Comparing with static loading, dynamic loading can cause more extensive damage to constructions, air crafts, and vehicles. The development of advanced materials with high impact resistance is no doubt crucial for the protection of air crafts from debris, armed soldiers from bullets, and passengers in vehicles from crash and explosion. Nowadays, the sophisticated microstructures found in many biological materials that possess excellent mechanical properties have been inspiring researchers in understanding the “constituent-microstructure-property” relationships. For instance, previous study has shown that a bundle of spider silks with the diameter of a pencil can even stop a flying Boeing 747 airplane!
On June 1st, 2018, Xiaoding Wei’s group published an article titled “Dynamic shear-lag model for understanding the role of matrix in energy dissipation in fiber-reinforced composites” in Acta Biomaterialia, a prestige international journal in the field of biological and bio-inspired composites, to explain the secret behind the excellent impact performance of many biological materials.
Current design philosophy for synthetic ballistic composites emphasize mainly the role of long fibers with high stiffness and high strength. The role of matrix materials has not received enough attention. Nonetheless, this work found that the elastic waves in continuous fibers will synchronize shortly within a certain distance, meaning a low efficiency of the matrix to contribute to the energy dissipation process. Interestingly, sophisticated staggered microstructures have been found in many natural materials with high impact performance, such as shell, spiders silk, and bone. By proposing a dynamic shear-lag theoretical model, this work disclosed the important role of the viscoelastic matrix in the impact performance of fiber reinforced composites. It also highlights the close correlation between the energy dissipation and the mechanical properties of matrix and morphology of microstructures, helping people to understand the intrinsic mechanisms for the remarkable impact performance of natural materials.
Fig. 1 Sophisticated staggered microstructures can reactive the energy dissipation in matrix and thus greatly enhance the impact performance of composites.
Prof. Xiaoding Wei is the corresponding author, and Ph.D. candidate Junjie Liu is the first author of this paper. This work was supported by National “Young 1000 Talents” Program of China, National Natural Science Foundation of China, National Key Research and Development Plan of China and Beijing Innovation Center for Engineering Science and Advanced Technology.