Experimental Investigation of Flexural Fatigue Behavior and Damage Mechanisms in Flax‐Epoxy/Date Palm Petiole Bio‐Sandwich Beams

ABSTRACT By this paper, an experimental investigation was conducted to evaluate the flexural fatigue behavior and damage mechanisms of new bio‐based sandwich beams (BBSBs) composed of flax fiber/epoxy face sheets and petiole date palm cores (PDPCs). Acoustic emission techniques were employed to monitor and analyze the damage evolution during three‐point bending tests. Subsequently, the fatigue life of the BBSBs was evaluated through three‐point bending fatigue tests. The mechanical response was quantified by analyzing the load–deflection behavior and the energy dissipated at each loading level. Due to the inherent flexibility of the PDPC, the bending tests showed that under moderate loads, the BBSBs exhibited predominantly elastic behavior without permanent deformation. Three distinct failure mechanisms were observed during testing: crushing at the mid‐span of the beam, followed by buckling of the upper face sheet, and finally the shearing of the core. Despite the presence of localized damage, the fatigue tests revealed that the BBSBs could withstand up to 90% of the static failure load, demonstrating a remarkable fatigue lifespan. Finally, BBSBs offer lightweight and durable solutions for building and transportation applications. Their predictable fatigue behavior allows for the design of components that withstand cyclic loads, while the use of agricultural residues promotes environmentally friendly, locally sourced materials.