Creep behavior of poly(methyl methacrylate) with growing damage

A simple optical technique is used to quantify creep crazing damage in a uniaxially stressed transparent glassy polymeric sheet of polymethyl methacrylate (PMMA) at room temperature. The areal craze densities are taken as a measure of the crazing damage. It is shown that the crazing damage increases with nominal applied stress and creep time. The crazing initiation time and the crazing damage evolution equation for PMMA is modeled from a mechanical viewpoint and the results are used to predict the nonlinear creep behavior of PMMA with growing damage. The predictions are in good agreement with the test results.