Freedom of design, mass customisation, waste minimisation and the ability to manufacture complex structures, as well as fast prototyping, are the main benefits of additive manufacturing (AM) or 3D printing. A comprehensive review of the main 3D printing methods, materials and their development in trending applications was carried out. In particular, the revolutionary applications of AM in biomedical, aerospace, buildings and protective structures were discussed. The current state of materials development, including metal alloys, polymer composites, ceramics and concrete, was presented. In addition, this paper discussed the main processing challenges with void formation, anisotropic behaviour, the limitation of computer design and layer-by-layer appearance. Overall, this paper gives an overview of 3D printing, including a survey on its benefits and drawbacks as a benchmark for future research and development.

Additive manufacturing (3D printing): A review of materials, methods, applications and challenges

It is widely known that the availability of lightweight structures with excellent energy absorption capacity is essential for numerous engineering applications. Inspired by many biological structures in nature, bio-inspired structures have been proved to exhibit a significant improvement over conventional structures in energy absorption capacity. Therefore, use of the biomimetic approach for designing novel lightweight structures with excellent energy absorption capacity has been increasing in engineering fields in recent years. This paper provides a comprehensive overview of recent advances in the development of bio-inspired structures for energy absorption applications. In particular, we describe the unique features and remarkable mechanical properties of biological structures such as plants and animals, which can be mimicked to design efficient energy absorbers. Next, we review and discuss the structural designs as well as the energy absorption characteristics of current bio-inspired structures with different configurations and structures, including multi-cell tubes, frusta, sandwich panels, composite plates, honeycombs, foams, building structures and lattices. These materials have been used for bio-inspired structures, including but not limited to metals, polymers, fibre-reinforced composites, concrete and glass. We also discussed the manufacturing techniques of bio-inspired structures based on conventional methods, and adaptive manufacturing (3D printing). Finally, contemporary challenges and future directions for bio-inspired structures are presented. This synopsis provides a useful platform for researchers and engineers to create novel designs of bio-inspired structures for energy absorption applications.

A review of recent research on bio-inspired structures and materials for energy absorption applications

The review outlines modern trends in theoretical developments, novel designs and modern applications of sandwich structures. The most recent work published at the time of writing of this review is considered, older sources are listed only on as-needed basis. The review begins with the discussion on the analytical models and methods of analysis of sandwich structures as well as representative problems utilizing or comparing these models. Novel designs of sandwich structures is further elucidated concentrating on miscellaneous cores, introduction of nanotubes and smart materials in the elements of a sandwich structure as well as using functionally graded designs. Examples of problems experienced by developers and designers of sandwich structures, including typical damage, response under miscellaneous loads, environmental effects and fire are considered. Sample applications of sandwich structures included in the review concentrate on aerospace, civil and marine engineering, electronics and biomedical areas. Finally, the authors suggest a list of areas where they envision a pressing need in further research.

Review of current trends in research and applications of sandwich structures

Over the past several decades, a noticeable amount of research efforts has been directed to minimising injuries and death to people inside a structure that is subjected to an impact loading. Thin-walled (TW) tubular components have been widely employed in energy absorbing structures to alleviate the detrimental effects of an impact loading during a collision event and thus enhance the crashworthiness performance of a structure. Comprehensive knowledge of the material properties and the structural behaviour of various TW components under various loading conditions is essential for designing an effective energy absorbing system. In this paper, based on a broad survey of the literature, a comprehensive overview of the recent developments in the area of crashworthiness performance of TW tubes is given with a special focus on the topics that emerged in the last ten years such as crashworthiness optimisation design and energy absorbing responses of unconventional TW components including multi-cells tubes, functionally graded thickness tubes and functionally graded foam filled tubes. Due to the huge number of studies that analysed and assessed the energy absorption behaviour of various TW components, this paper presents only a review of the crashworthiness behaviour of the components that can be used in vehicles structures including hollow and foam-filled TW tubes under lateral, axial, oblique and bending loading.

https://myresearchspace.uws.ac.uk/ws/files/1765038/Paper_2.pdf

On the crashworthiness performance of thin-walled energy absorbers: Recent advances and future developments

A variational free-discontinuity formulation of brittle fracture was given by Francfortand Marigo [1], where the total energy is minimized with respect to the crackgeometry and the displacement field simultaneously. The entire evolution of cracksincluding their initiation and branching is determined by this minimization principlerequiring no further criterion. However, a direct numerical discretization of themodel faces considerable difficulties as the displacement field is discontinuous inthe presence of cracks.

A Continuum Phase Field Model for Fracture

Experimental study on crashworthiness of empty/aluminum foam/honeycomb-filled CFRP tubes

Lightweight design of carbon twill weave fabric composite body structure for electric vehicle

Nature has provided us with extraordinary resources to tackle design challenges facing in modern society nowadays. The multistate structures inspired by animal shell have proven effective to improve the impact resistance of composite laminate. This study aims to identify the crash responses and crashworthiness characteristics of bio-inspired sandwich structures composed of carbon fiber reinforced plastic (CFRP) panels and aluminum honeycomb. The crash responses, failure mode as well as the effects of core side length, height and impact velocity on peak load and energy absorption were explored herein. The differences of crashworthiness characteristics between the CFRP aluminum honeycomb sandwiches and bare CFRP panel were quantified. Two typical load-displacement relations, namely single-peak and double-hump curves, were observed in the tests. It was noted in the energy-displacement curve, where the slopes corresponding to the failure stages of the upper and lower face-sheets, were greater than that in the honeycomb failure stage, indicating that the bare aluminum honeycomb was of lower energy absorption capacity than the CFRP face-sheet. By comparison, the honeycomb filling was an effective way to improve the impact resistance of CFRP structure, yielding higher energy absorption and lower peak load during the impact. It was also found that the crashworthiness characteristics were more sensitive to the core length than to the core height; and the specific energy absorption (SEA) varied insignificantly with the increase in the core height. It was noted that the peak load, absorbed energy and SEA increased significantly under high impact velocity.

Dynamic crash responses of bio-inspired aluminum honeycomb sandwich structures with CFRP panels

On design of multi-cell thin-wall structures for crashworthiness

Bio-inspired engineering design has drawn considerable attention in the recent years for its great structural and mechanical features. This study aimed to explore the energy absorption characteristics of a novel bionic-bamboo tube (BBT) structure subjected to axial crushing. The tubes with six different cross-sectional configurations were devised with inspiration of bamboo microstructure. The effects of rib shape and rib number were analyzed by using the finite element code LS-DYNA. The numerical results indicated that the BBT structures with the rib shape of “X” and the rib number of six exhibited the best crashworthiness. To further improve the energy absorption capabilities of these BBT structures, the multiobjective optimization was employed with respect to design variables of configurational structure, such as the rib angle of the “X” shaped cross-section, center distance and rib thickness. The response surface method (RSM) and multiobjective particle swarm optimization (MOPSO) algorithm were adopted to maximize specific energy absorption (SEA) while minimizing peak crushing force (PCF). The optimization results demonstrated that compared to the baseline design, the SEA value of the optimized BBT structure was further increased by 6.84% without sacrificing in peak crushing force.

Qiang Liu

Papers

Experimental study on crashworthiness of empty/aluminum foam/honeycomb-filled CFRP tubes

Lightweight design of carbon twill weave fabric composite body structure for electric vehicle

Dynamic crash responses of bio-inspired aluminum honeycomb sandwich structures with CFRP panels

On design of multi-cell thin-wall structures for crashworthiness

Design of bionic-bamboo thin-walled structures for energy absorption