Vibration of damaged bio-composite beams reinforced with random short Alfa fibers: Experimental and analytical investigations

Abstract

This paper describes an investigation of the vibration of a cracked bio-composite beam reinforced with random short Alfa fibers using both analytical and experimental methods. The main novelty is the incorporation of local natural short fibers in the dynamic study of bio-based beams in the presence of a transverse crack. In addition, damping coefficient was predicted versus the crack length, crack position and fibers content. In the experimental model, tensile tests were made to predict Young's modulus and ultimate strength of specimens. After that, vibration tests were made to predict natural frequencies and damping coefficients versus crack depths, crack positions and fibers content. In the absence of similar experimental works on Alfa fibers, a simplified analytical model of flexural vibration has been developed to compare the results of experimental measurements. For different boundaries conditions, the linear fracture mechanics combined with Castigliano's theorem were used to estimate the local flexibility matrix at the cracked zone. For the natural frequencies, close agreement was found between the experimentally measured values and those given by the analytical model. From obtained results, we showed the increase in fiber content tends to reduce the strength and the natural frequencies of Alfa reinforced composite beams. Finally, we concluded that depth and position of the crack had a significant effect on the natural frequencies and damping coefficients of the bio-composite beam.