The fracture behavior of oriented poly (methyl methacrylate) (PMMA) ha
s been investigated. The stress intensity factor K(IC), characteristic
distance a, and angle theta of switching propagation direction decrea
se with increasing draw ratio in the range of 1.25 and 3.25. The micro
structures 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 theta.