Durability of bonded FRP-to-steel jointsEffects of moisture, de-icing salt solution, temperature and FRP type

This paper investigates the effects of environmental ageing on the mechanical response of adhesively bonded double-lap shear joints made of steel and CFRP or GFRP adherents. One hundred and ninety-two specimens, 84 joints and 108 material coupons, were aged for up to three years in various environments including (i) immersion in distilled water at 20\ua0\ub0C and 45\ua0\ub0C, (ii) immersion in de-icing salt solution at 20\ua0\ub0C and 45\ua0\ub0C and (iii) exposure to 95% relative humidity at 45\ua0\ub0C. In general, immersion at 45\ua0\ub0C resulted in noticeably greater strength reductions at both material and joint level. While the strength and stiffness of the joints made of GFRP material underwent significant reductions, the CFRP/steel joints were affected to a considerably smaller degree. FE simulations showed the impact of the permeability of FRP adherents and moisture distribution at the FRP/adhesive interface on the integrity and strength of the joints. The joint-level results are compared with the most relevant durability data in the literature