A micromechanical model for multiple crazing in high impact polystyrene

In many classes of glassy polymers, much of the macroscopic response of the material is controlled by crazing. When crazing occurs under well-controll ed conditions, as in high impact polystyrene (HIPS) blends, it provides a m echanism of inelastic deformation improving the material toughness. Crazes, however, are also the precursors of cracks and, ultimately, failure. Micro mechanical features of the blend, such as particle size, compliance, and vo lume fraction, must be accurately tailored in order to attain the desired e ffects. In this work we present a micromechanical model for particle-toughe ned polystyrene (PS). The finite element model considers a representative v olume element (RVE) of the two-phase material and includes special craze el ements with nucleation and growth criteria based on experimental observatio ns of craze behavior in PS. The model enables the investigation of the effe cts of various parameters, such as the size, volume fraction and properties of the second-phase particles, on the inelastic behavior of toughened poly mers, with particular regard to craze initiation and growth. Here, we demon strate its utility by exploring the progression of multiple crazing in a re presentative HIPS system. (C) 2001 Elsevier Science Ltd. All rights reserve d.