VOLUME CHANGE AND LIGHT-SCATTERING DURING MECHANICAL DAMAGE IN POLYMETHYLMETHACRYLATE TOUGHENED WITH CORE-SHELL RUBBER PARTICLES

Mechanical damage was investigated in polymethyl methacrylate toughene d with core-shell (hard core) rubber particles. During a tensile exper iment, volume changes, light absorption, right scattering and a small strain elastic modulus were recorded. Light scattering was quantitativ ely related to the number of damaged particles and a fast partial unlo ading technique allowed determination of the non-elastic part of these changes in material properties. Experiments performed between 10(-5) and 10(-1) s(-1) and between 20 and 70 degrees C showed time-temperatu re transitions. These appeared to be different for each property, and measurement of the activation energy for each parameter enabled micros copic damage mechanisms to be inferred. Three types of microstructural damage were observed: pure matrix plasticity at very low strain rates or high temperatures, rubber cavitation at correlated locations at me dium strain rates and temperatures, and disordered cavitation, rubber tearing and matrix plasticity at high strain rates or low temperatures . The experimental mean stress triggering rubber cavitation was compar ed with the predicted value.