## 2 Materials and Methods
The detailed proportions of the samples are listed in Table 1. The impact tests are conducted on the samples, in order to understand the influence of the EPDM rubber proportion on the energy absorption characteristics. The tensile tests of M0 (0% rubber), M2 (10% rubber), and M4 (20% rubber) are conducted in Figure S1 of Supporting Material, to reflect the influence of the EPDM rubber proportion on the tensile characteristics. A machete hammer, an equipment for extreme impact tests (Figure 4a), is used in this paper. The kinetic energy, obtained from releasing the counterweight, accelerates the hammer bar, which is connected to the gear. Consequently, the hammer head, including the test device, hit the base at a certain speed. During the impact process, the speed of the hammer head decreases to zero rapidly within milliseconds, and the high acceleration is generated. As the hammer bar is connected to the gear, the release height can be controlled by adjusting the tap position number of the gear that turns. The test device is designed in Figure 4b, for the purpose of studying the energy absorption characteristics of samples. The base of the test device is fixed on the hammer head by screw thread, and the high-g acceleration sensor and aluminum structural part is sealed as a whole with black epoxy resin representing controller. The aluminum structural part (containing acceleration sensor) is placed in the base, and both sides of it are test material with thickness of 2 mm. During experiments, the power supply wires and signal wire of the high-g acceleration sensor are connected to a voltage-stabilized source and oscilloscope by three core shielding wire, respectively. The voltage-stabilized source \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Sample**} & \multicolumn{2}{c}{**Mass/g**} & \multirow{2}{*}{**Mass Ratio of EPDM**} \\ \cline{2-3}  & **Activated Carbon Film** & & **EPDM Rubber** \\ \hline M0 & 60 & 0 & 0\% \\ M1 & 60 & 3 & 5\% \\ M2 & 60 & 6 & 10\% \\ M3 & 60 & 9 & 15\% \\ M4 & 60 & 12 & 20\% \\ M5 & 60 & 18 & 30\% \\ M6 & 60 & 24 & 40\% \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Samples of different mass ratio of EPDM (Ethylene-Propylene-Diene Monomer) rubber. Figure 4: (a) Machete hammer test schematic diagram; (b) Structure drawing of the test device. can provide stable 3.3V for the acceleration sensor, and the oscilloscope can obtain output signals of the acceleration sensor in real time during the test process, in order to quantitatively analyze the record data and evaluate the energy absorption and buffering characteristics of the samples. Control variable method is adopted in the experiment to ensure that other influencing factors remain relatively consistent, including the thickness of test material and falling height of the counterweight of the machete hammer. The experiment steps are shown as follows. 1. Collect the overload acceleration of a height in the case of no buffering material. No material is placed on the upper and lower contact surfaces of the aluminum structural parts (including sensor) inside the test device. The machete hammer bar is lifted to the specified height and the gear is jammed by the limit switch. After releasing the limit switch, the hammer head hits the base and the acceleration sensor will collect the overload acceleration. 2. Collect the overload acceleration of the same height buffered by the test material. The test material is placed on both contact surfaces of the aluminum structural parts (including sensor) inside the test device, and the machete hammer bar is lifted to the same height. After releasing the limit switch, the hammer head hits the base and the acceleration sensor acquires the overload acceleration of the height, buffered by the test material. 3. If the energy absorption characteristics in the single impact process are studied, change the test material and repeat step 2; if the energy absorption characteristics in the multi-impact process are studied, repeat step 2 and do not change the test material.