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

Abstract

Effects of cold climate exposure on composite material structures 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 and 23 . 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 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 to that at ambient temperature. Finally, evidence of visco-elastic behaviour leading to changes in s − N curve slope parameter are reported. 1

Modelling the effect of temperature on the probabilistic stress–life fatigue diagram of glass fibre–polymer composites loaded in tension along the fibre direction

“…A goal of the current work is thus to provide such relationships. However, because of the temperature-sensitive creep-fatigue interactions present in off-axis composites [23,30,4] -which are not accounted for in the current modelling approach -the analysis is limited to tensile fatigue along the materials main fibre orientation. Therefore, equation 2 simplifies to:…”

“…However, even for thermosetting matrix composites, such a simple behaviour is not always borne out by experiment. For example, R = 0.1 fatigue results by Brassard [3] for UD glass-epoxy at −40℃ and 20℃ show a statistically significant downward shift of the normalized fatigue curve at low temperature and normalized fatigue curves at -40℃ and 23℃ for ±45 • glass-epoxy at R = 0.1 obtained by Cormier et al [4] show a statistically significant change in slope parameter with temperature.…”

Experimental and numerical research of temperature on tensile properties of multiaxial warp‐knitted composites

“…The main damage mechanism is attributed to resin softening, which results in cracks in braid yarn at elevated temperatures. Cornier et al [7] investigated the influence of low temperature on the quasi-static and fatigue behavior of glass fiber-reinforced composite. The result indicated that the compress strength and modulus were increased by 36% and 24%, respectively, when the temperature decreased from 23 C to −40 C. Youseef et al [8] studied the influence of elevated temperature on dynamic mechanical performance of E-glass composite and found that the dynamic mechanical properties are function of temperature and loading frequency.…”

“…The main damage mechanism is attributed to resin softening, which results in cracks in braid yarn at elevated temperatures. Cornier et al [ 7 ] investigated the influence of low temperature on the quasi‐static and fatigue behavior of glass fiber‐reinforced composite. The result indicated that the compress strength and modulus were increased by 36% and 24%, respectively, when the temperature decreased from 23°C to −40°C.…”

Temperature effect on compression property of multiaxial warp-knitted composites

“…Significant effects of temperature and the braided angle on the compressive behaviors of 3-D braided composites were observed. 16 Cormier et al 17 researched the low-temperature effect on the static tensile, compression, and fatigue behavior of glass fiber–epoxy composites. Li et al 18 reported the temperature effect on the in-plane and out-of-plane compression behavior of 3-D multiaxial warp-knitted glass fabric/epoxy composites.…”