| Abstract: | Viscous and elastomeric silicones have been applied as interlayers to carbon fibers in order to develop a tougher, micro-crack resistant, thermally stable polyimide (PMR-15) composite. Carbon fiber is continuously coated with very high molecular weight polydimethylsiloxane (PDMS) and polyvinyl-methylsiloxane (PVMS). Dynamic mechanical properties of the composites have been determined and compared with uncoated carbon fiber reinforced PMR-15 polyimide composites. The presence of the interlayer is shown by the appearance of a new relaxation peak. The peak temperature is found to be a good indication of the degree of the cure of the silicone elastomer. Comparison of the storage moduli of uncoated and coated carbon fiber composites at the service temperature range of the composites indicates that the presence of the silicone interlayer affects the shear moduli of the composites. Apparent activation energy of the α transition of the matrix in the modified composites varies with the amount of interlayer and composition in concert with the impact strength. |
