Crashworthiness Design Research Articles

Crashworthiness design of GFRP bar reinforced concrete bridge pier subjected to truck collision

This study investigates the failure behavior and post-impact damage of glass fiber reinforced polymer (GFRP) bar reinforced bridge pier under truck collision. The finite element model of a benchmark bridge with its pier reinforced with GFRP bars collided by a medium truck is established using LS-DYNA. The effectiveness of adopted material models and contact algorithm is verified by comparing the experimental and numerical observations of scaled GFRP reinforced concrete columns under horizontal impact loading. The failure analysis results show that the post-impact damage of the composite pier can be classified into four levels, and the shear force at pier bottom is a reasonable index that can represent the dynamic shear capacity of the composite pier. Besides, the influence of design variables on the dynamic shear capacity of the bridge pier is clarified, and a closed-form formula is proposed to predict the dynamic shear capacity based on response surface methodology. Furthermore, kinetic energy-based damage index and damage evaluation approach are developed to forecast the post-impact damage levels of the composite bridge pier. Finally, combining the post-impact performance objectives and damage evaluation approach, a performance-based crashworthiness design framework is developed and validated to provide a basic reference for design consideration of GFRP reinforced concrete bridge pier.

Multi-objective optimization of multi-core composite aluminum honeycomb sandwich panels for improved crashworthiness

This article presents the low-velocity impact response of the multi-core aluminum honeycomb sandwich panel with composite face sheets using LS-DYNA-based finite element simulation. The effect of geometric parameters like cell size, cell height, cell thickness, and facesheet thickness, on structural response, is explored. The interaction effect of these geometric parameters, effect of number of layers/cores and characteristic force-time and energy-time curves for multilayer composite sandwich panels are also studied. Finally, these geometric parameters are optimized for better crashworthiness designs, followed by crashworthiness design recommendations.

On axial crushing behavior of double hat-shaped CFRP and GFRP structures

This study aimed to investigate the energy-absorbing mechanisms of composite structures subjected to quasi-static and dynamic axial crushing loads. Double hat-shaped composite tubes were prepared using carbon fiber-reinforced polymer (CFRP) and glass fiber-reinforced polymer (GFRP) composite materials. The results indicated that these composite tubes exhibited a progressive end-crushing mode and had a comparable load-carrying capacity at a crushing velocity of 2 mm/min. When the loading rate was increased to 6.1 m/s, a 23.3% reduction in the energy absorption of the CFRP structures was observed; whereas the energy absorption of the GFRP structures remained relatively constant. A stacked-shell finite element model, which considered the effects of strain rate on intra-layer and inter-layer properties, was developed to simulate the axial crushing behavior of the CFRP and GFRP tubes. The predictions made by the finite element model were found to correlate well with the tested crushing process, force–displacement curves, and final failure mode. The mechanical properties of the composite materials were also observed to play a critical role in the energy-absorbing mechanisms, contributing to the distinct crushing responses of the CFRP and GFRP structures. The results of this study are expected to help clarify the differences in the energy-absorbing mechanisms between CFRP and GFRP tubes, thereby contributing to the crashworthiness design of composite energy-absorbing structures.

Experimental study on fuselage fuel hose guillotine test of civil aircraft

The crash-worthiness design of civil transport aircraft fuel systems is significance to improve the safety of the aircraft in the case of a crash. CCAR25.993 (f) requires that “fuel feed line in the fuselage shall be assembled to allow reasonable deformation and tension without fuel leakage”. Fuel system fuselage fuel supply line with the appropriate hose configuration can take the advantage of the ductility of the material, and the guillotine test is accepted by worldwide examiners to validate the deformation and tensile capacity of the fuel hose to keep it from leaking fuel.

Experimental Research on Dynamic Behavior of Stiffened Plates under Drop-Weight Impacts of a Wedge Impactor.

Deck structures subjected to drop-weight low-velocity impact are critical safety elements for ships and offshore structures. Therefore, the aim of the present study is to propose experimental research on dynamic responses of deck structures composed of stiffened plates subjected to drop-weight impact of a wedge impactor. The first step was to fabricate a conventional stiffened plate specimen and a strengthened stiffened plate specimen, as well as a drop-weight impact tower. Then, drop-weight impact tests were carried out. Test results show that local deformation and fracture occurred in the impact area. A sharp wedge impactor caused premature fracture, even under relative low impact energy; the permanent lateral deformation of the stiffened plate was reduced by 20-26% by the strengthening effect of a strengthening stiffer; residual stress and the stress concentration of the cross-joint caused by welding may cause undesired brittle fracture. The present investigation provides useful insight for improving the crashworthiness design of the deck structure of ships and offshore structures.

Dynamic bending behavior of double-hat beams filled with alloy hierarchical structure

Double-hat beams are widely used in vehicle body due to their light weight and high energy-absorbing properties. In this study, the dynamic three-point bending performance of the double-hat structure is improved by alloy hierarchical structure filling. The simulation model of the double-hat structure is established, and its accuracy is verified by experiments. Three different hierarchical structure models are proposed through the changes of structure and micro-element size. Compared with the traditional double-hat beam, the specific mean crushing force (SMCF) of triangular hierarchical structure (THS), parallelogram hierarchical structure (PHS) and hexagonal hierarchical structure (HHS) increased by 5.15, 4.35 and 3.92 kN/kg, and their deflections decreased by 180.56, 165.01 and 170.99 mm, respectively. The influence of geometric parameters of these three hierarchical models is studied. It is revealed that the increase in the number of microstructure columns significant enhanced the crashworthiness of the double-hat structure. It is also showed that the continuous expansion of the cell size affected the impact performance of different hierarchical structures. These results will make an important contribution to the crashworthiness design of double-hat beam and vehicle.

Crashworthiness of double-gradient hierarchical hexagonal tubes under multiple loads

Hierarchical design and gradient design have been shown to improve the crashworthiness of structures. However, fewer studies combine the two. Therefore, this study combines the two to design a novel double-gradient hierarchical hexagonal tube (DGHHT) based on a hexagonal tube (HT). According to the different axial gradients, they are divided into DGHHT-1 and DGHHT-2. The crashworthiness under multiple loads was studied by finite element simulation. Firstly, the reliability of the finite element model is validated by experimental results. Secondly, compared with single-gradient hierarchical hexagonal tubes (SGHHT), DGHHT have better resistance to global bending under multiple loads. When studying mass effects, it was found that both HT and DGHHT had increased peak force and SEA. When HT is designed as DGHHT-2, specific energy absorption (SEA) can be increased by up to 82.74%. Studying the effects of impact angle found that DGHHT-2 has better resistance to global bending than HT as the angle increases. Studying the effect of DGHHT-2 axial gradient distribution found that reasonable distribution of its axial gradient can further improve its ability to resist global bending. Finally, compared with the structures proposed in other studies, DGHHT-2 also has better resistance to global bending at an impact angle of 30°. The double-gradient hierarchical design in this study can provide new design ideas for crashworthiness design.

Design for bird strike crashworthiness using a building block approach applied to the Flying-V aircraft

The Flying-V aircraft concept promises better fuel-burn performance over conventional tube-and-wing configurations, integrating the passenger cabin and cargo volume into the lifting surface. However, the wing-fuselage and cockpit windows of the Flying-V are exposed to the flight direction, posing a new challenge to the design and certification of structures in terms of bird strikes. This study is a first step towards understanding the dynamic load path and contribution of each structural element on the bird strike resistance of the Flying-V leading-edge structures. The objective is to propose a building block approach to design the Flying-V's leading edge bird strike crashworthiness that complies with the EASA's certification CS25.631 using a 4lb bird impacted at a sea level cruising speed of 70 m/s. An additional requirement by the authors is to keep the structure within the elastic deformation during the impact of a 4lb bird to avoid the need for repairs in the Flying-V fuselage. Plasticity generated in the structure is regarded as damage and is used as a comparative parameter. At the highest building block level, a sensitivity analysis is performed to identify the effect of the thickness of each structural element on the plasticity and weight of the leading-edge structures. The trends are used to modify the baseline design and achieve a reduction of 80% of the plastic energy. The critical case of a 133 m/s impact of a 4lb bird at the cruise altitude of 37000 ft is also evaluated, and the results show penetration.

Crashworthiness design of CFRP/AL hybrid circular tube under lateral crushing

The metal hybrid method can effectively solve the problem of low energy absorption efficiency of CFRP under lateral crushing load, and the application prospect of the hybrid tube can be better explored through the related crashworthiness design. Therefore, the CFRP/AL hybrid circular tube parameters were analyzed in this paper and propose single, antisymmetric, and hybrid wrapping methods (Sap, Aap, and Hap). Based on the nonlinear progressive damage theory, the finite element model is established, considering intra- and inter-ply damage. The results show that the calculated results of the FE model are basically consistent with the experimental data, and can accurately capture the failure mode in the actual collapse. Increasing the wrapping angle can significantly improve the energy absorption of the CFRP/AL hybrid tube, with 40° antisymmetric wrapping (Aap-40) being the best, which can increase the specific energy absorption (SEA) by 54% compared with the initial hybrid tube. Finally, the parameters of the AL tube were studied, and the energy absorption mechanism of hybrid tubes with different thickness of the AL tube was revealed.

Axial crashworthiness design of double-hat beams with various cross-sections

In this work, five kinds of sinusoidal cross-sections, namely DCS1, DCS2, DCS3, DCS4 and DCS5, are proposed to improve the crashworthiness of double-hat beams (DHBs). The accuracy of simulation model is determined by experimental results. The influence of amplitude on their crashworthiness is discussed, and the mean crushing force (MCF) and specific mean crushing force (SMCF) values of DHB is significantly improved with these new cross-sections. DCS5, DCS2 and DCS3 models tend to have better collision performance compared with DCS4 and DCS1 models. On this basis, the influences of wavenumber and amplitude of DCS2 and DCS3 are further studied. Compared with DHB, the MCF and SMCF values of DCS2-4+10 and DCS3-4+10 increase by 102.07 % and 39.85 % as well as 105.99 % and 35.80 %, respectively. Furthermore, these sinusoidal DHBs show six typical deformation failure modes, namely axial collapse, irregular axial collapse, bending deformation, mixed deformation mode, lateral bending deformation and lower collapse. Two typical cross-sections are optimized with multi-objective algorithm to further improve the crashworthiness of DHBs. In summary, this work provides the design method of DHB, showing a variety of typical cross-sections, which is of great significance.

A radial-basis function mesh morphing and Bayesian optimization framework for vehicle crashworthiness design

A radial-basis function mesh morphing and Bayesian optimization framework for vehicle crashworthiness design

Dynamic Crushing Behaviors of Cylindrical Lithium-Ion Battery Under Multiple Impacts: An Experimental Study

Abstract To understand the dynamic failure mechanisms of cylindrical lithium-ion battery (LIB) under different impact loadings, the crushing behaviors of 18650 LIBs were experimentally investigated in this work. The drop weight impact tests with different impactor heads were conducted to analyze the crushing responses of the LIBs. By changing the state of charge (SOC) of the battery, impactor types, and impact energy, the force-electric responses of a LIB under multiple impacts were explored. Macro- and micro-deformation of the batteries were further studied including SOC dependency and the failure modes of the separator. Results show that except for impact energy, the mechanical responses and failure behaviors of the LIBs under repeated impacts also depended upon the SOC and impactor types. The relationship between impact velocity and the minimum impact times was established when a hard internal short circuit (ISC) appeared to evaluate the dynamic safety of the LIBs. These results can provide guidance for the crashworthiness design and safety assessment of the batteries under multiple impacts.

Experimental and numerical studies on bending characteristics of woven CFRP reinforced aluminum thin-walled automotive structures

Metal/composite hybrid thin-walled structure is the most preferential approach to achieve dual contradictive objectives of high crashworthiness and lightweight of auto body. Its collapse with regard to different fiber layup patterns is one of the governing mechanisms of energy dissipation, which is yet to be explored. Especially, the effect of different fiber layup angles and layup sequences on bending collapse, which is one of the most significant performance indicators, has received little attention. To this gap, this study investigates experimentally and numerically the bending characteristics of aluminum/carbon fiber reinforced plastic (Al/CFRP) hybrid structures with different layup angles and layup sequences. To start with, three-point bending tests are carried out on specimens to derive the bending failure behavior and crashworthiness, and the internal section damage is observed by CT scan. Finite element model is then constructed and benchmarked against the test results to be proficient. On this basis, the effects of Al thickness, number of CFRP layers and CFRP wrapping range on the bending performance of hybrid tube are analyzed numerically. The simulation results show that layup angle has greater effect on the bending performance than layup sequence. Increasing Al thickness and the number of CFRP layers can effectively improve the bending resistance of structure, and appropriate partial wrapping of CFRP can increase the specific energy absorption (SEA) by 10.92% compared with that of complete wrapping. The revelation from this study provides sound reference for the crashworthiness design of metal/composite hybrid thin-walled structure.

Tool Failure Analysis and Multi-Objective Optimization of a Cutting-Type Energy-Absorbing Structure for Subway Vehicles

This paper aims to provide essential guidance for the crashworthiness design of cutting energy-absorbing structures for subway vehicles. By investigating tool failure with experiment and numerical approaches, a new energy-absorbing tube structure was proposed and optimized to improve the crashworthiness and reliability of the cutting energy-absorption structure. The impact test results revealed that multiple failure modes occurred in the tool. Mechanical wear occurs mainly in the middle of the cutting edge, while the tool’s tip failure is primarily due to thermal wear. Impact forces were no longer stable due to tool failure. The simulation results of the established tool-tube thermal–structural coupling finite element model were consistent with the tests. The temperature distribution indirectly validated the failure modes in different tool areas. By eliminating the tearing-type fracture mode, the proposed new structure effectively reduced the high temperature of the tool’s tip, better maintained the uniform temperature of the cutting edge, and smoothed changing of the cutting force. Finally, the Kriging surrogate model and NSGA-II algorithm were utilized to obtain the tool’s minimum steady-state temperature (STT) and maximum mean average cutting force (MCF). The optimal solution determined by the minimum distance method is STT = 514 K, MCF = 131 kN.

Multi-objective crashworthiness design optimization of a rollover protective structure by an improved constraint-handling technique

<abstract> <p>This study proposes a multi-objective optimization (MOO) strategy with an improved constraint-handling technique to improve the crashworthiness of an excavator rollover protective structure (ROPS). First, the experimental test under the ISO 12117 criteria is conducted and the developed numerical model is verified. Then, the amounts of energy absorption and the cross-sectional forces of components in the ROPS are analyzed. The main energy absorbing and load carrying components are identified. Finally, the thicknesses of the identified components are considered as the design variables. A multi-objective crashworthiness optimization process aims at improving the safety distance and reducing the total mass is designed by the finite element analysis-based surrogate model technique and a modified MOO algorithm. The proposed algorithm modifies the objective function values of an individual with its constraint violations and the true objective function values, of which adaptive penalty weights fed back from the constraint violations are used to keep the balance. Compared with the existing methods, it is found that the optimal solutions obtained by the proposed algorithm show superiority on convergence rate and diversity of distribution. The optimal results show that the safety distance is 27.42% higher while the total mass is 7.06% lower than those of the baseline design when it meets the requirements of ISO 12117. This study provides an alternative crashworthiness design route for the ROPS of the construction machines.</p> </abstract>

Bionic design and multi-objective optimization of thin-walled structures inspired by conchs

<abstract> <p>Thin-walled structures have been widely used in various parts of vehicle subsystems because of their high-efficiency impact energy absorption and lightweight characteristics. However, the impact deformation mode of conventional thin-walled structures is unstable and the energy absorption efficiency is low. Therefore, a series of novel bionic conch structures (BCS) are proposed to find a more excellent crashworthiness design in this study. First, the finite element simulation model of BCS verified by experiments is established. Then, the energy absorption characteristics of bionic conch structures, and conventional single-cell and multi-cell tubes under axial loading are compared by employing finite element simulation. The results show that the thin-walled structures inspired by conchs have a higher energy absorption efficiency than the other two structures with the same mass. In addition, the influence of main design parameters (wall thickness, inner and outer ring diameter, and the number of inner and outer panels) on the crashworthiness of BCS is studied through parameter design and factor significance analysis. Finally, the optimal geometric configuration is found by combining the approximation model and multi-objective particle swarm optimization, and the crashworthiness of BCS is further optimized. The bionic crashworthiness design and optimization framework proposed in this study can also provide a reference for other engineering protective structures.</p> </abstract>

Optimization of sandwiched armour plate using energy conversion principle via dynamic analysis

Defence can play a paramount role in military organization thus designing light weight armour capable of protecting target from lethal damage is important. While the traditional armour plated use high hardness steel but in recent development of advanced ceramics with low density and high strength properties have opened new door of possibilities in the field. The presented paper bring outs a study regarding protection efficiency of superposed sandwiched panel with metal matrix interface and honeycomb structures against ballistic impacts is performed. The authors have developed a composite armour plate with non-ricochet properties capable of taking resisting multiple projectiles, using ceramics Honey-comb structure tile glued together encased within metal matrix. Paper discusses experimental data, geometry of the experimental setup, modelling (meshing and initial conditions). Numerical analysis has been done on different metals, ceramics and polymers and the best among them are selected. The stacking sequence of the selected materials is developed using crashworthy design concepts. Design parameters for optimized sandwiched panel are provided and superposed sandwiched panel responses with metal matrix interface and honeycomb structures are assessed.

Dynamic axial crushing behaviors of circular composite tubes with different reinforcing fibers and triggers

The choice for a proper external trigger and fiber hybridization configuration has a significant impact on the stability of the crushing process and material cost for composite structures in crashworthiness. However, there is still a lack of a thorough understanding of impact characteristics and energy-absorption mechanisms. This study explores the axial crushing responses and crashworthiness characteristics of energy-absorption composite structures by both experiment and finite element analysis. A series of dynamic crushing tests were conducted for three types of composite tubes under the same crushing velocity of 1.944 m/s, including carbon fiber reinforced polymers (CFRP), glass fiber reinforced polymers (GFRP), and CFRP/GFRP inter-layer hybridized composites. The configuration of the composite tubes includes: (i) CFRP composite tubes with a single 45° chamfer trigger (T1), a combined 45 °chamfer and outward-folding crush-cap (T2), and a combined 45 °chamfer and outward-folding crush-cap with a cavity (T3); (ii) GFRP and CFRP/GFRP hybrid composite tube with T2 trigger. A stacked-shell model was developed to investigate the energy-absorption mechanisms. Three distinct failure modes have been found for composite tubes with T1, T2, and T3 triggers, separately, named splaying, outward-folding, and outward-folding with local buckling. The CFRP composite tubes with the T1 trigger exhibited the best crashworthiness performance, while the T2 trigger reduced the friction interaction between the splaying fronds and the platen, causing a 67% reduction of specific energy absorption (SEA)/mean crushing force (MCF). In the meantime, the T3 trigger boosted 101.9% of SEA/MCF from T2. With the same T2 trigger, the GFRP composite tube showed a better crashworthiness performance than the CFRP composite tube: 35.5% reduction of initial peak crushing force (IPCF), 68.6% and 98.5% increment of MCF and SEA respectively. It has been found that the outermost layers dominated the energy absorption behavior, which matches well with the observation that replacing the central CFRP plies with GFRP ones results in similar crashworthiness characteristics between CFRP and CFRP/GFRP hybrid composite tubes. The findings in this study contribute to providing practical guidelines for the crashworthiness design of heavy duty composite structures, such as railway vehicles.

Crashworthiness design of a sponge-inspired multicell tube under axial crushing

A novel bio-inspired multicell tube (named UCGS), mimicking the unique double-diagonally reinforced configuration in the unit cell of glass sponge (GS), was proposed and fabricated by additive manufacturing. Crashworthiness analysis of UCGS was carried out via ABAQUS/Explicit and validated by quasi-static axial crushing tests. Due to its distinctive double-diagonal reinforcing strategy, the results demonstrated that UCGS had a high specific energy absorption (SEA) of up to 30.7 J/g, which was 32.2% to 53.1% higher than that of conventional multi-cell tubes and 7.7% to 28.1% higher than that of other bio-inspired tubes, respectively. Subsequently, the effects of geometric parameters and hierarchical designs on the energy absorption performance were investigated by numerical simulation. By choosing the proper geometric parameters and hierarchical design, the energy absorption capability of the presented bio-inspired multicell tube could be further increased, and the SEA was 3.3%–39% greater than the original design. Finally, a theoretical model was proposed to predict the mean crushing force, which was in good agreement with the numerical results. This study shed light on a deep understanding of the deformation mechanisms of bio-inspired tubes, and provided inspirations for designing and optimizing of energy absorber with high performance.

Smart Clothing with Built‐In Soft Sensing Network for Measuring Temporal and Spatial Distribution of Pressure under Impact Scenarios

AbstractNowadays, the need for protective devices at man–machine interfaces is increasing in the fields of traffic, sports, construction, and military, etc. Dynamic pressure sensing technology with wide measuring range, high sensitivity, softness, and fast response is crucial for evaluation and optimization of the personal protective equipment under impact scenarios. However, current sensors hardly possess all the aforesaid required characteristics. For the first time, this article reports the evaluation and application of an innovative soft pressure sensor with modulus of 2 MPa, maximum pressure of 8 MPa, and over 500‐Hz frequency. A theoretical model, taking strain rate into consideration, is established to characterize the dynamic sensing behavior. A sensing network in the form of smart clothing is developed and used in a sled crash test, which is a standard approach to evaluate the safety of automobiles in collisions. The pressure distribution over the dummy's surface during the crash is acquired in real‐time, and compared with numerical simulations. This study is important to the study of occupant injury and crashworthiness design for vehicles, and it will benefit the automotive industry. With the built‐in sensing network, the smart clothing has promising applications in the pressure mapping of 3D flexible man–machine interface under impact scenarios.