FATIGUE BEHAVIOR OF CARBON FIBER REINFORCED UNSATURATED POLYESTER COMPOSITES

Hand-lay up method was used to prepare the samples withunsaturated polyester(UPE)as a matnx reinforced with chopped carbon flbers(CCF).The fatigue behavior of unsaturated polyester resin/chopped carbon flber composites is studied with different weight percentage of chopped carbon ibers(2.5%,5%,7.5%,10%,12.5%).The fatigue test was carrled out under altemate bending method which made by applying sinusoidal wave with constant displacement(15 mm) the stress ratio R=-l and loading frequency 10Hz,which is believed to give a negligible temperature rise during the test. The results of the maximuln stress, fatigue strength and fatigue life of the tested composites are calculated from stress(S)- number Of cycles(N)(S- N) curves.It was shown that increasing percentage of reinforcement weight increase the values of maximum stress for all composites, while the values of fatigue strength and fatigue life increasing for all composites except the composite with reinforcing weight 12.5%,which suttect to rapid failure(fracture).ThiS failure could be due to the debonding of the chopped carbon flbers from the matrlx unsaturated polyester.