The Study of the Behaviour of Carbon Epoxy Composites Using Acoustic Emission

Acoustic Emission (AE) is a naturally occurring phenomenon whereby external stimuli, such as mechanical loading, generate sources of elastic waves. AE occurs when a small surface displacement of a material is produced. These AE are generated by localized sources within the structure, which travel through the interior of the material by the shortest path and get picked up by several AE sensors placed on its surface. The Acoustic Emission NDT technique is based on the detection and conversion of these high frequency elastic waves to electrical signals. These are accomplished by directly coupling piezoelectric transducers on the surface of the structure by means of a fluid coolant and are secured with tape, adhesive bonds or magnetic hold downs. The output of each piezoelectric sensor is amplified through a low noise preamplifier, filtered to remove any extraneous noise and furthered processed by suitable electronic equipment. This project aims at studying the behavior of carbon epoxy composite materials, under loaded condition that tend to fail mainly by the following modes, namely, matrix cracking, de-lamination, fiber breakage. The specimens are tested using the acoustic emission technique and sufficient amount of data is acquired from the acoustic emission equipment. Data acquired is processed using MATLAB and various plots are then plotted. The plots between various acoustic emission parameters obtained during the experiments were analysed to understand the process of failure in carbon-epoxy composite plate under tensile loading. Further the technique is applied for other specimens and data acquired is analysed to come to a strong conclusion about the behaviour of composites using the acoustic emission technique which proves to be a powerful NDT method