Modelling of the effect of ATH fillers on the rheology, curing kinetics, and flexural properties of the epoxy resin forming the hydraulic turbines' stay vanes extension

Abstract

Epoxy resins are essential for the manufacturing of GFRP/XPS foam sandwich structures used for hydraulic turbine extension stay vanes. Their properties during and after curing are key factors for the performance of the entire hybrid composite structure. This paper introduces experimental characterization and modeling of the influence of the quantity and size of ATH fillers on the curing and post-curing characteristics of the epoxy resin. The experimental investigation involves the maximum temperature, polymerization time, shrinkage, viscosity, and flexural properties. The mass fractions of the ATH were 10, 20, 30, 40, 50, and 60%, and the particle sizes were 2, 4, 6, 8, and 12 µm. In addition, we utilized the multivariate polynomial regression (MPR) and artificial neural network (ANN) methods to develop empirical models to predict the maximum temperature, polymerization time, shrinkage, and flexural modulus. The experimental results showed that increasing ATH mass fraction with smaller particle size delayed polymerization and lowered the maximum temperature. The experimental viscosity values showed that Mooney model can accurately calculate viscosity as a function of ATH mass fraction and particle size, compared to the Quemada and Krieger-Dougherty models. Adding ATH increased flexural strength, modulus, and breakage strain. The developed models achieved a higher than 0.9 correlation coefficient between the predicted and measured responses and can be used to enhance the design and control the casting of the proposed sandwich structures.