Crush Load Research Articles

Investigating the mechanical properties and crashworthiness of hybrid PLA/GFRP composites fabricated using FDM-filament winding

The failure and crashworthiness performance of hybrid Polylactide (PLA)/Glass Fiber Reinforced Polymer (GFRP) composite tubes subjected to axial and radial quasistatic compression loads were investigated in the present study. The composite tubes are fabricated using hand lay-up and Fused Deposition Modeling (FDM)-filament winding processes. The crashworthiness performance was studied using parameters such as the peak load, energy absorption, crush load, crushing load efficiency, and specific energy absorption. The highest peak loads from the compression test results in the axial and radial directions are calculated using variations in the filament winding PLA/GFRP (FPG) specimen, whose values were 16130.50 N and 12077.33 N, respectively. The highest mean crush load is found in the material variation with the FPG specimen, which is 5734.43 J/mm for axial loading and 4886.75 J/mm for radial loading. The highest energy absorption (EA) value is found in the material variation with the FPG specimen, which is 262.18 J for axial direction loading and 94.02 J for radial direction loading. The highest specific energy absorption (SEA) value is found in the material variation with the specimen Filament Winding PLA/GFRP, which is 16.92 J/g for axial loading and 10.98 J/g for radial loading. There are three main types of failure of the composite: matrix cracking, fiber damage, and folding. The study showed that by combining Additive Manufacturing and composite lamination, the hybrid PLA/GFRP specimen outperformed the existing structures.

A novel preparation of porous Li2TiO3 pebbles with a distinctive structure

Optimization of the pore structure stands out as an effective approach for bolstering the tritium release performance of lithium-based tritium breeding ceramics, particularly when employing a high open porosity configuration. In this study, Li2TiO3 fibers were synthesized via the hydrothermal method, with the assistance of TiO2-B nanowires acting as templates. Subsequently, porous Li2TiO3 pebbles with varying microstructures were fabricated through a combination of the wet method and a sintering process. Sintering process plays a crucial role in determining the microscopic morphology. An increase in temperature resulted in a suppression of the growth of fibrous grains and the transformation of fibrous grains into quasi-spherical grains. Moreover, a two-step sintering process was proposed as a means of improving the crush load (15.9 N vs. 22.0 N) of Li2TiO3 pebbles while simultaneously preserving their high porosity (24.91%). The Li2TiO3 pebbles, produced by the two-step sintering process, exhibited a distinctive micromorphology characterized by interconnected particles forming short rod-shaped microstructures. This distinctive micromorphology contributes to the maintenance of a high degree of open porosity (10.52%).

A comprehensive study on the phase composition, mechanical properties and stability of Li4SiO4-Li2ZrO3 biphasic ceramics

Lithium orthosilicate (Li4SiO4) is regarded as a candidate for tritium breeding in fusion reactors. In this study, the Li4SiO4-Li2ZrO3 biphasic was developed to improve the sinterability, density, and mechanical properties of Li4SiO4. The Li4SiO4-xLi2ZrO3 (x = 0.5, 1) composite powders were prepared using solid-state reaction via in-situ method. Li6Zr2O7 existed in the ceramic powders at low calcination temperatures. When the calcination temperature was increased to 900 °C, Li6Zr2O7 was transformed into Li2ZrO3 due to the decomposition of Li6Zr2O7 at high temperatures. The TEM observation confirmed that the powders consisted of Li4SiO4 and Li2ZrO3. The Li4SiO4 and Li4SiO4-xLi2ZrO3 (x = 0.5, 1) pebbles were fabricated by the sol-gel method. The measurement results showed that the pebbles had a narrow size distribution and fine sphericity. The density of Li4SiO4-Li2ZrO3 pebbles reached 96.01% of the theoretical density when it was sintered at 1000 °C for 4 h. Compared with the Li4SiO4, the grain size of ceramic pebbles was significantly reduced. Owing to decreased grain size, 139.0 N crush load for the pebbles and 92.4 MPa bending strength for the sintered bodies were achieved. Besides, the ceramics with the Li4SiO4 to Li2ZrO3 ratio of 2: 1 exhibited preferable mechanical properties. Further, to investigate the chemical stability of biphasic ceramics, the structure and mechanical properties were examined under high temperatures and continuous inert gas purging, simulating the working condition of fusion reactors. It was shown that there was almost no change in phase composition and grain size after purging for 60 h at 650 °C. For the mechanical properties, the crush load was decreased initially due to the cracking in the surface region of the ceramic and then increased because the cracking was recovered.

Fabrication, sintering behavior, and strength of tritium breeding ceramic pebbles with Pb addition

Lithium ceramics are regarded as potential candidates for tritium breeding in fusion reactors. Lead (Pb) was added to the ceramic to improve the strength and tritium release properties. The Li2TiO3-0.5Li4SiO4–Pb ceramic powders with the Pb contents of 5 wt% and 20 wt% were prepared by microwave-induced solution combustion synthesis. It was confirmed that the Pb was in the form of the Li2PbO3 phase in the powders. The Li2TiO3, Li4SiO4, and Li2PbO3 crystallites were composited at nanoscale level, which was confirmed by the transmission electron microscopy (TEM). During high-temperature sintering, the Li2PbO3 was transformed into PbO, which facilitated the densification process at low temperatures. The chemical state in the sintered body was characterized by X-ray photoelectron spectroscopy (XPS) with 3 keV Ar+ sputtering. The binding energies for Pb were 137.2 and 142.2 eV. There was almost no change in peak position during Ar+ sputtering, showing that Pb was firmly adherent with oxygen atoms. Besides, the as-synthesized powders were used for the pebble fabrication. The average crush load of Li2TiO3-0.5Li4SiO4–20%Pb pebbles sintered at 1223 K was 124 N, which was much higher than that without Pb addition. It was proved that the crush load increased almost linearly with the increase in the size of the pebbles. Thus, the bending strength of the sintered ceramic body was used to evaluate the mechanical properties. Further, the grain growth kinetics was studied. It was confirmed that the Pb addition reduced the activation energy of grain growth, which realized the densification of the ceramic pebbles at low temperatures.

Experimental and numerical studies on AFRP-reinforced thin-walled tubes under axial impact loading

With the increase in global threats to infrastructure, from unforeseen events particularly in steel structures, there is a growing urgency to strengthen the impact resistance of steel elements. This research aimed to investigate the potential of using AFRP (Aramid Fiber Reinforced Polymer) to improve the energy absorption and crushing resistance of thin-walled circular hollow steel (CHS) tubes subjected to axial impact loads. Key aspects of the investigation include conducting a series of experiments to evaluate the impact of AFRP layer thickness, steel tube thickness, and impact velocity on structural performance. The performance metrics were characterized by analyzing impact force versus displacement, energy absorption capacity, peak crush load, and mean crush load. The results show that AFRP strengthening significantly enhances peak load capacity, energy dissipation, and impact force absorption compared to plain steel tubes. The AFRP-strengthened specimens exhibit higher specific energy absorption (SEA) and crushing force efficiency (CFE) compared to non-strengthened specimens, with peak force increasing by 18 % to 160 % for low external energy and 14 % to 190 % for high external energy. The three-dimensional finite element (FE) model accurately predicts load-carrying capacity and AFRP failure, validated against experimental tests. This study provides quantitative evidence of the effectiveness of AFRP reinforcement in improving the crash performance of thin-walled tubes under axial impact loading, highlighting the potential for optimizing AFRP strengthening techniques in structural applications.

Finite element simulation of axial crushing of flat and C-channel composite coupons using a modified mesomodel

The present article investigates the axial crushing behavior of IM7/8552 material system. Two types of specimens are considered-(a) flat coupons with saw-tooth trigger and (b) C-channels with 45° chamfer as a trigger. All the crushing test data (load, displacement and velocity history curves) is shared in the Crashworthiness working group (CWG) consortium of the Composite material handbook (CMH17.org). Flat crush coupons are tested at the University of Utah and the C-channels are tested at the John H. Glenn Research Center of the National aeronautics and space administration (NASA). Three types of layups are considered for flat coupons: QI1-[90/±45/0]2S, HL2-[902/02/±45/02] and HL3-[90/45/02/90/-45/02]. Two types of layups are considered for C-channels: HL2-[902/02/±45/02] and HL3-[90/45/02/90/-45/02]. Both the specimens are subjected to crush loading with an initial velocity and lumped mass attached to the impactor. All the ply and interface material properties come from the current authors' testing campaign except for strength and stiffness in the fiber direction. The crushing test cases are simulated in LS-Dyna software. Ply and interface behavior is described via user-defined material subroutines of LS-Dyna software. Each ply is modeled using 3D solid elements and the interfaces are modeled explicitly using cohesive elements. Intraply behavior is described using a novel modified meso model proposed by the present authors. Intraply model accounts for nonlinear damage, plasticity, ply fracture toughness and finite element mesh size. Interply response is modeled using bi-linear law. Predictions from present FE models showed a good correlation with crush test data. The effect of finite element model parameters e.g., filtering frequency, mesh size, interface properties, ply fracture toughness, element erosion criterion, contact stiffness and friction coefficient on crushing predictions is demonstrated by conducting parametric studies.

Energy absorption characteristics of stepped multi-cell columns subjected to transverse loading

Automotive bumper beam is a vital component that shields passenger and vehicle from harm and damage generated by catastrophic collapse. Previous investigations on its bending behavior have largely concentrated on multi-cell tubes with the same length, whereas stepped multi-cell structures have received less attention. In this paper, a novel stepped multi-cell configuration is proposed to improve the energy absorption characteristics of thin-walled structures under transverse loading. The finite element method is employed to analyze the crushing behaviors of the stepped multi-cell tubes. The numerical results reveal that the stepped multi-cell structures (SM2 to SM5) can reduce the initial peak force by 23.44–45.91% while increasing the energy absorption capacity, crush load efficiency, and specific energy absorption by 5.87–29.51, 38.29–139.45, and 5.87–29.51%, respectively, when compared to a conventional square tube (M1). In addition, the effects of wall thickness, section width, load angle, punch radius, and punch shape on the bending behaviors and energy absorption characteristics are examined. The results indicate that these factors have a considerable influence on the deformation features of M1 and SM2, which leads to a significant reduction in their bending energy absorption characteristics. These variables have no influence on the deformation modes of SM3, SM4, and SM5, and they present local indentation deformation with a high energy absorption efficiency. Increasing the number of layers improves the comprehensive performance of stepped multi-cell tubes, with SM5 exhibiting the best energy absorption characteristics under transverse loading.

Additive manufacturing of high-quality tritium breeding pebbles using ceramic precursors

In this study, the fabrication of advanced lithium orthosilicate (Li4SiO4) ceramic tritium breeding pebbles through photopolymerization using ceramic precursors (i.e., SiO2 and Li2CO3) is reported for the first time. The pebbles exhibit excellent mechanical and physical properties. Through optimization of manufacturing parameters and a geometrical correction model to compensate printing deviations, the printing accuracy of the pebbles was enhanced. The resulting pebbles had a diameter of approximately 1 mm, a sphericity of 1.01, a uniformly distributed pore structure, a phase purity > 95%, and a satisfying relative density reaching 91.39%. The average crush load 25.7 ± 0.3 N, surpassed that achieved by previously reported methods. Furthermore, the thermal conductivity was enhanced compared to that of solid-phase synthesized Li4SiO4 powder, facilitating the tritium release process for fusion applications. This study may serve as a guidance for designing appropriate ceramic breeders, providing a cost-effective approach applicable to produce other high-precision ceramic components with complex compositions.

THE EFFECT OF DIFFERENT WINDING CONFIGURATIONS ON THE CRUSHING RESPONSE OF HELICAL WOUND WOVEN GLASS/EPOXY COMPOSITE TUBES

The crushing behavior of polymer matrix composite tubes depends on several factors, such as diameter, fiber orientation, wall thickness, and winding configuration. The current work aims at understanding the effect of winding configuration with different helical overlap portions (none, quarter, and half) and the number of layers on the crushing response of woven glass/epoxy composite tubes subjected to quasi-static compression and impact loading. The length-to-diameter ratio is kept constant, for all the cases of the specimen considered. Crashworthiness parameters, such as mean crushing load, initial peak load, specific energy absorption, and crush load efficiency are compared for different cases. Damage and failure characteristics of different helical wound composite specimens are examined and compared with straight wound composite tubes made with a winding angle of 0°. The study shows that the energy absorption capacity of helical wound specimens increases in almost the same proportion as the helical overlap portion increases from no overlap to half overlap. Also, experimental results for composite tubes having different helical overlap portions suggest that the helical overlap portion can be an important parameter in achieving tailor-made energy absorption properties with inbuilt triggering features.

Effects of long-term high temperature annealing on Li2TiO3 and advanced core-shell Li2TiO3-Li4SiO4 tritium breeders

The present work investigates the evolution of mechanical performance and provides a comprehensive study of the changes in microstructure, phase, and compositional elements of Li2TiO3 and core-shell Li2TiO3-Li4SiO4 pebbles resulting from annealing at 900 °C in He incl. 0.1 vol % H2 flow atmosphere for specific durations. Compression tests show that long-term annealing improves the mechanical performance of Li2TiO3 instead of degrading it. The mean crush load of Li2TiO3 increases from 41 N to 45 N after 1000 h of annealing. Li2TiO3 pebbles can maintain their microstructure stability, with only limited grain growth and a decrease in open porosity identified. These changes are believed to be responsible for the improvement in mechanical performance after 1000 h. The mechanical performance of core-shell Li2TiO3-Li4SiO4 pebbles primarily degrades during the initial 100 h, with a decrease in mean crush load from 118 N to 91 N. Subsequently, it gradually stabilizes with a mean crush load of 91 N over the remaining annealing period. An increase in open pores and slight Li4SiO4 grain growth was observed after 1000 h of annealing, which is the primary cause of the mechanical performance degradation in core-shell Li2TiO3-Li4SiO4 pebbles. The loss of lithium in core-shell Li2TiO3-Li4SiO4 pebbles is a combined effect of the Li2TiO3 phase and Li4SiO4 phase, with a stronger association to the Li4SiO4 phase.

Microfabrication of Li4SiO4 pebbles with complex pore structure via digital light processing: Accuracy control and properties optimizing

Li4SiO4 ceramic pebble is deemed as the most attractive tritium breeder for fusion reactor blanket. In this work, we fabricated a novel Li4SiO4 pebble with micrometer-scale pore structure by digital light processing to verify the feasibility of complex pore structure manufacturing for future breeders. The effects of processing parameters on printing accuracy, microstructure and mechanical properties of Li4SiO4 pebbles were investigated. For synthesizing the pure Li4SiO4 phase, the optimal stoichiometric ratio of Li2SiO3 to Li2CO3 was 1:1.09 in the premixed powder. The photosensitivity of dual-phase ceramic suspension was investigated according to an attenuation model, and the overgrowth was reduced to ∼50 μm by using the dimension formula. After optimizing the post-processing, the radial pore structure Li4SiO4 pebbles with excellent crush load (50.3 N, standard deviation = 4.4 N) and suitable open porosity (18.3 %) can be yielded. This work provides a fresh solution to control the pore structure of tritium breeding pebbles in an unprecedented micrometer scale.

Enhancing the density and crush load of Li2TiO3 tritium breeding ceramic pebbles by adding LiNO3-Li2CO3

The fabrication of Li2TiO3 ceramic pebbles with satisfactory density and excellent crush load while maintaining a fine grain structure is one of the research objectives of solid tritium breeders. However, densification and grain refinement are often contradictory in lithium-containing ceramics during the sintering process. In this work, LiNO3-Li2CO3 was added during the preparation of Li2TiO3 green spheres by the wet process, and the formation of LiNO3-Li2CO3 molten salt resulted in the significant sintering improvement of Li2TiO3 ceramic pebbles. The addition of LiNO3-Li2CO3 increased the density of Li2TiO3 ceramic pebbles by 10.47 % (92.63 % vs. 82.16 %) and the crush load by more than four times (144.54 N vs. 28.2 N). ICP-OES analysis showed that the lithium content of the Li2TiO3 ceramic pebbles was slightly increased by the addition of LiNO3-Li2CO3. Overall, the difficulty of balancing grain refinement and densification in lithium-containing tritium breeders can be addressed by the proposed method.

Design optimization of hybrid material B-pillar under crush loading

Abstract B-pillars are vital structural components in rollover-related accidents. In this study, the performances of homogeneous B-pillars designed from B1500HS-T25, AA2024-T351, and AA6061-T6 materials and hybrid B-pillars designed from their combinations under crushing load were compared in energy absorption using simulation results. Optimization studies were conducted utilizing the upper part B1500HS-T25 and lower part AA6061-T6 hybrid B-pillar, which gave the highest energy absorption value. Method of feasible directions was utilized to solve the single-objective optimization, and B-pillar mass decreased by 22.6 % from 2.736 to 2.117 kg compared with the reference B-pillar. Global Response Search Method and Multi-Objective Genetic Algorithm were used to solve the multi-objective optimization problem. B-pillar with min mass decreased mass value by 25 % from 2.736 to 2.052 kg for both methods. This optimum hybrid B-pillar can be utilized in car design.

Energy absorption capability of laterally loaded glass/epoxy tubular components containing halloysite nanotubes

The crashworthiness capability of laterally loaded glass/epoxy (GFRE) tubular components containing halloysite nanotubes (HNTs) was explored in this article. GFRE components filled with 0, 1, 2, 3, and 4 weight percent (wt.%) of HNTs were created using wet-wrapping by hand lay-up technique. For the laterally loaded tubes, the crushing load and the energy absorption versus displacement responses were presented. In addition, distortion histories were tracked. The crashworthiness analysis was carried out by evaluating different indicators, i.e., initial crush load [Formula: see text], average crush load ([Formula: see text]), crush load efficiency (CFE), energy absorption (U), and specific absorbed energy (SEA). Two parameters of the Weibull distribution were employed to assess the experimental findings statistically. In addition, mathematical regression models were built to predict the energy absorption indicators. Experimental results demonstrated that an unfilled tube demonstrated the largest CFE of 1.84, while the maximum [Formula: see text] was demonstrated by a tube filled with 2 wt.% of HNTs with a value of 3.70 kN. Additionally, the tube filled with 4 wt.% of HNTs represents the extremes [Formula: see text], U, and SEA with values of 4.26 kN, 128.82 J, and 3.84 J/g, respectively. Due to their improved crashworthiness characteristics, GFRE filled with 4 wt.% of HNTs is suitable for use as a crashworthy device in automobiles.

Grain growth mechanism and thermal stability of Li2TiO3 pebbles fabricated by wet method

Li2TiO3 ceramic pebbles with uniform structure, high density and good mechanical property were successfully fabricated by wet process. The Li2TiO3 pebbles sintered at 1000 °C for 4 h had satisfactory density (91% T.D.) and crush load (a.v. 27.1 N). The apparent activation energy of Li2TiO3 grain growth was 201 ± 7 kJ/mol. Accelerated densification was observed in a reducing atmosphere, this might be attributed to the oxygen vacancies generated by the reduction of Ti4+ to Ti3+ in 0.1%H2+He atmosphere, which facilitate the diffusion of ions through the lattice. The grain growth was controlled by lattice diffusion under reducing atmosphere, and the apparent activation energy was 168 ± 6 kJ/mol. The mechanical results show that the crush load of Li2TiO3 pebbles decreased with the increase of temperature, and the average crush load at 500 °C was 13.9 N. In addition, the thermal cycling and long-time annealing experiments suggested that Li2TiO3 pebbles have good structural and performance stability. The Li2TiO3 ceramics prepared by wet process were satisfactory tritium breeder materials with ideal application potential.

Crushing behavior of contact-aided AlSi10Mg sandwich structure based on chiral mechanical metamaterials

With additional rotation degrees of freedom, chiral mechanical metamaterials reveal a prospect in impact resistance and energy absorption by both facilitating the bending-dominated characteristics in deformation and enabling possible energy dissipation through contact among unit cells. However, the corresponding structure-property relationships are still understudied considering more complex deformation modes. In this paper, the impact of the compression-to-twist effect of chiral metamaterials on the crushing behavior was systematically investigated. We proposed a design framework of chiral metamaterials enabling the intercellular contact during twisting deformation. Through the manufacture, simulation, and experiment of AlSi10Mg sandwich structures composed of chiral metamaterials, the multi-segment mechanical response of the designed sandwich core to a crush load was demonstrated and discussed. Moreover, the unique deformation and failure mechanism was embodied in the derived specific energy absorption (SEA) and compressive modulus. The proposed metamaterial with a contact-aided twist is light-weight and high in SEA, elucidating a practical way of combining bending-dominated and stretching-dominated lattices. It paves the road for designing metamaterials with graded energy absorption performance, rigid-flexible coupling properties, multi-functional responses, etc.

Compression properties of beryllide pebbles at high temperatures

DEMO (demonstration) fusion reactors require advanced neutron multipliers with low swelling and high stability at high temperatures. Research on beryllium intermetallic compounds (beryllides (Be12V)) has been conducted, and the authors have successfully fabricated Be12V and Be12Ti0.3V0.7 ternary pebbles, which are considerably stable at high temperatures. In this study, to evaluate the mechanical properties of these pebbles, compression tests for a single pebble were performed at room temperature and high temperatures of 600 and 800 K. Be12Ti0.3V0.7 pebbles exhibited a higher crush load than Be12V pebbles; Be12Ti0.3V0.7 pebbles comprised remarkably fine grains due to dual phases. Scanning electron microscopy images of the fractured area demonstrated that the Be12V pebbles had a relatively large fracture with sharp edges, whereas the Be12Ti0.3V0.7 pebbles included considerably small grains. There was no noticeable temperature dependence of the crush load. The fracture and tensile strengths of Be12V and Be12Ti0.3 V0.7 pebbles were evaluated.

Preparation and characterization of Li2TiO3 ceramic pebbles by modification of the water‐based sol–gel method

AbstractLi2TiO3 is considered as one of the best candidates for breeding materials. This article adopted a modification water‐based sol–gel method to synthesize nano‐Li2TiO3 powders, which overcomes the poor phase purity, coarse grain, and inferior crushing strength described in the previous literature. In this paper, the thermal effect of the precursor, the crystal phase, and the morphology of the powders were characterized by thermogravimetric analysis/differential thermal analysis (TG/DTA), X‐ray diffraction (XRD), and transmission electron microscopy (TEM) techniques. The nano‐structured Li2TiO3 powders with good dispersion and an average particle size of 20–50 nm were successfully synthesized at 600°C by controlling PH and hydrolysis rate. Moreover, the phase transition temperature for the monoclinic phase β‐Li2TiO3 was as low as 600°C, which is lower than 750°C using the traditional solid‐state method. Meanwhile, the morphology, porosity, crushing load, and thermal conductivity of ceramic pebbles are characterized systematically by using scanning electron microscope (SEM), mercury injection meter, compression strength equipment, and laser scattering method, respectively. Experimental results showed that the Li2TiO3 ceramic pebbles with a sphericity of .98, crush load of 48.4 N, and relative density of 90.03 % were successfully prepared at 1050°C for 2 h. This method will provide new guidance for the preparation of tritium breeders.

Glass-fiber mat/PA6 composite tubes subjected to dynamic axial crush loading—Experimental evaluation and high fidelity modeling of failure phenomena

Thermoplastic composite materials are well suited for the development and design of energy absorbing lightweight structures. In this work, the damage initiation and failure phenomena of half-circle and full-circle tubular specimens, made of a novel mat reinforced thermoplastic composite material under axial dynamic crushing is investigated experimentally and numerically. Different specimen configurations were examined in detail, where wall thickness, length of test specimen, specimen shape as well as angle of chamfer trigger are varied. A pronounced splaying failure can be identified for all configurations resulting in a stable progressive crushing, as well as very promising force–displacement responses in terms of peak force and specific energy absorption. For numerical analysis on structural scale, a high-fidelity multi-layered solid modeling approach is used to predict the damage initiation and failure progress.

Lithium titanate foam for tritium breeding application

Lithium titanate (Li2TiO3) and hyper-stoichiometric lithium titanate (Li/Ti = 2.17 and 2.25) foams were synthesised and characterised for tritium breeder application in a fusion reactor. Ceramic foams were produced through sponge replication methodology that exhibits high porosity with interconnected pores. As compared to Li2TiO3, hyper-stoichiometric lithium titanate is reported to possess better performance due to excess lithium in the structure. Hyper-stoichiometric lithium titanate foam exhibited a maximum flexural strength of 0.75 MPa. The unique porous structure with highly dense struts of lithium titanate foams resulted in adequate crushing load at room temperature. The crush load of lithium titanate foam was also measured at an elevated temperature (600 °C) to examine the effect of operating temperature on the structural stability of foam based breeder module.