Effects of low temperature on the mechanical properties of glass fibre-epoxy composites: Static tension, compression, R = 0.1 and R =- 1 fatigue of ±45° laminates

Effects of cold climate exposure on structures made of composite materials are scarcely documented. As a result, even if exceptional wind conditions prevail in some cold regions, uncertainties related to composite materials durability at low temperatures may hinder development of wind energy projects in those regions. Therefore, as part of the Wind Energy Strategic Network (WESNet) of the Natural Sciences and Engineering Research Council (NSERC) of Canada, efforts were made to evaluate the effects of cold climate exposure on the mechanical properties of glass-epoxy composites. Tensile and compressive quasi-static tests as well as tensile (R = 0.1) and fully reversed (R =- 1) fatigue tests were performed on vacuum-infused [±45]2s glass-epoxy composites at -40°C and 23°C. Results for quasi-static tests show an increase of tensile, compressive and shear strengths and moduli at low temperatures. It is also demonstrated that for the stress range under scrutiny, fatigue performance is improved at -40°C for both the R = 0.1 and R =- 1 loading cases. Moreover, the failure mode for R =- 1 fatigue changed from compressive failure due to buckling of delaminated plies to tensile failure, suggesting a more efficient use of the material. However, if R =- 1 fatigue results at low temperature are extrapolated towards the very low stresses that are also part of wind turbine blades fatigue load spectrum, fatigue life may be degraded compared with that at ambient temperature. Finally, evidence of visco-elastic behaviour leading to changes in s - N curve slope parameter are reported.