Active craze front length

Active craze front length per unit volume. With subscripts C, M, P composite, matrix, particle, respectively... 

We expect that when craze sources are plentiful, resulting in a high active craze front length Q, the craze velocity that needs to be maintained to match the imposed strain rate can be proportionally lower resulting in a lower craze flow stress and an increased craze fracture time tf. The contrary will hold when craze sources are few, requiring high velocities and high craze flow stresses to be maintained. There is very little information available currently on the important dependence of the craze fracture time tf on the applied stress implied by Eq. (9). 

With the above considerations on initiation and inactivation of craze fronts we now develop relations for q, the steady state active craze front length per unit volume. Here it is necessary to distinguish two separate cases sinface initiation limited crazing and volume initiation limited crazing. The first category applies to the cases of most homopolymers and to many block copolymers with phase dimensions too small to result in stress concentrations in the requisite volume element that was mentioned above. In these instances crazes are observed to initiate from sources at... 

Vq PB diluent concentration at the solubility limit under a standard state Vp Poisson s ratio of block copolymer composite Vp Atomic frequency factor in molecular chain scission Q Active craze front length per unit volume a Negative pressure (mean normal stress)... 

The rate of craze front inactivation in this geometry will be distinctly dependent on mutual arrest of craze fronts when they encoimter within a critical distance 8, permitting the craze fronts to sweep out a mean free path of 1/2 in each direction from the source particle at the center, as shown in Fig. 3. Considering that the typical craze front per cell of P5 will be on the average only half as long as the periphery of the cell, we have for the active craze length per unit volume... 

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