Improved Energy Absorption Research Articles

Effects of Geometry, Triggering and Foam-Filling on Crashworthiness Behaviour of a Cylindrical Composite Crash Box

Crash boxes play an important role in different industries as energy absorbers to reduce damage of accidents. An ideal crash box has lower maximum force and higher energy absorption. The aim of this study is to investigate the effect of various parameters such as geometry (diameter and thickness), triggering and filling with polymeric foam on axial crash behaviour of a composite cylindrical cash box. To this end, a composite crash box is modelled in a commercial finite element software, Abaqus, utilising the Hashin failure criterion to predict damage initiation. Linking damage initiation with material degradation rules provides the capability for damage evolution prediction on the basis of fracture energy of different failure modes. A new parameter (β) is defined to study the performance of a crash box with different geometries, triggers and foam-filling. The results show that three different triggering geometries (chamfer, fillet, and tulip) decrease the maximum load about 7-33%, and improved energy absorption about 40-86% compared to the crash box without trigger. Filling a triggered crash box with polymeric foam also improves energy absorption about 20%. Applying both triggering and foam-filling simultaneously on a crash box has a complementary role to receive a better performance.

Quasi-static flattening energy absorption process on preformed circular tubes by numerical and experimental analyses

This article presents a novel method to improve energy absorption performance of thin-walled circular tubes under quasi-static lateral loading through the preforming process. Desirable investigations are carried out by experimental tests and numerical simulations. Firstly, simple circular tubes are shaped into four different types (P1–P4) of preformed specimens, using a semi–cylindrical Teflon die and various blade-shaped indenters with semi–cylindrical nose. Then, the preformed specimens are laterally compressed between two rigid platens to perform flattening tests and their mechanical behaviors are investigated during the lateral flattening experiments, based on viewpoint of energy absorption. Some experiments are carried out and due to the test limitations, numerical simulations are performed, using the ABAQUS/Explicit software. In the following, based on the finite element analysis, various preformed specimens with different geometrical characteristics are simulated to investigate influences of wall thickness, preformed type and internal spanof the specimen cross–section and also, effects of loading direction on energy absorption performance of the preformed specimens. Also, some simple circular tubes are flattened as the benchmark and results of four types of the preformed samples are compared with the corresponding benchmark. The obtained results illustrate that by shaping the simple circular tubes into the preformed specimen, a new hollow prismatic samples are produced that their energy absorption capability is 11.5 times of the corresponding value of the benchmark; consequently, the present article suggest the preformed specimens of various types instead of the corresponding simple circular tubes, as better energy absorber.

Correlative digital image correlation and infrared thermography measurements for the investigation of the mesoscopic deformation behaviour of foams

Open-cell metal/polymer hybrid foams are biomimetic open-porous composites, consisting of a polymeric foam electrochemically coated with a metallic layer. Due to their specific pore structure, they can be used in lightweight applications or as crash absorbers. The nanocrystalline coating leads to a strengthening effect and largely improved energy absorption capacity. Understanding the mesoscopic deformation behaviour of foams is essential for the design of intelligent and safe crash absorbers for the future. The present contribution focuses on the full-field thermomechanical analysis of the mesoscopic deformation of metal/polyurethane hybrid foams and hollow strut foams. Local strain fields from digital image correlation were directly coupled with local temperature fields from infrared thermography. A new software tool allows for the direct correlation of thermal and mechanical fields and for the corresponding experimental stress–strain data. Furthermore, the evolution of the energy absorption capacity as function of the strain rate was determined using infrared thermography.

Out-of-plane compressive performance and energy absorption of multi-layer graded sinusoidal corrugated sandwich panels

Corrugated sandwich panels with outstanding load-bearing and energy absorption capacities are widely used in aerospace, naval and automobile industries. Herein, a series of modified sinusoidal corrugated (MSC) sandwich panels, with multiple layers and gradient design, are developed and fabricated by additive manufacturing. An analytical model for quasi-static compression performance was established by using Timoshenko beam and plastic hinge theory. Corresponding experiments and finite element analysis are conducted to investigate the out-of-plane compressive failure mechanism and mechanical performance. The energy absorption capability of graded MSC sandwich panels is studied to reveal the influence of gradient design. The results reveal that the proposed analytical model can accurately predict the compressive modulus and ultimate strength of multi-layer MSC sandwich panels with a maximum deviation of <25%. The introduction of gradient design decreases the initial peak strength and the undulation of load-carrying capacity during nonlinear deformation. The energy absorption ratio slightly increased due to the improved energy absorption process, which can be attributed to the controllable deformation behavior of sandwich core.

Bioinspired foam composites resembling pomelo peel: Structural design and compressive, bursting and cushioning properties

Inspired by pomelo peel, this study proposes bioinspired foam composites, which are prepared by one-step foaming and a combination of different fabric structures. The bioinspired composites are evaluated in terms of compression resistance, bursting strength and cushioning efficacy, thereby examining the influential mechanisms of fabric structures. The experimental results indicate that the bio-inspired composites have superior functions due to the reinforcement of a nylon fabric as well as high stiffness and energy absorption of polyurethane -based small-mesh-size spacer fabrics. The bioinspired foam composites have maximum compression resistance is 131 kPa with a corresponding strain of 60%, which is 245% greater than the control group. The deformation-absorption energy of bioinspired foam composites is 2.3 J, which is 78% greater than that of pomelo peel. The maximum bursting strength of bioinspired foam composites is 3370 N, which is two and twenty times that of the control group and pomelo peel, respectively. Compared to spacer fabrics at 0° lamination, spacer fabrics at 90° lamination has a positive influence on the bursting strength but a negative influence on compressive strength of bioinspired foam composites. Bioinspired foam composites have a peak contact force that is 45.1% lower than that of the control group, which suggests remarkable improvement in energy absorption. The resultant bioinspired composites are expected to be used as packaging and personal protective materials for commercial applications in the future.

Compressive characteristics of unmodified and nanoclay treated banana fiber reinforced epoxy composite cylinders

The objective of this work was to prepare a natural fiber reinforced composite product by using nanoparticle technique method. Nanoclay particles were infused into the banana fiber and these modified banana fibers were then reinforced in epoxy polymer composites. A short banana fiber reinforced epoxy polymer composite cylinder was prepared by resin impregnation method, and the compressive, tensile, interfacial and energy absorption characteristics were studied. The properties of nanoclay infused banana fiber reinforced composites were compared with alkaline (NaOH) treated and untreated banana fiber reinforced epoxy composites. It was observed that the nanoclay infused banana fiber composites has resulted in 17%, ∼2 times and 43% improved compressive yield stress, modulus and strength when compared with untreated banana fiber reinforced epoxy composite cylinder. However, nanoclay infusion induces brittleness into the fiber affecting the elongational properties. Tensile, flexural and short beam properties show that the reinforcement effect of nanoclay was higher in flexural and short-beam modes when compared with tensile mode, due to higher level of surface interaction of nanoclay particles in flexural and short-beam modes. About 2 times improved energy absorption properties were obtained in nanoclay infused banana fiber reinforced epoxy composites when compared with untreated banana fiber reinforced epoxy composites. Microscopy examination revealed that the nanoclay infusion in fiber improved fiber-matrix interfacial and load transfer characteristics leading to the higher level of property improvement in nanoclay infused banana fiber reinforced epoxy composites. The outcome of the result suggest that the nano-technique is very much useful and can be simply applied onto the natural fibers to realize the potential application of these materials.

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.

Experimental analysis of additively manufactured thin-walled heat-treated circular tubes with slits using AlSi10Mg alloy by quasi-static axial crushing test

In this study, additively manufactured aluminum thin-walled tubes with different slit dimensions are proposed to improve energy absorption efficiency. A total of 18 samples, which varied in the number of slits, slit length, slit width, and slit ends, were tested under quasi-static axial compression at a rate of 20 mm/min. The deformation and failure modes, load-displacement curves, and a number of crashworthiness factors were investigated. The factors considered included, but were not limited to, the specific energy absorption, crushing force efficiency, and energy absorbed per stroke. The results indicated that all the considered physical parameters, except for the slit ends, had an influence on the crashworthiness of the structures. The initial peak load decreases significantly as the number, width, and length of the slits increase. The bulk of the tested tubes exhibited a crushing force efficiency greater than 0.8. Overall, the presence of slits with length 15 mm and width 5 mm resulted in lower and smoother crushing forces than the straight tubes and, therefore, greater crushing force efficiency, validating them as crashworthy structures.

Improved Energy Absorption in 3D Woven Composites by Weave Parameter Manipulation

3D woven composites show significantly improved out-of-plane properties over traditional 2D laminates. This high through-thickness reinforcement is desirable in crashworthiness applications where crushing energy can be increased by composites’ improved interlaminar toughness. However, their use in practical applications is stunted by the poor understanding of how small variations in weave parameters, whether intended or not, affect the performance of these materials. Here, we demonstrate that small changes in textile properties, in this case pick density and float length have a knock-on effect that can greatly improve or diminish the crush performance of a 3D woven layer-to-layer structural fabric. Quasi-static and dynamic energy absorption values up to approximately 95J/g and 92J/g respectively are achieved. Crush performance is investigated on omega-shaped coupons, under both quasi-static and dynamic loading conditions with crush rates between 2mm/min and 8.5m/s. The failure mechanisms present during progressive crush under quasi-static loading transitions between more expected brittle dominated failure and ductile dominated failure, which is more typical of metals under similar loading conditions. Whereas when dynamic loading is considered, the materials present a more typical splaying failure event. As a result, additional exploration of the three-point bending response of these varied architectures is presented as a means of further explaining the interplay between lamina bending and progressive folding/micro-buckling in these materials. The effect of the weave’s architectural alterations on physical composite properties such as weight, density and conformability to shape is also investigated.

Improving cushioning properties of a 3D weft knitted spacer fabric in a novel design with NiTi monofilaments

Cushioning pads alleviate the effects of mechanical stress on the human body due to impacts and daily activities. One relevant application for such pads is orthopedic insoles used for diabetic foot to improve energy absorption and reduce stress gradient by using suitable materials and structures. This article considers a novel design that improves the energy absorption capabilities of cushioning pads. Experiments were conducted to evaluate the properties of the designed weft knitted spacer fabrics. Six groups of samples were knitted in which steel, polyamide, and shape memory alloy materials were utilized as spacer monofilament. Stress–strain, energy absorption and efficiency diagrams were obtained following the quasi-static compression tests carried out on the samples. Three investigation groups were adopted to evaluate the effect of the spacer monofilament material, diameter, and slope on energy absorption capacity. It was determined that shape memory alloy monofilament with 0.1 mm diameter was the optimum configuration to be utilized as spacer yarn in a typical 3D weft knitted fabric. It was also concluded that higher-inclined spacer monofilament in spacer fabric was the optimum choice for knitting cushioning pads as it absorbed more energy. The energy absorption capacity of the optimum design of spacer fabric obtained in this study, increased by a factor of 2.4 compared with commercial polyamide pads. This design can be utilized in any cushioning pad exposed to high mechanical stress due to impact, sports and daily activities.

Experimental and numerical investigation into the crashworthiness of metal-foam-composite hybrid structures

To meet the growing demands for structural lightweight and safety, metal-foam-composite hybrid tubular sandwich structures, which combine low-cost metallic materials and high-strength composites with low-density cellular materials, have been recently introduced to be a class of energy absorber configurations for automotive engineering. This study proposed four different hybrid sandwich tubes and investigated their crashworthiness and performance to cost ratio under quasi-static axial condition. For a comparative purpose, individual carbon fiber reinforced plastic (CFRP) tube, aluminum tubes and aluminum foam were also tested here. From the energy absorption perspective, it is found that all the hybrid specimens exceeded the sum of the individual components. Of different configurations, specimen C-F-C (i.e. outer CFRP tube + aluminum foam + inner CFRP tube) had the highest energy absorption capacity (in energy absorption): 6.70 kJ, specific energy absorption (SEA): 37.32 kJ/kg, improvement of energy absorption: 39.1%, and material cost: 6.877 £, respectively. The specimen C-F-A (i.e. outer CFRP tube + aluminum foam + inner aluminum tube) exhibited the highest crushing force efficiency (0.87) and value-added performance of energy absorption (0.325 kJ/£). The specimen A-F-A (i.e. outer aluminum tube + aluminum foam + inner aluminum tube) exhibited the lowest peak crushing force (63.56 kN) and lowest material cost (2.227 £). Further, the finite element (FE) model was established to analyze the crashworthiness characteristics of hybrid sandwich tubes through validating the simulation results with the experimental data, which provided a basis for further parametric analysis and structural optimization.

Processing and Characterization of Beads with Graded Layer Compositions Based on Zirconia and TRIP‐Steel

A new and innovative coating process of metal matrix beads fabricated using a gel‐casting process by alginate gelation is presented. The suspensions contain austenitic stainless steel and magnesia partially stabilizes zirconia. The prepared beads are coated using two different methods − spraying and dipping. Sintered beads with the used spray coating have an adequate compressive strength (≈550 MPa), good surface quality, homogeneous microstructure, and high energy absorption capability. At lower strains (up to 20%), the spray coated beads obtain much higher specific energy absorption (SEA) in comparison to pure steel beads and in comparison to non‐coated MMC beads based on 90 vol% steel and 10 vol% zirconia: the coated beads show a significantly improved energy absorption capability with 10.7 kJ kg−1 at a strain of 20%. Pure steel only exhibits a SEA of 5.2 kJ kg−1.

Improvement of energy absorption on magnesium alloy mixed carbon-nanotube and lead reinforcement materials in terms of high velocity impact

This paper presents the fracture behaviour of magnesium alloy (AZ31B) with the reinforcement of carbon-nanotube (CNT) and lead subjected ballistic impact. Magnesium alloys are material that can absorb impact energy, however the absorption energy can be increased with the alloy reinforcement with nano-partial. This paper leads to two parts which are experiment and simulation of gas gun. The projectile used was a cone-nose type with diameter of 11 mm made by steel series 1006. The simulation used Cowper-Symonds model to see material behaviour with 25 mm thickness. The correlation of the experiment and simulations was evaluated to see the accuracy of simulations made. It was shown that the value of R2 was 0.9588 where simulation can be used to predict the ballistic impact on 600 m/s velocity. From the simulation results, it was found that the depth of penetration for Magnesium alloy AZ31B reinforced with CNT and Pb showed good agreement findings. The depth of penetrations onto the simulation were obtained between 15 to 25 mm. The added reinforcement materials provide a reduction in the depth of penetration of 40% compared to the original Magnesium alloy AZ31B. Thus, this type of magnesium alloy reinforced with CNT and Pb is suitable for ballistic resistant panel with weight saving determination on armoured vehicle.

Mechanical and Crash Performance of Unidirectional Oil Palm Empty Fruit Bunch Fibre-reinforced Polypropylene Composite

The mechanical properties of unidirectional oil palm empty fruit bunch (OPEFB) fibre / polypropylene (PP) composites were analysed. The composites were fabricated with unidirectional fibre orientations of 0°, 45°, and 90°, with mass fractions of 25%, 35%, and 45% for each fibre orientation angle. The composites were then subjected to tensile, flexural, and impact testing. Superior tensile, flexural, and impact strengths were observed for the unidirectional composites with 0° fibre orientation angle. A fibre loading of 35% provided the highest tensile strength, while fibre loadings of 25% and 45% yielded the greatest flexural and impact resistances, respectively. The crash performance of the unidirectional composite subjected to low-velocity impact in the automotive bumper fascia was investigated. The composite exhibited significantly improved energy absorption capability and comparable specific energy absorption when compared with the current material being used for the bumper fascia.

Crashworthiness of bionic fractal hierarchical structures

This paper presents a fractal hierarchical hexagon structure inspired by bionic structures, such as spider webs, as a novel lightweight energy absorber. Experimental testing and computational modeling are carried out to characterize the effects of fractal order and geometrical shapes on the crashworthiness of this new structure compared to a simple hierarchical structure. The computational results reveal that both simple hierarchical and fractal structures can present significant improvement in energy absorption over single wall nonhierarchical structure. Furthermore, fractal configuration, geometrical parameters and order have important effect on the energy absorption efficiency of fractal hierarchical structures, with the 2nd order design being the optimal for a given mass. The findings of this research offer a new route for designing novel lightweight energy absorbers with improved crash protection against impact.

Design and development of rear under ride protection device (RUPD) with improved energy absorption using ANSYS

Every year thousands of vehicle occupants are killed or injured due to road accidents. Out of which 8% are due to large truck accidents. Truck under ride accidents represents major part of the truck related accidents. Rear Under ride Protective Device(RUPD) of the truck is the main structure for absorbing the energy of collisions during rear impact. It is essential to improve the energy absorption characteristics of RUPD due to poor road conditions and primitive passenger safety systems in India. The current project is aimed at improving the energy absorption capacity of RUPD, for that two different designs are made and analyzed for improved deformation and strain energy storing capacity. The analysis was carried out in ANSYS and results are evaluated between two models for improvement in the deformation and strain energy storing capacity.

Optimization of H-shaped thin-walled energy absorber by Taguchi method and a new theoretical estimation for its energy absorption

To improve energy absorption performance of thin-walled sections, the present research work investigates energy absorption capability of a type of thin-walled profiles with H-shaped cross-section during quasi-static flattening process and optimizes its geometry, using the Taguchi method; and also derives some theoretical formulas to predict total absorbed energy by the H-shaped section. Two theoretical analyses are performed based on two different material models consist of Power hardening and Rigid-Linear work hardening. In each theoretical analysis, general formulations are derived to estimate absorbed energy by a plastic hinge line and an unbending process. In the optimization trend, design of experiment (DoE) is carried out by the Taguchi method. Due to experimental limitations in providing the various samples with different geometrical dimensions, ABAQUS/Explicit software is used. As control factors, influences of geometrical parameters and lateral loading angle are studies on specific energy absorption (SEA); and design of optimum geometry of the H-shaped profile is discussed. Contribution percentage of each control factor is determined on the SEA of the profile, which provides important reference for designing the H-shaped profile in practical energy absorption applications. Results show that wall thickness of the profile cross-section has the highest effect on the SEA of the H-shaped section with contribution ratio of 47.02%. Furthermore, loading angle has the smallest influence on the specific energy absorption capacity. Finally, optimum geometry of the profile is introduced. Also, comparison of the obtained results by theoretical predictions and numerical simulations illustrates precision and acceptable accuracy of the derived theories.

Experimental fabrication and compression analysis characterization of LM30 Al alloy foam with 5wt% SiCp at room temperature

Composite foam of aluminium alloy (LM30) is prepared by reinforcing the foam with 5 wt% of SiC particles, through Melt-stir processing route. The deformation and energy absorption characteristic of this composite foam is studied experimentally, under the application of axial compressive forces on the foam. The experimental results show that the composite foam has improved energy absorption properties because of higher plateau stress and specific energy absorption rate per unit volume. A new approach for utilizing optimization techniques such as Taguchi & ANOVA method, is performed for a better understanding of the effects of mass, density, relative density, pore size and strain rate on the plateau stress and specific energy absorption ability of the foam. Taguchi method is used for determining the optimizing parameters of plateau stress and specific energy absorption ability of the foam. ANOVA and Signal to Noise ratio are utilized for determining the contribution of each optimizing parameters on the results of plateau stress and specific energy absorption ability. Later the microstructure, crystal structure and phase analysis of composite foam samples are characterized by FE-SEM, EDX, XRD and FTIR respectively for perceptive superior analysis.

Optimization of energy absorption properties of thin-walled tubes with combined deformation of folding and circumferential expansion under axial load

Recently, the combined mechanism of energy absorption has been considered for increasing energy absorption efficiency. The combined deformation of circumferential expansion and folding in the cylindrical aluminum thin-walled tubes is one of these mechanisms that can be effective in improving energy absorption. In this paper, the effect of parameters of diameter, height and thickness of the tube, friction, and interference of the tube and punch, as well as the half-angle of the tip of the conical punch on the energy absorption have been investigated using LS_Dyna software. Taguchi method was used to design the experiments and response surface method was used for optimization. In the Taguchi method, the design limit has been significantly reduced and the effect of different parameters on energy absorption has been demonstrated. In optimization with response surface method, optimal states have been proposed that increased energy absorption compared to reference test. Finally, by providing a mathematical model for single-objective optimization, the specific energy absorption increased by 127%, but the maximum force in this case was increased by 130%. In multi-objective optimization, specific energy absorption and maximum force were considered as design parameters that optimized specific energy absorption increased by 77%, while the maximum force was only 37% higher. Thus, by combining suitable types of energy absorption mechanisms and optimizing them, absorbents with a higher specific energy absorption capacity and lower maximum force were designed.

Effect of Process Parameters on Joint Formation and Mechanical Performance in Friction Stir Blind Riveting of Aluminum Alloys

Aluminum alloys have been increasingly adopted in the fabrication of automotive body structures as an integral component of mass savings strategy. However, mixed use of dissimilar aluminum alloys, such as sheet metals, castings, and extrusions, poses significant challenges to the existing joining technologies, especially in regard to single-sided joint access. To address this issue, the current study applied the friction stir blind riveting (FSBR) process to join 1.2 mm-thick AA6022-T4 aluminum alloy to 3 mm-thick Aural-2 cast aluminum. A newly developed, robot mounted, servo-driven, FSBR equipment and the procedure using it to make FSBR joints were introduced systematically. The effect of rivet feed rate and spindle speed on joint formation and cross section geometry was investigated, and it was found that a high spindle speed and a low rivet feed rate, i.e., high heat input, are prone to produce good joints, and that low heat input can cause severe problems related to insufficient softening of the sheets. The rivet deformation, especially the notch location on the mandrel relative to the shank has significant influence on lap-shear strength and fracture mode of the final joints. A rivet pull-out fracture mode was observed at higher rivet feed rates and lower spindle speeds and exhibited significantly improved energy absorption capability, i.e., 62% higher compared to traditional blind riveted (BR) joints.