## 1 Introduction  
Recently, the material's performance of energy absorption under extremely (high energy, up to tens of thousands of g) mechanical impacts have attracted much attention in many application fields such as the military, the vehicle, ballistic armor, and clothing industries. As demanded in the military field, the energy absorbing materials are applied to protect core electronic devices from extreme multi-impact, when the missile attacks buildings with multi-layer structures (Figure 1a,b) [1; 2; 3; 4]. In automobile electronics, the energy absorption materials are also important for protecting the core electronics system in a collision accident or even the multiple-collision accident (Figure 1c). The mechanical impacts in these scenarios have extremely high energy and are repeated many times within milliseconds. Hence, the energy absorption material in such applications must have both high energy absorption characteristics and good recoverability (small attenuation of energy-absorbing ability of the material in multi-impact) synchronously, which raises a serious challenge. High energy absorption characteristics are critically important for the protective effects, and many researchers have devoted a lot of efforts to improve them. Currently, the most widely applied materials with high energy absorption characteristics were the porous materials [5, 6, 7, 8], which could absorb a great amount of energy by plastic deformation, resulting from the compressibility of the pore structures [9, 10]. Numerous theoretical and experimental studies proved that porous materials not only had excellent energy absorption characteristics under the mechanical impact with huge energy, but also had a low density and good flexibility [11, 12, 13, 14]. However, despite the advantages of high energy absorption characteristics, porous materials are prone to have irreversible deformation after the first impact, severely damaging the energy absorption characteristics during the subsequent impacts [15]. Therefore, they still cannot fully meet the demand of electronics protection in multi-impact applications. The recoverability of energy absorbing materials is important for their good protective performances under the multi-impact process. Currently, the most popular deformation-recoverable materials were the elastic polymer materials [16, 17], which were widely applied as cushions, vibration reducers and impact energy absorbers [18, 19, 20]. Many studies have been carried out on the mechanical characteristics of elastic polymers [21, 22, 23], revealing that elastic polymers can keep almost unchanged energy absorption ability under continuously loading and unloading by hysitron triboindenter (Hysitron, USA) [24]. However, despite good recoverability, the energy absorption  
Figure 1: Application of energy absorption material under multiple extreme mechanical impacts: (**a**) Process of multi-impact in military application; (**b**) Installation of buffering material and protected part; (**c**) Continuous collision between cars. characteristics of elastic polymers under the single mechanical impact is significantly lower than those of porous materials [25], making them unable to meet the demand of electronics protection in missiles, automobiles and other extreme mechanical impacts. To solve the trade-offs between high energy absorption characteristics and recoverability, in this paper, a novel energy absorption method based on elastic polymer-modified porous material is proposed. The composite material is well designed to achieve both good energy absorption characteristics and high restorability simultaneously in the multi-impact process: the energy absorption is mainly realized through the deformation of the porous structure, and the recoverability of the composite material is improved owing to the micro-network structure of the elastic polymer. The composite made from porous carbon and elastomeric polymer fiber is taken as a case in this study. Additionally, the material design and parameter optimization are shown in this paper.