The effect of temperature and water immersion on the interlaminar shear fatigue of glass fiber epoxy composites using the I-beam method

This work investigates the combined effect of water immersion and temperature on the interlaminar shear static and fatigue strength of glass fiber epoxy composites. Interlaminar shear tests were performed on I-beam shaped samples which enable faster fluid saturation at 20, 40 and 60 °C, both in air and in immersion. Analysis of fatigue parameters and optical micrography enabled understanding the phenomena that govern the static and fatigue degradation for each case. The dry properties are dominated by the matrix resistance at room temperature and by fiber/matrix interface strength for higher temperature. The immersed properties are dominated by the fiber/matrix interface degradation. An analytical model based on Arrhenius theory is presented for building a fatigue mastercurve that accounts for both temperature and water immersion. The effect of water immersion is modelled by accounting for the change of glass transition temperature of the material. The results show that the mastercurve describes well the conditions tested, provided that the material remains below its glass transition temperature.