Fatigue and Fracture Properties

Fatigue and Fracture Properties of High-Strength Steels... 

The first section of this book deals with current topics in network theory directed toward explaining the relationship between molecular architecture and macroscopic physical properties. The closely related questions of network formation and degradation are also discussed in this section. Deformation, fatigue, and fracture are discussed in the second section. The third section includes recent advances in cross-linking chemistry several chapters outline applications of new systems and detail the relationship between network structure and application properties. 

In the previous chapter, the relationships between structure and mechanical and fracture properties of neat thermosets were analyzed. It was shown that an increase in thermal resistance (Tg or HDT, heat deflection temperature) and yield stress leads to a decrease in toughness (KIc), and in impact or fatigue resistance. So the challenge is how to increase toughness without sacrificing thermal and mechanical properties ... 

The interphase provided by the adhesion promoter may be hard or soft and could affect the mechanical properties. A soft interphase, for example, can significantly improve fatigue and other properties. A soft interphase will reduce stress concentrations. A rigid interphase improves stress transfer of resin to the filler or adherend and improves interfacial shear strength. Adhesion promoters generally increase adhesion between the resin matrix and substrate, thus raising the fracture energy required to initiate a crack. 

Data taken from C. J. Gilbert, D. R. Bloyer. M. W. Barsoum. T. El-Raghy, A. P. Tomsia and R. O. Ritchie, Fatigue-Crack Growth and Fracture Properties of Coarse and Fine-Grained TijSiCi , Scripta Mater.. 42 761-767 (2000). 

Physically based, using detailed thermodynamics and kinetics of phase transformations, cahbrated on direct measurement of micro-structural features and able to predict hardness and strength, with the potential for extension to ductility, fracture toughness, fatigue, and corrosion properties. 

Susuki I. Static and fatigue strength properties of composite laminates under in-plane biaxial loadings. In Proceedings of 5th international conference on biaxial/multiaxial fatigue and fracture 1997. pp. 79—89. Cracow, Poland. 

Mechanical properties of materials strength, hardness, toughness, resistance to fatigue and fracture... 

Figure 18.11b Data from Gilbert, C.J., Bloyer, D.R., Barsoum, M.W., El-Raghy, X, Tomsia, A.P., and Ritchie, R.O. (2000) Fatigue-crack growth and fracture properties of coarse and fine-grained TisSiC , Scripta Mater. 42,761. Figure 18.13a Guinel, M. and MGN.

D. Chen, K. Shirato, M.W. Barsoum, T. EL-Raghy, R.O. Ritchie, Cychc fatigue-crack growth and fracture properties in TisSiC2 ceramics at elevated temperatures, J. Am. Ceram. Soc. 84 (2001) 2914-2920. 

Although crosslinking is highly beneficial from the perspective of wear resistance, it comes at the price of less molecular mobility, lower material ductility, and reduced fatigue and fracture resistance due to the crosslinking of the molecular chains [170]. Thus crosslinking improves certain properties at the expense of others, so developers of orthopedic implants must balance the amount of crosslinking achieved with the maintenance of mechanical properties and/or oxidation resistance. 

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