Pyrolysis, carbonization and other reactions would occur in laser irradiated Glass fiber reinforced epoxy resin composite (GFREC). Different laser irradiation time experiments were carried out to get some ablation samples. With the help of X-ray diffraction (XRD) and Raman spectroscopy(RS, graphite microcrystals were found in the severe ablation GFREC. The temperature of laser irradiated GFREC was calculated by using energy conservation equation and pyrolytic decomposition equation, and we found the temperature of laser induced graphite production was about 800°C. And then the information of graphite microcrystals was characterized by 5th order Gaussian function curve-fitting analysis. Results showed that the sizes of graphite microcrystals were several nanometers.
The energy deposition efficiency of high energy laser irradiation on painted metal was studied. Experiments of uniform 1 070 nm continuous wave (CW) laser beams irradiating an entire 10 mm quadrate surface of gray epoxy painted iron were performed to investigate the laser-heating-induced changes of the surface absorption behavior. Laser power densities were set as 54-233 W/cm2 and temperature rising processes of the painted iron specimens were monitored. By means of heat transfer inversion calculation, the absorptivity data during laser irradiation were obtained, of which the good accuracy was further proven by optical measurements. It is found that the absorptivity showed strong temperature-dependence properties in spite of the different laser power densities. During temperature increasing from 20 to 1 300°C, the temperature-dependent absorptivity experienced four stages, i.e. slowly decline, rapidly decline, slowly increase, and rapidly increase.The visualized color of gray coating layer changing to white at 510°C and physical broken at 1 050°C were the main reasons for absorptivity rapid changes.
For mechanical properties temperature dependence test in high temperature rising rate, a method of heating specimen using two-sided laser irradiation is proposed. Simulation about different materials in laser heating about different laser power density and different laser duration were conducted. The result shows that two-sided laser irradiation can obviously improve the temperature field of the specimen in normal laser irradiating. The simulation shows that this method is better for metal than composite materials because of the heating pyrolisys may have a bad influence on the thermal balance. Based on this method, the tensile strength temperature dependence of the T700 carbon fiber laminate was obtained. The result is close to the parameter obtained in electrical mechanical machine by furnace heating. The research can make a reference for the mechanical properties test of composite materials or metal in high temperature with high heating rate.