The performance of triply periodic minimum surface (TPMS) lattice structuresStructure was evaluated for use as energy absorbers in automobile crash structuresStructure. Schoen’s Gyroid TPMS lattice structuresStructure were manufactured from colorFabb carbon fibre reinforced nylon (PA-CF) filament using fusion deposition modelling (FDM) 3D printing3D printing. Compressive and energy absorption performance was quantified experimentally using quasi-static compression testing. Test samples were replicated at different gyroid cell size and continuous surface thickness combinations. Results were compared to published data from other lattice structuresStructure to assess relative performance, and analysed to develop a recommended gyroid TPMS geometry. It was determined that varying either the continuous surface thickness, or unit cell size influenced the performance of the structureStructure. A gyroid TPMS structureStructure with a cell size of 10 mm, and a continuous surface thickness of 2 mm was found to perform the best, achieving an impressively high specific energy absorption capacity of 13.06 J/g (± 0.15), significantly outperforming both 3D truss and traditional 2D lattice structuresStructure for use in the automotive industry.

This paper presents an investigation on the stiffness and energy absorption capabilities of three proposed biomimetic structures based on the internal architecture of a cornstalk. 3D printing was used to manufacture specimens using a tough and impact-resistant thermoplastic material, acrylonitrile butadiene styrene (ABS). The structural stiffness, maximum stress, densification strain, and energy absorption were extracted from the compression tests performed at a strain rate of 10(-3) s(-1). A numerical model was developed to analyse the behaviour of the biomimetic structures under compression loading. Further, a damage examination was conducted through optical microscopy and profilometry. The results showed that the cornstalk-inspired biomimetic structure exhibited a superior specific energy absorption (SEA) capability that was three times higher than that of the other core designs as reported in the literature.

This paper presents an investigation into the flexural behaviour of bio-inspired engineered cementitious composite (ECC) beams under quasi-static and dynamic bending loads. These beams included a monolithic structure and three additional beams inspired by the structure of nacre. Three-point bending tests were conducted on the beams with different loading rates. The forcedisplacement response, failure modes, and energy absorption characteristics of these ECC beams were studied. The results indicated that the bio-inspired beams were more ductile, sustaining larger deformation, absorbed more energy, and were more resistant to impact than the monolithic beams. Specifically, under quasi-static bending, the bio-inspired beams sustained 150-300% larger maximum deformation and 55-195% higher energy absorption than the monolithic beams. Moreover, under dynamic bending, the layered beam incorporating polyurethane interlayers showed 27% more energy absorption than the monolithic counterpart. When surface asperities and steel wire mesh were incorporated, the energy absorption capacity was more than doubled.

This study examines the mechanical response and microstructural evolution of modern manufactured high carbon pattern welded Damascus steels. The characterisation consists of quasi-static and dynamicDynamic compression testing, optical microscopy, ultrasonic sound speed measurements, and Vickers hardness. The results from the quasi-static compression testing at a strain rate of 10–3/s show that the yield strength of the materials is approximately 500 MPa, which is comparable to that of plain carbon steel (~450 MPa) and display similar strain hardening properties. The compression results also display a slightly higher Young’s Modulus for samples with layer orientation perpendicular to the uniaxial load than those with layer orientation of approximately 45° to the uniaxial load. DynamicDynamic testing using a Split-Hopkinson Bar results showed a similar yield strength of ~ 1150 MPa for the samples with 45° layer orientation, whereas samples with perpendicular orientation showed a slight increase in the yield stress with increasing the strain rate.

The influence of peak compressive stress on the dyamic tensile fracture (spall) in a multi-phase steel, austenite, ferrite and martensite phases, was investigated in as-received and pre-strained conditions. Plate impact experiments were done at-3.0 GPa and-6.0 GPa compressive peak stresses. Results showed that peak stress increase results in about 20% increase in the spall strength for samples tested in the as-received condition, and about 15% increase for the pre-strained samples. These increases could be related to the effects of peak stress on the tensile stress that causes spallation. However, introducing plastic deformations in the pre-strained samples had negligible effects on the spall strength. Microstructural examinations revealed that incipient spall damage was parallel to the phase boundaries and mainly accommodated by ferrite grains as quasi-cleavage transgranular fracture. Samples shocked in the as-received condition with full spallation experienced a quasi-cleavage fracture within the ferrite compared with a cleavage fracture within the ferrite for samples shocked in the pre-strained condition. Deformation within the austenite phase due to plate-impact testing was dependent on the initial sample condition, the pre-strained samples showed more deformation than the as-received samples.

As a result of their mechanical characteristics, biological structures often provide inspiration for the development of high-performance mechanical structures. Nevertheless, traditional production processes are often incapable of precisely reproducing the intricate and exquisite nature of biological systems. Modern additive manufacturing techniques provide a pathway to the creation of materials with complex patterns that are inspired by biological processes. In this paper, we identify the different types of biomimetic porous structures seen in nature, many of which are composite structures, and categorise them. We also identify the natural species with porous structures and illustrate their functions. In addition, this review paper presents how these porous structures have been mimicked for engineering applications. Figures are shown to demonstrate the scale (meso, micro, and nano) at which the porous structures are emulated. As biological porous structures have been successfully mimicked into synthetic materials using additive manufacturing (AM), we classify the types of 3D printing with respect to impact loading applications and describe the various types of additive manufacturing processes used to manufacture biomimetic porous structures. This review paper will be of interest to academics looking to design innovative lightweight porous composite structures and use emerging technologies to investigate their energy absorption properties, which have a wide range of engineering applications.

The quasistatic compressive behaviour of additively manufactured titanium-carbide (Ti-6Al4-V-C or Ti-C) was investigated through quasistatic compression and microhardness tests. The carbon content within the titanium-carbide samples was varied in order to identify the influence of graphite on the properties of the material. The information gathered through the mechanical tests and optical microscopy was used in order to identify the effectiveness of titanium-carbide as a functionally graded material applied in ballistic protection. Initial QS compression testing on 5.3 and 6 wt%C content yielded similar results in mechanical properties. This contradicts the hypothesis which predicts an increase in strength with an increase in carbon content. Further details on the results will be presented in this study.

This paper reports on the results of an experimental study on glass fibre reinforced polymer (GFRP) pultruded profiles subjected to low-velocity impact loading. The effects of impactor mass on the impact response of pultruded composites were investigated. Composite specimens were tested under two series of loading conditions using a drop-weight impact facility. The first set of tests was conducted with different impactor masses (i.e. 5.5, 10.5, 15.5 and 20.5 kg) under the same impact energy of 67 J. The specimens in the second set were subjected to varying impactor masses of 6, 12, 24 and 36 kg at the same initial velocity of 4.4 m/s, resulting in different impact energies. The internal and external damage of pultruded composites was analysed to compare the failure mechanisms, including matrix cracking, delamination, and fibre breakage, as functions of the initial impact energy. The results showed that the extent of impact-induced damage increased with ascending impact energies (ascending impactor masses) up to the point at which the specimen was perforated. The initial impact energy was the dominant parameter that controlled the damage tolerance characteristics of pultruded composites. Furthermore, it was found that a significant longitudinal crack was a precursor to ultimate failure. (C) 2021 Elsevier Ltd. All rights reserved.

Microstructural changes and ferrite phase transformation under shock loading, between 8.5 GPa and 17.5 GPa, in a hot-rolled Lean Duplex Stainless Steel (commercially known as LDX 2101) were investigated in as-received and pre-deformed conditions. The latter condition was considered to distinguish classical deformation twins at high strain rates from those associated to the reversible ferrite phase transformation. Plate impact experiments were used to introduce compressive shock loading at peak stresses below and above the stress threshold of the ferrite phase transformation, 13 GPa. Effects of shock loading were also examined by compressing shocked samples quasi-statically and comparing their response with those tested in the as-received condition. The microstructural examinations revealed that the ferrite in LDX 2101 experienced a reversible phase transformation at a peak stress of ~17 GPa. The fingerprints for this transformation were {112}<111> primary twins and {332}<113> primary and secondary twins. In addition, the yield stress of the sample pre-shocked at ~17 GPa showed a considerable increase (⁓150 MPa) compared to the flow stress in as-received conditions.

A pre-stressing technique for improving the ballistic performance of a circular silicon carbide tile has been tested against ø12-mm spherical steel projectile. The confining pre-stress was achieved through a heat-shrunk steel collar and was evaluated through neutron diffraction for the ceramic-collar system. Subsequent ballistic experiments and simulations of the impact event were used to elucidate the mechanisms and benefits of pre-stress on the ballistic response. CT-scans of various specimens, post-impact, show that the pre-stress affects the trajectory of the Hertzian cone and limits the overall damage. Furthermore, simulations qualitatively agreed with the experimental result, showing a reduction in crack propagation and altered paths of damage. Greater confining stress led to higher negative triaxiality, which act to arrest the tensile hoop stresses and corresponding cracks.

This study examines the dynamic fracture behavior and spall strength of a high hardness armor (HHA) steel and an improved rolled homogenous armor (IRHA) steel. Flyer plate impact tests were conducted at three different velocities, which provided peak stresses of 3.75 GPa causing no damage, 4.72 GPa that generated incipient spall damage, and 8.47 GPa which resulted in full spall, respectively. Free surface velocities were measured by Photon Doppler Velocimetry (PDV), and the damage examination was conducted by conventional optical microscopy and scanning electron microscopy (SEM). Results show that HHA specimens exhibited higher spall strength and Hugoniot elastic limit (HEL) than IRHA specimens at the same peak compressive stresses. Post-mortem examinations revealed that the HHA steel showed brittle fracture indicated by cleavage seen on the fracture surface and crack propagation through the thickness. In contrast, a more ductile fracture indicative of void growth and coalescence mechanisms was observed throughout the fracture surface of IRHA.

The effect of the history of plastic deformation on the mechanical response of hot rolled Lean Duplex Stainless Steel 2101 (LDSS2101) was investigated at high strain rates. Samples of LDSS2101 were quasi-statically compressed up to 25% strain to introduce an intermediate state of plastic deformation before high strain rate compression. Microstructural analyses were conducted using optical microscopy to correlate the mechanical responses with microstructural evolution. Results show that the dynamic yield stress of LDSS2101 increases with pre-deformation. However, significant work-softening was also observed at high strain rates. Microstructural analyses of LDSS2101 revealed the phase transformations which likely affect the mechanical response. Our findings support the use of LDSS2101 in applications that involve a combination of serial quasi-static and dynamic loadings.

The effect of peak stress and deformation history on the spall strength and associated microstructure evolution in a dual phase (50% a, 50% gamma) stainless steel has been investigated. Symmetric plate impact experiments using a single stage gas- gun were performed at peak stresses in the 3.0-6.0 GPa range, pulse duration and strain rate were kept constant in all tests. The steel specimens tested were in as-received and pre-compressed (similar to 25% true strain) conditions. Microstructural examinations were performed using optical Microscopy and Electron Backscatter Diffraction and micro-hardness indentations. Results indicate that peak stress influences the spall strength, whereas the Hugoniot elastic limited is primarily affected by the deformation history. The spall damage, in the form of coalesced voids and cracks, is mainly accommodated by the ferrite phase, whereas the austenite phase does not experience considerable deformation. Furthermore, it is observed that the ferrite/austenite phase boundaries work as barriers for the spall damage.

The rate and temperature-dependent deformation mechanism of high carbon steel (HCS) are of fundamental significance due to their comprehensive application in the mining industries. The influences of high strain rate under the influence of thermal loading on the deformation behaviour of HCS under compressive loading are investigated in this paper. Dynamic compressive tests at two different strain rates (750/s and 1750/s), as well as three different temperatures of 25 degrees C, 100 degrees C and 175 CC, were performed using a Split Hopkinson Pressure Bar (SHPB) testing machine and the corresponding changes in the microstructures were observed. The material exhibited four stages In the strain hardening rate behaviour during the deformation process along with an irregular trend in the ultimate strength and total elongation. X-Ray diffraction (XRD) peaks at ambient condition exhibited martensitic transformation, whereas, this transformation was suppressed with increasing strain rate. At elevated temperatures, the transformation of martensite into ferrite/tempered martensite (TM) and carbide precipitates was noticed. Moreover, the fractographic study of the deformed specimens provided an insight into the change in the distribution of the dimples which were mainly caused due to the different deformation activities. Transmission electron microscopy (TEM) results confirmed the formation of adiabatic shear bands for all the loading histories. Increase in the width of the shear bands was recorded with increasing strain rates whereas, concerning the influence of temperature, an overall decrease in the width was noticed. Substantial effect of the formation of carbide precipitates on the mechanical behaviour of the material was noticed during the high-temperature deformation process.

The plastic anisotropies of two hot-rolled Lean Duplex Stainless Steels (commercially known as LDX 2101 and LDX 2404) were investigated by applying compressive strains, at 10−3 s−1 rate, along the rolling- and transverse-directions (RD and TD). The microstructural changes were elucidated by Electron Backscatter Diffraction (EBSD) as a function of strain level and loading direction. In both alloy grades, the austenite phase shows a weaker texture development than the ferrite phase; the later develops {001}<110> and {110}<110> textures in LDX 2101 and LDX 2404 alloys, respectively. Also, in both alloys, the yield stress along the TD is larger by 10% than along the RD. Anisotropies are also detected in the rate of property changes with deformations; after 30% true strain, the flow stress along the RD in LDX 2101 alloy starts exceeding the stress along the TD. Microstructural studies indicate that the load partitioning, grains shape, phase boundaries and austenite to martensite phase transformations are the origins of the anisotropic phenomena in LDX 2101 alloy, whereas the crystallographic texture of ferrite phase, phase boundaries and load partitioning are the plausible origins of plastic anisotropies in LDX 2404 alloy.

Themechanical response and microstructural evolution of cold-rolled lean duplex stainless steel 2101 (LDX 2101) has been investigated along the rolling and transverse directions. Compression tests at 10(-3) s(-1) strain rate and up to a strain of 24 and 40% were conducted in a universal testing machine. A comparison was drawn between the cold-rolled LDX 2101 and previously studied hot-rolled LDX 2101. Microstructural examinations were conducted via Electron Backscatter Diffraction (EBSD). Results show that cold-rolled LDX 2101 has a higher yield stress than hot-rolled LDX 2101. Furthermore, the response of cold-rolled LDX 2101 was found isotropic, due to the similar phase morphology along each direction. Finally, phase transformation was observed to occur within the austenite phase for the two strains tested.

This paper investigates the compression behaviour of 18 Parallel Bamboo Strand Lumber specimens. 25 mm × 25 mm square specimens with varying heights and fibre orientations were tested. Test results indicated typical 5-stage failure path, and a 45º failure plane in all specimens when the compression load was applied parallel to the fibres. Specimen height did not affect the ultimate load carrying capacities but showed considerable influence on the initial stiffness as well as the post-ultimate loading regime. Experimental results showed that the deformation ratio and the energy absorption ratio for longer specimens were not affected by fibre orientations.

Under ballistic impact or blast loading, the strength and fracture behaviour of armour steels is key to their response, however a comprehensive understanding and modelling of material behaviour for multiple grades of high strength armour steels has not been presented in literature. This experimental and numerical investigation comprehensively characterises the plasticity and ductile fracture behaviour of four high strength armour steels: rolled homogenous armour (RHA); improved rolled homogenous armour (IRHA); high hardness armour (HHA); high strength abrasive resistant steel (ARS) with a TRIP strengthening mechanism. Thirteen specimen types are used to investigate a range of stress states from uniaxial tension to high stress triaxiality plane strain as well as elevated temperatures and strain rates. A modified Johnson-Cook strength model with combined Voce-Ludwik strain hardening and a J3-dependant yield function was calibrated and used. A new calibration approach for the ductile fracture model is presented that incorporates the time-dependence of the stress state taken from inverse numerical modelling of each experiment. The modelling is shown to accurately capture material response up to fracture across all specimens. High strain rate experiments identified dislocation drag effects at 2700s−1, which were captured by the modelling approach. The experimental results provide a characterisation of armour steels to an extent not previously seen in literature, particularly considering comparison of four materials across identical test conditions.

The blast response of a High Strength Steel (HSS), classified as a High Hardness Armour (HHA), subjected to a 60 g charge mass at a Stand-Off Distance (SOD) of 25 mm has been investigated. Electron Backscatter Diffraction (EBSD) and microhardness measurements were used to determine the microstructural evolution in the through thickness and the associated mechanical properties changes. Results show that the blast wave travelling through the material increased the deformation and reduced the grain size. These observations correlated with the hardness increasing along the direction of travel of the blast wave.