Helmet Shell Research Articles

차세대 한국형 방탄헬멧 디자인에 관한 연구 : 방탄헬멧 쉘 형상 디자인 중심으로

차세대 한국형 방탄헬멧 디자인에 관한 연구 : 방탄헬멧 쉘 형상 디자인 중심으로

Efficacy of visor and helmet for blast protection assessed using a computational head model

Head injury resulting from blast exposure has been identified as a challenge that may be addressed, in part, through improved protective systems. Existing detailed head models validated for blast loading were applied to investigate the influence of helmet visor configuration, liner properties, and shell material stiffness. Response metrics including head acceleration and intracranial pressures (ICPs) generated in brain tissue during primary blast exposure were used to assess and compare helmet configurations. The addition of a visor was found to reduce peak head acceleration and positive ICPs. However, negative ICPs associated with a potential for injury were increased when a visor and a foam liner were present. In general, the foam liner material was found to be more significant in affecting the negative ICP response than positive ICP or acceleration. Shell stiffness was found to have relatively small effects on either metric. A strap suspension system, modeled as an air gap between the head and helmet, was more effective in reducing response metrics compared to a foam liner. In cases with a foam liner, lower-density foam offered a greater reduction of negative ICPs. The models demonstrated the “underwash” effect in cases where no foam liner was present; however, the reflected pressures generated between the helmet and head did not translate to significant ICPs in adjacent tissue, when compared to peak ICPs from initial blast wave interaction. This study demonstrated that the efficacy of head protection can be expressed in terms of load transmission pathways when assessed with a detailed computational model.

Quantifying the effect of the facemask on helmet performance

Evaluating and improving helmet design play a crucial role in reducing sports-related concussions. Despite widespread use of facemasks by football and hockey players, no helmet standards currently exist to test helmets equipped with facemasks. The purpose of this study was to determine the effect that attached facial protection has on the head kinematics resulting from impacts to the helmet shell. Helmets were fit to a modified NOCSAE (National Operating Committee on Standards for Athletic Equipment) headform and subjected to blows from a pneumatic impactor. A total of 240 impact tests were performed to evaluate the effect of the facemask on four helmet models (two for football, two for hockey). For each helmet model, one sample was tested with a facemask and another without a facemask. Tests were conducted at two impact velocities (6, 9 m/s) and three impact locations (front, side, and rear boss) for a total of six impact conditions. Five trials were performed for each helmet sample at each condition. Two-factor analyses of variance were used to quantify effects on linear and rotational head acceleration and Severity Index due to impact location and facemask presence. Significant effects varied by helmet model and impact location and were more commonly associated with football helmets. Differences in facemask effects between sports are likely attributed to differences in facemask-shell attachment mechanisms, and differences in the structure of the facemask itself. The effects of the facemask on linear and rotational acceleration were small, approximately 5% for both football and hockey helmets. On average, peak accelerations were decreased with the addition of a facemask, but individual differences were mixed and varied by helmet type and impact location. These small differences would not greatly affect impact performance tests in the lab. The results of this study have direct applications toward helmet standard development.

Understanding how a sport-helmet protects the head from closed injury by virtual impacttests.

Understanding how a helmet protects the head, especially the soft brain tissues, is the prerequisite for improving helmet design. Intracranial pressure and stresses/strains in the brain tissues are the direct indicators of traumatic brain injury and they can be used to measure helmet performance. In this study, the effects of helmet design parameters such as the helmet shell stiffness, liner compliance and thickness on the brain injury indicators were investigated by virtual impact tests. A finite element head model (FEHM) was first constructed from medical images; a personally-fitted helmet made of composite material and foam was virtually prototyped using geometric information extracted from the FEHM; a helmet-head finite element model was then assembled. Virtual impact tests were conducted using the resulting helmet-head model. The obtained results suggested that, if the helmet shell already has adequate strength to resist excessive deformation and fracture, further increasing shell stiffness and strength would not considerably reduce intracranial pressure and brain strains; to reach the maximum protection with the available materials, the key is to effectively use the second stage in the stress-strain history of the liner foam material.

Modeling of Non-elastic Properties of Polymeric Foams Used in Sports Helmets

Personal protection equipment for the head used in various sporting disciplines must meet at least three fundamental criteria: safety, comfort and aesthetics. Safety is understood as protecting as much head area as possible and, in case of a crash, spreading the resultant forces over the maximum area and absorbing as much impact energy as possible. After the occurrence of non-elastic deformations, this energy is absorbed by the helmet shell and protective liner, most commonly made of polymeric foams. Non-elastic properties of the foams are evaluated with the use of descriptors of energy absorption capability.

Effect of kenaf fibers on trauma penetration depth and ballistic impact resistance for laminated composites

Combat helmets have been utilized to provide protection against a variety of ballistic threats, by reducing traumatic head injuries and fatalities. Nevertheless, head protection from injury is critical to function and for survivability. Soldiers and civilians incur Traumatic Brain Injury (TBI) most commonly from exposure to homemade bombs or improvised explosive devices. Although the Personal Armor System for Ground Troops (PASGT) helmet is expensive, environmental issues are some technical advantages that encourage using natural/synthetic hybrid laminated composites. The effects of different configuration patterns of kenaf fibers on the Backface Signature and energy absorbed by a military helmet (PASGT) were investigated. The ballistic behaviors of the 19 layers of aramid composite and plain woven kenaf composite were compared to hybrid laminated composites. The ballistic impact tests were performed using a 9 mm full metal jacket bullet and fragment simulating projectiles at various impact velocities, using a powder gun on fabricated square panels and helmets. The results showed the positive effect of hybridization in terms of energy absorbed (i.e. penetration), Backface Signature and damage mechanisms for ballistic impact and NIJ (National Institute of Justice) tests. Hybridization of plain woven kenaf/Kevlar laminated composites will open new avenues to reduce the dependency on the ballistic resistance component (Kevlar) in the helmet shell.

Ballistic Impact Resistance of Plain Woven Kenaf/Aramid Reinforced Polyvinyl Butyral Laminated Hybrid Composite

Traditionally, the helmet shell has been used to provide protection against head injuries and fatalities caused by ballistic threats. In this study, because of the high cost of aramid fibres and the necessity for environmentally friendly alternatives, a portion of aramid was replaced with plain woven kenaf fibre, with different arrangements and thicknesses, without jeopardising the requirements demanded by U.S. Army helmet specifications. Furthermore, novel helmets were produced and tested to reduce the dependency on the ballistic resistance components. Their use could lead to helmets that are less costly and more easily available than conventional helmet armour. The hybrid materials subjected to ballistic tests were composed of 19 layers and were fabricated by the hot press technique using different numbers and configurations of plain woven kenaf and aramid layers. In the case of ballistic performance tests, a positive effect was found for the hybridisation of kenaf and aramid laminated composites.

Evaluation of military helmets and roof padding on head injury potential from vertical impacts

ABSTRACTObjective: Soldiers in military vehicles subjected to underbelly blasts can sustain traumatic head and neck injuries due to a head impact with the roof. The severity of head and neck trauma can be influenced by the amount of head clearance available to the occupant as well as factors such as wearing a military helmet or the presence of padding on the interior roof. The aim of the current study was to examine the interaction between a Hybrid III headform, the helmet system, and the interior roof of the vehicle under vertical loading.Methods: Using a head impact machine and a Hybrid III headform, tests were conducted on a rigid steel plate in a number of different configurations and velocities to assess helmet shell and padding performance, to evaluate different vehicle roof padding materials, and to determine the relative injury mitigating contributions of both the helmet and the roof padding. The resultant translational head acceleration was measured and the head injury criterion (HIC) was calculated for each impact.Results: For impacts with a helmeted headform hitting the steel plate only, which represented a common scenario in an underbelly blast event, velocities of ≤6 m/s resulted in HIC values below the FMVSS 201U threshold of 1,000, and a velocity of 7 m/s resulted in HIC values well over the threshold. Roof padding was found to reduce the peak translational head acceleration and the HIC, with rigid IMPAXX foams performing better than semirigid ethylene vinyl acetate (EVA) foam. However, the head injury potential was reduced considerably more by wearing a helmet than by the addition of roof padding.Conclusions: The results of this study provide initial quantitative findings that provide a better understanding of helmet–roof interactions in vertical impacts and the contributions of the military helmet and roof padding to mitigating head injury potential. Findings from this study will be used to inform further testing with the future aim of developing a new minimum head clearance standard for occupants of light armored vehicles.

Response of a full-face motorcycle helmet FE model to the UNECE 22.05 chin bar impact test

ABSTRACTThis study investigates the role of full-face motorcycle helmet components in reducing the severity of chin bar impacts to a motorcyclist. A finite element helmet model was created for chin bar impacts by carrying out component tests on the chin bar padding, helmet shell and the chinstrap. Addition of two composite layers to the chin bar, stiffening the shell, reduced the peak headform centre of gravity acceleration from 168.3 g to 122.6 g in the UNECE 22.05 chin bar impact test configuration. The presence of chin bar foam was necessary to avoid excessive headform responses but optimal foam stiffness was dependent on shell stiffness. The lowest peak headform acceleration of 113.1 g was achieved by stiffening the helmet shell and softening the chin bar foam padding in comparison to the validated helmet model. The chinstrap was also critical, causing peak acceleration increases of 27.3 g and 118 g when slightly loose and absent, respectively. The significance of the shell and chinstrap in chin bar impacts is in contrast to cranial helmet impacts which are predominantly controlled by the crushable foam liner. The fact that chinstrap pre-test tightness influences the headform acceleration response is important for the helmet test technician.

Behind helmet blunt trauma induced by ballistic impact: A computational model

Behind helmet blunt trauma (BHBT) has emerged as a serious injury type experienced by soldiers in battlefields. BHBT has been found to range from skin lacerations to brain damage and extensive skull fracture. It has been believed that such injuries are caused by forces transmitted from the helmet's back face deformation (BFD), which result in local deformations of the skull and translation or rotation of the head, leading to brain injuries. In this study, head injury risks resulting from the BFD of the Advanced Combat Helmet (ACH) under ballistic impact are evaluated using finite element simulations. The head model developed at KTH in Sweden is adopted, and a helmet shell model (including foam pads) is constructed. The examined mechanical parameters include the maximum von Mises stress in the skull, pressure (mean normal stress) and maximum principal strain in the brain tissue, contact force, and head acceleration. The influences of the foam pad hardness, stand-off distance, helmet shell thickness, and impact direction on head injury risks are studied. It is found that a softer foam pad offers a better protection, but the foam pad cannot be too soft. Also, it is shown that a slightly larger stand-off distance leads to a significant reduction in head injury. In addition, the simulation results reveal that an increase in the helmet thickness reduces the injury risk. It is further observed that a 45-degree oblique frontal impact results in a lower head injury risk than a 90-degree frontal impact. Moreover, for a helmet protected head under ballistic impact, it is seen that a high risk of skull fracture does not necessarily mean an equally high risk of injury to the brain tissue. The predictions from the current model of a helmeted head under ballistic impact agree with experimental findings independently obtained by others. The newly developed model provides a useful tool for studying injury mechanisms of BHBT and evaluating the existing standards for testing and designing combat helmets.

Impact attenuation properties of new and used lacrosse helmets

The National Operating Committee on Standards for Athletic Equipment (NOCSAE) has developed impact attenuation thresholds that protective helmets worn in sport must meet to be commercially available in an attempt to prevent injury. It remains unknown how normal helmet use in athletic activity alters the force attenuation ability of lacrosse helmets. We tested 3 new and 3 randomly selected used helmets from 2 popular lacrosse models (Cascade Pro7, Cascade CPXR). All used helmets had been worn for 3 collegiate seasons prior to testing and had never been refurbished. Helmets were drop-tested using 3 prescribed impact velocities at 6 locations according to the NOCSAE lacrosse helmet standard, and we compared the Gadd Severity Index (GSI) scores between new and used helmets using a repeated measure ANOVA with location as the repeated variable and data separated by impact velocity. All 12 helmets passed the NOCSAE GSI threshold for all testing conditions; however 1 used helmet shell cracked resulting in a failed test. We found a significant main effect for helmet age at the low (F5,50=2.98, P=.02), medium (F5,50=3.71, P=.006), and high (F5,50=2.70, P=.03) velocities. We suspect that helmet use can degrade materials under some conditions, but improve performance in others due to changes in helmet composition from use. The clinical implications of the differences in GSI scores noted remain unclear. Because one helmet shell cracked resulting in a failed test, used helmets should be regularly inspected for cracks or other signs of mechanical fatigue that may weaken helmet integrity.

Modeling of Advanced Combat Helmet Under Ballistic Impact

The use of combat helmets has greatly reduced penetrating injuries and saved lives of many soldiers. However, behind helmet blunt trauma (BHBT) has emerged as a serious injury type experienced by soldiers in battlefields. BHBT results from nonpenetrating ballistic impacts and is often associated with helmet back face deformation (BFD). In the current study, a finite element-based computational model is developed for simulating the ballistic performance of the Advanced Combat Helmet (ACH), which is validated against the experimental data obtained at the Army Research Laboratory. Both the maximum value and time history of the BFD are considered, unlike existing studies focusing on the maximum BFD only. The simulation results show that the maximum BFD, the time history of the BFD, and the shape and size of the effective area of the helmet shell agree fairly well with the experimental findings. In addition, it is found that ballistic impacts on the helmet at different locations and in different directions result in different BFD values. The largest BFD value is obtained for a frontal impact, which is followed by that for a crown impact and then by that for a lateral impact. Also, the BFD value is seen to decrease as the oblique impact angle decreases. Furthermore, helmets of four different sizes—extra large, large, medium, and small—are simulated and compared. It is shown that at the same bullet impact velocity the small-size helmet has the largest BFD, which is followed by the medium-size helmet, then by the large-size helmet, and finally by the extra large-size helmet. Moreover, ballistic impact simulations are performed for an ACH placed on a ballistic dummy head form embedded with clay as specified in the current ACH testing standard by using the validated helmet model. It is observed that the BFD values as recorded by the clay in the head form are in good agreement with the experimental data.

Comparison of face mask removal times in lacrosse helmets

In the event of a head or neck injury in helmeted sports, it has been recommended to remove just the facemask (FM) rather than the entire helmet. Research surrounding FM removal time and difficulty, however, has focused primarily on football helmets. To date, there has been limited controlled research regarding men’s lacrosse helmet FM removal. The purpose of this study was to examine the effect of helmet type on FM removal time and difficulty. Design Repeated measure design conducted in a laboratory setting. Eight certified athletic trainers (male = 4, female = 4; age = 24.13 ± 2.17 yr, experience = 1.75 ± .71 yr). Intervention and main outcome measures included the independent variable of helmet type (Warrior Venom, Cascade CPX-R, Cascade Pro7, and Riddell Revolution) and the dependent variables of FM removal time (seconds), rate of perceived exertion (Borg Scale 0-10), and failure rate (trials failed divided by total trials). Results The Cascade Pro7 FM took 61%, 93%, and 108%. longer to remove than the Warrior Venom, Cascade CPX-R, and Riddell Revolution FMs, respectively. The Warrior Venom FM took 29% longer to remove compared to the Riddell Revolution FM. The participants found the Cascade Pro7 FM to be 59%, 100%, and 199% more difficult to remove than the Warrior Venom, Riddell Revolution, and Cascade CPX-R, respectively. There were no other statistically significant differences identified. The Cascade Pro7 FM was the most difficult to remove due to additional removal sites and the Velcro that helped to adhere the chin guard to the helmet shell.

Produto Sustentável: Equipamento de Proteção Individual Fabricado com Plástico Verde

This study analyzed the case of manufacturing of Personal Protective Equipment (PPE) using as raw material biopolymers produced from ethanol from sugar cane, known as green polypropylene, produced since 2008 by BRASKEM. This article studied the PPE for the employee’s head protection, named helmet by NR 6, which is used in situations of exposure to weather and work scenarios in places where there is risk of impact from falling or projecting objects, burns, electric shock, and solar radiation. The MSA, green helmet manufacturer, made an inventory of greenhouse gas emissions into the atmosphere by comparing the two manufacturing processes of the helmet shell, covering the January 1 to December 31, 2011 period. It concluded that the sustainable helmet (green polyethylene and pigments) robs 231g of CO 2 from the atmosphere per produced unit, while the helmet’s production with traditional raw materials (polyethylene and petrochemical pigments) found that, for each unit produced, 1029g of CO 2 are emitted into the atmosphere. The study showed that substitution of raw materials has led to reduction in the impact generated in the helmets’ production.

Effect of liner for single-piece continuously textile reinforced riot helmet shells

This work is a part of research carried out for the manufacturing and evaluation of riot helmet shells having continuous textile reinforcement. The paper is focused only on the effect of expanded polystyrene internal liner on the riot police helmet shells. Energy absorption and force attenuation at different position on the developed single-piece continuously textile reinforcement helmet shells have been studied. Low energy impact tests were carried out at different positions on the developed riot helmet shells. The result shows the internal liner plays a vital role in energy absorption and in force attenuation for a riot helmet shell.

Finite Element Bicycle Helmet Models Development

Abstract Impact attenuation performance of three different range of commercial bicycle helmet were investigated in lateral drop impact test in accordance to AS/NZS 2063:2008, Australian/New Zealand Standard for bicycle helmet using numerical simulation and and experimental impact test. The aim of this research is to develop a simulation model of drop impact test, which to be used in further investigations of user-centred design approach of bicycle helmet. Three commercial bicycle helmet models were used in this study. All helmets and J headform were scanned using Flexscan 3D scanning equipment. Post-scan processing jobs of scanned geometry models such as helmet liner, shell and headform were conducted in Geomagic Studio 12. The experimental impact test is carried out using 2-wire drop test facility in accordance to the AS/NZS 2063:2008, Australian Standard for bicycle helmet. A few samples were cut from the liner of each helmet to determine the density of Expanded Polystyrene (EPS). Headform peak linear acceleration, impact duration and impact speed of each helmet were measured and recorded from the drop test. The scanned geometry models were imported into Abaqus. A drop impact simulation was developed based on the density and impact speed data obtained from the physical test. Inner liner of bicycle helmet, made from Expanded Polystyrene (EPS), was modeled using crushable foam properties, while headform and anvil were modeled as rigid bodies. Peak linear accelerations and impact duration of the headform on each helmet at three different impact locations of helmet were recorded. A robust correlation study using peak linear acceleration score, impact duration score and Pearson correlation coefficient between the data from physical test and numerical model was conducted. Good correlation scores (>80%) were achieved between the numerical model and experimental impact test in terms of headform peak linear acceleration and impact duration score, suggesting that the simulation model is in good correlation with those from physical test.

Analysis of Anti-Riot Helmet Material Based on Numerical Simulation

Focusing on the problem that the modern anti-riot helmet has been revealed a number of deficiencies such as poor performance under impact, the material of helmet shell is analyzed based on numerical simulation in this paper. A finite element model of anti-riot helmet and simple finite element models of head, trunk and blunt object are established by CAD software and ABAQUS software. PP, PC and ABS are chosen as three different engineering plastics for anti-riot helmet shell material, and then carry a numerically simulation on the process of anti-riot helmet impact moment. Results show that the overall system kinetic energy curves present overall downward trends firstly, then present irregular waves with smaller ups and downs. PC is a more excellent helmet material while comparing to PP and ABS.

Influence of different types of the internal system of the ballistic helmet shell on the thermal insulation measured by a manikin headform

The head is a part of the body whose temperature influences not only physiological parameters of the whole body but also the perception of a thermal environment and psychomotor parameters of a human. For this reason, it is important to prevent the head from overheating and to use head covers which render it possible to release heat from head surface to the environment.There exist a number of professions where head covers serve as protection against injuries caused by an accident, trip, or striking the head against a fixed or protruding object. Ballistic helmets are one of such elements, their crucial parameter being ballistic resistance against dynamic deflection caused by a bullet or bullet-fragment. To enhance security and comfort of use of ballistic helmets internal systems are used underneath. Their character depends on the type of a helmet.Thermal insulation is a parameter defining the amount of heat which can be released from a human body to the environment using all types of body covers.The objective of the research was to compare thermal insulation of 4 ballistic helmets with different types of the internal system.The conducted research showed the lowest thermal insulation was noted for the helmet D (with a suspension system made of cotton technical straps), the highest for the helmet B (with multi-segments pads, made of polyurethane). As the structures of the helmets did not differ significantly, it can be assumed that a decisive influence on thermal insulation was exerted by the internal system and the application of a suspension system results in better heat release than it is the case with the padding system. Relevance to industryThe knowledge about the thermal insulation of the ballistic helmets and the effect of diversity of internal system on their thermal insulations provides information that extends current understanding of the risks faced by soldiers using ballistic protections. This information may be particularly useful in the design and implementation of the different kind of head protections.

Aerodynamics of Ribbed Bicycle Racing Helmets

In competitive cycling, aero-helmets have been used around since 1980 to reduce aerodynamic resistance. Considerable design effort has been made to improve the aerodynamic efficiency of racing bicycle helmets over the years. However, the demand for further improvement has forced helmet manufacturers and designers to introduce new designs progressively. Recently several helmet manufacturers (e.g., LG, Lazer and Giro) have introduced dimples on the outer shell of helmet mimicking the so called ‘Golf-ball’ dimple effects with a view to further reduce aerodynamic drag of the helmet. However, no independently verifiable research so far has been reported in the public domain about the aerodynamic performance of ribbed bicycle helmets compared to smooth surfaced helmets. Hence, the primary objective of this work was to undertake an experimental study on four smooth aero-helmets including two latest model ribbed aero-helmets to understand their aerodynamic performance and the effect of dimples on helmets. The investigation was undertaken in an wind tunnel environment over a range of wind speeds, pitch and yaw angles. The experimental data indicate no measurable advantage between the smooth and ribbed helmets under varied pitch angles and at zero yaw angle.

Impact performance of single-piece continuously textile reinforced riot helmet shells

This paper is a part of research carried out for the manufacturing and evaluation of riot helmet shells having continuous textile reinforcement. Low energy impact tests were carried out on the developed riot helmet shells at different locations on the helmet shell with different impact energy levels. Energy absorption and force blocking effectiveness at different impact locations at the helmet shells were evaluated. The result shows the helmet top location is the least vulnerable location against the impact as compared to the helmet back and helmet side location.