High cycle fatigue life analysis of unidirectional flax/PLA composites through infrared thermography

The durability of structural components under fatigue loading is a huge concern, especially in laminated composites. During the last few years, flax fibers have also gained an outstanding position as a reinforcement of biopolymeric matrices as polylactic acid (PLA). However, there is limited reported information regarding the fatigue behavior of unidirectional flax/PLA composites. Therefore, fatigue properties of unidirectional flax/PLA composites are evaluated in this work; tools such as infrared thermography and dissipated energy were used in order to establish the fatigue limit, and fracture surface was analyzed. Results show consistent and reliable tensile properties (σ_ut = 234.4 MPa, E = 20.56 GPa, and ε_f = 0.0181). The fatigue stress-cycle curve was established and fitted to the Basquin and Weibull fatigue models and the fatigue limit (σ_∞) was obtained as 0.4343 and 0.426 using the thermography and dissipated energy, respectively. Furthermore, the fatigue fracture surface presents a striation on the matrix due to the progressive crack propagation.