Evaluation of Influence of Surface Roughness Orientation in CFRP Lap Joints using AE and DIC

Abstract

This paper investigates the effects of emery abraded surface roughness orientation on the shear strength of the carbon fiber reinforced polymer (CFRP) single lap joint (SLJ). For this purpose, three roughness patterns of angles 0°, 45°, and 90° with the longitudinal axis of adherend were considered in the overlap area of the SLJ. The surface roughness was characterized by contact-based roughness measurement and contact angle between the water droplet and the adherend surface. Through-the-thickness full-strain field measurement was carried out during shear strength tests using digital image correlation (DIC). The peel and shear stress at the overlap end were highest in the 90° coupons and least in 0° coupons. Acoustic emission testing (AE) was carried out during the shear strength testing of the SLJ. The investigation proves that the surface roughness orientation at the interface of bonded joints affects the acoustic emissions generated. AE hits and amplitude parameter distribution was found to change with the change in orientation. AE hits were more in 90° samples and least in 0° samples.