Matrix resin damage

Thermal Analysis. Figure 4 shows a plot of percent weight loss versus temperature for the FRC materials. As can be noted, the FRC materials sustain little thermal damage below 200°C. Major weight loss due to the decomposition of the matrix resin occurs between 300... 

One of the most important properties which control the damage tolerance under impact loading and the CAI is the failure strain of the matrix resin (see Fig. 8.8). The matrix failure strain influences the critical transverse strain level at which transverse cracks initiate in shear mode under impact loading, and the resistance to further delamination in predominantly opening mode under subsequent compressive loading (Hirschbuehler, 1987 Evans and Masters, 1987 Masters, 1987a, b Recker et al., 1990). The CAI of near quasi-isotropic composite laminates which are reinforced with AS-4 carbon fibers of volume fractions in the range of 65-69% has... 

While the approach described above works reasonably well for the polyester and epoxy matrix resins which do not show extensive ductility there is clearly a need for an alternative approach when very ductile stmctural adhesives are applied. The development of extensive damage zones can be treated more efficiently using damage mechanics models and these are now being examined. 

A finish could also be an after treatment for fiber or fabrics. Here, finishes are applied to reduce the damage during processing, promote adhesion to matrix resins, and improve the end properties such as hand (softness), water repellency, and wash-wear characteristic of textile products. 

If the interfacial bonding strength of the composite material is less than the cohesive strength of the matrix resin and the strength of the filler, a stress concentration near the filler can easily occur when composite materials are subjected to shear or tensile stress. Debonding damage will occur near the interface if the interfacial bonding is weak. 

The alternative approach is surface abrasion or grit blasting to remove the outermost layer of matrix resin. However, this can be labor-intensive for large structures and exhibits two areas of concern nonuniformity and the inherent balance of removing enough material to ehminate surface contamination while not damaging the fibers in the composite. There is also the possibility of abrasion of merely smearing contamination from one area to another. 

Thermal decomposition of the matrix material offers a simple way of recovering the relatively expensive reinforcing fibres from a fibre-reinforced laminate. The epoxy resin matrix was made to decompose by thermal treatment in air or nitrogen, this treatment allowing the carbon fibres to be recovered without damage. 

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