Life prediction of adhesive steel joints under ageing stress – experimentally based model validation

Predicting the ageing behaviour of adhesively bonded joints is a key challenge in adhesive bonding technology and is essential for their broader use in steel construction. This paper presents a method for predicting the long-term performance of thick-layer adhesive bonds under hygro-thermo-mechanical (htm) stress. This approach is based on experimental investigations into the water absorption of the adhesive, which is recorded gravimetrically and described using Fickian´s diffusion model. Different temperature and humidity influences on the diffusion parameters are considered using an Arrhenius approach. The mechanical behaviour is analysed by means of quasi-static tests and systematic creep experiments different specimen geometries. Numerical modelling is based on an adhesive layer equivalent model that represents the linear viscoelastic behaviour and damage resulting from htm loading. Temperature and humidity influences are recorded via a time-temperature-water concentration shift, and the multi-axial nature of the failure is described via a comparative stress. Validation is performed using component-like specimens and transient FE simulations with LS-DYNA, which utilise the coupling of diffusion and heat conduction problems. The case study shows that the developed concept enables a reliable life prediction and thus contributes significantly to confidence in adhesive bonding technology.