Fracture surface analysis

Fracture Surface Analysis of Oxide/Oxide Composites... 

Fracture surface analysis of fibers can provide useful information. In particular, for noncrystalline fibers, the following fracture parameters can be obtained from an analysis of features on the fracture surface morphology the mirror constant, an estimation of fracture toughness K c, failure stress, flaw-to-mirror radius ratio, fracture surface energy, and the time to failure. 

Mecholsky, J.J., Freiman, S.W. and Morey, S.M. (1979) Fracture surface analysis of optical fibers. In Fiber Optics, pp. 187-207, B. Bendow and S.S. Mitra (Eds.). Plenum Press, New York. 

Fracture surface analysis shows that the transverse crack runs straight through the adhesion treated filaments while it circumvents the untreated filaments. Further improvement in the off-axis strength of aramid-epoxy composites seems unlikely since it is limited by the shear and transverse tensile strength of the aramid fibre itself. 

Any assessment of this kind of damaging process must pay special attention to these changes. It is therefore vital to And characteristics that help to interpret this process. This is the primary objective of fracture surface analysis, or fractography. 

Based on the fracture surface analysis, the brittle interfacial fracture occurs at the interface between the Ni(P)+ and Ni3Su4, possibly in the Ni3Sn2 or NigSn. It was thought initially that the brittle interfacial intermetaUic was due to the phosphorus segregation. As shown later, this hypothesis does not seem to be the root cause. 

H. L. Marcus and P. W. Palmberg, Auger fracture surface analysis of a temper embrittled 3340 steel, Trans. TMS-AIME 245, 1664 (1969). 

Novel olefin block copolymers synthesized via catalytic block technology were evaluated for polyolefin blend compatibilization. It was found that OBC is an effective polyolefin blend compatibilizer for polypropylene-high density polyethylene blend. Significant improvements in mechanical properties were observed. Morphology showed that OBC compatibilized blends displayed reduction in phase size. Cryo-fractured surface analysis and adhesion data from microlayered tapes with OBC as tie layers suggested improved interfacial adhesion for OBC compatibilized blends. 

Fracture mechanics analysis requires the determination of the mode I stress intensity factor for a surface crack having a circular section profile. Here the circular section flaw will be approximated by a semi-elliptical flaw. 

Step 3. The set of fracture properties G(t) are related to the interfaee structure H(t) through suitable deformation mechanisms deduced from the micromechanics of fracture. This is the most difficult part of the problem but the analysis of the fracture process in situ can lead to valuable information on the microscopic deformation mechanisms. SEM, optical and XPS analysis of the fractured interface usually determine the mode of fracture (cohesive, adhesive or mixed) and details of the fracture micromechanics. However, considerable modeling may be required with entanglement and chain fracture mechanisms to realize useful solutions since most of the important events occur within the deformation zone before new fracture surfaces are created. We then obtain a solution to the problem. 

Observations of smooth spalls in iron provided an early, dramatic demonstration of the importance of release wave behaviors. In 1956, Dally [61E01] reported the existence of remarkably smooth fracture surfaces in explosively compressed steel. The existence of these smooth spalls was a sensitive function of the sample thickness. Analysis and experiments by Erkman [61E01] confirmed that the smooth spalls were associated with interaction of release-wave shocks and shocks from reduction of pressure at free surfaces. These release shocks are a consequence of differences in compressibility at pressures just below and just above the 13 GPa transformation. 

Scanning electron micrographs of fracture surfaces revealed the presence of both amorphous and crystalline phases which corresponded to results from XRD analysis (Figure 6.12). What is of interest is that the crystalline phase is MgHP04.3H20 and not Mg(H2P04)2.2H2O or... 

The ATR-FTIR spectrum of the middle opaque polyethylene layer of the "bad" sample is shown in Figure 70. This spectrum was acquired from the fracture surface where the outer polyester film and tie layer delaminated from the polyethylene layer. The highest-scoring library match in Figure 70 indicates that the middle layer is a polyethylene with a low branch content, most likely a HDPE or a LLDPE, although a much more detailed spectral analysis would be required to confirm this. 

Composite interfaces exist in a variety of forms of differing materials. A convenient way to characterize composite interfaces embedded within the bulk material is to analyze the surfaces of the composite constituents before they are combined together, or the surfaces created by fracture. Surface layers represent only a small portion of the total volume of bulk material. The structure and composition of the local surface often differ from the bulk material, yet they can provide critical information in predicting the overall properties and performance. The basic unknown parameters in physico-chemical surface analysis are the chemical composition, depth, purity and the distribution of specific constituents and their atomic/microscopic structures, which constitute the interfaces. Many factors such as process variables, contaminants, surface treatments and exposure to environmental conditions must be considered in the analysis. 

---