Crazing and acoustic emission in poly(methyl methacrylate)/acetone and polystyrene/methanol systems

Abstract

AbstractCraze initiation and growth in the poly(methyl methacrylate)/acetone and polystyrene/methanol systems was studied using photographic and acoustic emission techniques. The poly(methyl methacrylate) system was the only one that produced detectable acoustic emission; however, it was found that craze initiation occurs predominantly in the first half of a sample's lifetime while acoustic emission is detected predominantly in the second half. The detected acoustic emission in the poly(methyl methacrylate) system is believed to be due to the rupture of craze fibrils. Craze initiation in both polymer systems was found to be dependent on stress and time with higher stresses initiating more crazes at earlier times. Although the craze growth rate in both systems exhibited extreme variability, the average growth rate tended to increase with craze size and applied stress. In the poly(methyl methacrylate) system, craze velocity was independent of time but in the polystyrene system it decreased with time. None of the existing craze growth theories were capable of explaining these results.