Multi-hit Capability Research Articles

Design of an add-on ceramic composite armour against 14.5 × 114 mm API/B32 projectile for the armoured vehicles and investigation of the ballistic performance of the armour

Abstract A ceramic/composite add-on armour system with innovative ceramic geometry (cylindrical) against 14.5 × 114 mm API/B32 projectile was developed and ballistic performance of the armour was investigated both experimentally and numerically. Numerical analysis was used to calculate exit velocities of the projectile after passing through the ceramic/composite layer (before penetrating the Armox 500T which simulates hull structure of an armoured vehicle) and also contributed to the selection of optimum ceramic thickness. The calculated projectile velocity-time curves (from numerical analysis) for three different ceramic thicknesses are given comparatively in the study. The curve characteristics are the same for three different analyses. The duration of the total absorption of the projectile energy is about 0.2 microseconds (ms). There were differences in the transmission of the stress wave and the delamination in the Ultra-High-Molecular-Weight Polyethylene (UHMWPE) layers differed as ceramic thickness increases. The separation between the layers varied with the change in projectile energy. As a result of the ballistic test, the armour prevented 14.5 × 114 mm API/B32 ammunition with desired damage mechanisms. In the x-ray image taken after the shootings, it was seen that the ceramic damage was local which enhanced multi-hit resistance capability and the geometry of the cylindrical alumina played an important role in the localization of the ceramic zone damage during the projectile penetration process. Due to this cylindrical ceramic geometry, the projectile moving on after the moment of impact constantly encounters a curved and new surface, and thus it is deflected and exposed to more wear. The areal density of the armour was also reduced by using the UHMWPE (which is one of the composite material whose fibres have the lowest density and good mechanical properties) composite plate as the backing plate.

Beyond honeycombs: Core topology's role in 3D-printed sandwich panels

Innovative sandwich structures have gained prominence due to their potential to revolutionize industries with multifunctional performance. This study investigates the impact of different core topologies on the energy absorption capability of 3D-printed sandwich panels. Triply periodic minimal surfaces-based lattice structures and bioinspired spherical closed-cell foam structures were designed and compared against a traditional honeycomb structure to find the most suitable core topology. The fused deposition modeling technique was used to print samples in polylactic acid. The mechanical behavior of the 3D printing material was comprehensively characterized through a uniaxial tensile test. The sandwich panels were subjected to low-velocity impact loads to determine the dependence of their mechanical properties’ responses on their topological features. Deformation mechanisms were investigated experimentally and numerically using ANSYS. The impact of cellular core topologies on deformation mechanisms, multi-hit (and impact location), and energy absorption capabilities demonstrated the possibility of enhancing mechanical performance of the panels. It is found that the sandwich panels with Tetra Radial and Schwarz P core topologies exhibit higher performance, denoted by higher dynamic energy absorption (up to 11% and 16%, respectively, for the 1st impact) and stiffness (up to 42%, and 43%, respectively, for the 1st impact) than the honeycomb structure (with a constant relative density). Significant enhancements in energy absorption, particularly in Schwarz P and Mono Radial panels compared to the previously reported Octet core structure, offer valuable insights for lightweight, durable 3D-printed sandwich structures, with broad applications in multifunctional industries and future trends in materials engineering, promising applications in aerospace, automotive, and construction for the development of weight-efficient, structurally robust materials.

Orientation mapping of YbSn3 single crystals based on Bragg-dip analysis using a delay-line superconducting sensor

Recent progress in high-power pulsed neutron sources has stimulated the development of the Bragg-dip and Bragg-edge analysis methods using a two-dimensional neutron detector with high temporal resolution to resolve the neutron energy by the time-of-flight method. A delay-line current-biased kinetic inductance detector (CB-KID) is a two-dimensional superconducting sensor with a high temporal resolution and multi-hit capability. Here, it is demonstrated that a delay-line CB-KID with a 10B neutron conversion layer can be applied to high-spatial-resolution neutron transmission imaging and spectroscopy up to 100 eV. Dip structures are observed in the transmission spectra of YbSn3 single crystals, induced by Bragg diffraction and nuclear resonance absorption. The orientation mapping of YbSn3 crystals is successfully performed via the analysis of observed Bragg-dip positions in the transmission spectra.

A Numerical Modelling Framework for Investigating the Ballistic Performance of Bio-Inspired Body Armours.

Biological structures possess excellent damage tolerance, which makes them attractive for ballistic protection applications. This paper develops a finite element modelling framework to investigate the performance of several biological structures that are most relevant for ballistic protection, including nacre, conch, fish scales, and crustacean exoskeleton. Finite element simulations were conducted to determine the geometric parameters of the bio-inspired structures that can survive projectile impact. The performances of the bio-inspired panels were benchmarked against a monolithic panel with the same 4.5 mm overall thickness and projectile impact condition. It was found that the biomimetic panels that were considered possessed better multi-hit resistant capabilities compared to the selected monolithic panel. Certain configurations arrested a fragment simulating projectile with an initial impact velocity of 500 m/s, which was similar to the performance of the monolithic panel.

Development of FPGA based 128-Channel TDC for Time Projection Chambers

Time Projection Chamber (TPC) is a gaseous detector used for tracking charged particles. These detectors comprise of a sensitive gas volumes applied with high electric field between the end plates. When a charged particle traverses the TPC volume, it ionizes the gas atoms along its trajectory. The free electrons produced move towards anode with a speed depending on the gas mixture and the applied field. Arrival times and hit channel information are used to track the particle. In order to measure accurately, the arrival times of these slow-moving electrons at the anode, an FPGA-based start-Stop type TDC is designed. The TDC starts on trigger and stops on the arrival of electrons at each anode channel. Dynamic range of 160us and least count of 2.5 ns are obtained, which cover the entire particle trajectory. Also, another useful feature of this TDC is its multi-hit capability of up to 4 hits. Design features and preliminary test results of the TDC will be presented.

Ballistic performance of powder metal Al5Cu-B4C composite as monolithic and laminated armor

Abstract In this study, ballistic performances of x wt.-% B4C (x = 5, 10, and 20) reinforced Al5Cu matrix composite samples were investigated as a monolithic and laminated composite armor component. Composite armor plates were produced by the powder metallurgy method. The prepared powders were pressed under 400 MPa pressing pressure. Green compacts were pre-sintered at 400 °C for 30 minutes in order to blow the lubricant. Subsequently, liquid phase sintering was performed at 610 °C for 210 minutes. In ballistic tests, 7.62 mm caliber armor-piercing bullets were used as the ballistic threat. In the ballistic tests of monolithic armors, only 10 mm thick powder metal composite plates were tested. In the ballistic tests of laminated composite armors, these powdered metal plates were layered with 10 mm thick alumina ceramic plate front layers and 10 mm thick AA5083 plates. Although all of the monolithic powder metal composite armors were penetrated, they showed multi-hit capability. All of the laminated composite armors provided full ballistic protection. It was determined that with the increase in B4C reinforcement rate, the ballistic resistance also increased due to the improvement in strength, hardness, and abrasive feature.

A three-dimensional velocity-map imaging setup designed for crossed ion-molecule scattering studies

In this study, we report the design and simulation of an electrostatic ion lens system consisting of 22 round metal plates. The opening of the extractor plate is covered with metal mesh, which is for shielding the interaction region of the lens system from the high DC voltages applied to all other plates than the repeller and extractor plates. The Simion simulation shows that both velocity-mapping and time focusing can be achieved simultaneously when appropriate voltages are applied to each of the plates. This makes the ion lens system be able to focus large ionic volumes in all three dimensions, which is an essential requirement for crossed ion-molecule scattering studies. A three-dimensional ion velocity measurement system with multi-hit and potential multi-mass capability is built, which consists of a microchannel plate (MCP), a P47 phosphor screen, a CMOS camera, a fast photomultiplier tube (PMT), and a high-speed digitizer. The two velocity components perpendicular to the flight axis are measured by the CMOS camera, and the time-of-flight, from which the velocity component along the flight axis can be deduced, is measured by the PMT. A Labview program is written to combine the two measurements for building the full three-dimensional ion velocity in real time on a frame-by-frame basis. The multi-hit capability comes from the fact that multiple ions from the camera and PMT in the same frame can be correlated with each other based on their various intensities. We demonstrate this by using the photodissociation of CH3I at 304 nm.

Development of a novel MPGD-based drift chamber for the NSCL/FRIB S800 spectrometer

The performance of a novel tracking detector developed for the focal plane of the NSCL/FRIB S800 magnetic spectrometer is presented. The detector comprises a large-area drift chamber equipped with a hybrid Micro-Pattern Gaseous Detector (MPGD)-based readout. The latter consists of a position-sensitive Micromegas detector preceded by a two-layer M-THGEM multiplier as a pre-amplification stage. The signals from the Micromegas readout are processed by a data acquisition system based on the General Electronics for TPC (GET). The drift chamber has an effective area of around 60 × 30 cm2, which matches to the very large acceptance of the S800 spectrometer. This work discusses in detail the results of performance evaluation tests carried out with a low-energy alpha-particles source, and with high-energy heavy-ion beams with the detector installed at the S800 focal plane. In this latter case, the detector was irradiated with a 150 MeV/u 78Kr36+ beam as well as a heavy-ion fragmentation cocktail beam produced by the 78Kr36+ beam impinging on a thin beryllium target. The new detector allows sub-millimeter position resolution in both dispersive and non-dispersive directions. The new read out scheme, coupled to the GET electronics, has several advantages compared to the old Cathode Readout Drift Chamber (CRDC), including a four time higher detection rate (of around 20 kHz), multi-hit capability, and a better operation stability. The new improved performance are needed to take full advantage of FRIB's rare-isotope beam portfolio and expected high intensity.

Developing a camera-based 3D momentum imaging system capable of 1 Mhits/s.

A camera-based three-dimensional (3D) imaging system with a superb time-of-flight (TOF) resolution and multi-hit capability was recently developed for electron/ion imaging [Lee et al. J. Chem. Phys. 141, 221101 (2014)]. In this work, we report further improvement of the event rate of the system by adopting an event-driven camera, Tpx3Cam, for detecting the 2D positions of electrons, while a high-speed digitizer provides highly accurate (∼30 ps) TOF information for each event at a rate approaching 1 Mhits/sec.

Multilayered architectured ceramic panels with weak interfaces: energy absorption and multi-hit capabilities

Combining high strength and high toughness still remains a challenge in engineered materials. With the aim of improving the toughness of high-strength ceramics, multilayered architectured ceramic panels were developed inspired by natural materials such as nacre and conch shell. These panels were manufactured by stacking laser-engraved architectured ceramic tiles and commercial monomer Surlyn or Ethylene-vinyl acetate (EVA) resins. The mechanics of the multilayered architectured ceramics was investigated both numerically and experimentally by subjecting them to out-of-plane quasi-static and impact loads. Digital image correlation (DIC), computed radiography technique, micro-CT scanning and 3D laser scanning microscopy were used for multiscale damage assessment during and after loading. The finite element analysis was performed using ANSYS LS-DYNA to model the quasi-static and impact responses and to investigate the effects of architectural parameters on the energy absorption and multi-hit capabilities of architectured ceramic panels. It was found that the multilayered ceramic panels with optimized architectures showed up to 20% and 48% improvements in energy absorption performance in quasi-static testing and impact loading, respectively, with only a 5–10% stiffness reduction compared to plain ceramics. The deformation analysis showed localized failure in the architectured ceramics (opposed to the plain ones) and improved impact resistance of architectured ceramics originating mostly from the energy dissipation due to the plastic deformation in adhesives (up to 35%) as well as the frictional energy dissipation (up to 55%) upon sliding of the tiles, mechanisms that are absent in plain ceramics.

3D printed meta-sandwich structures: Failure mechanism, energy absorption and multi-hit capability

A new class of lightweight and 3D printable architected sandwich structures, named as meta-sandwich structures, has been introduced. These lightweight sandwich structures, which have been made of mechanical metamaterials as the core, show many advantages such as high stiffness-to-weight ratio and high energy absorption capability. In this paper, finite element simulation and experimental testing were implemented to evaluate the structural durability of 3D printed meta-sandwiches under quasi-static flexure and low-velocity impact tests. We specifically investigated the failure mechanism, energy absorption and multi-hit capability of 3D printed polymeric meta-sandwich structures made of cubic, octet and Isomax cellular cores. Three-point bending experiments on 3D printed meta-sandwich beams were conducted to evaluate their flexural stiffness and quasi-static energy absorption, followed by low-velocity impact tests to determine their dynamic energy absorption and multi-hit capabilities. Analytical formulations were also developed to capture the failure mechanism in the architected sandwich structures. It is found that the core topology and geometrical parameters have significant effects on failure mechanism and energy absorption of meta-sandwich structures. For example, Isomax meta-sandwich structures show high quasi-static and dynamic impact energy absorption capabilities.

Demonstration of multi-hit and multi-mass capability of 3D imaging in a conventional velocity map imaging experiment.

Coincidence and three-dimensional (3D) imaging offer unique capability in photodissociation and scattering experiments, and a variety of methods have been developed. The basic concept behind all these approaches is to register both the position (x, y) at which the particle hits the detector and the arrival time (t). A novel advance to the time and position sensitive detection was introduced recently by Li and co-workers [Rev. Sci. Instrum. 85(12), 123303 (2014)]. This method utilizes a high-speed digitizer and a computer algorithm along with the camera and detector usually employed in a conventional velocity map imaging apparatus. Due to the normal intensity variations of the ion spots, a correlation can be made between ion intensity recorded by the camera and peak intensity in the digitizer. This makes it possible to associate each ion spot's position with its respective arrival time, thereby constructing a 3D distribution. The technique was primarily introduced for ultrafast ion and electron imaging experiments at high repetition rate with single or few events per image frame. We have recently succeeded in adapting this approach at low repetition rate. Modifications were done to the initial setup to enhance the acquisition efficiency to obtain and correlate multiple hits per laser shot rather than single-hit events. The results are demonstrated in two experiments, dimethyl amine dissociative ionization at 205 nm and carbonyl sulfide photodissociation at 217 nm, with up to 27 events correlated in a single frame. Temporal and spatial slicing capabilities were achieved with good resolution, giving the photofragment velocity and angular distribution for multiple masses simultaneously.

Multi-impact mechanical behaviour of short fibre reinforced composites

High velocity transverse impact on reinforced composites is a matter of interest in the automotive, aeronautical and biomedical sectors. Most existing studies have addressed this problem by single isolated impacts; however, this work deals with the distinction between single, sequential and simultaneous impacts on composite structures. This paper proposes an experimental methodology to study the mechanical behaviour of materials under single and multi-impact loadings. The overall objective is to investigate the mechanical response of short carbon fibre reinforced PEEK when is subjected to single and multiple high velocity impacts. Experimental tests are conducted covering impact velocities from 90 m/s to 470 m/s. Energy absorption, damage extension and failure mechanisms are compared to assess additive and cumulative effects in high velocity impact scenarios. Experimental results show that the specific deformation and fracture mechanisms observed during multi-hitting events change with impact velocity. Compared to the behaviour of unreinforced thermoplastics, short fibre reinforced composites present significant limitations at velocities close to the ballistic limit, but multi-hit capability is observed at high impact velocity when the damage is mainly local. As key conclusion, the ballistic limit obtained in single impact test cannot be extrapolated to sequential and simultaneous tests. Multi-impact tests, especially close to the ballistic limit, are necessary to guarantee the structural integrity of composite structures in realistic impact scenarios.

Quantitativeness in laser-assisted atom probe analysis of boron and carbon codoped in silicon

Boron and carbon codoped in polysilicon thin films and carbon implanted in silicon substrates have been examined by laser-assisted atom probe tomography (La-APT). Clusters of dopants were observed in annealed samples. Compared with the results obtained by secondary ion mass spectrometry (SIMS), significant miscounts of both boron and carbon were found in La-APT results. On the basis of measurements using two different La-APT systems, it was suggested that the insufficiency of the multihit capability of the detection systems is an important origin of the miscounts.

Role of Microstructural Features in Toughness Improvement of Zirconia Toughened Alumina

Ceramics constitute an integral part of highly efficient armours due to their low density, high hardness, strength and stiffness. However, they lack toughness and multi-hit capability. Therefore, zirconia toughened alumina is investigated. The hardness is evaluated using Vickers, Knoop and instrumented indentations, while the fracture toughness is evaluated using the indentation technique and Charpy tests. The strength is evaluated using ring-on-ring, four point bend and drop weight tests. The Young’s modulus is evaluated using the unloading instrumented indentation curves. Microstructure, porosity and density are characterised using ultrasonic scanning, Archimedes principle, optical and scanning electron microscopy. Results show an indentation size effect on all mechanical properties. A substantial improvement in toughness is achieved through retardation of crack initiation by tetragonal-to-monoclinic phase transformation in zirconia particles, crack deviation thanks to appropriate grain structure, as well as energy absorption by densification due to remaining porosity. This improved toughness is expected to promote multi-hit capability.

Instrumented and Vickers Indentation for the Characterization of Stiffness, Hardness and Toughness of Zirconia Toughened Al2O3 and SiC Armor

Instrumented and Vickers indentation testing and microstructure analysis were used to investigate zirconia toughened alumina (ZTA) and silicon carbide (SiC). Several equations were studied to relate the Vickers indentation hardness, Young's modulus and crack behavior to the fracture toughness. The fracture in SiC is unstable and occurs primarily by cleavage leading to a relatively low toughness of 3 MPa m1/2, which may be inappropriate for multi-hit capability. ZTA absorbs energy by plastic deformation, pore collapse, crack deviation and crack bridging and exhibits time dependent creep. With a relatively high toughness around 6.6 MPa m1/2, ZTA is promising for multi-hit capability. The higher accuracy of median equations in calculating the indentation fracture toughness and the relatively high c/a ratios above 2.5 suggest median type cracking for both SiC and ZTA. The Young's modulus of both ceramics was most accurately measured at lower indentation loads of about 0.5 kgf, while more accurate hardness and fracture toughness values were obtained at intermediate and at higher indentation loads beyond 5 kgf, respectively. A strong indentation size effect (ISE) was observed in both materials. The load independent hardness of SiC is 2563 HV, putting it far above the standard armor hardness requirement of 1500 HV that is barely met by ZTA.

Coincidence ion imaging with a fast frame camera.

A new time- and position-sensitive particle detection system based on a fast frame CMOS (complementary metal-oxide semiconductors) camera is developed for coincidence ion imaging. The system is composed of four major components: a conventional microchannel plate/phosphor screen ion imager, a fast frame CMOS camera, a single anode photomultiplier tube (PMT), and a high-speed digitizer. The system collects the positional information of ions from a fast frame camera through real-time centroiding while the arrival times are obtained from the timing signal of a PMT processed by a high-speed digitizer. Multi-hit capability is achieved by correlating the intensity of ion spots on each camera frame with the peak heights on the corresponding time-of-flight spectrum of a PMT. Efficient computer algorithms are developed to process camera frames and digitizer traces in real-time at 1 kHz laser repetition rate. We demonstrate the capability of this system by detecting a momentum-matched co-fragments pair (methyl and iodine cations) produced from strong field dissociative double ionization of methyl iodide.

A new design of MRPC to reduce noise and crosstalk

The CBM time of flight wall is proposed to be built with MRPC technology. In the past few years we have successfuly improved the rate capability of MRPCs to CBM level. However, in a relative high particle multiplicity situation (over 20 kHz/cm2), multi-hit capability is one of the most demanding requirement of the detector. In a free running mode too many noise not only affect the performance of MRPC but also enlarge the data file or even damage the FIFO. So it is needed to develop low crosstalk and low noise MRPC to meet CBM-TOF requirement. Three strip-readout MRPC with or without shielding grounds were designed to study how to reduce noise and crosstalk of MRPCs. In this paper we report on the performance of three different structures of MRPCs named G-0, G-2 and G-3. Tests with cosmic rays were performed at Tsinghua University. The results show that MRPC G-2 can perform better than other two structures, the average cluster size of G-2 is lower than 1.28 strips and the noise level is below 0.5 Hz/cm2. The detection efficiency is over 98% and the time resolution is around 65 ps.

On the ballistic response of comminuted ceramics

Recent results have strongly suggested that the ballistic-resistance of different comminuted ceramics is similar, independent of the original strength of the material. In particular, experimental work focused on the ballistic response of such materials has suggested that ballistic response is largely controlled by shattered material morphology. Consequently, it has been postulated that control of the nature of ceramic fragmentation should provide a potential route to optimise post-impact ballistic resistance. In particular, such an approach would open up a route to control in multi-hit capabilities. Here, ballistic tests into pre-formed 'fragmented-ceramic' analogues assembled from compacted alumina powders with two differing morphologies were conducted. Strong hints of a morphology-based contribution to ballistic resistance were apparent, although there was insufficient fidelity in the experimental data set to categorically identify the nature of this contribution.

Pervasive nanoscale deformation twinning as a catalyst for efficient energy dissipation in a bioceramic armour

Hierarchical composite materials design in biological exoskeletons achieves penetration resistance through a variety of energy-dissipating mechanisms while simultaneously balancing the need for damage localization to avoid compromising the mechanical integrity of the entire structure and to maintain multi-hit capability. Here, we show that the shell of the bivalve Placuna placenta (~99 wt% calcite), which possesses the unique optical property of ~80% total transmission of visible light, simultaneously achieves penetration resistance and deformation localization via increasing energy dissipation density (0.290±0.072 nJ μm(-3)) by approximately an order of magnitude relative to single-crystal geological calcite (0.034±0.013 nJ μm(-3)). P. placenta, which is composed of a layered assembly of elongated diamond-shaped calcite crystals, undergoes pervasive nanoscale deformation twinning (width ~50 nm) surrounding the penetration zone, which catalyses a series of additional inelastic energy dissipating mechanisms such as interfacial and intracrystalline nanocracking, viscoplastic stretching of interfacial organic material, and nanograin formation and reorientation.