Abstract

Fly ash is a spherical micron sized particle and suitable as filler of polymers (i.e. epoxy) to increase their mechanical properties. To obtain a compromise result of mechanical properties (such as tensile strength and elastic modulus) of fly ash-filled polymer, the content of fly ash is a key factor. The objective of the present paper is to investigate the effect of fly ash volume fraction on the tensile properties of epoxy adhesive and the strength of adhesively bonded steel joints. Fly ash was surface-treated using alkali solution (10% by weight) before being used to fill the epoxy resin. The epoxy was based on a diglycidyl ether of bisphenol-A (DGEBA) with a hardener of a cycloaliphatic amine, EPH 555. The content of fly ash in the epoxy resin was 0, 5, 10, 15, 20 and 25% (by volume). The results show that the tensile strength of fly ash-filled epoxy tends to decrease in essentially linear with the increase of fly ash content. The decrease of tensile strength is significant when the fly content is higher than 5%. The same trend as for the tensile strength is also shown for the strain at break. As a result of introducting rigid particles into the epoxy, the elastic modulus of fly ash-filled epoxy tends to increase with increasing the fly ash content. In adhesive joints, the effect of fly ash content on the shear strength of steel bonded joints seems not to be significant as the failure of the joints is mostly interfacial.

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