Abstract
In glassy polymers crazes initiate at surface or interface stress concentrations where localized plastic flow produces microcavities by intense inhomogeneous plastic shear at a molecular scale. The rate of such cavity formation depends primarily on the local concentrated deviatoric stress while their subsequent plastic expansion into craze nuclei by their mutual interaction is in response to the global negative pressure. Once a craze nucleus forms into a spongy heterogeneity of significant aspect ratio it grows by the meniscus instability in which new craze matter, having continuously interconnected air passages, forms by the repeated convolutions of the concave interface of air and yielded polymer at the craze tip. The proposed theory not only gives quantitative agreement with the experimental measurements on the rates of initiation and growth of crazes at room temperature and below, but also predicts the scale factor of the structure of craze matter.