Optimization of Mechanical and Thermal Properties of Elastomer Modified Carbon Fibers/Phenolic Resin Composites

In this study, the effect of simultaneously using of chapped carbon fibers and an elastomer as hydroxyl terminated poly butadiene (HTPB) on tensile and impact strength and thermal resistance of phenolic matrix composite was investigated and optimized experimentally. This optimization was done by designing of weight percentages of components using design expert software. To fabricate all of composite samples, mix of resole and novalac phenolic resins (80-20 wt.%) was used as matrix and the HTPB and then carbon chapped fibers were added. Also thermal behavior of composite and pure phenolic was studied through thermogravimetric analyses (TGA) and differential TGA (DTGA). The best result about tensile tests is related to composite contains 55.48 wt.% of carbon fibers and 2.2 wt.% of HTPB. Also the highest impact strength was obtained for composite contain 38.41 wt.% of carbon fibers and 12.8 wt.% of HTPB. Integration of experimental and analytical results showed the optimum weight percentages about 38.41 wt.% of carbon fibers and 2.2 wt.% of HTPB with the achievable tensile and impact strength about 6 times more than phenolic resin. The results of TGA and DTGA tests showed that the thermal resistance of phenolic matrix composite is higher than pure phenolic, so its destruction rate up to 500 ºC is less than pure matrix depend on wt.% of carbon fibers. But the effect of HTPB on thermal resistance of phenolic matrix is negligible and a little negative because of it’s fully destruction at 390 ºC.