Cyclic ageing of adhesive materials

ABSTRACT

In real-world applications, adhesive joints are often exposed to the environment and can experience cyclic ageing conditions caused. However, the adhesive response under cyclic ageing is still relatively unexplored. In this study, hygrothermal ageing of an epoxy-based adhesive has been investigated by performing single cycle and cyclic ageing experiments. Different cyclic ageing strategies were followed in this research. In the first strategy the ageing time was set to a constant value and in the second approach, the maximum absorbed water content was limited for each ageing cycle. Absorption and desorption processes for each ageing cycle have been analysed using Fick’s law. This analysis allowed to determine the diffusion coefficients and assess how they are affected by cyclic ageing. Other parameters, such as the ability to absorb water, saturation time and the glass transition temperature were also studied as a function of the different ageing conditions. The experimental results of the cyclic ageing studies showed that the water diffusion process changes with ageing cycles. It was also found that the glass transition temperature decreases with ageing cycles. Numerical analysis was also conducted using Fick’s law constants. Good agreement between the experimental and numerical results was obtained.

KEYWORD:

• Adhesive
• hygrothermal ageing
• cyclic ageing
• Fick’s law
• diffusion coefficient