Abstract
The fracture behavior of oriented poly (methyl methacrylate) (PMMA) has been investigated. The stress intensity factor K IC , characteristic distance a, and angle θ of switching propagation direction decrease with increasing draw ratio in the range of 1.25 and 3.25. The microstructures such as the plastic zone and the features of morphology are in good agreement with the variations of these three variables. i.e.. K IC a, and θ.