Role of Fiber Sizing in Interfacial Relaxation, Water Uptake and Fatigue Properties of Acrylic‐Matrix Composites

ABSTRACT Fiber‐reinforced infusible acrylic monomer resins are of interest as recyclable alternatives to epoxy and other thermoset resin composites, but the novelty of these resins causes published studies on acrylic‐matrix composites to often rely on multi‐compatible or other non‐tailored fiber sizing agents. It has been suggested that improvements to the mechanical properties, water absorption, and fatigue behavior may be gained with a sizing agent tailored specifically to acrylic resins. In this study, glass‐fiber/acrylic composites, treated with either a multi‐compatible sizing agent or an acrylic‐tailored sizing agent, are compared. Their retention of mechanical and fatigue properties after saturation with seawater, and the degree of interfacial relaxation during repeated absorption–desorption cycles, are used to explore the role of the sizing in water absorption. These results, supported by fractography, suggest that the tailored sizing agent did not significantly improve the water absorption behavior of the materials. The fatigue performance of the composites with the different sizing agents was similar. The static mechanical properties which are dominated by the fiber‐matrix interface, such as transverse tensile and flexural strengths, showed that the multi‐compatible sizing agent performed better than the tailored acrylic sizing agent.