Optimal Energy Absorption Research Articles

Investigation of the experimental, statistical and optimisation of 3D printed lattice core sandwich panel energy absorber with novel configuration using response surface method

This paper focuses on the energy absorption of additively manufactured or 3D printed lattice-core sandwich structures of different configurations. The compressive behavior of 3D lattice structures with rhombic dodecahedron unit cells is investigated at Quasi-static loading. A parametric analysis was performed, using a Box-Behnken design (BBD), as a method for design of experiments (DOE). Then, the influence of the angle between struts and their diameter were investigated. It was observed from experimental data that the angle between struts had the highest degree of influence on the specific energy absorption. The results showed that the diameter of struts has been the most influential parameter to increase mean and peak forces. The results from using the design expert software showed the optimal specific energy absorption and peak force to be 2.1014 J/gr and 2224.87 N, respectively.

Experimental and numerical study and multi-objective optimisation of quasi-static compressive test on three-dimensional printed lattice-core sandwich structures

This paper focuses on the energy absorption of additively-manufactured or 3D-printed lattice-core sandwich structures of different configurations. The rhombic dodecahedron lattice unit cell, which has been extensively investigated for energy absorption, is the starting point for this research. The compressive behaviour of 3D lattice structures with rhombic dodecahedron unit cells was examined at quasi-static loading along with the influence of the angle between struts, struts diameter, and the number of layers in the core. The angle between struts had the highest degree of influence on the specific energy absorption. The results showed that the diameter of struts has been the most influential parameter to increase mean and peak forces. The results of using the design expert software showed the optimal specific energy absorption and peak force to be 3.8779 J/gr and 3458.25 N, respectively.

Compressive response of multi-layered thermoplastic composite corrugated sandwich panels: Modelling and experiments

Multi-layered thermoplastic composite (TPC) corrugated sandwich panels (CSPs) were designed and fabricated from glass fiber reinforced polypropylene prepregs by hot-pressing and hot-melting bonding methods. Quasi-static compressive response including failure deformation modes of TPC CSPs were experimentally and numerically investigated to reveal the effect of layer numbers and core configurations namely regular, perpendicular and symmetrical. For two-layered CSPs, core layers of the regular configuration panels were firstly compressed to overlapping and then failed together, core layers of the perpendicular ones failed step by step. But for the symmetrical configuration, assembly deviations were found to affect the deformation modes sensitively by comparing the experimental and numerical results. Among three configurations, the perpendicular one has the optimal specific energy absorption (SEA) and crushing force efficiency (CFE), while the regular one has the biggest peak crushing force (PCF). Increasing layer number can enhance the SEA and MCF due to the bending of the interlayer face sheets.

Energy absorption in the axial crushing of hierarchical circular tubes

In this numerical study by means of finite element modeling, the concept of hierarchy is incorporated into thin-walled circular tubes for a configuration with optimum energy absorption. Hierarchical circular tubes (HCTs) are constructed by replacing the wall of an initially single-cell circular tube (SCT) with a series of small tubes placed next to each other (Fully packed, HCT-F) or at a distance apart (partially packed, HCT-P); the total net cross-sectional area and hence the mass is kept the same. The behavior of these new classes of hierarchical tubes under axial crushing is investigated in terms of deformation modes, crushing forces and energy absorption. Two deformation modes are identified and they have different crushing behavior of the HCTs. The initial peak force (PF) remains almost constant after micro-cell tubes are hierarchically introduced, but the mean crushing force (MCF) and hence the specific energy absorption (SEA) can be significantly improved by choosing suitable configurations. It is also demonstrated that partial hierarchy performs better in enhancing the crushing performance of the tubes compared with the full hierarchy.

The in-plane crashworthiness of multi-layer regularly arranged circular honeycombs.

The in-plane crashworthiness of multi-layer regularly arranged circular honeycombs are investigated numerically at v = 1-250 m/s, with aim to disclose the influences of t/R ratio and crushing velocity, v. A novel evaluation methodology of crashworthiness and a new mechanical term, most appropriate strain, are put forward, which results in some new evaluation parameters. The theoretical analysis shows the most appropriate strain is a significant parameter for measuring the crashworthiness. Different deformation modes cause different change rules of these evaluation parameters. Under the quasi-static homogeneous mode and transition mode, the most appropriate strain is linear with the t/R ratio for a given v; the crushing force efficiency is approximately independent of t/R and sensitive to the v; the maximum energy absorption efficiency roughly decreases and then fluctuates. With the increase of v, the crushing force efficiency first becomes smaller sharply, and then fluctuates. Under dynamic mode, the maximum energy absorption efficiency is nearly constant for a given t/R ratio. Based on the finite element results, the empirical expressions of all evaluation parameters are given. The finite element calculated results of optimal specific energy absorption are consistent with those calculated by empirical expressions, which validates all empirical expressions.

Compressive responses and strengthening mechanisms of aluminum composite foams reinforced with graphene nanosheets

The controllable design of composition and structure makes incorporating reinforcements to be a promising way to fabricate aluminum (Al) composite foams. In this work, graphene nanosheets (GNSs) decorated with copper (Cu) nanoparticles reinforced Al composite foams are successfully synthesized via shift-speed ball-milling and space-holder method. The compressive properties and energy absorption capacity of composite foams increase first and then decrease with the increase of the GNSs@Cu content. Unexpectedly, the introduction of the GNSs@Cu has not changed the ductile failure mode of pure Al foams. The strengthening mechanisms of composite foams include load transfer strengthening and dispersion strengthening, and the toughening mechanism of composite foams is considered as crack bridging. The 0.75 wt% GNSs@Cu/Al composite foams possess the optimal yield stress (24.7 MPa), plateau stress (41.3 MPa) and energy absorption capacity (22.8 MJ/m3), which has an improvement of 104.7%, 113.7% and 115.1% in comparison with that of pure Al foams.

Expanded Vermiculite-Filled Polyurethane Foam-Core Bionic Composites: Preparation and Thermal, Compression, and Dynamic Cushion Properties.

In this article, expanded vermiculite (EV)-enhanced polyurethane foam bionic composites inspired by pomelo peel is proposed. The columnar lattice structure mold is employed to constitute the periodic interface structure and gradient foam structure, and the nylon nonwoven fabric is combined as the surface layer. The effects of EV content on the thermal, compression, and dynamic cushion properties of bionic composites are investigated. Results show that residual char increases with EV content, which conduces to decrease the release of heat flow. The proposed bionic composite with columnar lattice structure has optimal compressive modulus, energy absorption and dynamic cushion efficacy when 1 wt% EV is added. However, its performance decreases slowly when EV fillers are continuously added because the cell morphology is changed from round to irregular shape and the interfacial adhesion of filler–matrix is weakened. Owing to their unique bionic structure, composites can absorb 99% of the energy impacted by flat impactor within a smaller deformation and achieve 97% absorption efficiency for a hemispheric impactor in cushion test.

Wave tank and bench-top control testing of a wave energy converter

An increasing number of experiments are being conducted to study the design and performance of wave energy converters. Often in these tests, a real-time realization of prospective control algorithms is applied in order to assess and optimize energy absorption as well as other factors. This paper details the design and execution of an experiment for evaluating the capability of a model-scale WEC to execute basic control algorithms. Model-scale hardware, system, and experimental design are considered, with a focus on providing an experimental setup capable of meeting the dynamic requirements of a control system. To more efficiently execute such tests, a dry bench testing method is proposed and utilized to allow for controller tuning and to give an initial assessment of controller performance; this is followed by wave tank testing. The trends from the dry bench test and wave tank test results show good agreement with theory and confirm the ability of a relatively simple feedback controller to substantially improve energy absorption. Additionally, the dry bench testing approach is shown to be an effective and efficient means of designing and testing both controllers and actuator systems for wave energy converters.

Design and Development of Truck Rear Underrun Protection Device

Underride truck crashes occur when a passenger car rides under the rear of a large truck. These kinds of accidents are especially dangerous because of the size difference between trucks and passenger cars. Therefore, it is necessary to install the Rear Underrun Protection Device (RUPD) at the rear of trucks for safety enhancement. The aim of this research is to design an effective RUPD which is strong enough to prevent a passenger car falling under the rear of the truck and able to absorb large amount of crash energy to minimize accident severity. The novel RUPD design, equipped with energy absorption guard and proper support structure is proposed in this paper. The study on the angle and separation distance of support structures is performed to find the proper design for the support structure of RUPD. The internal energy and displacement of various design of support structures are investigated by performing Finite element crash simulation in LS-Dyna. The FMVSS 223 standard is utilized as reference for the standard design of RUPD. The result shows that the support structure angle of 20 degree yields optimal displacement and energy absorption. Moreover, the new proposed RUPD is able to avoid the A-pillar deformation and eliminates underride altogether.

Three-Dimensional High-Entropy Alloy-Polymer Composite Nanolattices That Overcome the Strength-Recoverability Trade-off.

Mechanical metamaterials with three-dimensional micro- and nanoarchitectures exhibit unique mechanical properties, such as high specific modulus, specific strength, and energy absorption. However, a conflict exists between strength and recoverability in nearly all the mechanical metamaterials reported recently, in particular the architected micro/nanolattices, which restricts the applications of these materials in energy storage/absorption and mechanical actuation. Here, we demonstrated the fabrication of three-dimensional architected composite nanolattices that overcome the strength-recoverability trade-off. The nanolattices under study are made up of a high-entropy alloy-coated (14.2-126.1 nm in thickness) polymer strut (approximately 260 nm in the characteristic size) fabricated via two-photon lithography and magnetron sputtering deposition. In situ uniaxial compression inside a scanning electron microscope showed that these composite nanolattices exhibit a high specific strength of 0.027 MPa/kg m3, an ultrahigh energy absorption per unit volume of 4.0 MJ/m3, and nearly complete recovery after compression under strains exceeding 50%, thus overcoming the traditional strength-recoverability trade-off. During multiple compression cycles, the composite nanolattices exhibit a high energy loss coefficient (converged value after multiple cycles) of 0.5-0.6 at a compressive strain beyond 50%, surpassing the coefficients of all the micro/nanolattices fabricated recently. Our experiments also revealed that, for a given unit cell size, the composite nanolattices coated with a high entropy alloy with thickness in the range of 14-50 nm have the optimal specific modulus, specific strength, and energy absorption per unit volume, which is related to a transition of the dominant deformation mechanism from local buckling to brittle fracture of the struts.

Fabrication of polymeric lattice structures for optimum energy absorption using Multi Jet Fusion technology

Unlike stochastic foams, 3D printed lattice structures can be created with a tailored microstructure to achieve the desired global mechanical properties. In this study, quasi-static energy absorption of six polymeric lattice structures of different unit cell topologies and deformation behaviours but with identical relative density are investigated. For the first time, a recently developed powerful 3D printing technology, namely Multi Jet Fusion (MJF), is utilized to produce high quality and performance lattices. Nonlinear finite element analysis (FEA) is used to analyse their compressive response and energy-absorbing characteristics. To validate the FEA results, experimental compression tests are performed on two types of lattices. The results of this investigation showed that the global energy absorption of lattices can be improved through controlling and manipulating their micro-topology. It is found that the lattice structures with bending-dominated deformation have low stiffness and strength but provide good energy absorption capability. The stretch and buckling dominated structures are shown to be stiffer and stronger but have low energy absorption performance. The findings of this research identify high performing unit cell geometries that can be used for energy absorption application of lattice structures in the development of advanced 3D printed structures that are superior to stochastic foams.

Drop-weight impact characteristics of additively manufactured sandwich structures with different cellular designs

In the design of sandwich panels with cellular cores for energy absorption, the geometrical effect of the cellular core design has not been investigated in details previously. In this work three cellular core designs, including re-entrant auxetic, octet-truss, and BCC lattice, were experimentally investigated for their performance under low-energy impact as sandwich structures. Samples with different cellular core designs were fabricated by laser sintering additive manufacturing process using Nylon 12 as material, and evaluated by drop weight testing under multiple strikes and at two levels of elevated temperatures (93°C and 121°C). It was found that beside relative densities, the geometrical design of the cellular cores could also significantly influence the impact energy absorption performance of the sandwich structures. It was also found that the impact energy absorption of the cellular structures investigated in this study does not have a significant correlation with either the quasi-static mechanical properties or the temperature. In addition, the auxetic cellular structure exhibits optimal overall energy absorption performance compared to both the octet-truss and the BCC lattice.

Effects of Fall Height and Impact Strategy on Energy Absorption Ratio Between Shoulder Joint and Elbow Joint

Falls onto an outstretched hand are the leading cause of upper extremity injury. However, little information is available regarding the effects of fall height and impact strategy on energy absorption ratio between shoulder joint and elbow joint. Twelve male subjects participated in the study. The subjects were asked to perform simulated falls from three different fall heights (5, 10 and 15) using three different conscious strategies, namely Conscious Elbow Dominant Strategy, Conscious Shoulder Dominant Strategy, and Conscious Intermediate Dominant Strategy, corresponding with three different theoretical strategies, namely Elbow Dominant Strategy, Intermediate Dominant Strategy and Shoulder Dominant Strategy for biomechanical analysis. For a fall height of 5 cm, the Elbow Dominant Strategy was found better than other impact strategies, resulting in an Optimal Energy Absorption Ratio of 1.60. For an increased fall height of 10 cm, the Intermediate Dominant Strategy was found better than other impact strategies, with an Optimal Energy Absorption Ratio of 1.99. Finally, for a fall height of 15 cm, the Shoulder Dominant Strategy was found better than other impact strategies, with an Optimal Energy Absorption Ratio of 2.40. The findings presented in this study provide a useful source of reference to clinicians, sports coaches and instructors in devising optimal fall strategies for minimizing the risk of upper extremity injuries in the event of forward falls onto the outstretched hand.

Enteroendocrine-derived glucagon-like peptide-2 controls intestinal amino acid transport

ObjectiveGlucagon-like peptide-2 (GLP-2) is co-secreted with GLP-1 from gut endocrine cells, and both peptides act as growth factors to expand the surface area of the mucosal epithelium. Notably, GLP-2 also enhances glucose and lipid transport in enterocytes; however, its actions on control of amino acid (AA) transport remain unclear. Here we examined the mechanisms linking gain and loss of GLP-2 receptor (GLP-2R) signaling to control of intestinal amino acid absorption in mice. MethodsAbsorption, transport, and clearance of essential AAs, specifically lysine, were measured in vivo by Liquid Chromatography triple quadrupole Mass Spectrometry (LC-MS/MS) and ex vivo with Ussing chambers using intestinal preparations from Glp2r+/+ and Glp2r−/− mice. Immunoblotting determined jejunal levels of protein components of signaling pathways (PI3K-AKT, and mTORC1-pS6-p4E-BP1) following administration of GLP-2, protein gavage, and rapamycin to fasted Glp2r+/+ and Glp2r−/− mice. Expression of AA transporters from full thickness jejunum and 4F2hc from brush border membrane vesicles (BBMVs) was measured by real-time PCR and immunoblotting, respectively. ResultsAcute administration of GLP-2 increased basal AA absorption in vivo and augmented basal lysine transport ex vivo. GLP-2-stimulated lysine transport was attenuated by co-incubation with wortmannin, rapamycin, or tetrodotoxin ex vivo. Phosphorylation of mTORC1 effector proteins S6 and 4E-BP1 was significantly increased in wild-type mice in response to GLP-2 alone, or when co-administered with protein gavage, and abolished following oral gavage of rapamycin. In contrast, activation of GLP-1R signaling did not enhance S6 phosphorylation. Disruption of GLP-2 action in Glp2r−/− mice reduced lysine transport ex vivo and attenuated the phosphorylation of S6 and 4E-BP1 in response to oral protein. Moreover, the expression of cationic AA transporter slc7a9 in response to refeeding, and the abundance of 4F2hc in BBMVs following protein gavage, was significantly attenuated in Glp2r−/− mice. ConclusionsThese findings reveal an important role for GLP-2R signaling in the physiological and pharmacological control of enteral amino acid sensing and assimilation, defining an enteroendocrine cell-enterocyte axis for optimal energy absorption.

Energy-absorption optimisation of locomotives and scaled equivalent model validation

ABSTRACTIn order to improve crashworthiness, the optimum energy-absorption design of locomotives was performed in MADYMO multibody dynamics software, and a three-dimensional computational model for locomotive vehicles was built. The results of calculations using the model were then fitted by multiple linear-regression functions, and a scaled equivalent model test was carried out to validate the fitting formula results. The results showed how to influence the energy absorption of a locomotive by studying the mass and velocity of the locomotive, as well as the plastic deformation platform force of the middle car's crushing tube. The fitting formula related to the plastic deformation platform force of the crushing of the middle car's tube and the kinetic energy of the locomotive was also obtained. The fitting accuracy of the model was 99.98%, and the error between the calculation results from the fitting formula and the scaled equivalent model test results was less than 5%. These results reveal the mode of energy dissipation, and they can be applied to the preliminary conceptual design of train. The dynamic tests of prototype are essential before serial production.

Nano-honeycomb structures for optimal energy absorption: numerical analysis and experiments

Significant progress has been made over the past years in order to better understanding of the materials used in nanoscience and nanotechnology. In addition, due to the development in additive manufacturing [1] and laser lithography, based on the photon polymerization of a variety of UV-curable photoresist it is now possible to manufacture of almost any type of nano-structural configuration, of almost any relative density, and at almost any length scale above a few nanometers.

Experimental and numerical analysis on the geometrical parameters towards the maximum SEA of CFRP components

An experimental and finite element based numerical evaluation on the effects of geometrical parameters towards the energy absorption capacity of [0/90] carbon/epoxy composite tubes is presented. The optimum energy absorption characteristics of such carbon fibre polymer composites (CFRP) elements are considered towards the implementation in crashworthy structures. The effects of the CFRP tube wall-thickness-to-diameter (t/D) ratio, along with the triggering radius of the plug-type initiators, on the specific energy absorption (SEA) capacity were examined to determine the optimum parametric values for SEA. Additionally, different types of chamfers such as; inward folding chamfer, outward splaying chamfer and a flat-ended tube were investigated. Experiments were conducted to confirm the optimum trigger radius at which the critical change in energy absorption occurs and validation study were performed using finite element based LS-Dyna.The numerical prediction followed with experimental validation, confirming that the energy absorption capacity of carbon composite tubes increased to a maximum t/D ratio at 0.092, before experiencing a reduction. It has also been found that the geometry of the triggering mechanisms contributed to a change in the initial peak and mean crush loads of composite tubes. In this paper, the effect of the triggering mechanisms on the energy absorption characteristics of composite tubes for crashworthy applications are successfully demonstrated.

Inertial effects on the mechanical response of aluminium foam-filled braided stainless steel tubes under transverse loading

ABSTRACTMechanical responses of quasi-static and dynamic transversely loaded empty/foam-filled braided tubes were investigated with a custom load frame and pneumatic gun/projectile at velocities ranging from 21 to 27 m/s. Braided tubing was woven from AISI 304 wire (wire diameter: 0.51 mm, external diameter: 64.5 mm, length: 330 mm). Foam density ranged between 162 and 520 kg/m3. Localised foam collapse at mid-span under impact resulted in greater energy absorption for foam-filled specimens compared to quasi-static tests. Foam density significantly influenced force efficiency for reduced deflections. For low-density quasi-static tests, the average force efficiency was 58.3% decreasing to 41.9% under impact. Force efficiency for high-density foam under quasi-static loading was 42.8% decreasing to 23.4%. High-density foam cores exhibited minimal foam crushing as the increased mechanical properties of the foam resulted in braided tube failure. Low/medium-density foam cores yielded both optimal specific energy absorption over the full deflection range and force efficiency for reduced deflections.

Systems engineering optimization of Omid-2 in the conceptual design phase

Due to the importance and role of systems engineering in space mission developments, optimization of Omid's systems engineering as a milestone to its current and future generations is focused. In this regard systems engineering management organization as the basis of optimization work flow in the conceptual design phase is proposed for improvement. To improve the systems engineering management, an agile enhanced organization chart is developed that defines various system duties. This is a type of concurrent engineering approach that promotes direct communication and data interchange between the team members. Due to the importance of decision making in the conceptual design phase, two design matrices are constructed that portray merits of various design options in terms of improved satellite life as well as specific choices of remote sensing capability for the Omid second generation (Omid-2). Conceptual design optimization is explored considering several structural objectives as well as optimal solar energy absorption utilizing a multiple criteria decision making approach. The Eigenvector method is utilized to formulate the objective function via expert judgment. This approach is robust with respect to designer probable miss-judgment. The optimized version of Omid-2 turned out to be a passive Z-axis spin stabilized satellite made of hexagonal honeycomb configuration with carbon-epoxy side panels and Aluminum bottom plate.

Flexural properties of composite gypsum partition panel

Bending tests were conducted on prismatic samples of gypsum panels with a core of textile waste fibres. The samples were prepared by confining the waste textile fibres with glass fibre mesh (GFM). The dimensions of the fibre core and the type of mesh employed were used as variables to obtain optimal flexural strength and energy absorption capability. The test results revealed that the gypsum panels with a central core of textile waste fibres have high ductility and high energy absorption capacity. It was concluded that using textile waste materials and GFMs embedded in gypsum can produce three-layer partitions and reduce the landfilling of textile wastes.