Microdeformation in core-shell particle modified polymethylmethacrylates

We have investigated the microdeformation mechanisms in thin films and bulk samples of impact-modified PMMA over a range of experimental conditions by TEM. The extent of cavitation of the modifier particles and the competitio n between crazing and simple shear deformation are discussed, as well as th e extent to which the thin film behaviour is representative of that of the bulk. In both cases cavitation and crazing tend to dominate at intermediate strain rates and low temperatures, but are suppressed as the strain rate i s decreased and/or the temperature is raised. However, cavitation is also s uppressed at impact speeds in both thin films and bulk samples tested at ro om temperature, this being reflected by macroscopically brittle failure via propagation of single unstable cracks/crazes across the whole sample. (C) 1999 Elsevier Science B.V. All rights reserved.