冲击载荷下硼酸改性端羟基聚硅氧烷-二氧化硅复合材料的响应特性

为研究硼酸改性端羟基聚硅氧烷-二氧化硅轻质冲击硬化聚合物复合材料抗冲击特性及其机理，进行了单轴压缩、冲击试验；结合高速摄影和数字图像相关技术以及有限元仿真，研究材料的变形过程。结果表明：该材料在准静态载荷下呈黏性流动态，而在动态载荷下呈现固体状态，其流动应力提高了10⁴倍以上；当受到冲击载荷时，材料表现出一定的抗冲击性能，且抗冲击性能随着冲击速度和颗粒含量的提高而增强，材料在冲击过程中处于压力-剪力耦合应力状态，剪力所起作用随着冲击速度提高而逐渐增强；高速摄影结果显示，材料在冲击过程中发生阻塞转变，其中动态压缩导致材料局部硬化并表现出抗冲击特性，剪应力决定了材料抗冲击性能的应变率敏感性。因此，提高材料动态剪切响应是改善材料抗冲击性能的最优途径。

Mechanical Responses of PBDMS-silica under Impact Loading

The impact testing,quasi-static and dynamic compressions and finite element simulation were performed to investigate the impact-resistant properties and rate-dependence mechanism of an impacthardening polymer composite (PBDMS-silica).PBDMS-silica shows liquid-to-solid transition under impact loading,and such impact-resistant behavior is volume fraction-dependent and rate-dependent.This is confirmed by over 104 times increase in compressive and shear strength in the range from quasi-static to dynamic loading.Finite element method (FEM) shows a compression-shear-coupled stress state in PBDMS-silica during impact loading,and the shear stress plays an increasingly important role in impact resistance.Jamming transition is captured during the deformation of the impact-hardening polymer by high-speed imaging with digital image correlation (DIC) technique.Combined with the mechanical responses,the conclusions are made that jamming transition induced by dynamic compression is the source of impactresistant behavior,and the dynamic shear during impact determines how such behavior is rate-dependent.This provides a solution for the improvement of impact resistance by strengthening the dynamic shear response of the material.