## 1 Introduction
Furthermore, boundary conditions also have an obvious effect on the damage degree of composite materials during experiments. There are also representative studies on numerical simulation of the thermo-dynamic response of composite materials. [PERSON] et al. [11] analyzed the temperature distribution in composite laminates from the perspective of electric-thermal coupling. The results indicate that Joule heat influences lightning strike damage significantly. Specifically, intra-laminar delamination is caused by the decomposition of resin and a concave pit is formed due to the sublimation of fibers. [PERSON] et al. [12] predicted the thermal damage of composite panels subjected to lightning strike through electric-thermal coupling element. Meanwhile, the temperature-dependence material properties were considered as well. The results show that this simulation method is capable of capturing the damage size and the temperature profile in composite panels exactly. [PERSON] et al. [13] studied the intra-laminar delamination of CFRP laminates induced by lightning strike using temperature-dependence interface elements. [PERSON] et al. [14, 15, 16] has further conducted a series of studies on the thermo-dynamic response and the residual strength of composite materials after lightning strike, with fruitful results being achieved. Numerous studies on lightning strike protection have been conducted by many scholars [17, 18, 19, 20, 21]. Protective performances of different designs were compared and the best design scheme was proposed. In general, the above studies of composite materials induced by lightning strike have important reference value and guiding significance. But previous studies mainly focused on the ablation analysis of composite materials, the blow-off impulse effect caused by the thermal explosion was rarely studied. Nevertheless, the structural response of composite materials subjected to lightning strike involves complex damage types, such as thermal shock wave, phase transition and thermal explosion, etc. Therefore, lightning strike response cannot be analyzed only by ablation damage and the blow-off impulse effect should be considered. The vaporized gas enclosed in materials will lead to a thermal explosion when thermal pressure continues to increase, then the inner explosion phenomenon will be formed and result in blow-off impulse damage. Therefore, it is necessary to study the blow-off impulse effect of composite materials under high temperature, high pressure, and high energy. However, there are few studies on the blow-off impulse effect of composite materials subjected to lightning strike so far, and the related reports are rare too. Only a small amount of studies about the thermal shock wave effect of composite materials under radiation conditions such as laser and X-Ray are reported. At present, studies concerning the blow-off impulse effect are mainly presented as follows: For example, [PERSON] et al. [22; 23; 24] have conducted research about multi-physics effects on the surface of composite materials radiated by pulse, the material spatter caused by the pulse is called blow-off impulse. [PERSON] et al. [25; 26] studied the propagation rules of thermal shock wave in anisotropic material induced by X-Ray, damage characteristics of anisotropic material under strong radiation were also discussed. The results indicate that thermal shock waves exhibit different shapes under the radiation of soft and hard X-Ray, great differences exist in the form mechanisms of thermal shock wave, wave peak, penetration depth, gasification phenomenon, tensile intensity and so on. In this paper, a method which integrates electric-thermal coupling with an explicit dynamic is put forward to study the blow-off impulse effect of a composite reinforced panel induced by lightning strike. The dynamic failure model of a composite reinforced panel is established and the temperature distribution in the benchmark skin is analyzed. Blow-off elements are obtained according to the temperature distribution in benchmark skin.