLICATION TO THE TENSILE BEHAVIOR OF RT-PMMA

A computer assisted optical extensometer has been set-up in order to record volume strain evolution during the tensile testing of polymer materials. Such a technique provides fruitful information on the sequences of events contributing to the non elastic deformation of ductile polymers. It is of special interest in the case of rubber-toughened systems in which cavitational modes (crazing, rubber cavitation) as well as fairly constant volume modes (shear banding) may contribute in various amounts to the overall deformation. Illustration of the capabilities and limitations of the technique are given with preliminary results obtained on Rubber-Toughened Poly(methylmethacrylate) (RT-PMMA) at various particle volume fractions.