Evaluating the mechanical behavior of carbon composites with varied ply-thicknesses using acoustic emission measurements

Abstract

Laminates are produced by stacking prefabricated plies composed of fiber products. Within the aerospace industry, a ply thickness of 125µm is commonly regarded as the standard. Ply thicknesses of less than 100µm are generally considered as thin plies. Due to their ability to provide superior mechanical properties relative to conventional laminates thin-ply (TP) laminates are gaining interest in several high-tech industries. Although the research on TP laminates increased over the past few years, a comprehensive evaluation of the mechanical behavior of TP laminates accounting for the ply-thickness is an ongoing challenge due to the intricacies of ply interactions, and experimental difficulties. The mechanical response of fiber reinforced polymer laminates is governed by damage progression during loading, with the thickness of individual plies playing a crucial role in influencing the initiation and evolution of local cracks and failures. Therefore, in this study, the effective mechanical properties of carbon fiber reinforced polymer composite with varied ply thicknesses have been experimentally evaluated and the accumulation of the damage events has been monitored using acoustic emission measurements, utilizing a contactless laser vibrometer. In this experimental study, the ply thickness is increased in a systematic manner (ranging from 50µm to 200µm). Experimental investigation has been carried out in quasi-static tension and compression. The results show that unnotched TP laminates subjected to tensile loading demonstrate enhanced effective strength, attributed to less premature failure. Conversely, as the thickness of the lamina increases, there is a reduction in the overall strength of the laminate. However, in the case of the notched specimen lowest strength has been observed at a ply-thickness of 100µm in this study. Under compressive loading, unnotched and notched specimen tends to show similar mechanical behavior to unnotched specimens under tensile loading. The overall strength is raised with decreasing ply thickness. The findings from this study may be valuable for incorporating ply-thickness considerations into models for predicting the mechanical performance of laminates under dynamic loading.