Design Of Protective Equipment Research Articles

Ballistic response mechanism and resistance-driven evaluation method of UHMWPE composite

The use of ultra-high molecular weight polyethylene (UHMWPE) composite in the design of lightweight protective equipment, has gained a lot of interest. However, there is an urgent need to understand the ballistic response mechanism and theoretical prediction model of performance. This paper explores the ballistic response mechanism of UHMWPE composite through experimental and simulation analyses. Then, a resistance-driven modeling method was proposed to establish a theoretical model for predicting the bulletproof performance. The ballistic response mechanism of UHMWPE composite encompassed three fundamental modes: local response, structural response, and coupled response. The occurrence ratio of these fundamental response modes during impact was dependent on the projectile velocity and laminate thickness. The bulletproof performance of laminate under different response modes was assessed based on the penetration depth of the projectile, the bulging height on the rear face of the laminate, the thickness of remaining sub-laminate, and residual velocity of the projectile. The absolute deviations of bulletproof performance indicator between theoretical value and experimental value were well within 11.13%, demonstrating that the established evaluation model possessed high degree of prediction accuracy.

Perancangan dan Penempatan Alat Pemadam Kebakaran Jenis Sprinkler

The fire suppression ability of this sprinkler installation compared to other fire extinguishing equipment has been proven to be more effective. Because the sprinkler system does not require an operator when operating, fires can be prevented earlier before causing greater losses. For this reason, the implementation of sprinkler systems in buildings is crucial. According to KEPMEN PU NO. 10/KPTS/2000, a building must have elements that can maintain structural stability to a certain level during a fire. This research was conducted directly in the field, and the necessary data was obtained independently through interviews with relevant parties. The author conducted research observations in the archive warehouse to obtain both primary and secondary data. Primary data included field documentation and calculations. Planning calculations were done directly by calculating the number of sprinklers, water requirements, and reservoirs to determine the precise needs. Based on the survey, it was found that the size of the archive warehouse is 48 x 48 m, totaling 2304 m2. The maximum distance between sprinklers used was 4.6 m. Therefore, the effective distance between sprinkler heads is 193 units. The result of the calculation for the water supply for the sprinkler system obtained 34,139.77 liters, with the total overall cost for the equipment and materials used being Rp. 63,121,925.74. Based on the data and calculation results regarding the planning and design of fire protection equipment in open active spaces adhering to the NFPA-13 Standard for the Year 2019, it is expected to provide comfort and safety against the threat of fire incidents.

Adsorption of DMMP and water vapor on granular activated carbon: An experimental and molecular simulation study

The adsorption behavior of Dimethyl methylphosphonate (DMMP), as a simulant of sarin nerve agent, especially in the presence of water vapor, is crucial for the design of efficient chemical protection equipment. Experimental results reveal DMMP's adsorption isotherm on granular activated carbon (GAC) as a typical type I. The adsorption process was a spontaneous and exothermic physical adsorption process, and the adsorption mechanism was in accordance with Dubinin's micropore filling theory. In the relative humidity range of 10 % ∼ 90 %, the isotherm remained I-type, and the effect of water vapor on the equilibrium adsorption capacity and apparent adsorption rate was weak. Molecular simulations also show that DMMP adsorption on GAC follows a type I isotherm, primarily driven by van der Waals forces of physical adsorption. The adsorption potential energy between DMMP and GAC surpasses that of water molecules, resulting in negligible effects from water vapor on DMMP adsorption equilibrium. Meanwhile, water molecules had minimal effect on the diffusion of DMMP molecules in the GAC pores, and the positional distribution of DMMP multilayer adsorption was consistent under different relative humidity conditions. Furthermore, the presence of polar functional groups such as hydroxyl groups significantly affects the adsorption equilibrium of DMMP.

Insights and mechanics-driven modeling of human cutaneous impact injuries

Cutaneous damage mechanisms related to dynamic fragment impacts are dependent on the impact angle, impact energy, and fragment characteristics including shape, volume, contact friction, and orientation. Understanding the cutaneous injury mechanism and its relationship to the fragment parameters is lacking compromising damage classification, treatment, and protection. Here we develop a high-fidelity dynamic mechanics-driven model for partial-thickness skin injuries and demonstrate the influence of fragment parameters on the injury mechanism and damage sequence. The model quantitatively predicts the wound shape, area, and depth into the skin layers for selected impact angles, kinetic energy density, and the fragment projectile type including shape and material. The detailed sequence of impact damage including epidermal tearing that occurs ahead of the fragments initial contact location, subsequent stripping of the epidermal/dermal junction, and crushing of the underlying dermis are revealed. We demonstrate that the fragment contact friction with skin plays a key role in redistributing impact energy affecting the extent of epidermal tearing and dermal crushing. Furthermore, projectile edges markedly affect injury severity dependent on the orientation of the edge during initial impact. The model provides a quantitative framework for understanding the detailed mechanisms of cutaneous damage and a basis for the design of protective equipment.

Retrospective Analysis of Head and Maxillofacial Injuries: FIFA World Cup 2022 Report

Objectives: The aim of this study is to analyze the incidence, causes and consequences of head and maxillofacial injuries in the 2022 FIFA World Cup. Methods: This retrospective study, following the STROBE guideline, conducted an online investigation during the 2022 World Cup, with a specific focus on injuries resulting in player substitutions or absences of at least one match. To mitigate potential injury exaggeration, journalistic reports were prioritized over video analysis. The analysis of injuries involved the utilization of descriptive statistics, the Kolmogorov-Smirnov test, and the Pearson correlation test, with a significance threshold set at p<0.05. The analytical tools Microsoft Excel and RStudio were employed. Comparative insights were derived from previous FIFA World Cup data; however, injuries lacking sufficient recovery time were classified as preseason injuries, potentially introducing an element of bias to the analysis. Results: During the FIFA World Cup 2022, a comprehensive analysis revealed a total of 123 injuries leading to player substitutions or subsequent game absences, of which seven were localized in the head or maxillofacial region. Statistical analysis indicated a departure from normal data distribution, and a robust correlation was observed between the number of players in national leagues and injury incidence. Noteworthy is the participation of 42 distinct national soccer leagues in contributing players to the tournament's national squads, with no specific league demonstrating a predisposition to higher injury rates. Within the dataset, three maxillofacial injuries were identified. It is of interest that five athletes opted for facemasks as protective measures for the maxillofacial region, and remarkably, only one of them experienced an injury during the World Cup but subsequently resumed play in subsequent matches, while the remaining four athletes had sustained injuries prior to the tournament. Conclusion: The 2022 FIFA World Cup was associated with a low number of head and maxillofacial injuries, with collisions with other players being the most common cause. Despite their limited occurrence, these injuries can have severe implications. In response to the increase in concussions, FIFA implemented an improved safety protocol, which involves immediate game halts for medical assessment and allows player substitutions without affecting the team's allotted substitutions. This change has been well-received by stakeholders. Furthermore, the use of protective equipment, such as custom-made shields, is growing in popularity and has the potential to reduce injury severity and shorten recovery time. Modern technology enables the creation of comfortable and effective protective gear, enhancing player safety. Overall, the study emphasizes the importance of injury prevention strategies in sports, calling for continued advancements in protective equipment design and increased transparency in injury reporting.

The carbon footprint of Bubble-PAPR™: A novel item of personal protective equipment.

Personal protective equipment has important environmental impacts, assessing these impacts is therefore an important element of personal protective equipment design. We applied carbon footprinting methodology to Bubble-PAPR™, a novel, part-reusable and part-recyclable powered air-purifying respirator, designed at our institution. Current guidance states that disposable respirator masks can be worn for 1-h in the United Kingdom, whilst the Bubble-PAPR™ allows prolonged use. Following a detailed use-case analysis, the carbon footprint of each component was estimated using a bottom-up (attributional) cradle-to-grave process-based analysis. Modelling considered the use of virgin or closed loop recycled polyvinyl chloride for the disposable hood element, and disposal via infectious or recycling waste streams to estimate a per-use carbon footprint. The per-use carbon footprint with manufacture from virgin polyvinyl chloride and disposal via incineration is 0.805 kgCO2e. With nine cycles of closed loop recycling and manufacture of the polyvinyl chloride hood (10 uses), the carbon footprint falls to an average of 0.570 kgCO2e per use. Carbon footprinting may contribute to the value proposition of this novel technology. We estimate that a single Bubble-PAPR™ use has a higher carbon footprint than disposable respirator mask-based PPE. However, this is mitigated in circumstances when multiple disposable mask changes are required (e.g. prolonged use) and use may be justifiable when user comfort, visualisation and communication with patients and colleagues are essential.

A finite rotation, small strain 2D elastic head model, with applications in mild traumatic brain injury

Rotational head motions have been shown to play a key role in traumatic brain injury. There is great interest in developing methods to rapidly predict brain tissue strains and strain rates resulting from rotational head motions to estimate brain injury risk and to guide the design of protective equipment. Idealized continuum mechanics based head models provide an attractive approach for rapidly estimating brain strains and strain rates. These models are capable of capturing the wave dynamics and transient response of the brain while being significantly easier and faster to apply compared to more sophisticated and detailed finite element head models. In this work, we present a new idealized continuum mechanics based head model that accounts for the head’s finite rotations, which is an improvement upon prior models that have been based on a small rotation assumption. Despite the simplicity of the model, we show that the proposed 2D elastic finite rotations head model predicts comparable strains to a more detailed finite element head model, demonstrating the potential usefulness of the model in rapidly estimating brain injury risk. This newly proposed model can serve as a basis for introducing finite rotations into more sophisticated head models in the future.

Research on Energy Absorption Characteristics of Bouligand Biomimetic Structure Based on CFRP Composite Materials

Enhancing the impact resistance performance of carbon fiber-reinforced polymer (CFRP) laminates stands as a prominent research focus among various nations. Existing studies have shown a tendency towards arbitrary selection of the inter-ply helix angle values in CFRP laminates, which is accompanied by a limited number of samples representing the chosen helix angles. However, existing studies have shown a relatively random selection of spiral angle values between CFRP laminates, and the sample size of selected spiral angles is limited, posing certain limitations. In order to tackle this problem, we have employed a systematic arrangement of combinations to select the optimal helix angle for CFRP laminates. Inspired by the biological structures of Bouligand, we have sequentially chosen 19 distinct sets of helix angles, aiming to overcome the inherent limitations and enhance the research outcomes in this field. In this study, we established 19 finite element models to investigate the behavior of Bouligand-inspired CFRP composite panels under high-velocity bullet impact. The models were created by selecting 19 sets of helix angles within the range of 0 to 90° with a 5° interval. The results show that the energy absorption of the Bouligand layer-stacking composite plate is better than that of the conventional plate. The optimal spiral angles of the CFRP laminate are 25° and 30°, and the energy absorption characteristics of the laminate are the best at these angles. The impact resistance is also the best at these angles. The energy absorption of the Bouligand layer-stacking composite plate is 396% higher in absorbed internal energy and 361% higher in absorbed kinetic energy compared to the conventional layer-stacking composite plate, significantly improving the ballistic performance of the CFRP bulletproof material and providing a reference for the design of individual protection equipment.

Research onthedelamination damage algorithm offiber reinforced composites

Aiming at the typical delamination damage mode of fiber-reinforced composites, the constitutive model and failure criterion of composites that commonly used in dynamic simulation are studied, and the principles and characteristics of cohesive element and tiebreak contact algorithm are analyzed.Then the simulation calculation of two fiber-reinforced composite targets anti penetration is take as an example,The accuracy of the cohesive element and the tiebreak contact algorithm are verified respectively, and the protection mechanism of fiber-reinforced composites in the process of anti penetration is revealed, which provides an important reference for the development and design of new composite protection structures and equipment.

Dynamic responses of metal foam sandwich beam under repeated impacts considering impact location and face thickness distribution

Owing to the excellent mechanical performance, the metal foam sandwich structures have potential applications in the design of protective equipment, which can improve the impact resistance of engineering structures. In this paper, the nonlinear finite element model is employed to investigate the dynamic behaviors of metal foam sandwich beam (MFSB), and the accuracy of the finite element method is verified by repeated impact tests. In addition, the effects of impact location and face thickness on the dynamic behavior of the MFSB are examined. Results show that, as the distance from the impact position to the middle span of the beam increases, the deflections of face sheets decrease gradually, and the loading and unloading stiffness increases. The thickness of front face sheet affects the depth of indentation, while the total thickness of the front and back face sheets decides the overall deformation, loading and unloading stiffness. Overall, as the impact number increases, the influences of impact location and face thickness on the dynamic behavior of MFSB enhances gradually.

Hand anthropometric survey of Iranian healthcare workers

AbstractBackgroundHand anthropometric data can help properly design hand tools and protective equipment for healthcare workers. This study aimed to measure and analyze the hand anthropometric data of Iranian healthcare workers.MethodsIn this cross‐sectional study, 33 hand dimensions were measured among 540 Iranian healthcare workers (270 male and 270 female) in six ethnic groups. Two‐dimensional imaging and traditional measurement methods were used. The data were classified and compared based on gender and ethnicity.ResultsThe results revealed a difference between the dimensions of males' and females' hands, which indicated that the dimensions of males' hands were larger. The results showed significant differences between different regions of Iran and other countries including the United States, Bangladesh, Nigeria, and Colombia.ConclusionDifferences in hand anthropometric dimensions should be considered in the design and manufacture of hand tools and hand protection equipment to prevent reduced productivity, occupational injuries, and diseases.

Effects of High-collision Plasma on Radiation Protection of Human Brain

Objective: The purpose of this paper is to find a reasonable composite structure of electromagnetic protection device, especially the distribution characteristics of plasma parameters and operation conditions. Methods: Due to its high collision frequency, the high-pressure discharge plasma can be usedas a filling medium to take the electromagnetic protection effect. The strategies and algorithmsare presented to solve the propagation characteristics of electromagnetic wave (EMW) in plasma with complex dielectric constant. When the real and imaginary part of permittivity are of the same order of magnitude, the imaginary part value will impact on the feature of plasma dielectric constant, also affect the behavior of propagation of EMW. The propagation process of EMW in virtual human brain (VHB) model is investigated by finite difference time domain method. By optimizing the layout of plasma layer and air layer, an effective phase regulator is constructed, and the reflected wave amplitude is greatly reduced. Results: The simulation results show that plasma makes the amplitude of the electromagnetic fields in VHB decrease to different degrees. their maximum average decrease is about 25% and the corresponding reduction of SAR value is more than 40% in the frequency range of 1.8-3.6GHz. Conclusion: The existence of plasma can make the scalp and muscle possess the excellent performance in resisting the incident of EMW, so that the amplitude of the electromagnetic field inside the brain body is small, so as to effectively protect the brain tissue. These research results have good reference value and engineering applicability for the structure design of protection equipment with high frequency of EMW.

Modelling localised progressive failure of composite sandwich panels under in-plane compression

Localised progressive failure of composite sandwich panels under in-plane loads is massively seen in engineering practice, e.g. fasteners, etc. This study develops a finite element analysis (FEA) model for accounting localised progressive failure of carbon fibre reinforced polymer (CFRP) composite sandwich panels when subjected to in-plane compression. In-plane crushing experiments on the CFRP composite sandwich panels were conducted, in which the localised progressive damage was initiated by three geometric initiators, i.e., rectangular, semicircular and triangular indenters. Good agreements between the FEA and experimental results were observed for all three types of crushing scenarios. Lamina bending was found to be the predominant failure mode while other failure modes are insignificant. Besides, it was shown that the composite sandwich panels under the semicircular indenter absorbed more (∼9%) energies than those under the rectangular indenters, due to a greater contact area with more thorough crushing and cracking of the fronds when using the semicircular indenter. An ∼8% variation of the FEA results to those of tests under all loading scenarios, proving the accuracy and effectiveness using the present models for prediction of localised progressive failure behaviours. This study sets a foundation for the future design and development of protective structures or equipment with high energy-absorption capabilities.

Engineering a Holistic Response to the Global Crisis of Forced Displacement.

The global coronavirus pandemic has demonstrated the necessity of engineering approaches, from research and development to rapid prototyping and production, in saving lives all across the world [1]. From personal protective equipment design to vaccine production and distribution, engineering has been the bedrock of an effective global response. However, despite major gains made in the last several decades, there are still millions all across the world, including the vulnerable displaced, who rarely benefit from new developments at the interface of engineering, biology, and health.

Multi-stage penetration characteristics of thick ultra-high molecular weight polyethylene laminates

To further reveal the failure mechanisms of thick ultra-high molecular weight polyethylene (UHMWPE) laminates, field firing tests were conducted for 10-, 20-, and 30-mm thick laminates against 12.7-mm calibre wedge-shaped fragment simulated projectiles at high velocities between 450 and 1200 m/s. The ballistic performance, deformation process, and staged failure characteristics of the laminates with different thicknesses were compared and analysed. The results demonstrate that the ballistic limits of the UHMWPE laminates increase almost linearly with laminate thickness. The 10-mm thick laminate generally experiences two-stage failure characteristics, whereas three-staged failure occurs in the 20- and 30-mm thick laminates and the progressive delamination is evident. The energy limit concept representing the maximum energy absorption efficiency and the idea of reuse of the thick UHMWPE laminates are proposed in this study. The findings of this research will be useful in the design of flexible and effective UHMWPE-based protective equipment.

Study on protective performance and gradient optimization of helmet foam liner under bullet impact.

Protective equipment in war plays a vital role in the safety of soldiers, the threat to soldiers from brain damage caused by deformation at the back of the helmet cannot be ignored, so research on reduce blunt post-cranial injury has great significance and value. This study first conducted gunshot experiments, used rifle bullets impact bulletproof plate and different density liner foam to record the incident process and internal response of craniocerebral model. After verifying the accuracy of finite element model through experimental data, optimization model is established based on response surface method to optimize the structure of gradient foam, analyze the cranial strain and energy absorption to select the best density and thickness distribution of each foam layer. Optimization results show that liner foam which designed to have lower density and thicker thickness for impact and brace layers, higher density and thinner thickness for middle layer can significantly improve the energy absorption efficiency. Compared to the 40.65 J of energy absorption before optimization, the optimized gradient foam can absorb 109.3 J of energy, with a 169% increase in the absorption ratio. The skull strain in the craniocerebral model was reduced from 1.260 × 10–2 to 1.034 × 10–2, with a reduction of about 22%. This study provides references for the design and development of protective equipment and plays an important role in ensuring the safety of soldiers in the battlefield environment.

Dynamic response of CFRP-lattice sandwich structures subjected to underwater shock wave loading

Carbon fiber reinforced composites (CFRP) and porous lattice structures possess the advantages of high specific strength and outstanding energy absorption efficiency. However, the structures combining their merits for underwater explosion protection receives little attention, and the underlying mechanics are still not clear. In this work, a CFRP-lattice sandwich structure is proposed, and its responses subjected to the underwater shock wave loading is studied via the finite element code ABAQUS/Explicit. The numerical results are first validated by the existing experiments (Huang et al., 2016), and the influences of the geometrical and load factors on the deformation modes and energy absorption performances are further explored. Results shows that with the variation of the load intensity and structural configuration, the failure modes of the plates can be mainly divided into three types. The failure occurs in the middle layer of the metal porous lattice core along the thickness direction. The thickness of the back plate has a greater influence on the overall deformation of the structure than that of the front plate. When the thickness of the back plate increases, the energy absorption of the front plate increases first and then decreases under the condition of a small shock wave load. The impact resistance of composite sandwich structure is the result of the coupling of core layer and plates. The proportion of energy absorption of each layer is affected by the form of structural energy transfer. The work of this paper provides guidance for the design of underwater protective equipment.

Low velocity impact behavior of bioinspired hierarchical armor with filling layer

Some biological carapaces in the natural world have distinctive structures and excellent performance in impact resistance and light weight, which can be used to compensate for the shortcomings of traditional protective equipment in terms of wearing flexibility and energy absorption. A bioinspired hierarchical armor is designed in this article based on the inspiration provided by the internal filling layer of the biological carapace. The outer layer of the armor is made of ultra-high molecular weight polyethylene as the hard front plate, while the soft layer is made of silicone rubber filled with viscous fluid. Impact responses of the fluid filled armors with different soft layers are studied under low velocity impact load. The resistance behavior of the armor with multicell filling layer is analyzed stage by stage using experimental data and images obtained by the high speed camera. The research has found that the armor's synergistic effect of the hard layer, the soft layer and the substrate allows it to absorb enough impact energy and decrease blunt injuries while keeping a certain degree of flexibility in wearing. Furthermore, the fluid filled in the soft layer improves the defect of local excessive intrusion in the previous bioinspired protection studies. The study can provide a reference for the design of new protective equipment.

Revealing the Effect of Skull Deformation on Intracranial Pressure Variation During the Direct Interaction Between Blast Wave and Surrogate Head.

Intracranial pressure (ICP) during the interaction between blast wave and the head is a crucial evaluation criterion for blast-induced traumatic brain injury (bTBI). ICP variation is mainly induced by the blast wave transmission and skull deformation. However, how the skull deformation influences the ICP remains unclear, which is meaningful for mitigating bTBI. In this study, both experimental and numerical models are developed to elucidate the effect of skull deformation on ICP variation. Firstly, we performed the shock tube experiment of the high-fidelity surrogate head to measure the ICP, the blast overpressure, and the skull surface strain of specific positions. The results show that the ICP profiles of all measured points show oscillations with positive and negative change, and the variation is consistent with the skull surface strain. Further numerical analysis reveals that when the blast wave reaches the measured point, the peak overpressure transmits directly through the skull to the brain, forming the local positive ICP peak, and the impulse induces the local inward deformation of the skull. As the peak overpressure passes through, the blast impulse impacts the nearby skull supported by the soft and incompressible brain tissue and extrudes the skull outward in the initial position. The inward and outward skull deformation leads to the oscillation of ICP. These numerical analyses agree with experimental results, which explain the appearance of negative and positive ICP peaks and the synchronization of negative ICP with surface strain. The study has implications for medical injury diagnosis and protective equipment design.

REGIONAL AND DIRECTIONAL DIFFERENCES OF THE INTERVERTEBRAL DISC ANNULUS FIBROSUS MECHANICAL PROPERTIES

The loading experienced by military helicopter and fighter aircrew can lead to spinal injury by degrading the soft tissues. Fighter pilots endure low frequency high magnitude loading, while helicopter pilots endure high frequency vibrational loading over longer periods of time. The purpose of this study is to analyze intervertebral disc material properties, including elastic modulus, failure strain, and failure stress. This will provide data to model the annulus fibrosus to predict the risk of injuries. Quantifying the risk to specific spinal locations could provide insight to improve the design of protective clothing and equipment. Single layers of the porcine annulus fibrosus were subjected to tensile failure tests to determine the mechanical properties. Results showed a significantly (p< 0.05) higher elastic modulus in the circumferential direction compared to the axial direction. There was also a significantly greater elastic modulus for samples from the lateral region of the disc compared to the posterior region. There was no significant difference for the anterior region or specimen depth with regards to elastic modulus. Failure stress showed significant differences between superficial and deep specimens as circumferential and axial testing directions. Failure strain only had differences between circumferential and axial directions. This data can be used to help predict where in the disc an injury may occur. Because of the decreased posterior elastic modulus, tensile failure is more likely to occur in that region.