Bamboo-inspired hierarchical microlattice structures (BHMSs) for high strength and energy absorption

AbstractMechanical metamaterials as a category of lightweight materials have exhibited superior specific mechanical properties and energy absorption. However, lack of reasonable structural design always results in weakening or failure to achieve the optimal mechanical performance of metamaterials. Here, we firstly adopted bio-inspired and structural optimization methods to guideline the design of microlattice structures. Inspired by the strong and ductile 'Moso' bamboo, three bamboo-inspired hierarchical microlattice structures (BHMSs) were initially designed, and the bamboo's features, viz., hollow, gradient distribution, and cellular, were imitated by designed BHMSs. Optimization design with the objective of maximum ratio of strain energy and reaction force was carried out to furthermore improve the mechanical properties of BHMSs. Afterwards, the optimal BHMSs were printed via Stereolithography. The compressive responses of BHMSs were elaborated by experiments and simulation. Results show that these designed biomimetic structures can be easily tailored via tuning the geometric sizes of unit cell, achieving high compressive specific modulus and strength 48.16 kPa m3 kg−1 and 1389.23 Pa m3 kg−1 and the energy-absorbing efficient 85.43% in the octet bamboo-inspired hierarchical microlattice structures (OCT BHMSs). The design strategies and findings shed light on the realization of advanced metamaterials with tailored mechanical properties. How to design ordered cellular structures for lightweight structures with high mechanical strength and energy absorption efficiency remains a crucial challenge in automation, aerospace and lightweight construction fields. Inspired by the lightweight and high load-bearing capacity of nature bamboos and metamaterials in the previous researches (Song et al., Materials & Design, 2019, 173: 107773; Song et al., International Journal of Fatigue, 2017, 100: 126), here a comprehensive approach of bionics and optimization was proposed to design hierarchical microlattice structures with lightweight, good mechanical properties and high energy absorption efficiency. The bamboo's characteristics, including hollow, gradient enhancement, and cellular, were completely copied to reasonably produce hierarchical microlattice configurations, while the optimal sizes were obtained though the optimization design.HighlightsA combination strategy of bamboo-inspired and optimization design to realize light-weight and high mechanical metamaterials was provided.Mechanical properties of biomimetic structures can be tailored by tuning dimensions based on optimization.A high energy absorption efficiency in octet-truss bamboo-inspired hierarchical microlattice structures.Keywords: Bionicsoptimizationlattice materials3D printingcompressive behaviorenergy absorption Authors' contributionJian Song: Writing- review & editing. Junfei Yan: Conceptualization. Bengang Yi: Supervision. Wenyuan Gong, Zhaojun Du, Zihao Pu: Simulation. Tengyong Liu, Changchun Xie, Darong Liang: Experiment.Disclosure statementWe declare that we have no financial and personal relationships with other people or organizations that can inappropriately influence our work, there is no professional or other personal interest of any nature or kind in any product, service and/or company that could be construed as influencing the position presented in, or the review of, the manuscript entitled, "Bamboo-inspired hierarchical microlattice structures (BHMSs) for high strength and energy absorption".Additional informationFundingThe authors would like to gratefully acknowledge the financial support of the Shenzhen Science and Technology Innovation Program (Grant Nos. KQTD20200820113004005, KQTD20180412181337494).