|
Abstract
|
The durability of the notch and un-notch composites is mainly affected by environmental aging, the condition of mechanical load and mechanical aging. Fiber mat reinforced thermosetting composites are usually post-cured at elevated temperatures and then cooled at room temperature. Due to the dissimilarity of two components, (e.g. fiber and resin) thermal stress and strain can be generated and raised by moisture, temperature variation, thermal aging and mechanical aging in any working environment. The aim of this study is to investigate the effect of thermal ageing fatigue and mechanical ageing fatigue on the mechanical durability and notch sensitivity properties of glass fiber mat unsaturated polyester resin composites (GM/UP) and kenaf fiber mat/UP composites (KM/UP). Tensile test of smooth and notched specimens, low cycle tensile fatigue (LCF) tests, dynamic mechanical analysis, stress distribution by point-stress failure criteria and notch sensitivity analysis were performed to both types of the specimens. Both were previously taken under a certain number of freeze-thaw aging (from +58ºC to -25ºC). It is found that the tensile modulus and un-notched strength of KM/UP were decreased more serious than that of GM/UP composites. After a definite number of thermal ageing cycle notch (open hole) did not diminish strength property of KM/UP. That is to say GM/UP had superior mechanical and other properties, after thermal ageing, while KM/UP had better energy absorption and notch sensitivity properties.
|