Maximum craze width

In a thermoplastic material it is, therefore, important to distinguish between the crack opening stretch (= COS) and the maximum craze width 2v. To characterize plastic deformation and fracture behavior of a thermoplastic material the maximum length of stretched fibrils and hence the maximum craze width 2v is a more fundamental parameter than the crack opening stretch. The latter, in addition, depends on the relaxation behavior of the broken remnants on the fracture surface. 

Fig. It a and b. Variation with crack speed of the dimensions of the craze zone at the tip of a propagating crack in PMMA a maximum craze width 2Vj b craze length s...

Figure 11 a shows the maximum craze width 2v as a function of crack speed d and Fig. lib the corresponding craze length s. Initially the results were interpreted as... 

In the context of the results for moving cracks discussed in the previous section it should be noted that the craze sizes reported in this section have been measured from just after onset of slow crack propagation to speeds up to 10 " mm/s Quantitative results of maximum craze width as a function of temperature T are compiled in Fig. 15 for PMMA pc and PVC At a first glance there... 

In PMMA the effects of molecular weight and of molecular weight distribution on craze dimensions and on crack opening have been intensively studied In Fig. 17 the results of the maximum craze width are represented as function... 

Fig. 16. Maximum craze width 2Ve in polycarbonate measured at —30 °C as a function of, molecular weigth M ...

Fig. 17. Maximum craze width 2V(. in PMMA of different molecular weight distributions as a function of molecular weight M at different temperatures...

Fig. 23a and b. Growth of a primary craze at a stationary crack tip in PMMA in air, K, = 19 N/mm a craze length s as a function of loading time t b maximum craze width 2v as a function of loading time t... 

Fig. 32. Maximum craze width 2v, at the crack tip as a function of crack propagation rate da/dN...

In order to obtain information on the craze growth and on the fibrillation process the maximum craze widths are plotted against craze lengths s for high molecular... 

The quantitative development of craze length s and maximum craze width 2v at the crack tip are given in Fig. 50 as functions of the cycle number N for several successive crack jumps. In this experiment (AK, = 15.2 N/mm, R < 0.1) the crack remained stationary up to a critical cycle number Ne which is connected with a critical end length Se or end width 2v respectively. Together with the result of Fig. 49 it is obvious that the crack does not go through the craze all the way up to the craze tip as is usually assumed It stops well ahead of the craze tip, even at this... 

It should be noted that this growth behavior differs from that reported previously which showed a linear increase in a log-log-plot. In that and a subsequent paper the increase in craze length was assumed to occur without a significant increase im maximum craze width and the latter remaining well below the critical displacement at fracture. In Fig. 3.6 also the measured time-dependent behavior of maximum craze width 2v is shown. Contrary to the above assumption, the maximum craze width exhibits a dramatic growth, in reaching three times its critical value at fracture after times under load approaching 10 s (cf. 3.2). 

Figure 3.22 shows the maximum craze width 2v and the corresponding craze length s as functions of crack speed a in HMW and LMW PMMA. The crack speeds for the HMW material cover the complete range of slow crack growth, while LMW PMMA has been investigated only up to speeds around 10 mm/s... 

Fig. 3.22a, b. Speed dependent variation of the craze dimensions at the tips of propagating cracks in PMMA of different molecular weights a craze kngth s and b maximum craze width 2v ... 

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