In this study, matrix is polypropylene, and reinforcement is glass fiber for manufacturing GFRP. Effect of fiber content and fiber orientation angle on tensile strength is evaluated. In addition, IR thermography is applied to detect temperature distribution during crack propagation and temperature change due to load on test specimen, which is not the existing non-destructive analysis method. Using lock-in IR thermography method that can detect minute change of temperature, temperature change from energy dissipation during tensile test and temperature distribution during crack propagation is monitored. Tensile strength of unidirectional GFRP is decreased from 0 degrees to 90 degrees. In addition, 20 wt% of fiber content shows the higher decrease of tensile strength than the one with 10 wt%. For higher than theta = 40 degrees of fiber orientation angle, tensile strength ratio becomes lower than the one for polypropylene (matrix), and there is no effect of fiber reinforcement. Get nearer to 90 degrees of fiber orientation angle forces longer fracture time, and maximum temperature is decreased accordingly. Fracture is occurred right after maximum stress point, and it is related with tensile strength. (C) 2014 Elsevier Ltd. All rights reserved.