Determinating optimum combination of ageing and manufacturing parameters for laminated composites using response surface methodology

This study mainly focuses on the effects of ageing and manufacturing parameters on the water absorption behaviour and mechanical characteristics of the glass-fibre reinforced polymer (GFRP) composites, and multiple optimizations of these parameters based on the quasi-static mechanical properties and low-velocity impact performances. Utilizing response surface methodology (RSM), an experimental design was executed varying curing temperature (20-100°C), ageing temperature (20-70°C) and salinity (3-35%). After 59-days ageing period, gravimetric, tensile and low-velocity impact tests were conducted to assess weight gain at saturation, changes in tensile strength, elasticity modulus, peak force and peak energy. Tensile fracture surfaces of aged and un-aged samples were examined using scanning electron microscopy. ANOVA results indicated the adequacy of RSM models, supported by high R² (>80%) and R²_adj (>65%) and proper residual distribution. Gravimetric tests revealed that higher curing and ageing temperatures resulted in greater water sorption-induced weight gain, while elevated salinity had the opposite effect. Ageing temperature and salinity are the most influential factors on tensile strength change. Optimal mechanical properties, minimizing differences between aged and un-aged samples, were achieved at 100°C curing temperature, 20°C ageing temperature and 19.8% salinity. Data from this study can be a valuable reference for designing GFRP composites, particularly in marine applications.