Bond behaviour of composite sandwich panel and epoxy polymer matrix: Taguchi design of experiments and theoretical predictions

Structural sandwich panels made of glass fibre reinforced polymer (GFRP) and a phenolic core are used to manufacture a new type of composite railway sleeper. As these sandwich panels are produced in limited thicknesses for production efficiency, they are bonded together by an epoxy-based polymer matrix with structural filler to manufacture the composite railway sleepers. In this paper, an investigation into the effects of the matrix properties, bond length, bond thickness and bond width on the bond behaviour between a composite sandwich panel and polymer matrix is discussed. The experimental program was designed by Taguchi method to minimise the number of required experiments, and the percentage contribution of each variable on the bond strength was evaluated using the analysis of variance (ANOVA). The results indicated that a polymer matrix with 40% filler and 60% resin (by volume) is optimal to satisfactorily bind the sandwich panels together. A bond length of at least 70 mm and bond thickness of 5 mm are necessary to effectively utilise the strength of the composite sandwich panel. The ANOVA showed that the bond thickness has the greatest influence, contributing 51% to the bond strength, while the properties of the polymer matrix, bond length and bond width contribute 33%, 15% and 1%, respectively. The proposed theoretical equations can reliably predict the failure load and failure mode of the bonded joints