Terms Of Energy Absorption Capacity Research Articles

In-plane dynamic crashing behavior and energy absorption of novel bionic honeycomb structures

A series of novel bionic honeycombs (bio-honeycombs) are proposed by incorporating the microstructure of the beetle elytra intersection unit into the regular hexagonal honeycomb (Hex) cell. To explore the in-plane mechanical properties and energy absorption performance of bio-honeycombs under different impact speeds, finite element (FE) models are established and verified by empirical formulas and current experiments. The results indicate that the bio-honeycombs outperform the Hex in terms of energy absorption capacity, and the nominal stress–strain curves of the bio-honeycombs show two prominent stages (stage Ⅰ and stage Ⅱ) under quasi-static and mid-impact. Bionic units also undergo two evident deformation stages: preliminary collapse and further crushing. The bending and traction of bionic units make more adjacent cells added to the collapse earlier, forming a global crushed trend, leading to an interesting phenomenon that the localized band of bio-honeycombs are always wider than that of Hex. Also, negative Poisson’s ratio is observed in stage Ⅱ from several bio-honeycombs under quasi-static and mid-speed due to bionic units' bending and traction in the further crushing stage. Besides, the number and distribution of ribs have a considerable impact on the crashworthiness of bio-honeycombs. Compared with the Hex, the incorporated bionic units reduce the peak crushing force (PCF) while improving the crashworthiness of bio-honeycomb in the case of the same relative density, which provides a promising potential solution to strengthen the energy absorption performance of honeycomb structures.

4D Metamaterials with Zero Poisson's Ratio, Shape Recovery, and Energy Absorption Features

This article introduces novel 3D zero Poisson's ratio (ZPR) metamaterials for reversible energy absorption applications fabricated by 4D printing technology. The designs are introduced based on piecemeal energy absorption (PEA) and conventional energy absorption (CEA) approaches. Topologically, the design of the 3D metamaterials is founded on star‐shaped unit cells herein. To achieve the PEA behavior, horizontal bars are merged into the parent star‐shaped unit cell. This leads to introducing multistiffness unit cells (controllable unit‐cell densifications) to provide stability and different peak force levels during compression. For further evaluation, finite element analysis (FEA) is employed. To illustrate the design functions during physical operation and validate the FEA, lattice‐based metamaterials are fabricated from resin with a shape recovery property by an SLA 3D printer and tested mechanically. Close coincidence is observed between the FEA and the experiments, showing the accuracy of the modeling. A thermal test, via a heating–cooling process, is also carried out to display the shape recovery capability of metamaterials where plastic deformations are fully released, and samples get back to their original shapes. Finally, the newly proposed ZPRs are compared with conventional 3D reentrant metamaterials in terms of energy absorption capacity, demonstrating their considerable mechanical performances.

Mechanical properties and energy absorption of bio-inspired hierarchical circular honeycomb

This study proposed a new bio-inspired hierarchical circular honeycomb (BHCH), mimicking the hierarchical structures from wood. The mechanical properties and energy absorption characteristics of the proposed structures were investigated by means of quasi-static compression tests and finite element (FE) analysis. Subsequently, the influences of geometric parameters and material selections on the energy absorption capacity were investigated. The experimental results and parametric study indicated that the BHCH outperformed the conventional circular honeycomb (CH) in terms of energy absorption capacity. Specifically, the BHCH had a higher specific energy absorption (SEA) than the corresponding CH with the same wall thickness (i.e. 45.3%) and the same volume of honeycombs (i.e. 71.2%). Furthermore, the relative stiffness, relative strength, and relative energy absorption of the BHCH were significantly higher than other popular cellular structures. Finally, a theoretical model was developed to estimate the mean crushing stress (MCS) and interaction effect of the proposed structure, which further demonstrated its enhanced energy absorption mechanisms. A good correlation between the predicted values and the numerical results proved the reliability of the proposed analytical models. With its excellent performance, the proposed BHCH provided a promising solution for the enhanced energy absorption of the honeycomb structure used in a wide range of applications from structural components of defence structures to protection systems in vehicles.

3D-printed bio-inspired zero Poisson’s ratio graded metamaterials with high energy absorption performance

This study aims at introducing a number of two-dimensional (2D) re-entrant based zero Poisson’s ratio (ZPR) graded metamaterials for energy absorption applications. The metamaterials’ designs are inspired by the 2D image of a DNA molecule. This inspiration indicates how a re-entrant unit cell must be patterned along with the two orthogonal directions to obtain a ZPR behavior. Also, how much metamaterials’ energy absorption capacity can be enhanced by taking slots and horizontal beams into account with the inspiration of the DNA molecule’s base pairs. The ZPR metamaterials comprise multi-stiffness unit cells, so-called soft and stiff re-entrant unit cells. The variability in unit cells’ stiffness is caused by the specific design of the unit cells. A finite element analysis (FEA) is employed to simulate the deformation patterns of the ZPRs. Following that, meta-structures are fabricated with 3D printing of TPU as hyperelastic materials to validate the FEA results. A good correlation is observed between FEA and experimental results. The experimental and numerical results show that due to the presence of multi-stiffness re-entrant unit cells, the deformation mechanisms and the unit cells’ densifications are adjustable under quasi-static compression. Also, the structure designed based on the DNA molecule’s base pairs, so-called structure F‴, exhibits the highest energy absorption capacity. Apart from the diversity in metamaterial unit cells’ designs, the effect of multi-thickness cell walls is also evaluated. The results show that the diversity in cell wall thicknesses leads to boosting the energy absorption capacity. In this regard, the energy absorption capacity of structure ‘E’ enhances by up to 33% than that of its counterpart with constant cell wall thicknesses. Finally, a comparison in terms of energy absorption capacity and stability between the newly designed ZPRs, traditional ZPRs, and auxetic metamaterial is performed, approving the superiority of the newly designed ZPR metamaterials over both traditional ZPRs and auxetic metamaterials.

SHORT NOTES: THE LOW-VELOCITY IMPACT RESPONSE OF BIO-COMPOSITES

In this paper, an experimental investigation on the low-velocity impact response of wood-based bio-composites is presented. This study is to map the suitability of plant-based materials instead of petroleum-based plastic as a constituent raw material in composites. Wood-basedcomposites panels were made from southern yellow pine (SYP), corn starch (CS), and methylene diphenyl diisocyanate (MDI) using a Diefenbacher hot press. The impact performance of thespecimens was evaluated in terms of energy absorption capacity. Five types of bio-composites were prepared with varying compositions with SYP: 4% MDI; 2% CS and 2% MDI; 2% CS and 4% MDI; 4% CS and 4% MDI. These samples were prepared at two different manufacturing pressures. The bio-composite produced with higher manufacturing pressure had the highest absorbed energy among five different types of bio-composites, this shows that material behavior at impact loading is strongly dependent on the manufacturing pressure during fabrication.

Nanomodified Cementitious Composites Incorporating Basalt Fiber Pellets under Tensile and Impact Loads

This study investigated the behavior of nanomodified cementitious composites reinforced with innovative basalt fiber pellets (BFP), with specially tailored surface texture under quasi-static (direct) tensile as well as static and dynamic compression (split Hopkinson pressure bar) loading schemes. The composites comprised two different binder formulations (50% fly ash or slag replacement) with/without nanosilica modification. Thermogravimetric and microscopy studies were conducted to evaluate the hydration development and microstructure of the binders. Moreover, the pellet/matrix interfacial bond properties were assessed using the single pellet pullout test. The results showed the efficacy of BFP in reinforcing the cementitious composites and highlighted the role of nanosilica at enhancing the postcracking performance of high-volume fly ash– and slag-based mixtures under all loading schemes. Furthermore, the increase of the pellets’ dosage improved the ductility of composites in terms of energy absorption capacity and strain at failure. The pellet/matrix interface, which is responsible for the main toughening mechanism of the composites by pullout, was sensitive to the type of binder and imposed displacement rate.

Effect of elevated temperature on Stress-Strain behaviour of Self-Compacting concrete

Self-Compacting Concrete (SCC) is an emerging building material as it has unique benefits over conventional concrete. SCC is a High-Performance Concrete (HPC) having the filling ability, passing ability and segregation resistance. In addition, SCC does not require vibration. However, to develop SCC, an appropriate mix design has to be carried out following EFNARC guidelines. This paper attempts to develop a design mix proportion for grades of SCC such as M25, M30, M35, and M40. The requirements of fresh SCC are validated with appropriate experiments such as the V-funnel test, J-ring test, and slump flow test. Cube compressive strength of different grades of hardened SCC was validated at 28 and 56 days. The other mechanical properties, such as tensile strength, flexural strength, and modulus of elasticity, were also examined for different grades of SCC, and the test results are reported. Fire-resistance of building materials has to be assessed to ensure the fire safety of humans and infrastructure during the event of fire accidents. Stress–strain curves were developed to characterize the behaviour of different grades of SCC under elevated temperatures. Three stages of elevated temperatures, such as 300, 600, and 900 °C with two methods of heating, were considered in this experimental investigation. It was observed that the maximum stress capacity of SCC linearly decreases with respect to the elevated temperature. Also, the peak strain of different grades of SCC increased as the exposure temperature increases. The changes in the ductile property of different grades of SCC are found to be quantitatively evaluated in terms of Energy Absorption Capacity (EAC). The EAC values are found to be decreased when the exposure temperature increases.

Three point bending flexural strength of cemented soil reinforced by PVA and Jute fiber

In this paper, the flexural and post-cracking performance of deep soil–cement column reinforced by Jute fiber and PVA fiber, respectively were investigated. The results indicates that both Jute and Polyvinyl alcohol fiber significantly improved the first crack flexural strength and peak flexural strength. In addition, the fiber content play a critical role for enhancing the post-cracking performance of specimens, the peak strength ratio, residual flexural strength ratio, ductility index and energy absorption capacity increased with increasing fiber content. Jute fiber group exhibited slightly better in terms of energy absorption capacity.

Experimental investigation on deformation behavior and energy absorption capability of nested steel tubes under lateral loading

The energy absorption behavior of nested tubes under lateral loading conditions was investigated in this study. Nested tubes are considered as an alternative to energy absorption structures used in many industries including automotive, military, and aerospace. Steel tubes with the same wall thickness and different diameters were used in the experiments. First, experiments of single tubes were carried out, and the deformation behavior of tubes under lateral load was examined in detail. Afterward, experiments were carried out on nested tube samples in which a minimum of 2 and a maximum of 6 tubes were used together in different numbers and sequences. It was seen from the experiments that the best-nested tube configuration in terms of energy absorption capacity was the sample that contains 6 tubes with 1767 J. While this sample absorbed 5% higher energy than the sample with 5 tubes, the specific energy absorption value was calculated to be 10% lower. Additionally, the sample with 6 tubes has a value of 43% in terms of energy efficiency which is 7% lower compared to that of the sample with 5 tubes. It was determined that the sample with 5 tubes yielded the most efficient design when specific energy absorption capability, work effectiveness, and energy efficiency parameters were considered.

English

The seismic performance of non ductile reinforced concrete (RC) buildings with eccentric steel bracing of inverted Y type is investigated. 10, 15 and 20 storey buildings are analyzed by using pushover analysis. The analysis is carried out by using software SAP2000v17. The effect of distribution of steel bracing over the height of RC frame was studied. The study also concentrates on effect of link length of eccentric bracing on seismic performance of RC frame. The performance of RC frame with inverted eccentric bracing is evaluated in terms of energy absorption capacity, stiffness of frame and ductility. The behavior of eccentric braced frame (EBF) is compared with conventional RC frame and inverted V bracing.

Crashworthiness optimization of honeycomb structures under out‐of‐plane impact using radial basis functions

AbstractCrashworthiness design and development of lightweight structures have become important engineering challenges because of the high standards of energy consumption and safety regulations. Within this context, the use of honeycomb structures as crush absorber is continuously growing in automotive and aircraft industries, once honeycombs are known for their high strength‐to‐weight ratio and excellent energy absorbing capacity. Thus, this paper presents a method that combines radial basis functions with expected improvement to optimize the specific energy absorption of honeycomb cellular materials, while the peak crush force is constrained at low levels for safety reasons. Honeycomb's cell size, cell shape and thickness are the design variables. Concerning the cell shape, the results indicate the hexagonal configuration has a higher out‐of‐plane performance compared to auxetic and rectangular cells in terms of energy absorption capacity. Lastly, a multi‐objective optimization using only the radial basis function predictor (without sequential sampling) is carried out to seek simultaneously for optimal solutions with minimum peak force and maximum specific energy absorption.

Energy absorption mechanisms and capabilities for magnesium extrusions under impact

There is significant interest in replacing conventional materials with novel, lightweight alternatives. Magnesium alloys are favorable candidates since magnesium is the lightest structural metal available. The impetus of this investigation was to examine the mechanical performance for AM30 magnesium extrusions subjected to quasi-static and dynamic progressive crushing and axial cutting with impact velocities up to 18 m/s investigated. These magnitudes replicated high speed, transportation-related impacts in a range where experimental data is crucial but absent from the literature. The collected data was compared in terms of total energy absorption, force efficiency and overall deformation stability to assess the feasibility of this novel material as a potential substitute for vehicular safety systems which are traditionally composed of steel. Axial cutting was generally outperformed in terms of energy absorption capacity when compared to crushing, except for the case of 10-bladed cutting. However, the degree of fracture observed and corresponding lack of stability under crushing was unacceptable for a safety system while every cutting test proceeded with a highly repeatable, near-constant force response which successfully mitigated fracture. The average cutting force efficiency was approximately 85%, compared to 30% for the progressively crushed specimens. A fully analytical model to predict the complete force-displacement response under a cutting deformation mode was derived and validated, based upon experimental observations, with an average error of 4% for a series of geometries, alloys, loading rates and cutting tools. Additionally, this revised model possesses a stronger theoretical basis than the original by considering the influence of strain energy release rate per unit area (J-integral) and a brittle cutting membrane rather than empirical correction factors. The influence of mechanical leverage on the axial cutting force, by radial clamping of the flared sidewalls, was also considered in the revised analytical model and validated for an expanded parametric scope.

Experimental investigation on low-velocity impact response of wood skinned sandwich composites with different core configurations

In this paper, an experimental investigation on the low-velocity impact response of wood skinned hybrid sandwich composites was presented. Several alternative design configurations were developed by using rubber-cork and E-glass composite layers between the foam core and wood skin in order to improve the impact performance of conventional sandwich composites. Low-velocity impact (LVI) testing was performed using a drop weight test machine at different impact energies and destructive cross-sectioning was performed to examine the interior damage growth and penetration depth of the specimens. The impact performance of the specimens was evaluated in terms of energy absorption capacity, maximum contact force and penetration depth. The multi-core design concept significantly improved the energy absorption capacity with a reduced extent of impact induced damage. The proportion of recyclable materials in each configuration and the energy absorption level per unit cost were also presented for the interest of product designers.

Energy absorption study considering crush test on carbon fiber/epoxy and carbon fiber/polyurethane structural composite beams

Crashworthiness of a high-performance composite structure is associated to its energy absorption capacity through controlled failure mechanisms during an impact or crushing event. Furthermore, crush and compression testing usually characterize the failure mechanisms, which considers the specimen geometry, material type, fiber architecture and loading rate. This study focuses on energy absorption capability of carbon fiber/epoxy (CF/Epoxy) and carbon fiber/polyurethane (CF/PU) composite hat beams (HB) by a nonstandard quasi-static crush test for crashworthiness applications, including a discussion of how the material properties affect the structural behavior. In addition, the materials evaluation by low velocity impact (LVI), compression after impact (CAI) test, and in-plane shear response by tensile test was performed to determine and compare mechanical behavior and damage modes caused by the impact event. Despite the differences observed on the CF/Epoxy and CF/PU composites in terms of energy absorption capacity on impact, post-impact compression strength and shear strength, the HB specimens presented similar average crush force when subjected to the crush loading, but different types of failure modes. A multiple linear regression model has been developed which is able to predict the HB absorbed energy on crush considering the matrix behavior and energy absorption capability corresponding the failure mechanisms observed.

On functionally-graded crashworthy shape of conical structures for multiple load cases

Many studies on energy absorbers have been focused on tapered tubes because they have significant advantages in crashworthiness and provide a desired constant load-deflection response. However, few studies have been reported on tapered tubes with nonlinearlyvariable diameters along the longitudinal direction. This paper presents thin-walled Functionally graded tapered tube (FGTT) with a diameter varying nonlinearly subject to axial (0°) and oblique (10°, 20°, 30°) impacts. To explore the advantages of FGTT, conventional Straight/Conical circular tube (SCT/CCT) with the same mass are compared; and FGTTs with a gradient exponent n > 1 are found to be preferable to others in terms of energy absorption capacity under small impact angles. Then, crashworthiness analyses of different crushing distances are conducted and it is found that under a large impact angle (e.g. 20°, 30°), FGTT with a short crushing distance (e.g. 40 mm) have a higher mean crashing force than long crushing distance (e.g. 120 mm), especially for n > 1. In addition, the effect of geometric parameters, such as the gradient exponent n and diameter range ΔD between top (incident) and bottom (distal) diameters of FGTTs, are also studied and it is found that the FGTT with ΔD = 40 mm and n > 1 exhibits better crashworthiness than the others under small impact angles (0°, 10°). This paper demonstrates that such FGTT structures have a certain potential to be an energy absorber.

Influence of auxetic foam in quasi-static axial crushing

Abstract This paper treats the influence of auxetic foam on the crush response and energy absorption response of square-section tubes when subjected to uniaxial quasi-static loading. The study aims at quantifying the energy absorption capability of auxetic foam-filled square tubes for variations in wall thickness, initial height, aspect ratio and slenderness ratio of the tube. The capability of simulating the crush response of auxetic foam-filled tubes using the validated numerical models is also presented. Based on the experimental results, the influence of the auxetic foam in the thin-walled square tubes was quantified in terms of energy absorption capacity, specific energy absorption and crush force efficiency. It is evident that a thicker tube filled with auxetic foam is preferable if the energy absorption level is the primary goal, yet this compromises the crush force efficiency. The outcome of this present study is the establishment of empirical models for estimating the quasi-static crushing response of auxetic foam-filled tubes with varying slenderness ratio and aspect ratio.

Experimental Investigation on Energy Absorption of Auxetic Foam-filled Thin-walled Square Tubes under Quasi-static Loading

Auxetic materials are modern class of materials that have recently been gaining popularity within the research community due to their enhanced mechanical properties. Unlike conventional materials, they exhibit a negative Poisson's ratio when subjected to a uniaxial loading. This present research experimentally investigates the crush response and energy absorption performances of auxetic foam-filled square tubes under axial loading. For comparison, the crush response and energy absorption of empty and conventional foam-filled squares tubes have also been examined with respect to deformation modes and force displacement curve. Standard compression tests were conducted on a series number of thin-walled tube samples. An additional compression test on conventional and auxetic foam has also been conducted to observe the behavior of foam itself. It is evident that the auxetic foam-filled square tubes are superior to empty and conventional foam-filled square tubes in terms of energy absorption capacity. It shows that such tube is preferable as an impact energy absorber due to their ability to withstand axial loads effectively. Furthermore, it is found that the load capacity increases as the crush length increases. The primary outcome of this study is design information for the use of auxetic foam-filled square tubes as energy absorbers where impact loading is expected particularly in crashworthiness applications.

Internal Damage Investigation of Composites Subjected to Low-Velocity Impact

The application of composite materials for lightweight structures in the transportation engineering requires a better understanding of their impact response. The aim of this paper was the experimental investigation of different types of composites (laminated composites, PVC foam sandwiches, aluminium foam and honeycomb sandwiches, laminated wood) subjected to low-velocity impact tests and the analysis of their collapse modes as well as the study of their structural response in terms of energy absorption capacity. The failure mode and the internal damage of the impacted composites have been investigated using two experimental techniques: three-dimensional (3D) computed tomography and IR thermography.

Computed Tomography analysis of damage in composites subjected to impact loading

The composites, used in the transportation engineering, include different classes with a wide range of materials and properties within each type. The following different typologies of composites have been investigated: laminated composites, PVC foam sandwiches, aluminium foam and honeycomb sandwiches. Aim of this paper was the analysis of low-velocity impact response of such composites and the investigation of their collapse modes. Low velocity impact tests were carried out by a drop test machine in order to investigate and compare their structural response in terms of energy absorption capacity. The failure mode and the internal damage of the impacted composites have been, also, investigated using 3D Computed Tomography.

超高張力鋼のプレース架構の耐震性の研究

It is generally known that sum of seismic energy inputted into a building is governed mainly by primary natural period and total mass of the building. It is very cost effective in aseismic design of a building to design a structural frame as a flexural system of which each story is designed to be injured during an earthquake to a same extent, thus securing effective energy absorption capacity of the system as a whole. In this paper, super-high tensile steel braced frames proposed by authors are compared in terms of energy absorption capacity with ordinary rigid frames by conducting incremental analyses and experiments. As a result, the braced frames are proved to be effective aseismic frames.