Mechanical behaviour and durability of an epoxy adhesive for structural glass-to-steel connections in a ship

Abstract

The luxury yacht industry demands increased vessel transparency by enlarging glazed areas. Structurally integrating glass into yacht structures offers a solution to this. However, this requires a rigid and reliable connection between glass and metal components, which needs to be validated. Consequently, an epoxy adhesive is tested experimentally to evaluate its structural performance for such applications. First, tensile tests on dumbbell specimens are conducted at crosshead speeds of 0.1, 1, 10 and 50 mm/min and temperatures of −20, 23, 50 and 80 °C. Results show that both stiffness and strength increase with strain rate but decrease with increasing temperature, with significant loss at 80 °C. Second, shear tests on double-lap glass-to-steel specimens evaluate adhesion, using a bond thickness of 7 mm to accommodate geometric tolerances in a ship. This thickness is significantly larger than what is recommended by the manufacturer for maximum bond strength. Third, ageing tests are performed on dumbbell and double-lap specimens stored at 50 °C ± 1 °C and 94 ± 1 % relative humidity for six weeks. After ageing, tensile strength and stiffness of the epoxy reduced by 24 % and 51 %, respectively. While double-lap specimens exhibited reduced stiffness after ageing, the scatter on results could not be used to quantify stiffness and strength reduction. During the ageing period the amount of water absorbed by dumbbell specimens was estimated by weighing the specimens periodically. A correlation was found between amount of absorbed water and degraded properties. Based on its high strength and stiffness, epoxy has potential for structural glass-to-steel bonding. However, its viscoelastic behaviour makes it susceptible to temperature and load rate variations.