Fatigue and impact response of gel-coated glass mats/polyester composites

Composites based on polyester matrices reinforced with fiber glass mats are widely used in the automotive industry, incorporating in many cases a gel coat surface layer. This paper presents the results of a current study in polyester/short fiber glass mat composites processed by hand lay-up moulding. Different lay-up architectures were tested under impact and fatigue bending loadings. Furthermore, the influence of the gel coat surface layer on fatigue and impact loading performances was also analysed. The composites tested with gel coat layer under compression loading exhibit significant higher bending stiffness, static and fatigue strength than when the gel coat layer was under tensile loading. The impact response showed a slight variation of the peak load and on the elastic recuperation and a significant increase on maximum displacement and absorbed energy with the increase of the incident impact energy. Both energy recovery, in percentage of the incident impact energy, and residual bending strength showed a marked and almost linear decreasing with the increase of the impact energy for all loading conditions, while the absorbed energy increased with the incident impact energy, reaching about 80% of impact energy for the highest impact energies