Collapsible Energy Absorbers Research Articles

Folding Auxetic Polygonal Kirigami Tubes

Abstract Tubular auxetic structures have wide-ranging applications including medical stents, collapsible energy absorbers, and novel fasteners. To accelerate the development in these areas, and open up new application directions, an expanded range of design and construction methods for auxetic tubes is required. In this study, we propose a new method to construct polygonal cross-sectional auxetic tubes using the principles of origami and kirigami. These tubes exhibit useful global auxetic behavior under axial extension, despite the individual polygon faces not being auxetic themselves. In general, a flat kirigami sheet cannot be simply folded into a polygonal tube since this creates kinematic incompatibilities along the polygon edges. We resolve this issue by replacing the edge folds with an origami mechanism consisting of a pair of triangular facets. This approach eliminates the incompatibilities at the edges while maintaining a connection between faces. The proposed edge connection also introduces additional control parameters for the tube kinematics: for example, introducing a kinematic limit on tube extension and enabling non-uniform behavior along the length of the tube. The rich kinematic behavior possible with polygonal cross-sectional kirigami tubes has potential applications ranging from soft robotics to energy-dissipating devices.

Improvements in the lateral crushing behavior of syntactic foam‐filled glass fiber reinforced polymer tubes by the addition of straight and helical multiwalled carbon nanotubes

AbstractTo diminish the brittleness of glass fiber reinforced polymer tubes and syntactic foams, a novel composite tube filled with syntactic foam was proposed, in which thin‐walled tubes were reinforced by ribs and the syntactic foam core reinforced with multiwalled carbon nanotubes (MWCNTs). The influence of the ribs and the type and content of MWCNTs on the lateral crashworthy characteristics of composite tubes was investigated. Crushing experimental results indicated that the ribs contributed to improving the crashworthy performance for both hollow and foam‐filled tubes. The effect of the ribs on the energy absorption was more pronounced for the hollow tubes. Incorporation of straight or helical MWCNTs lead to improvement of the crush resistance and energy absorption for foam‐filled tubes. With the same MWCNT content, the peak load and absorbed energy of specimens with helical MWCNTs were nearly 14% and 13% higher than those of specimens with straight MWCNTs, respectively. Furthermore, analytical models were proposed to predict the load–displacement responses for foam‐filled tubes in the linear‐elastic, postcrushing, and foam‐compaction stages. The predicted results agreed well with experimental results. The resulting composite tubes are potential light‐weighted and crashworthy structures, which could be applied as collapsible energy absorbers in engineering fields.

Composite Plastic Hybrid for Automotive Front Bumper Beam

The bumper beam is a crucial component of the automobile bumper system, responsible for absorbing impact energy and enhancing the safety of passengers during collisions. This paper presents the design and experimental analysis of a 3D-printed composite–plastic hybrid light structure, designed as a collapsible energy absorber. Exploratory testing was conducted using low-impact tests to investigate the failure mechanism and energy absorption capacity of a spiral structure. The design process involved optimizing the spiral diameter by testing specimens with varying diameters between 0.5 cm and 2.5 cm, while keeping other geometric parameters constant. The study employed three types of 3D composite structures, including printed thermoplastic, printed thermoplastic reinforced with Kevlar fiber composite, and printed thermoplastic filled with foam. The thermoplastic–foam composite with nine spirals (diameter = 0.97 cm) yielded the best results. The new design demonstrated high energy absorption capacity and a controlled and progressive failure mechanism, making it a suitable candidate for energy absorption applications.

Effect of geometric irregularities induced during manufacturing of a crash-box on its crashworthiness performance

Imperfections associated with the geometric features of any component are inevitable during its fabrication and some of those can even have a drastic impact on its functionalities. One such case arises while fabricating one of the essential passive safety devices in an automobile called as 'thin-walled collapsible energy absorbers'. Thin-walled collapsible energy absorbers also known as crash-boxes are the tubular shell structures located in between the bumper and front side rails of an automobile. Crash-boxes collapse in a stable progressive manner to absorb kinetic energy of an external impact to protect the occupants during an accident. Tubular crash-boxes are generally manufactured by extrusion. Geometric imperfections in the form of irregularities in the shell thickness may be induced during extrusion of the crash-boxes. The present study aims to gauge the effects of irregularities present in the thickness of the extruded crash-box on it’s crashworthiness performance, numerically. Cylindrical aluminium alloy tubes are modelled as crash-boxes using ABAQUS/Explicit. The irregularities in the thickness of the tubular crash-box are modelled with the help of three different imperfect models. In every imperfect model, maximum variation in the thickness is kept within the tolerance value, provided by the standards DIN EN-755-9. The quasi-static axial collapse of these ‘imperfect’ cylindrical tubes is simulated and their crashworthiness performance indicators are compared with those of an ‘ideal’ circular crash-box. It is seen that the energy absorption and the mean crushing force reduced drastically due to these shell thickness irregularities in comparison to the ideal model. It is also observed that the mode of collapse of the circular tube changed from axi-symmetric concertina mode to the diamond mode due to irregularities in their thickness. Such significant change in the crashworthiness performance of crash-box may lead to a huge disaster in terms of human lives. Hence, crash-boxes should be fabricated carefully with more tight geometric and dimensional tolerances.

Crashworthy capacity of a hybridized epoxy-glass fiber aluminum columnar tube using repeated axial resistive force

A combination of aluminum columnar member with composite laminate to form a hybrid structure can be used as collapsible energy absorbers especially in automotive vehicular structures to protect occupants and cargo. A key advantage of aluminum member in composite is that it provides ductile and stable plastic collapse mechanisms with progressive deformation in a stable manner by increasing energy absorption during collision. This paper presents an experimental investigation on the influence of the number of hybrid epoxyglass layers in overwrap composite columnar tubes. Three columnar tube specimens were used and fabricated by hand lay-up method. Aluminum square hollow shape was combined with externally wrapped by using an isophathalic epoxy resin reinforced with glass fiber skin with an orientation angle of 0°/90°. The aluminum columnar tube was used as reference material. Crushed hybrid-composite columnar tubes were prepared using one, two, and three layers to determine the crashworthy capacity. Quasi-static crush test was conducted using INSTRON machine with an axial loading. Results showed that crush force and the number of layers were related to the enhancement of energy absorption before the collapse of columnar tubes. The energy absorption properties of the crushed hybrid-composite columnar tubes improved significantly with the addition of layers in the overwrap. Microscopic analysis on the modes of epoxy-glass fiber laminate failure was conducted by using scanning electron microscopy.

Separating the influence of the cortex and foam on the mechanical properties of porcupine quills

Lightweight thin cylinders filled with a foam have applications as collapsible energy absorbers for crashworthy and flotation applications. The local buckling compressive strength and Young’s modulus are dependent on material and geometrical properties. Porcupine quills have a thin cortex filled with closed-cell foam, and are entirely composed of α-keratin. The cortex carries the majority of the compressive load, but the foam is able to accommodate and release some of the deformation of the cortex during buckling. The presence of the foam increases the critical buckling strength, buckling strain and elastic strain energy absorption over that of the cortex. Good agreement is found between experimental results and modeled predictions. A strain distribution map of the foam close to the buckled cortex demonstrates that the deformation of the cells plays an important role in accommodating local buckling of the cortex. The robust connection between the foam and cortex results in superior crushing properties compared to synthetic sandwich structure where the foam normally separates from the shell. The foam/cortex construction of the quill can guide future biomimetic fabrications of light weight buckle-resistant columns.

Impact Response of Thin-Walled Tubes: A Prospective Review

Thin-walled structures have been widely used in various structural applications asimpact energy absorbing devices. During an impact situation, thin-walled tubesdemonstrate excellent capability in absorbing greater energy through plastic deformation. In this paper, a review of thin-walled tubes as collapsible energy absorbers is presented.As a mean of improving the impact energy absorption of thin-walled tubes, the influence of geometrical parameters such as length, diameter and wall thickness on the response of thin-walled tubes under compression axial loading are briefly discussed. Several design improvements proposed by previous researchers are also presented. The scope of this review is mainly focus on axial deformation under quasi-static and dynamic compressive loading. Other deformations, such as lateral indentation, inversion and splitting are considered beyond the scope of this paper. This review is intended to assist the future development of thin-walled tubes as efficient energy absorbing elements.

Development of a new methodology capable of characterizing the contribution of a controlled venting system to impact attenuation in chamber structures for head protection

Abstract Currently, ice hockey helmet technologies are based mainly around foam energy absorbers. There is a need in the head protection industry for improved designs, capable of protecting the brain under a wide range of impact conditions. Air chambers are new, thin-walled collapsible energy absorber structures which have the potential to replace or to be used in conjunction with current helmet technology. The chambers consist of several engineering parameters, each of which needs to be examined to understand its mechanical response under impacts. This study was designed to investigate a new methodology capable of investigating the air venting system. This research thereby analyzed the role the chamber’s controlled air release device plays in managing impact energy. The results demonstrated that, as the air chamber approaches the critical failure region, the air released though the controlled vent can prevent larger peak forces. This research identified that an engineered thin-walled collapsible chamber does use air as a mechanism to absorb impacting force.

Many aspects to improve the energy absorption capacity of collapsible energy absorber devices

The behaviour of core and core-less composite elliptical thin-walled tubes subjected to quasi-static axial crushing is examined experimentally. The core-less tubes have two different arrangement systems (single and double). For the core tubes, natural cellular fibre was used as filler. Experiments showed that the crushing behaviours of the core-less tubes were found to be sensitive to their ellipticity ratio. Catastrophic failure mode is eradicated by both the arrangement system and the existence of the core, while the elastic energy is significantly suppressed by the existence of the core. The presence of core provides significant enhancement in tube damage tolerance and energy absorption per unit volume compared to the core-less tubes.

Collapsible impact energy absorbers: an overview

This paper reviews the common shapes of collapsible energy absorbers and the different modes of deformation of the most common ones. Common shapes include circular tubes, square tubes, frusta, struts, honeycombs, and sandwich plates. Common modes of deformation for circular tubes include axial crushing, lateral indentation, lateral flattening, inversion and splitting. Non-collapsible systems, such as lead extrusions or tube expansions, are considered to be beyond the scope of this review.

Investigation Of Axially Compressed Frusta AsImpact Energy Absorbers

This paper reports, both experimentally and analytically, two new modes of plastic deformations of frusta when used as collapsible energy absorbers. Deformable energy absorbers are briefly introduced, and their relevance in crash protection systems is stressed. A general review of literature is presented on energy absorption by metallic absorber of various cross sections with special attention to frusta. Experimental results for the two deformation modes of capped spun aluminum frusta under quasi-static testing condition are given. An Explicit version of ABAQUS 5.7-3 FE code is used for computing and describing the deformation modes of the frusta. Good agreement is obtained between the experimental results and the FE predictions.