Interfacial damage debonding

In short fiber composites, energy absorption mechanisms, such as interfacial debonding and matrix cracking, most often occur at the fiber ends (Curtis et al., 1978). The damage model proposed by Bader et al. (1979) assumes that short fiber composites fail over a critical cross-section which has been weakened by the accumulation of cracks, since the short fibers bridging this critical zone are unable to carry the load. In fatigue loading, sudden fracture takes place as a direct result from the far-field effect of the composite, rather than due to the near field of the crack tip... 

A low velocity impact induces various types of damage in fiber reinforced laminated composite structures. In addition to the visible or barely visible indentation on the impacted surface and cracking on the back surface, the most prevalent damage inside a laminated composite includes delamination, matrix cracking, fiber/matrix interfacial debonding, and fiber fracture (see Figure 1.1) [3]. 

Figure 11.15 Fluorescent protein as a mechanophore at the fibre-epoxy resin interface in self-reporting fibre-reinforced composites, (a) The formation of microdamages promotes interfacial debonding between resin and fibre, therefore causing the protein to unfold and to lose its fluorescence. (b) Confocal fluorescence microscopy image of a damaged glass fibre-eYFP/epo>y composite, (c) Z-stack projection of confocal fluorescence microscopy images of a damaged carbon fibre-eYFP/ epoxy composite. (F yellow fluorescence channel, O overlay of fluorescence and transmission images).

The cross-sections of impression for different combination of specimen and indenter size are shown in from Figs. 13 to Fig. 16. For the observation of plastic zone immediately below the impression" . While there was little distinction in the fracture of spray film and the formation of plastic zone in different specimens, they presented clear differences depending on the indenter size. In case of indenter 1 mminterfacial debonding" . As the indenter size increased, the fracture tended to turn closer to the interfacial debonding. With smaller indenter, the indentation pressure is greater, to produce plastic deformation in the substrate. With 1 mmc[) indenter, plastic deformation occurred in proportion to the size of damage area, while with 4mmc[) indenter, the plastic... 

Voyiadjis, G. Z., and D. H. Allen (eds.) Damage and Interfacial Debonding in Composites, Elsevier, Amsterdam, The Netherlands, 1996. 

For fine fibers with very smooth snrfaces, healing can also occur after debond, so that interfacial dislocations are produced. For fat fibers with rough surfaces, molecular contact cannot be reformed easily. Consequently frictional pull-out is then observed, with damage at the interface. 

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