Importance of fibre sizing on the seawater durability of carbon fibre laminates

The strong influence of the fibre sizing agent on the water absorption properties of carbon fibre laminates is demonstrated. A comparative experimental study is performed into the water absorption kinetics and maximum amount of absorbed water for laminates with sizing agent on the carbon fibres which are chemically compatible or incompatible with the polymer matrix. The water absorption rate is higher (by ~3 times), the time to saturation is much shorter (by ~ 6 times), and the water content at saturation is greater (by ~1.5 times) for the laminate with the incompatible fibre sizing agent. This laminate has relatively weaker fibre-matrix interfacial strength and contains a fine fibre-matrix interfacial cracks which aid the absorption and diffusion of water. The effect of the fibre sizing on the reduction to the strength properties of the laminates caused by the absorption of water is also investigated.