Acoustic emission characterization of failure modes in banana/ramie/epoxy composites under flexural loading

A sufficient understanding of the failure mechanisms that govern the mechanical behavior and failure modes of natural fiber composites is essential. In this regard, acoustic emission (AE) is a potential technique to monitor the mechanical behaviour and to provide the required information about the failure mechanism of natural fiber-reinforced polymer composites. The purpose and novelty of this study is to investigate for first time, the fracture behaviour of banana/ramie/epoxy composites under a 3-point bending test. During the test procedure, the AE parameters were recorded to evaluate the crack growth from the initial crack to the final fracture of the specimen and to determine the damage locations. AE parameters, such as amplitude, frequency, cumulative hits, and AE energy distributions, were used to identify the failure mechanisms associated with matrix cracking, delamination, fiber-matrix debonding, and fiber breakage. Based on these findings, the cumulative effect of AE events (counts/hits) represents the stress risers that cause failure in the specimen. Because natural fiber composites are brittle materials, they weaken when subjected to tensile loads. For this reason, the outermost bottom layer experienced more failure than the compressive layers during the bending of the specimen. The failure modes were studied using scanning electron microscopy. It was observed from the AE activity that the stress level at the crack initiation is 10–15% higher than the stress magnitude at the fracture stage.

Graphical abstract