Long-term effects of low and high temperatures on the mechanical performance of hybrid FRP composite laminates: Experimental and model assessment

Abstract

The present paper investigates the long-term effects of low and high temperatures on the mechanical performance of hybrid composite laminates applicable to the structural design of spar caps of the blade. The top and bottom layers of hybrid laminates were specified as carbon fibre-reinforced polymer and the middle layer as glass fibre-reinforced polymer. Hybrid laminates were prepared using resin transfer molding methods. Compressive strength, tensile strength, and stiffness parameters such as storage modulus, loss modulus, and damping factors of hybrid laminates were tested under low and high temperatures. The experimental results confirmed that the compressive and tensile properties of the hybrid laminates were not affected significantly at low temperatures. This may be due to the closely compacted epoxy chain segments that delay the elastic deformation of the materials. Additionally, degradation in the storage and loss modulus of the laminates was observed in the glass transition regions due to the mobilization of the epoxy molecules. The relationships between glass transition temperature and frequency were assessed. The glass transition temperature shifts to higher temperatures as the frequency increases due to a reduction in the gaps between the crosslinking of the epoxy network. The accuracy of the storage modulus results was compared with the empirical models. The model developed using the Arrhenius law provided the closest correlation. The model developed by Gibson et al. [1] needs further research to be used to predict when gamma and beta relaxation occur before the glass transition temperature of the epoxy matrix turns into a glassy state.

Keywords

• Hybrid laminate
• Resin transfer molding
• Mechanical properties
• Temperature-dependent properties
• Empirical models