Relationship between fracture energy and

Daghyani, Fl.R, Ye. L. and Mai, Y.W. (1995a). Mode 1 fracture behaviour of adhesive joints, I, Relationship between fracture energy and bond thickness. J. Adhesion 53, 149-162. 

Kinloch and Hunston [163, 167] and others used the concept of time-temperature superpositioning, and separated the effect of changing the volume fraction and the properties of the matrix phase. No definite relationship between fracture energy and volume fraction of rubber was observed. The maximal value of volume fraction that can be achieved is about 0.2-0.3. Attempts to produce higher volume fraction result in phase inversion and loss of mechanical fracture properties. Though in most of the studies [168, 169], phase inversion was reported at a volume fraction >20%, in some recent studies inversion has been reported [170,171] at a very low volume fraction ( 2%) of rubber. 

Figure 5. Relationship between fracture energy and viscosity-average molecular weight.

The relationships between the K1C and fracture surface energy are similar to each other, and generally decrease with increasing spinel content, apart from the in situ formed composites which show different microstructures and fracture paths. It is therefore clear that the development of thermal shock resistance in the magnesia-spinel composites cannot be linked to any increased fracture toughness. 

FRACTURE. Brittle, or fast fracture occurs when the intensified stress at a crack tip exceeds the fracture stress of the material (i.e. the force is sufficient to break the interactive bonds). The crack then propagates catastrophically rapidly. Brittle fracture is characterized by a very small (sub-millimetre) microcrack zone at the crack tip, low (0.01 kJm-2) fracture energy and a linear relationship between the load and the load-point displacement in fracture tests. This type of fracture is typical of low-toughness ceramics such as glass and fine-grained monolithic ceramics. 

The classic Griffith-Orowan theory describes the relationship between the strength and toughness of brittle materials such as ceramics (Griffith, 1920 Orowan, 1949). In the simple basic equation of the theory, the stress to fracture Of is related to Young s elastic modulus E, the fracture energy y, and the critical crack length c, by ... 

With the rapid increase in numerical computing power, there have been attempts to formalize the different environmental contributions in order to provide a procedure to predict assembly durability (Crocombe 1997 Loh et al. 2002 Bordes et al. 2009). PigMre4S.IS shows a simple scheme. This is based on an initial identification of diffusion coefficients and mechanical parameters. The relationships between water content and properties such as tensile modulus, tensile strength, and interfacial fracture energy are then established. A coupled numerical model for the joint of interest is then constructed. This allows local water content to be defined and resulting changes in adhesive and interface properties to be predicted. At present, there are... 

Figure 19 Relationship between the fracture energy and rubber phase volume fraction in a rubber-toughened epoxy...

The most-often cited theoretical underpinning for a relationship between practical adhesion energy and the work of adhesion is the generalized fracture mechanics theory of Gent and coworkers [23-25] and contributed to by Andrews and Kinloch [26-29]. This defines a linear relationship between the mechanical work of separation, kj, , and the thermodynamic work of adhesion ... 

If a material exhibits linear-elastic stress-strain behavior prior to rupture (an ideal behavior approximated by many thermosets), then a simple relationship exists between the material s fracture toughness and its fracture surface energy, J (or G),... 

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