## 4 Conclusions  
Based on the anti-lightning strike background of composite materials widely used in aircraft structure design, the thermal explosion phenomenon of composite materials is rarely studied. The blow-off impulse effect of a composite reinforced panel induced by lightning strike is studied through numerical simulation in this paper. A method integrating electric-thermal coupling with an explicit dynamic is proposed in order to study the blow-off impulse effect of a composite reinforced  
Figure 16: Contours of von Mises and pressure in the T stripper. (**a**) Contours of von Mises stress; (**b**) pressure contours.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Serial Number** & \begin{tabular}{c} **Element** \\ **Dimension/mm** \\ \end{tabular} & \begin{tabular}{c} **Damage** \\ **Depth/mm** \\ \end{tabular} & \
\begin{tabular}{c} **Error** \\ **Area/mm2** \\ \end{tabular} &
\begin{tabular}{c} **Failure** \\ **Error** \\ \end{tabular} \\ \hline Mesh-1 & 8.33 \(\times\) 7.0 \(\times\) 0.15 & 1.088 & - & 1050 & - \\ Mesh-2 & 8.47 \(\times\) 7.0 \(\times\) 0.15 & 1.080 & 7.30\% & 936 & 10.8\% \\ Mesh-3 & 8.62 \(\times\) 7.0 \(\times\) 0.15 & 0.962 & 11.58\% & 864 & 17.7\% \\ Mesh-4 & 8.92 \(\times\) 7.0 \(\times\) 0.15 & 0.615 & 43.47\% & 670 & 36.2\% \\ Mesh-5 & 10.0 \(\times\) 7.0 \(\times\) 0.15 & 0.550 & 49.48\% & 500 & 52.3\% \\ \hline \hline \end{tabular}
\end{table}
Table 8: Comparison of calculation results for different element dimensions.  
Figure 15: Overall pressure contours of the composite reinforced panel.  
panel. The damage mechanism of a composite reinforced panel caused by the blow-off impulse effect is discussed. The conclusions can be summarized as follows:  
1. The blow-off impulse effect alters the damage distribution caused by the electric-thermal coupling effect, which makes the damage distribution deviate from the initial fiber direction in each layer.
2. The blow-off impulse effect could well present the internal damage, concave pit, and bulge phenomenon around the attachment area of lightning strike, and the failure modes in the blow-off impulse area are similar to the damage forms caused by lightning strike.
3. Pressure increases sharply when explosion begins, and then decreases gradually with the increase of time and tends to balance in the end. The pressure of composite materials is not presented as anisotropic but isotropic, agreeing well with the observed characteristic that mechanical behavior of composite materials exhibits anisotropic in low pressure while isotropic in high pressure.  
The results obtained in this study can reflect the dynamical damage behavior of composite materials induced by lightning strike to some extent. However, phase transition and delamination are other important damage modes of composite materials, which have not been involved in this study. Therefore, this field needs to be further considered in future investigations.  
Data curation, S.J. and W.H.; formal analysis, S.J., F.W., W.H. and B.X.; methodology, S.J., F.W. and B.X.; writing--original draft, S.J. and F.W.  
This research was funded by the National Natural Science Foundation of China, grant number: 51875463 & 51475369, the Natural Science Basic Research Plan in Shaanxi Province of China, grant number: 2018 JM1001.  
This study is supported by the National Natural Science Foundation of China (No.: 51875463 & No.: 51475369), the Natural Science Basic Research Plan in Shaanxi Province of China (No.: 2018 JM1001).  
The authors declare no conflict of interest.