Experimental Testing of Composite T-Joints

Abstract

Composite T-joints are adhesively bonded joints between a base plate and a panel normal to it. These are crucial, yet, they remain a structural weakness of marine composite structures. A new T-joint configuration, namely, bonding ties, has recently emerged but has never been experimentally characterised. Moreover, honeycomb cores have been favoured over foam for high-performance applications, but the former remains comparatively understudied. Consequently, this paper undertakes the mechanical testing of both foam and honeycomb-cored T-joints, using four configurations: resin fillets, bonding angles, bonding angles with fillets and bonding ties. The results show that (i) peel strength is independent of the core employed; (ii) both resin fillets and bonding ties achieve the lowest peel strength, and thus, bonding ties are not recommended; (iii) for foam-cored T-joints bonding angles and bonding angles with fillets respectively yield a 42% and 96% increase in peel strength compared to resin fillets; and (iv) for honeycomb-cored T-joints, an increase in peel strength of 46% and 84% compared to resin fillets is achieved for bonding angles and bonding angles with fillets, respectively. These findings provide novel insights into the strength of composite T-joints and may inform regulatory developments, future numerical studies and the design of marine T-joints.