FATIGUE STRENGTH AND CRACK PROPAGATION STUDY OF FIBRE REINFORCED PLASTICS

Abstract

The fatigue strength of E-glass/Epoxy resin chopped strand mat (CSM) composite material has . been investigated. Axial fatigue tests are carried out on plain specimens for stress ratios `0', `0.5' and '-0.1'. Comparison is made for fatigue behaviour of CSM reinforcement and 00/900 woven type of reinforcement of same fibre and resin combination at same stress ratios. Efforts are also made to investigate the crack growth properties in the above two types of reinforcements of E-glass/Epoxy resin composite. The results show that fatigue life at higher stress levels increases with stress ratio. But at lower stress levels all the data falls fairly within a narrow band and giving approximately same endurance strength corresponds to 106 cycles. The fatigue performance of 00/900 woven reinforcement is far better than CSM reinforcement only at higher stress levels. But at lower stress level both types of reinforcement exhibited almost equal strength. The results of fatigue crack growth test show that crack growth occurs intermittently in composites and resistance to crack propagation for woven reinforcement is more than for CSM. Crack propagation in woven reinforcement is more sensitive to applied stress range but in CSM reinforcement the applied stress range has less influence. Probable reasons for such a behaviour has been discussed.