This work investigates the tensile testing of glass fibre-reinforced polymer (GFRP) composite material and its most influencing parameter. The GFRP constitutes bi-axial glass-fibre and epoxy-matrix. The three parameters considered for the tensile test are the load, elongation, thickness, and the experiment's factorial design is L9 orthogonal array. The percentage contribution of load, extension, and thickness for stress and strain is calculated using variance (ANOVA) analysis. Optimizating parameters made using response surface method (RSM). Since the solutions arrived at by this optimization process are promising, the optimized outcomes are high load, low elongation, and high thickness. Such works are beneficial for replacing concrete slabs constructed on the roads for rainwater harvesting. In such applications, non-crimp GFR panels with openings at regular intervals may replace concrete slab structures. A mathematical response surface model for the stress and strain parameters has been formulated. The model validation is done using the Pearson product-moment coefficient.