Fracture surface morphology

S. Suresh and R. O. Ritchie, A Geometric Model for Fatigue Crack Closure Induced by Fracture Surface Morphology , Metallurgical Transactions, 13A, 1982, pp. 1627 1631. 

Fracture Surface Morphology and Phase Relationships of Polystyrene/Poly(methyl Methacrylate) Systems... 

A scanning electron microscope was used to correlate the fracture surface morphology of the A1203 and the 29% versus SiCVA Os CMC with Kjyn which increased threefold over KId in both materials at the highest impact velocity. The fracture surfaces exhibited as many as four distinct regions. The precrack region was a relatively flat and uniformly textured surface. This was... 

Complex Formation and Fracture Surface Morphology of a Highly Doubly Oriented Nylon 66 Rod... 

Although much of the work referred to in this paper was done several years ago, it was not reported previously. The content and implications are sufficiently novel to merit mention even at this time. The fracture surface morphology of doubly oriented nylon 66 was studied in its untreated and I2-KI complexed state. All the work reported here was done on doubly oriented samples made from an unoriented nylon 66 rod according to the techniques outlined below. 

Fracture surface morphology is markedly different for fatigue fracture than for tensile fracture Figure 8a shows an SEM scan of a typical fatigue fracture... 

The SEM scans of Figs. 28 a and 28 b show that molecular weight also has an effect on fracture surface morphology. For the lowest molecular weight sample with... 

Haward, this implies less tendency for localized deformation. The tension test results (Fig. 25), and the fracture surface morphology, both imply that the extent of crazing is reduced with increase in the percentage of acrylonitrile. 

All of the SAN samples, whether of 25% or 30% AN tested in fatigue at 21 Hz, displayed a fracture surface morphology that was in some respects akin to that of PS and in other respects quite different. Like PS, fracture developed from a surface source and the region surrounding the source was comparatively smooth but, unlike PS tested at this frequency, discontinuous growth bands were seen in this region. 

Fracture surface morphology varies with stress amplitude and test frequency as well as with composition and molecular weight. Even under fully reversed cycling, discontinuous crack growth bands have been observed on the fatigue fracture surface in PS, SAN and ABS but they have not been seen in HIPS. 

Post-failure studies of the fracture surface morphology of bulk semi-crystalline polymers are more difficult than those of amorphous materials due to the more complex multiphase structure associated with semi-crystalline materials However, it was shown that some fractographic details point to the formation of a stress whitened region ahead of a notch prior to final fracture of the material. In particular, stress-whitened regions were easily visible in semi-crystalline polymers such as LDPE and HDPE The resulting, macroscopically apparently brittle fracture... 

A third method which recently provided considerable insight into the role of crazes in deformation and fracture of amorphous polymers is the optical interference measurement of crazes (preceding a crack). Since the pioneer work of Kambour, this method has been widely used to determine characteristic craze dimensions and critical displacements. W. Doll gives an overview on recent results and on their interpretation in terms of fracture mechanics parameters (stress intensity factor, plastic zone sizes, fracture surface morphology, fracture energy). 

---