Papers by Keyword: Energy Absorption

Abstract: Occupant safety is one of the critical performance criteria established in the aerospace industry. Several composite materials have been developed but the energy absorption properties are not yet satisfactory. This study investigates the energy absorption characteristics of aluminum tubes reinforced with coir-fiber/epoxy system at varying proportions (10-90%) according to the specifications of hybrid tube thickness compositions (10T, 15T, 20T) towards evolving a criterion for optimal performance. Finite element analysis was conducted in ABAQUS to determine the load–displacement response and the crashworthiness properties of the tubes while a representative volume element (RVE) model was formulated to obtain the elastic properties of the reinforcement phase. The results indicated that the incidence of high peak forces P_max is related to tube thickness variations where the 20T tubes were found to give the best performance, while the 15T tubes showed a superior performance under progressive crushing and presented the best responses for specific energy absorption (SEA). A multi-objective optimization plan was implemented and through the Pareto fronts, tube configurations (C20T60F), (C15T70F) and (C20T40F) were found to be most consistent with the design criteria. Results from experimental validation were found to be in close agreement with numerical predictions and satisfied the overall objective of achieving a good balance in lightweight design for crashworthiness applications.

Abstract: Concrete is extremely vulnerable against impact loading due to its low tensile strength and pronounced brittleness. The application of thin strengthening layers, containing Textile Reinforced Concrete (TRC) and Strain-Hardening Cement-based Composites (SHCCs) in a ductile cement-based composite, is a promising solution to enhance the impact resistance of existing concrete structures. Three-dimensional (3D) textile structures exhibit numerous advantages over two-dimensional (2D) ones, most importantly higher shear, bending and energy absorption capacity, hence, appear to be instrumental in providing sufficient reinforcement to the target strengthening layers. However, design variability and optimization possibility of available 3D textile reinforcement are restricted. This paper presents the development of novel textile-based 3D truss reinforcement that can overcome these limitations. On the basis of woven 3D cellular structures, innovative pyramidal 3D truss reinforcement with favorable load-bearing capacity as well as notable energy absorption capability is developed and successfully realized. To investigate the feasibility and efficacy, cement-based composite consisting SHCC and newly developed pyramidal 3D truss reinforcement is prepared and tested under high-speed tensile loading as well as transversal impact loading. The experimental results show that woven 3D truss reinforcement is highly compatible with SHCC, and significantly enhances its impact resistance. Furthermore, SHCC reinforced with novel pyramidal 3D truss structure remarkably outperforms that with 2D carbon reinforcing structure approved for commercial use.

Abstract: The aim of this study was to determine the compressive mechanical properties and the energy absorption characteristics of a bio-composite material based on lime, wheat straw, and additives (protein and entraining agent). The selected samples with fiber to binder ratio of 30% were subjected to compression tests at different strain rates (1 mm/min, 10 mm/min, and 100 mm/min), in the perpendicular and parallel directions to fiber orientation. Image analysis supported with Digital Image Correlation (DIC) method is performed to follow longitudinal and lateral deformations, thus making it possible to evaluate elastic properties. The results show that the highest density and compressive strength in the parallel direction are ~349 kg/m³ and ~0.101 MPa, respectively. The perpendicular specimens at 100 mm/min of speed test showed the highest values of densification strain, stress plateau, energy efficiency, and absorbed-energy of 47.27%, 0.32 MPa, 16.98 %, and 13.84 kJ/m², respectively. The values of Young’s modulus identified with DIC are significantly different from those determined by the slope of the linear part of the stress-strain curve. A slight influence of strain rate on mechanical properties is observed.

Abstract: There exist some problems in the crash box and anti-collision beam sandwich structure, such as monotone deformation pattern and uneconomical energy absorption performance. In order to raise the deformation capacity and energy absorption performance of sandwich structure, centrosymmetric reentrant honeycomb (CRH) and hexagonal centrosymmetric reentrant honeycomb (HCRH) are proposed based on auxetic reentrant honeycomb (ARH) in this work. Based on HCRH, four kinds of transverse combination structures and two kinds of longitudinal combination structures are obtained. The results of specific energy absorption show that the energy absorption capacity of the angular contact homodromous combination structure (ACOC) is about 3 times that of the other three transverse combination structures. Compared with longitudinal heterodromous combination structure (LHEC), the energy absorption capacity of longitudinal homodromous combination structure (LHOC) is improved by 72.7%.

Abstract: In this paper, the post ballistic impact behaviour of kevlar-glass fibre hybrid composite laminates was investigated against 9×19 mm projectile. Eight different types of composite laminates with different ratios of kevlar woven fibre to glass fibre were fabricated using hand lay-up with epoxy matrix. Ballistic behaviour like ballistic Limit (V₅₀), energy absorption, specific energy absorption and Back Face Signature (BFS) were studied after bullet impact. The results indicated that as the Percentage of glass fibre is increased there was a linear increment in the ballistic behaviour. Addition of 16% kevlar fabric, composite sample meets the performance requirement of NIJ0101.06 Level III-A. Since the maximum specific energy absorption was observed in Pure Kevlar samples and the adding of glass fibre increases the weight and Areal Density of the sample, further investigations need to be carried out to utilize the potential of glass fibre for ballistic applications.

Abstract: Experimental work has been performed on the behaviour of glass/epoxy, aluminum, and aluminum-glass/epoxy empty and polyurethane foam filled tubes subjected to three-point bending. Tubes were of circular and square cross section area. Hand layup method was used to fabricate the tubes. Each tube is made of six layers. Inner diameter and total length of the tubes were 50 mm and 250 mm respectively. Bending load-displacement response, crush force efficiency, and absorbed energy were drawn and discussed. Effect of foam filler, material of the tube and stacking sequence on the maximum bending load was investigated. Energy absorption was determined and discussed. failure mode was investigated. It has been found that the polyurethane foam filler increased the maximum bending load and the energy absorption of the circular and square cross section area tubes. Using hybrid aluminum-glass/ epoxy enhanced the bending load and absorbed energy of the aluminum tubes. Cracks were observed at the upper and lower surfaces at the centre of the glass/epoxy tubes. While the aluminum tubes deformed significantly with either no cracking or with one crack appeared at the centre of the top surface of the tube.

Abstract: This research studied the effect of eggshell powder as a partial replacement of cement on fresh and hardened properties of concrete. The cement was partially replaced with eggshell powder at these percentage 0%, 2.5 %, 5 %, 7.5% and 10%, (by weight of cement). The resulting concrete was compared for impact resistance, energy absorption, load-slip characteristics and ultimate bond strength. setting time (initial and final), slump, density and compressive strength also have been found. The obtaining results indicated the advantage of incorporation of eggshell powder in concrete. The concrete unit weight has not obviously affected by eggshell powder content. The 2.5% eggshell powder give the best results compared to reference mix.

Abstract: Composite steel-concrete sections have a broad benefit through increasing structural strength as well as minimizing the self-loads. All past researches were concerned with pre-installed shear connectors (PRSC) in the manufacturing of composite sections. A new fabrication technique for steel-concrete-steel composite sections were presented in the current study by the post-installation shear connectors (POSC) passed-through an embedded polymerizing vinyl chloride (PVC) pipes. The performance of normal strength concrete prisms with a specified strength of 32 MPa connected to square steel tubes (SST) was investigated. Six specimens were fabricated in both methodologies, PRSC and POSC were experimentally tested by Push-out test. The spacing of the shear connectors was changed for every two specimens fabricated in two different ways in order to obtain a full behavioral view. However, POSC does not have full-bond to concrete prisms, the test revealed a comparable strength of POSC specimens. The test shows a slight increase in the ultimate strength of PRSC specimens by (12.11, 11.19, and 9.45) % than POSC specimens for 100mm, 150mm, and 200mm spaced shear connectors.

Abstract: The energy absorbing performance in the progressive failure of glass long-fiber-reinforced polyamide was evaluated by using the split Hopkinson pressure-bar method. An impact compression test of glass long-fiber-reinforced polyamide was performed from –30 °C to 90 °C, and the temperature-independent energy absorbing performance was confirmed only for the progressive failure mode. To clarify this phenomenon, compression tests, interlaminar compressive shear tests and mode-I fracture-toughness tests were conducted under static and impact conditions. The compression strength and the shear strength of all specimens decreased with an increase in temperature. The toughness improved with temperature. In addition to the mechanical tests, failure-mode analysis was performed by using a three-dimensional X-ray microscope to clarify the absorbing mechanism. From the above, it was concluded that the temperature-independent energy absorbing performance results from a balance of these mechanical properties against the temperature change.

Abstract: The aim of this paper is to study the quasi-static axial compressive performance of newly developed steel foam-filled tubes (SFFTs). The energy absorption capability of steel foam-filled tubes was assessed. The results show that steel foam-filled tubes collapse in the axisymmetric-concertina deformation mode. The plateau stress of the plastic deformation of the steel foam-filled tubes decreases with the increase of porosity of steel foams, and is significantly higher than the sum of the identical steel foam and aluminum tube. The absorbed energy per unit volume of the steel foam-filled tubes is 8%~ 15% higher than the sum of those of identical aluminum tubes and steel foams with porosity ranging from 65% to 80%.