Crashworthiness – the ability of the structure to absorb impact energy, plays a critical role in protecting humans and objects from impact energy-induced friction, deformation and fracture. Porous structures have attracted significant research attention owing to their excellent physical and mechanical properties and energy absorption capacity. Porous structures can be grouped into two: two-dimensional (2D) ones like honeycomb structures and three-dimensional (3D) ones like lattices, bones and foam structures. These structures, some of which are complex, have been effectively produced with the advances in 3D manufacturing technologies.
Generally, 3D lattice structures possess great mechanical and physical properties. Among them is the Triply Periodic Minimal Surface (TPMS) which is familiar in many fields due to its high energy absorption capability and efficiency as well as excellent performance. Numerous theoretical and experimental studies have been conducted to study different TPMS-based lattice structures, their performance, properties and the influence of different parameters. However, there are no studies on their crashworthiness properties.
Recently, there has been an increasing number of studies exploring the characteristics of animals and plants, which have inspired the design of different structures capable of adapting to various environmental conditions. Specifically, animal bones have remarkable impact resistance as their microstructures have continuous, porosity and non-uniform wall thickness characteristics. Despite the significant progress, there are still no reports on applying bionic-inspired ideas to improve the original structure and mechanical properties of the TPMS structures that are generally akin to natural biological microstructure.
To this note, Hunan University researchers: Mr. Hui Wang, Mr. Dingwen Tan, Professor Hanfeng Yin and Professor Guilin Wen together with Mr. Zhipeng Liu from Shanghai Jiao Tong University designed and investigated the crashworthiness properties of three novel composite TPMS-based porous structures consisting of inner and outer surfaces: PI-type, PIP-type, and PN-type. The design, which involved splicing TPMS structures using Sigmoid function surface splicing technique, was inspired by the microscopic porous structure of animal bones. The deformation and crashworthiness properties of the structure under impact loading were simulated using the finite element method. A quasi-static compression experiment on PI structures fabricated via 3D printing was used to validate the finite element models. The work is currently published in the journal, Engineering Structures.
The authors showed that the energy absorption capability and deformation mode of the structures were significantly influenced by the thickness ratio of the outer and inner surfaces. At a thickness ratio of 0.5, a large platform area of the force curve characterized by better energy absorption efficiency was obtained. Compared with the traditional foam structures, it was shown that the PIP structures with thickness ratios of 0.4 and 0.5 and the PI structures with thickness ratios of 0.3 and 0.4 exhibited superior energy absorption efficiency and capacity as well as lower peak crushing force. For example, the energy absorption efficiency and capacity of the PI-0.4 were 12.1% and 10.8%, respectively, higher than those of foam.
A combination of numerical simulation, full factor method and complex proportional assessment was utilized to study the relationship between the thickness parameter and the crashworthiness index. Based on the evaluated crashworthiness indicators, results showed that the PI structure with a thickness ratio of 0.4 produced the best crashworthiness property, followed by PIP structure with a thickness ratio of 0.5. Furthermore, an approximate formula for determining the average crushing force of the structure was proposed based on the Gibson empirical formula.
In summary, the design of novel composite TPMS-based porous structures with better crashworthiness properties (energy absorption capacity, improved energy absorption efficiency and lower peak crushing force) was reported. The experimental results agreed well with the simulation results. These structures have good application prospects in different fields, especially in the military and aerospace industries. In a statement to Advances in Engineering, Professor Hanfeng Yin, the corresponding author stated that their study provided valuable insights that would guide the design of novel TPMS-based porous structures with a smooth transition, better crashworthiness properties and improved overall performance.
Wang, H., Tan, D., Liu, Z., Yin, H., & Wen, G. (2022). On crashworthiness of novel porous structure based on composite TPMS structures. Engineering Structures, 252, 113640.