The table also shows that the failure stresses of samples crazed at 40 MPa were approximately 10% smaller than for uncrazed samples.

Also, it is clear that at a crazing stress of 40 MPa, the failure stress is lower for 1% crazed samples than for uncrazed samples, but the failure stress is relatively constant when going from 1 to 10% relative craze density.

Table 1 shows that the ductility of polycarbonate crazed at 40 MPa is much lower than for polycarbonate crazed at 45 MPa.

Therefore, the predictive model for the yield stress of crazed polycarbonate will contain only these two terms, as shown by

These results show that the model produces a good prediction of the yield stress of crazed polycarbonate at the endpoints, with a slight underestimation at non-endpoint conditions, which is more desirable than overestimation.

Since the model shows that strain rate is the only important experimental factor in predicting the yield stress of crazed polycarbonate, the Eyring stress-rate model for thermally activated deformation processes will now be considered.

However, there exist an intense damage strip along the crack wake and ahead of the crack tip, and a larger overall crazed zone in PP/SEP specimen.

In PP/Noryl, large Noryl particles are effective to bigger crazing so that large crazed zone is developed at the crack tip.

The first three samples had a relatively large critical strain or did not craze at all, whereas the other samples crazed very well, more or less depending on the solvent used and the sample studied.

The final observation concerns the solvent uptakes in the unstressed and the crazed samples - each solvent has a different behavior:

Furthermore, as shown by Rice (13), J[v.sub.ss] is equal to the time rate of energy flow to the crazed zone.

[[Sigma].sub.d] is the craze-widening stress of the homopolymer and [v.sub.f] is the ratio of the density of the crazed mate rial to the density of the material in the surrounding homogeneous polymer.