In-plane shear tensile characteristics of polyester composites: Effects of sunlight exposition

•In-plane shear tensile test is suitable for determine sunlight effect in composites.•The in-plane shear properties fit to exponent decreasing with exposition time.•Ageing of medium and high reactivity O-Phthalic polyester resins is studied.•The method for determination of service-life time to sun exposition is presented. This work focusses on the analysis of in-plane shear tensile test carried out on samples aged by UV–Visible light. The tendency of in-plane shear properties with exposure time fits to a decreasing exponential curve. Different thermosetting polyester resins, curing temperatures profiles, and fibreglass fabrics are employed for this study. The type of resin and curing temperature influence on elastic modulus and shear strength of composite. The ageing degree varies between 14% and 25%, depending on shear property and the composition.