Influence of seawater immersion on acrylic adhesive properties and bond strength on wet composites

This paper describes a study on an acrylic based adhesive developed for marine repair applications. The adhesive alone was aged for over 12 months and tensile samples were tested periodically to characterize the influence of seawater aging at 40 °C. The adhesive alone plasticizes in seawater, losing around 40 % of both modulus and strength after 12 months, but these are largely recovered after drying. In parallel, adhesively bonded glass and carbon fibre composite assemblies were tested after similar aging times. Both retain over 80 % of unaged apparent shear strength after 12 months in natural seawater at 40 °C. Adhesive bonding of wet composite substrates, which had been immersed in seawater for up to 12 months before bonding, was also evaluated to determine residual bond strength. The break strengths of assemblies of wet glass fibre composites were not affected by substrate immersion for up to 12 months before bonding, while strengths of carbon fibre composite assemblies dropped to around 50 % after prolonged substrate immersion. Reasons for this difference are discussed. The results suggest that this adhesive shows good durability and should be considered for marine repair applications.