Acoustic emission for monitoring the mechanical behaviour of natural fibre composites: A literature review

In recent years, natural fibres are increasingly used as reinforcements for the production of low-cost and lightweight polymer composites: other advantages include non-abrasive nature, high specific properties, and biodegradability. However, their limitations, including moisture absorption, poor wettability and large scattering in mechanical properties, and the not sufficient understanding of mechanisms controlling their mechanical behaviour and failure modes, still confine the use of natural fibre reinforced composites in non-structural applications. Acoustic emission (AE) proved useful for its capability of real-time monitoring over the whole material volume and high sensitivity to any process generating stress waves. This paper presents a literature review of AE applications in studies on natural fibre composites. The following fields of application are covered: (1) interface studies in single fibre composite (SFC) tests, (2) damage evolution and failure mechanisms detection and (3) crack propagation, including also current limitations of existing literature and future work.