The paper presents water uptake and tensile properties of epoxy filled with inorganic fillers having different reactivity to water, namely Portland cement, fly ash, and calcium carbonate (CaCO 3) particles. Portland cement and CaCO 3, respectively have the highest and the lowest water reactivity. The filler volume fraction was ranging from 0 to 25 %. The results showed that for the reactive filler, with the increase of volume fraction, the water uptake increased and behaved as non-Fickian, whereas for the less reactive filler, the water uptake decreased and behaved as pseudo-Fickian. In dry condition, with the increase of volume fraction, the elastic modulus and tensile strength increased and tended to decrease, respectively, regardless of the filler type. However, in wet condition, the positive effect of filler on the elastic modulus diminished due to excessive plasticization of the matrix, and the reduction of elastic modulus of the most reactive filler is the lowest.

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The paper presents water absorption and its effect on the tensile properties of hybrid of fly ash-CaCO3-filled epoxy. The total filler content was 20wt%, with the fly ash to CaCO3 ratios were 20/0, 15/5, 10/10, 5/15 and 0/20. Adding fillers into epoxy decreased the water uptake in the ranges of 15 - 22%, where the lowest and the highest water uptake of the hybrid systems belonged to the fly ash/CaCO3 ratios of 15/5 and 20/0, respectively. The tensile strength and elastic modulus continued to decrease with aging time for all epoxy systems. At the saturation level, the tensile strength and elastic modulus of filled epoxies were improved compared to the unfilled epoxy, except for the hybrid of fly ash/CaCO3 of 15/5. The fracture strain as well as the tensile toughness were considerably increased at the equilibrium. A scanning electron microscopy revealed that in dry condition the fly ash was well bonded with the matrix, but not for the CaCO3 particles. In the semi equilibrium and equilibrium states, the fly ash and CaCO3 were mostly detached from the epoxy. The hybrid of fly ash/CaCO3 of 15/5 was not recommended as it decreased the tensile properties more than the other hybrid compositions.

This paper presents the effect of adhesive layer thickness on the static strength of adhesively bonded steel-glass fiber-reinforced unsaturated polyester resin (GFRP) lap joints after being aged in water at a temperature of 60°C for 15 days. The adhesive thickness was varied from 0.1 mm to 0.5 mm. It was found that for the dry joints, the static strength increased with the increase of adhesive thickness. However, in wet condition, water really had a significant detrimental effect on the strength of the joints, as most of the strengths of wet joints were much lower than those of the dry joints. In dry condition, mode of failure changed from interfacial (at the adhesive thickness of 0.1 mm) to mix failure; however, for the wet joints; most of failures were at the interface of adhesive/steel.

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