Interfacial: debonding 19 layers

Fig. 17. Tensile detachment of a thick elastic layer with a circular interfacial debond, radius a.

Fig.3 Fractography of the composite showing the interfacial debonding The flexural strength is about 474.0 36.9MPa, indicating that T-pulsing CVI may provide another way to design and fabricate CMCs with well controlled interfacial layers and improved...

Failure locations depend on the type of adhesive and the mode mixity acting in the bonding line. When the crack starts propagation, the directional stability can change from a cohesive to an interfacial debonding (see Fig. 43.17). The failure can move to the first layer of the GFRP adherend under certain circumstances. 

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

This brings us back to more interfacial properties. It is interesting to investigate what becomes of the effect of adding diblock in the adhesive when the PSA is detached not from steel but from a low-adhesion surface such as a polyolefin, a silicone layer, or any other release surface. We have carried out a comprehensive investigation of the debonding mechanisms of the adhesives of Table 22.1 from a surface of ethylene-propylene (EP) copolymer [45]. The copolymer layer was spin-coated from a xylene solution onto the flat end of the steel probe. 

Two representative probe test curves for the detachment of an SIS adhesive from steel and from EP surfaces are shown in Pig. 22.17 while the initial portion of the curve is identical, the force drops rapidly to zero for the EP surface, and never forms the characteristic fibrillar plateau observed on steel surfaces. How does this happen As qualitatively described by Creton et al. [55] for a detachment from a polydimethylsiloxane layer, when the resistance to crack propagation is low, cavities are nucleated (around the peak stress) and then propagate as interfacial cracks at the interface between the probe and the adhesive, and eventually coalesce. This process of crack propagation and coalescence is responsible for the sharp drop in force observed in Fig. 22.17 for the EP surface and occurs at rather low values of nominal strain. In this case no formation of the characteristic foam stracture responsible for the high debonding energy is observed. 

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