Reversible energy absorption of elasto-plastic auxetic, hexagonal, and AuxHex structures fabricated by FDM 4D printing

Abstract

The present study aims at introducing reconfigurable mechanical metamaterials by utilising four-dimensional (4D) printing process for recoverable energy dissipation and absorption applications with shape memory effects. The architected mechanical metamaterials are designed as a repeating arrangement of re-entrant auxetic, hexagonal, and AuxHex unit-cells and manufactured using 3D printing fused deposition modelling process. The AuxHex cellular structure is composed of auxetic re-entrant and hexagonal components. Architected cellular metamaterials are developed based on a comprehension of the elasto-plastic features of shape memory polylactic acid materials and cold programming deduced from theory and experiments. Computational models based on ABAQUS/Standard are used to simulate the mechanical properties of the 4D-printed mechanical metamaterials under quasi-static uniaxial compression loading, and the results are validated by experimental data. Research trials show that metamaterial with re-entrant auxetic unit-cells has better energy absorption capability compared to the other structures studied in this paper, mainly because of the unique deformation mechanisms of unit-cells. It is shown that mechanical metamaterials with elasto-plastic behaviors exhibit mechanical hysteresis and energy dissipation when undergoing a loading-unloading cycle. It is experimentally revealed that the residual plastic strain and dissipation processes induced by cold programming are completely reversible through simple heating. The results and concepts presented in this work can potentially be useful towards 4D printing reconfigurable cellular structures for reversible energy absorption and dissipation engineering applications.

Femtosecond laser direct writing of functional stimulus-responsive structures and applications

“…In the last few years, the most promising stimuli-responsive structures with multiple customized functions have been made from shape memory polymers (SMPs) [20,21], liquid crystal (LC) polymeric materials [22,23], hydrogels [24,25], and tailored composite materials [26], among others. Furthermore, various manufacturing methods have been devised to prepare these intelligent structures with favorable characteristics of fast responses to external stimuli, such as fused deposition modeling, stereolithography, direct ink writing, digital light processing, electrospinning, and selective laser sintering [22,[27][28][29][30][31][32][33][34][35]. However, these fabrication techniques are subject to inherent limitations, including poor material applicability, low resolution, poor biocompatibility, complicated multiple processing steps, restrictions in surface design, and difficulty in fabricating three-dimensional (3D) structures with sophisticated morphologies.…”

Metamaterial boat fenders with supreme shape recovery and energy absorption/dissipation via FFF 4D printing

“…Lately, several researchers have attempted to investigate the shape recovery properties of different structures with complex geometries [30][31][32]. Namvar et al [30] proposed three architected metamaterials, including hexagonal, re-entrant, and AuxHex, with the aid of 4D printing for energy absorption applications with shape recovery properties. Results indicated that re-entrant lattice structures provided higher energy absorption capacity compared to the other proposed designs.…”

In-plane elastic property prediction of straight-arc coupled auxetic structures

“…A variety of auxetic structures have been designed, such as the re-entrant [15], AuxHux [16], star shape [17], and double-V [18] structures. Re-entrant structure is one of the most extensively investigated cells due to its easily controllable mechanical properties and convenient fabrication.…”