Tensile Fatigue Behavior of Carbon-Flax/Epoxy Hybrid Composites

Hybridation of carbon fiber composites with flax fiber offer interesting bio-degradability, respect of the environment, reduced cost and important dynamic properties. The purpose of this work is to study the effect of hybridation on the mechanical fatigue behavior of unidirectional carbon-flax hybrid composites. Static and fatigue tensile tests were realized for different laminates made of carbon fibers and carbon-flax hybrid fibers with an epoxy resin. The carbon laminates and two different staking sequences of hybrid laminates were manufactured by hand lay-up process. Monotonic tensile tests were realized to identify the mechanical properties of composites and the ultimate loading. Then, load-controlled tensile fatigue tests were conducted on standard specimens with applied load ratio R-F of 0.1. Specimens were subjected to different applied fatigue load level until the failure (60%, 65%, 75% and 85%). Damage was observed early after a few loading cycles. The decrease in the Young's modulus was depending on the ratio of fibers on the composites. Overall, the stiffness decreases by showing three stages for all studied samples. It has been found that the stress-number of cycle S-N curves show that carbon laminates have higher fatigue endurance than hybrid composites.