Interfacial fracture

It follows that consists of two stress components a crack tip debond stress, at, and a friction stress component, at is not only a function of the interfacial fracture toughness, G c, but is also dependent on the debond length, t, relative to the total... 

The results are plotted in Fig. 14. The upper two lines refer to the A fiber and the lower two lines to the HM fiber. For both fibers, the addition and removal of surface chemical groups did not produce reversible interfacial behavior. The untreated fiber surfaces produced results that could not be duplicated when the surface groups were removed. Microtoming of single fiber specimens pinpointed changes in the locus of interfacial fracture that were relatable to the interphase conditions caused by the surface treatment. 

Critical flaw size predicted to cause a crack to kink out of the BN interphase, plotted against the ratio of the interfacial fracture resistance to the fracture resistance of Si3N4 (adapted from ref. [30]). 

Kinloch, A. J., Interfacial Fracture Mechanical Aspects of Adhesion Bonded Joints, Review Article, Journal of Adhesion, vol. 10, 1979, p. 193. 

In both derivations of toughening behavior, increases in toughness for whisker-reinforced composites are dependent on the following parameters (1) whisker strength, (2) volume fraction of whiskers, (3) elastic modulus of the composite and whisker, (4) whisker diameter, and (5) interfacial fracture energies. 

Using fracture mechanics and the Griffith s energy criterion, Chow et al. have derived an analytical relation to determine the interfacial fracture energy between a brittle film and a polymeric substrate. 

For each system, the adhesion of the film to the substrate is characterized by an interfacial fracture energy value. The interfacial fracture energy term is calculated using an energetic approach which was proposed for analyzing the loss of adhesion of cracked films from the... 

The interfacial fracture energy associated with adhesion failure can then be calculated taking into account the elastic properties of the film and the defined critical strains. 

Table 4 presents, for each system, the average dimension of the de-adhered areas, the critical strains, and the corresponding interfacial fracture energy. 

Table 4. Decohesion Parameters Average Dimensions of the Decohered Areas (a X b), Critical Strains (e) and Corresponding Interfacial Fracture Energies (y)...

Even if the Al Oj interlayer accelerates the activation of the transverse cracking, it seems to have the opposite effect on adhesion failure. Indeed, we observe for both systems with an Al Oj interlayer (B and E) that the debonding and buckling are delayed. Therefore, the adhesion of the films is improved. The presence of this thermally grown Al Oj interlayer increases the interfacial fracture energy values to about 15 J.m in both systems. Two qualitative explanations can be proposed for the adhesion improvement. First, the Al Oj certainly permits an increase in the number of 0-Si bonds between the interlayer and the film. Second, prior to the... 

Interfacial fracture energy determination associated with the decohesion and buckling process. 

The interfacial fracture energy associated with the debonding of a layer. 

The ratio of the mode I interlaminar fracture toughness in 77K-LNj to that in RT-air was 1.8 for ALF/epoxy laminates. This ratio was decreased to 1.2 to 1.3 for CF/epoxy laminates. Thus, the increase of the matrix toughness was directly translated into the increase of the interlaminar fracture toughness for ALF/epoxy laminates. The effect was smaller for CF/epoxy laminates. Fractographic observation indicated foe contribution of resin is larger for ALF/epoxy laminates. Dominant interfacial fracture concealed the effect of resin for CF/epoxy laminates. 

Despite those difficulties, some reactive systems have been used to study the reinforcement of interfaces between semicrystalline polymers. Within the context of interfacial fracture, the possibility of crystallization introduces two new important aspects that need to be taken into account when interpreting experimental data ... 

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