High Energy Absorption Capacity Research Articles

Performance Evaluation of Sandwich Structures Printed by Vat Photopolymerization.

Additive manufacturing such as vat photopolymerization allows to fabricate intricate geometric structures than conventional manufacturing techniques. However, the manufacturing of lightweight sandwich structures with integrated core and facesheet is rarely fabricated using this process. In this study, photoactivatable liquid resin was used to fabricate sandwich structures with various intricate core topologies including the honeycomb, re-entrant honeycomb, diamond, and square by a vat photopolymerization technique. Uniaxial compression tests were performed to investigate the compressive modulus and strength of these lightweight structures. Sandwich cores with the diamond structure exhibited superior compressive and weight-saving properties whereas the re-entrant structures showed high energy absorption capacity. The fractured regions of the cellular cores were visualized by scanning electron microscopy. Elastoplastic finite element analyses showed the stress distribution of the sandwich structures under compressive loading, which are found to be in good agreement with the experimental results. Dynamic mechanical analysis was performed to compare the behavior of these structures under varying temperatures. All the sandwich structures exhibited more stable thermomechanical properties than the solid materials at elevated temperatures. The findings of this study offer insights into the superior structural and thermal properties of sandwich structures printed by a vat photopolymerization technique, which can benefit a wide range of engineering applications.

Recent advances in auxetics: Applications in cementitious composites

Auxetic materials, possessing negative Poisson’s ratios (NPRs), have the ability to shrink (or expand) in the lateral direction under an axial compressive (or tensile) force respectively. Due to this unique feature, an auxetic material is found to sustain high energy absorption capacity, fracture toughness and shear resistance and thus regarded as one of the future materials in the field of impact protection. However, civil engineering applications of auxetic structures or materials are minimal due to miscellaneous restrictions on NPR effects. Accumulative developments in auxetics have facilitated their applications in cementitious materials in recent years. This paper presents an overview of recent advances in the development of auxetic cementitious composites and analyses and summarises their mechanical properties under different loading conditions. Prior to extensive finite element simulations, more attention has been given to the limited experimental results. Particular attention is paid to the expansionary feasibility of the parent material to introduce auxetic behaviour, with precise identification of the limitations, innovative composition methods and facilitation of auxetic features. Finally, the paper outlines the limitations of the current research and envisages few future research opportunities in auxetic cementitious composites.

Design and optimization of bio-inspired thin-walled structures for energy absorption applications

Thin-walled structures are widely used in the automobile, aerospace, and other engineering disciplines for impact energy absorption purposes for their lightweight and high energy absorption capacities. In this study, the energy absorption characteristics of various designs of the bionic structures inspired from bamboo are investigated so that the optimum design with the highest energy absorption can be achieved. For high-velocity impact applications (100 m/s), a rate-dependent material model is employed in all analyzes. Different design-cases with various connecting ribs are studied, and the optimum number of connecting ribs is obtained for each design-case. For the best performing designs, design parameters are optimized using Non-Sorting Genetic Algorithm 2 (NSGA2) to enhance the energy absorption properties further, yielding a 17% increase in the energy absorption capacity. Finally, for a more popular number of ribs, i.e. 4 and 6, design parameters are optimized using NSGA2 for practical applications. It is shown that it is crucial to employ a rate-dependent material model in the impact modeling as the results are highly reliant on the dynamic behavior of the material.

Introducing new nested absorbers with square cross-sections and optimization of their performance using Response Surface Method under quasi-static loading

Thin-walled structures with nested cross-sections have been introduced in recent years as structures with high energy absorption capacity. In this research, a new type of energy absorbers is introduced, which is a combination of two different elements which are subjected to lateral and axial loads simultaneously. The study has been done experimentally and numerically; in the numerical part, LS-DYNA software was used for computer simulations. The outer part of the introduced absorbers has square shells with a thickness of two millimeters that absorbs energy under lateral loading. The inner part of new absorbers is a shell with a rectangular cross-section that collapses under axial compression. The obtained results showed that these structures can increase the energy absorption by 36 and 32% of the total energy absorbed through each component separately. In the experimental part, the accuracy of numerical results was checked, and good agreement was observed. In the final part of this research, using Minitab software and based on the response surface method (RSM), the most optimal absorbers in terms of specific energy and maximum force were introduced.

Mechanical responses of sheet-based gyroid-type triply periodic minimal surface lattice structures fabricated using selective laser melting

Owing to their lightweight design, high energy absorption capacity, and excellent thermal and sound insulation properties, lattice structures have many potential applications in the fields of security, aerospace, biomedicine, and heat dissipation. In this study, a gyroid-type triply periodic minimal surface is used to design lattice structures. Gyroid uniform lattice structures and gyroid graded lattice structures are mathematically designed and fabricated using selective laser melting with a SS 316 L stainless steel powder. The mechanical properties of these structures are studied under a compression load, and the deformation differences between the graded and uniform structures are compared. The finite element method is used to simulate the compression process, and the experimental and simulation results are qualitatively compared. Results show that during plastic deformation, the stress change in the graded structure is larger than that in the uniform structure. By controlling the volume fraction, mechanical properties can be specifically tailored, which provides the design guidelines for the application of this structure.

Dynamic responses of corrugated cylindrical shells subjected to nonlinear low-velocity impact

Owing to high capacity of energy absorption, high compressive strength, high stiffness to weight ratio, good ductility and other excellent characteristics, corrugated structures are widely used in aerospace, civil, petrochemical engineering and other industries. These structures are often subjected to low-velocity impact during operation, which has a destructive effect on the strength and stiffness of engineering structures. However, since the process of low-velocity impact is a strongly nonlinear time-varying process, it is difficult to obtain the impact force. The present study proposes a novel computational method for nonlinear impact force in the local contact area, and analyzes the dynamic response of corrugated structures. Firstly, a new equivalent shell model of corrugated cylindrical shells is established. Afterwards, the governing equations are obtained by using the Love thin shell theory and Hamilton principle, and then turned into ordinary differential equations by the Galerkin procedure, upon which numerical solutions are achieved by the Duhamel integration and small-time increment technique. Then, numerical examples are given to illustrate validity and efficiency of the proposed method. Finally, the influence of key parameters on impact response of different types of corrugated shells is analyzed.

Energy absorption behavior of tapered and ribbed thin-walled structures under compressive crushing forces

This paper investigates the energy absorption behavior of straight and tapered square, hexagonal and octagonal tubes with two types ribbed connection inside. The parameters studied are the geometry of section, rib configuration and taper angle. In this study, a numerical model is introduced and justified by both the analytical and numerical models in the literature. The results show that octagonal tubes have the highest energy absorption capacity followed by hexagonal and square sections. The ribbed profiles have better energy absorption per unit mass by an increased number of corners. The energy absorption per unit mass and crushing force efficiency decrease with increasing taper angle.Results also indicate that the tapered profile delivers more stable crushing behavior. The research findings can be used to quantify energy absorption in the design of energy absorbers for impact applications.

Mechanical Properties of Banyan Fiber‐Reinforced Sawdust Nanofiller Particulate Hybrid Polymer Composite

The utilization of renewable raw materials, such as natural fiber composites, can be prioritized in the building industry as it transitions to a bioeconomy. The sustainable product can improve environmental protection; therefore, the present work is stated with the natural fibers of chopped banyan fiber reinforced with sawdust nanocellulose epoxy‐based composite fabricated by hand layup process. To identify the mechanical effects of tensile strength, flexural strength, impact strength, and hardness value for five different weight ratios of chopped banyan fibers and sawdust nanofiller materials, the composite weight ratio was made with 60% of matrix phase that was fixed for all five samples and 40% of reinforcement phase in which the fibers and filler percentage can vary for five samples. The results are revealed sample E (50 g of banyan, 25 g of saw dust, 110 g of epoxy, and 185 g of laminate) given a more tensile strength of 39 MPa and a flexural strength of 34 MPa, and sample A was given a high impact energy absorption capacity of 18 Joule compared with other samples of hybrid composite; and also, the SEM morphological was used to identify the surface interaction and failure mode of this composite laminates.

On bending crashworthiness of smooth-shell lattice-filled structures

Thin-walled structures are widely used in engineering applications. In order to improve the mechanical properties of thin-walled structures, porous structures are usually filled into thin-walled tubes. However, the widely used porous structures have the disadvantages of randomness, heterogeneity and anisotropy. Recently, a novel porous structure called as smooth-shell lattice has gain attention for its high energy absorption capacity. The crashworthiness of thin-walled tube may be highly improved if it is filled by smooth-shell lattice. However, there are few researches on studying the crashworthiness of the smooth-shell lattice-filled structures. To this end, the bending crashworthiness of the smooth-shell lattice-filled structure is investigated jointly using experiment, numerical simulation and empirical formula in this study. The smooth-shell lattice of this study is constructed based on the triply periodic minimal surface (TPMS). Three kinds of TPMS-based smooth-shell lattices are considered in our study. The influence of the design parameters such as the shell thickness of lattice, unit-cell size of lattice and thickness of tube on the crashworthiness is studied. In order to obtain the optimal designs of smooth-shell lattice-filled structures, the PRS metamodels and NSGA-II are employed, while the peak crushing force (PCF) and specific energy absorption (SEA) are chosen as the optimization objectives. The force–displacement responses of three filled-tubes are fitted in the end. The investigation results show that the smooth-shell lattice-filled tube has more bending crashworthiness than the traditional foam-filled tube with the same weight. The smooth-shell lattice-filled tube can be used as excellent energy absorption structure in impact engineering.

An innovative system of coupled steel plate shear wall with pin FUSE in link beam: Cyclic behavior and energy dissipation

Coupled steel plate shear wall (C-SPSW) is one of the resisting systems with high ductility and energy absorption capacity. Energy dissipation in the C-SPSW system is accomplished by the bending and shear behavior of the link beams and SPSW. Energy dissipation and floor displacement control occur through link beams at low seismic levels, easily replaced after an earthquake. In this study, an innovative coupled steel plate shear wall with a yielding FUSE is presented. The system uses a high-ductility FUSE pin element instead of a link beam, which has good replaceability after the earthquake. In this study, four models of coupled steel plate shear walls were investigated with I-shaped link beam, I-shaped link beam with reduced beam section (RBS), box-link beam with RBS, and FUSE pin element under cyclic loading. The finite element method was used through ABAQUS software to develop the C-SPSW models. Two test specimens of coupled steel plate shear walls were validated to verify the finite element method results. Comparative results of the hysteresis curves obtained from the finite element analysis with the experimental curves indicated that the finite element model offered a good prediction of the hysteresis behavior of C-SPSW. It is demonstrated in this study that the FUSE pin can improve and increase the strength and energy dissipation of a C-SPSW system by 19% and 20%, respectively.

On crashworthiness of novel porous structure based on composite TPMS structures

Porous structure based on triply periodic minimal surface (TPMS) has received extensive attention due to its excellent performance and lightweight. This study aimed to propose three novel types of composite TPMS-based porous structures (PI-type, PIP-type, and PN-type) inspired by the microscopic porous structure of bones and investigate their crashworthiness properties. The finite element method was used to simulate the deformation process of porous structures, and the finite element models were validated by the quasi-static compression experiment on PI structures manufactured by 3D printing. The simulation results revealed that the thickness ratio of the inner and outer surfaces significantly influenced the structure’s deformation modes and energy absorption capability. The PI structures with thickness ratios of 0.3 and 0.4 (PI-0.3 and PI-0.4) and the PIP structures with thickness ratios of 0.4 and 0.5 (PIP-0.4 and PIP-0.5) were found to have higher energy absorption capacity and efficiency and lower peak crushing force than traditional foam structures. Especially, the energy absorption capacity and efficiency of PI-0.4 are 10.8% and 12.1% higher than those of the foam, respectively. It was found that the PI structure with the thickness ratio of 0.4 has the best crashworthiness, evaluating the crashworthiness indicators (PCF, SEA, MCF, and CFE) by the complex proportional assessment (CPA) method. Moreover, the theoretical formula of the average crush force of the structure was predicted based on the Gibson empirical formula, which can provide a guideline for the crashworthiness design of TPMS-based porous structures.

Experimental study of concrete floating slab municipal road with steel spring isolators under vehicle loads

The application of the steel spring floating slab on the railway tracking system for vibration mitigation can be transferable for the construction of the municipal road suspended above the underground concrete framing structures. In this study, the presence and performance of the steel spring floating slab subjected to the various traffic loads along with different driving speeds were experimentally conducted by monitoring the acceleration-time responses, 1/3 octave frequency - acceleration levels relationships, and acceleration – velocity curves. Subsequently, the capacities of the steel spring floating slab in vibration acceleration reductions and also the energy transmission losses were quantified through the analysis of the experimental outcomes. The results indicate that with the presence of the steel spring vibrational isolators, the natural frequency of the slabs for underground structures was reduced significantly compared to the floating slabs without additional steel springs. Hence, the natural frequency was differentiated with the main frequency of excitation of vehicle load to avoid the occurrence of the resonance in the underground structure. Moreover, the uplifting effects of the steel spring floating slab and vibration isolators significantly reduced the amplitudes of the acceleration in low-frequency vibration induced by the traffic loads and hence achieved a high energy absorption capacity. Additionally, with the presence of the spring floating slab as well as the vibration isolators, the vertical acceleration peaks, acceleration levels increase with an increase of the One-third (1/3) octave frequency until it reached 16 Hz.

The Research of Blast Resistant of Reinforcement Concrete Beams in Concrete Structures at Off-site Oil and Gas Plant

In the recent decades, blasts and gas explosions at the off-site of oil and gas plants have increased leading to destruction of important concrete structures, essential equipment and loss of human life. In response, structural engineers have come up with different ways of reinforcing beams of concrete structures using fiber reinforced polymers composite materials to produce blast resistant structures to minimize the impact of the blast loads, due to their unique and individual characteristics like high flexural and shear strength. This paper seeks to research the dynamic behavior, response and performance of reinforce concrete beams strengthened with Carbon Fiber Reinforced Polymer composites when subjected to blast loading. The study aims at proposing a design model of strengthening reinforce concrete beams with Carbon Fiber Reinforced Polymer in supporting concrete structures at off-site oil and gas plants against hydrocarbon explosions. Carbon Fiber Reinforced Polymer composites exhibit higher modulus of elasticity, higher energy absorption capacity, resistant to all forms of alkali and higher tensile strength compared to all other fiber reinforced polymers reinforcements and therefore the need to assess its capacity in protecting concrete structures at oil and gas plants against dynamic loads. The research will be carried out through numerical analysis using the finite element analysis computer program, ANSYS.

Evaluation of Effective Polymer Fiber Length on Energy Absorption Capacity of Reinforced Beams by EBR and NSM Methods

This study presents a comparison of two methods used for retrofitting Reinforced Concrete (RC) beams, namely, the Externally Bonded Reinforcement (EBR) and the Near-Surface Mounting (NSM) methods. A parametric analysis was carried out using variables such as the retrofitted, the retrofitting method (EBR and NSM), and the thickness of the Carbon Fiber-Reinforced Polymer (CFRP) sheets. To achieve this goal, the finite element method and ABAQUS software were employed. An un-retrofitted beam was also simulated as the control specimen for comparison. Beam responses were compared through load–displacement and energy absorption capacity diagrams. Results show that the higher energy absorption capacity in all CFRP-retrofitted RC beams, which was 1.69–5.54 times higher than in un-retrofitted beams. In the case where half of the beam was reinforced using CFRP sheets, the entire beam assembly and the CFRP sheet contributed to load-bearing, thus delaying crack nucleation in the beam and increasing its energy absorption capacity. As a result, the energy absorption capacity of the beam, in this case, was less than that obtained in the previous one where half the span of the beam was retrofitted.

Crashworthiness of Circular Tubes with Rhombus Star Grooving Pattern

Thin-walled structures are widely used as energy absorbers in aircraft and automobiles. They have a high load-bearing capacity despite their small thickness. Due to their lightweight and high energy absorbing capacity, their application is becoming increasingly diverse. In this study, the structural response and crashworthiness performance of circular thin-walled grooved tubes were investigated under axial loading. Rhombus star grooving patterns were introduced to relatively short and thin tubes to enhance crashworthiness performance. The optimum crashworthy performance should provide a proper initial stiffness and a stable crushing force after the initial collapse. Experimental and numerical analyses have been conducted to investigate the influence of various geometrical patterns on crushing behavior and crashworthiness parameters. It was found that several multi-lobe diamond deformation modes can be triggered for a tube with a constant diameter to thickness ratio (D/t = 59.25). An increased number of lobes and folds led to higher specific energy absorption (SEA) and crushing load efficiency (CLE), up to 31% and 34.5% respectively. Parametric studies showed that groove depth can be used to achieve a desirable deformation mode that increases both SEA and CLE simultaneously. The proposed tubes would apply to the crashworthiness design of helicopter subfloor structures and vehicle bodies.

Preparation and compression performance of porous magnesium alloy composite with ceramic hollow spheres

Using two different ceramic hollow spheres (the commercial alumina hollow sphere and the self-made silicon-containing ceramic hollow sphere) as reinforcements, two kinds of lightweight porous magnesium alloy composite materials were successfully fabricated by sintering at 600 °C for 3 h 20 min. The microstructure of samples with the self-made silicon-containing ceramic hollow sphere reveals that an alloy phase containing MgO and Mg2Si was formed by an interfacial reaction at the interface between the magnesium alloy and the self-made ceramic hollow sphere. The formation of the alloy phase is beneficial to improve the mechanical properties of the sample. The influence of different types of ceramic hollow spheres on the apparent density, compressive strength, specific strength, energy absorption, and energy absorption efficiency was studied for these porous products. The results show that the apparent density of these two porous samples is markedly lower than that of the magnesium alloy. The Compression curves of both samples have the elastic stage, the yield platform, and the densification stage, which are the typical compression characteristics of porous materials. The compressive strength and specific strength of the samples made by self-made silicon-containing ceramic hollow spheres are both significantly higher than those made by commercial alumina hollow spheres. Moreover, the energy absorption performance of the sample made by self-made silicon-containing ceramic hollow spheres is better than that of the sample made by alumina hollow spheres. The higher energy absorption capacity and the wider strain range of maintaining the maximum energy absorption efficiency mean the sample made by self-made silicon-containing ceramic hollow spheres can absorb more energy.

Deformation pattern classification and energy absorption optimization of the eccentric body centered cubic lattice structures

Lattice structures have shown excellent mechanical properties, such as high energy absorption capacity. In this work, the extended body centered cubic lattice was proposed by offsetting the position of the body center. The pattern recognition method of nonlinear discriminant function was creatively used to classify the proposed eccentric body centered cubic (EBCC) lattice structures according to their deformation patterns. The results indicated that the lattice structures belong to X-Pattern possessed the best energy absorption capability. Further, the relationship between the energy absorption properties and the configuration was captured using a modified symmetric radius basis function (RBF) surrogate model showing higher computational efficiency and approximately equal accuracy compared to the original RBF model. The nondominated sorting genetic algorithm II (NSGA-II) was carried out to obtain the Pareto optimal set, rendering the EBCC structure with balanced properties of high specific energy absorption and low peak crushing force. This work presents a first effort in optimizing the energy absorption of lattice structures through pattern recognition, thus expanding the approaches for designing new lattice structures.

Review on advances in porous Al composites and the possible way forward

Porous aluminum (Al) composites are lightweight and high-strength materials composing of Al as a matrix material with some strengthening reinforcements and pore-forming agents that result in the formation of new material with superior physical properties and energy absorption capacities. This work gives an overview of the porous Al-foams developed thus far, including the foaming agents and space holders, their properties, production techniques, and applications. First, it deliberates the foaming agents and space holders responsible for the foaming and formation of pores in the composites followed by the mechanical properties of the foams. Al has huge potential for applications that require lightweight, high-strength, and high-energy absorption capacity materials, especially in structural construction and automobile manufacturing. Although Al-foams have been successfully used in automobiles for crashworthiness, lightweight structure, and other functional applications, the development of Al foams with enhanced characteristics and properties has limitations. This review discusses various reinforcements used for improving the characteristics of Al-foams. This review also provides an overview of various commercial foams and their contribution to several applications. Finally, it attempts to reveal impediments in foam production with suggested solutions for overcoming the problems in this area.

Metal-alike polymer composites: The effect of inter-layer content on the pseudo-ductile behaviour of carbon fibre/epoxy resin materials

With interfacially engineered pseudo-ductile carbon fibre reinforced polymer composites, a higher energy absorption capacity and metal-like stress-strain response can be achieved during failure. Due to incorporated inter-layer additives deposited with fused filament fabrication, locally weakened zones can be printed on the surface of the reinforcing material, which provides better energy absorption capability during the composite laminates’ damage process by the alteration of crack propagation. The reason for this phenomenon is that cracks near the inter-layered zones require more energy to propagate, which delays the onset of final failure in the form of local damage. The modified layers are then infiltrated with an amine-cured epoxy by vacuum assisted infusion. The change in pseudo-ductile behaviour as a function of the interfacial additive content was investigated, along with the change in mechanical properties.The stress-strain relationship was determined by various tests, quasi-static and dynamic, from unmodified composites (0% interlayer used) up to 100% interlayer content (i.e. polymer film) between the matrix and the reinforcement. We have investigated a method to repair the specimens after the bending tests via melting the thermoplastic interlayer. The results show that with the use of interlayer material, the critical stress intensity factor increased, and ductile behaviour improved thanks to the altered crack propagation.

Study on mechanical performance of 3D printed composite material with topology shape using finite element method

Application of the topology shape within a control space of the structure can ensure high energy absorption capacity, stiffness and strength for a load and boundary condition. In recent years, researchers have studied a continuous fiber 3D printing method with enhanced mechanical performance while being able to flexibly manufacture a complex shape in the application of a topology shape. Therefore, in this study structural analysis using a finite element method was performed for the conditions under which tension and bending load act on a continuous fiber 3D printed composite specimens with various topology shapes. To investigate the influence of topology shape on the mechanical performance, the diverse topology shapes were designed as a square, rectangle, rhombus, and hexagon. Also, to examine the effect of infill density, 40 and 80 holes were considered. As a result of finite element analysis, according to the topology shape, it was found that the rhombus has the highest mechanical performance under tension load. For the bending load, the hexagon has high strength and stiffness while being the shape that can be lightened. Additionally, there were shapes in which the mechanical strength was decreased or maintained even with the increase of the infill density, and the result was that the increase in strength and stiffness was not constant. In conclusion, it is necessary to perform an optimization design for not only the topology shape but the infill density to design an efficient 3D printed composite structure.