Influence of Quick Ageing on the Fatigue Behaviour of SMC Composite Materials

Abstract

This paper summarises the results of an investigation on the influence of environmental exposure, simulated by means of quick ageing conditioning, on the static and fatigue strength of an SMC-R25 composite material. The material under investigation consisted of an unsaturated polyester matrix reinforced with 25% E-glass fibres and with 50% of aluminium hydroxide as filler. Three environmental conditionings were analysed: thermal cycles, salt mist, thermal cycles and salt mist; the static and fatigue properties were evaluated on specimens taken from the SMC blanks after conditioning and the results were compared with those obtained for the material as moulded. An increase both in the static and fatigue strength together with a decrease in the static tensile modulus was noticed for the conditioned material, although the scatter of the results was in some cases too wide to identify a well defined influence. The analysis of the stiffness reduction during the fatigue tests showed differences in the damage evolution between as moulded and preconditioned material.