Composite Helmet Research Articles

Research on topology optimization of carbon fiber reinforced composite electric vehicle helmet based on deep learning

Abstract To study the topology optimization of carbon fiber composite helmets, a method of optimizing the three-dimensional (hereinafter referred to as 3D) model based on a deep learning network after dimensionality reduction is proposed. In this method, the 3D shell model is expanded and tiled into two-dimensional (hereinafter referred to as 2D) grids based on the one-step inverse forming method. The variable density method (Isotropic Material Penalty Density method) is used to collect the data set required for deep learning training, and the U-Net neural network is built to complete the training. To obtain the input tensor of the neural network, the mechanical analysis of the 3D model is carried out, and the physical properties are imported into the network for learning. In this way, the 2D optimization results of the helmet model are obtained and then reflected in the 3D model according to the unit topology relationship to obtain the final optimization results. Then, the ordinary helmet and the optimized helmet are simulated and compared under the same quality to test their mechanical properties. The results show that the stiffness performance and energy absorption effect of the optimized helmet are stronger when the quality of the two helmets is the same.

In-Silico Model Validation of Impact on a Composite Helmet Shell

Abstract Numerical impact simulation plays a critical role in the development and improvement of helmet systems. Due to the curvature of the helmet, the selection of impact position on the helmet may affect the ability to correlate results between numerical models and experimental results. In this study, high-velocity impact simulations were performed on composite plates, as well as a model of a modern composite helmet to validate helmet model performance. Results of the composite plate simulation show a non-converging increase in composite deformation with mesh refinement, indicating that model validation is a function of both material properties and mesh selection. Results of impact on the helmet model show that the calculated deformation of the helmet increases by up to 35% with a 20 mm change in impact position. The positional variation of helmet deformation is most pronounced on the front of the helmet. Due to the significant effect that impact position has on helmet deformation, the numerical model validation cannot be performed against experimental tests of a “small” sample size.

Fabrication of natural fibre based industrial safety helmet

In all industries, the safety helmet is considered as one of the most significant parts of personal protection equipment worn by workers to protect against head injuries caused due to falling items. The majority of head injuries caused by falling objects are serious, and they can even be deadly. Thermal discomfort, heavyweight, and plastic material are among the issues that workers face when wearing industrial safety helmets. Many researchers are striving to enhance the quality of the material used in safety helmets by using advanced materials like polymers, natural fibres, and composites in order to improve the shock absorption characteristics. The aim of this research is to improve the strength of the helmet by combining different materials such as glass fibre, jute fibre, and banana fibre (mat/chopped) with epoxy resin to form a composite helmet. Three-layer and five-layer composite helmets of different stacking sequences are fabricated by hand layup technique and tested for shock absorption resistance, penetration resistance, flammability resistance, electrical resistance, and water absorption conforming to the Indian standard specification for industrial safety helmets (IS 2925). The results revealed that both the fabricated composite helmets satisfy the requirements of IS 2925, which are lighter and more eco-friendly, and are suitable for replacing conventional industrial safety helmets.

Design and finite element study of Kevlar based combat helmet for protection against high-velocity impacts

High-velocity impact-resistant helmets are used by police forces, law enforcement and military personnel, firefighters, as well as civilians working in construction, manufacturing, mining and material handling industries among other sectors as protection against impact damage caused by projectiles of various shapes and sizes. In this study, an attempt was made to investigate the impact-resistance of fiber-reinforced polymer composite based helmets through finite element analysis. The composite helmets were modelled in different sacking sequences using bi-directional woven fabrics such as Kevlar-129 (K), 3 K-Carbon (C) and EC9-Glass (G) fabrics as reinforcements and an epoxy matrix formulation. Investigation was focused to study the high-velocity impact resistance and energy absorption performance of composite helmets in hybrid and non-hybrid stacking sequences such as KKK, KGK, KCK, KCG and GCK subjected to high-velocity impact simulations at 398 m.s−1. It was observed that neat Kevlar and Kevlar-glass sandwich hybrid composite helmets withstood the projectile, while all other hybrid helmets were completely perforated during impact. It was also found that Kevlar-glass sandwich helmets offered cost savings of about 21% compared to neat Kevlar-epoxy composite. Hence Kevlar-glass sandwich composite can be used to develop protective helmets due to their attractive impact resistance properties and lower cost. The variation in helmet weight among all the considered composite material combinations was only about 5%.

Non-Destructive Evaluation of Composite Helmets Using IR Thermography and Ultrasonic Excitation

The paper presents selected results of non-destructive testing of composite helmets with deliberately introduced defects. Ultrasound pulsed infrared thermography was used for the tests. In order to determine the initial possibilities of this method, artificial defects made of Teflon featuring different area sizes and designed to simulate delamination were placed between layers of the aramid composite from which the helmet was made. The obtained results confirmed the effectiveness of the NDT method used in these tests.

Fabrication technique using a core and cavity mold of a hybrid composite ballistic helmet

Material used for helmet technology has transformed moderately little since the introduction of aramids, which ballistic helmets still uses woven aramids with a thermoset resin system. Most widely used strengthening material for ballistic helmet is Kevlar fibers which comprise outstanding impact resistance and high strength to weight ratio. For Kevlar reinforcement and resin shaping process, composite materials uses molding process in the fabrication methods. The most vital fabrication method is the hand lay-up process. Hand lay-up process normally consists of laying a dry fabric layer by hand onto a mold to shape into desirable design and shape. After the lay-up process is done, resin is then applied to the dry plies. There are several accessible curing methods and the most commonly used method is to let the product to cure at room temperature. This paper presents the fabrication process of ballistic helmet using a hand lay-up fabrication process with a core and cavity mold. This paper also describes the helmet mold design, materials and processing methods.

Enhanced impact energy absorption and failure characteristics of novel fully thermoplastic and hybrid composite bicycle helmet shells

Current research realize to develop a safer, lighter and higher energy absorbing fully thermoplastic (polypropylene fibres and acrylic Elium resin) and hybrid composite helmets (polypropylene/carbon hybrid and Elium resin) and perform the CPSC 1203 certification tests on different anvils. The failure and energy absorption mechanisms were studied and compared with widely used polycarbonate helmets (PC/EPS) and the composite shells manufactured with epoxy resin. The fully thermoplastic and hybrid composite shells have shown up to 65% of absorbed energy while the polycarbonate shells have absorbed a maximum of 13% of the absorbed energy. The usage of composite shells has lead to minimal energy transfer to the foam which is directly attached to the human head and provided improved safety. The high-speed camera has shown clear deformation of the thermoplastic composite shell owing to the ductile behaviour while the catastrophic failure with significant cracks was observed in the Epoxy-based composite shell. Considering the head injury criteria, the PC/EPS helmet showed the highest fatality rate (6%) when impacted on the flat anvil. The usage of fully thermoplastic and hybrid composite shell reduces the probability of critical and fatal injury by around 40% and 60% respectively when compared to PC/EPS configuration.

Development and impact characterization of acrylic thermoplastic composite bicycle helmet shell with improved safety and performance

Fiber-reinforced composites are increasingly used as an outer shell of sporting helmets as an alternative to conventional thermoplastic shells like Acrylonitrile butadiene styrene (ABS), Polyurethane (PU), and polycarbonate (PC) for improved protection. The current research presents a detailed study to manufacture novel woven carbon/Elium® (WEL) thermoplastic composite helmets and investigate the details based on the impact tests following the industrial safety certification criteria (CPSC 1203 helmet certification) tests on the flat, curb-stone, and the hemispherical anvils. The effect of thermoplastic Elium® resin toughened thermoplastic Elium® IM, and Epoxy resin is investigated to understand the benefits offered by the thermoplastic variants in terms of safety, energy absorption, and the impact failure mechanisms. Post-failed Carbon/Elium® thermoplastic composite shells have shown more ductile and less catastrophic damage as opposed to the Carbon/Epoxy composite shell damage. The impact damage mechanisms as observed from the in-situ high-speed camera images have shown more deformation-dominated failure mechanisms for the composite shells manufactured with Elium® and toughened Elium® resin. Carbon/Epoxy composite shells have shown lower energy absorption and the nature of the failure was more catastrophic and more cracks were noticed on the inner side of the foam which is directly attached to the human head. In case of an impact on a flat anvil, the PC shell configuration has shown a critical injury rate of 28.7% and a fatality rate of 6%. With the manufactured Carbon/Elium® composite helmets, the chances of critical and fatal injury rates are reduced to 16.7% and 3% respectively.

Mechanical properties and moisture behaviour of neem/banyan fibres reinforced with polymer matrix hybrid composite

ABSTRACT In this research work, chopped neem fibre and woven banyan fibre were stacked into seven different sequences and fabricated by the hand lay-up technique. The laminates consist of 70% epoxy matrix, 25% natural fibre reinforcements and 5% sawdust filler material. The mechanical properties of the composite such as tensile strength, flexural strength, compression strength and impact strength were studied and also identify the water absorption capacity under different weight fractions of fibres. It is more effective by increasing the weight fraction of bi-directional woven banyan fibres which give better tensile strength of 25.55 MPa, flexural strength of 21.23 MPa, compression strength of 25.21 MPa and increasing of chopped neem fibre gave higher impact strength of 18 J in sample G was found in natural composite. Also, in sample G was given less moisture absorption capacity of 0.1% compared with other sample of hybrid composite. Therefore, the sample G sequence can replace to polycarbonate synthetic helmet and it is a potential alternate material for making natural composite helmet. The surface morphology was studied by SEM analysis before and after fracture of the hybrid composite to reveal the surface finish and failure mode of the epoxy composite laminates.

Experimental Investigations to Promote Better Adaptability of Safety Helmets Using Jute Fiber Reinforced Polyester Composites– A Waste Utilization Approach

ABSTRACT Injuries and accidents that occur in the workplace are also due to improper usage of Personal Protective Equipment’s (PPE). This research made an attempt to investigate the behavior and attitude of the worker toward PPE. Risk associated with the non-usage of PPE is quantified using the likelihood and severity values of the hazards and it is found that safety helmets have higher risk value of 28. A qualitative approach say face-to-face interviews done to know the underlying reasons for avoiding the use of safety helmets and it is identified that discomfort is the major reason behind the negligence of safety helmets. In order to address this issue jute reinforced polyester composite helmet is fabricated with 44% of jute fiber and the remaining percentage of polyester resin using hand lay-up technique. Shock absorption test in the composites (44% of fiber and 56% of polyester) exhibited cracks on the top layer of the shell, so in order to further enhance the strength of composites bio char of 5% and 10% is added as filler and it is noted that the biochar-based helmet shows improved strength. The results satisfy the requirements as mentioned in Indian standards and helps in environmental sustainability.

Mechanical investigations on Neem/Banyan fibers reinforced with ceramic powder particulates hybrid polymer composite helmet

The major investigation of this work is to replace the synthetic fiber polymer composite helmet to natural fiber reinforced polymer helmet. This study examines the mechanical properties such as impact strength, impact modulus, flexural strength, hardness and water absorption capacity. It is performed to develop the natural fiber hybrid composite helmet. The fiber reinforcements are short neem fiber and alkali treated banyan woven fabric is used. The weight percentage of laminates contain as matrix 85% (510g) and reinforcement 15% (90g), the matrix consists of epoxy resin (450g), hardner (45g) and the granite powder is used as a filler material (15g), which is fixed for all samples and varied in the fiber weight ratio of Neem/Banyan (grams), natural fibers are 15/75, 30/60, 45/45, 60/30, 75/15. The result shows the weight fraction of neem fiber 12.5% (75g) and banyan 2.5% (15g) gives high impact strength and it can be applied for fabricating the motorcycle driving helmet.

A study of the dissipation of energy in the helmet due to a blast on a helmet–skull–brain assembly

We present a mathematical model to study the dissipation of energy in a composite helmet that is subjected to blast loading. In addition to assuming a constitutive relation for the material of the helmet, we also assume models for the skull, and brain, all of them being treated as homogeneous isotropic bodies. A rate type model with non-linear dissipative response characteristics is assumed within the context of a thermodynamic framework for the helmet, as well as the skull, and brain. We study the effect of orientation, the region of impact, the dissipative materials used in the helmet, and the interface condition between the helmet and head assembly. We present a numerical simulation corresponding to different dissipative mechanisms that lead to multiple wave transmissions and reflections that could be detrimental to the brain, highlighting the necessity to pick the materials for the helmet with great care.

Process-Induced Distortions Characterization of MBWK Fabric Reinforced Composite Helmet Shell.

In order to characterize the process-induced distortions of 3D thin shell composites with complex shape, the multilayered biaxial weft knitted (MBWK) fabric reinforced high-performance composite helmet was selected as the research object, and the 3D laser scanning machine was used to scan the helmet surface, then the 3D scanning data was compared with the CAD model to evaluate the deformation. The results and discussion indicated that the conventional method was workable, but the speed of convergence was slow and the calculation results were easy to drop into local optimization. According to detailed analysis, a measurement method focusing on the principle of “Feature Distance” was developed. The measurement results shown that this method can not only give accurate results, but also reduce working procedure and greatly save the computing resources, which is proved to be a feasible approach for the deformation measurement foundation of 3D thin shell textile composites.

Assessment of the shock adsorption properties of bike helmets: a numerical/experimental approach

In this paper, a numerical and experimental study of the shock absorption properties of bike helmets is presented. Laboratory compression and tensile tests were carried out on samples of expanded polystyrene (EPS) and polycarbonate (PC), respectively constituting the internal shock absorption layer and the external hard shell of composite helmets. The measured responses of the two materials were then exploited to calibrate the relevant elasto-plastic constitutive models, adopted in full-scale finite element analyses of a helmet subject to standardized impacts. The simulations allowed assessing the time evolution of the acceleration measured inside the headform (according e.g., to EN 1078) and the failure mechanisms of the helmet, if any, as induced by the localization of plastic deformations.

Analysis and Characterization Helm Based on Hyacint Water Composites

Material engineering in the field of natural fiber composites has potential prospects. The availability of natural resource was very abundant. Composite with natural fiber reinforcement was called Bio composite. The promising natural resource were water hyacinth. Water hyacinth was a source of fiber that can be used optimally as a filler in composites. Bio composite properties are be affected by several factors including filler volume, process parameters and filler interface properties in the matrix. The use of water hyacinth bio composite was developed as a substitute for shipbuilding materials, board and leg sockets for prosthetic limbs. This research identified the nature of fibers as fillers in the application of motorcycle helmet that meet Standar Nasional Indonesia (SNI). Hyacint fibers are made from water hyacinth plants, the plant is dried by sun shine. The material was crushed into powder and woven fibers with yarn spinner and the both materials are mixed using resin. The bio composite was tested by tensile test and impact test using variations weight fraction. The best high strength of bio composite was used as material helm shell by using a vacuum bagging system. The value of Impact absorption strength and penetration testing will be tested on helmet shell composites. Tests conducted on bio composite helmets are carried out to meet standard safety according to SNI 1811: 2007.

Effects of pressure, boundary conditions, and cutting reliefs on thermo-hydroforming of fiber-reinforced thermoplastic composite helmet based on numerical optimization

Compared with layup techniques, thermo-hydroforming is shown to be a viable process for mass production of thermoplastic composite structures due to its relatively rapid cycle time and low impact on the microstructure of the material. However, unlike layup technique, thermo-hydroforming can produce wrinkles in the formed part. A research was conducted wherein ABAQUS/CAE (6.14-1) was employed to numerically study the impact of thermo-hydroforming process parameters on the formation of wrinkles in a thermoplastic helmet. The optimized properties of the fiber-reinforced polymer composite was previously determined by the authors using the preferred fiber orientation model implemented as a user material subroutine (VUMAT). To account for the interaction between different layers of the laminated composite, the cohesive zone model was employed. The objective of the study was to use the simulation tool to minimize the overall wrinkle density and wrinkle height in the formed helmet as a function of the fluid pressure, boundary conditions, and especially the blank shape and the relief cuts made in the blank.

DEVELOPMENTS IN LIGHTWEIGHT COMPOSITE BALLISTIC HELMET MANUFACTURE


 
 The design and manufacturing considerations for modern
 lightweight military helmets are discussed by an original equipment
 manufacturer (OEM.). The core functional requirements of contemporary military
 helmets are outlined, describing the performance measures that are routinely
 requested to quantify these requirements within specifications. The challenges
 for OEM and end-user are highlighted, as there are many ways of measuring this
 performance and many different levels of performance desired by different end
 users.  
 
 The OEM states the compromises that are made in order
 to maximise helmet performance whilst balancing the complex and competing
 requirements of military helmets. The use of lightweight fibre-reinforced
 composite structures in modern military helmets is described. The composite
 materials commonly used in these helmets are discussed, highlighting the key
 properties of the materials used and the use of hybridised shell constructions
 using many different materials in order to achieve optimum helmet shell
 performance. The challenges faced when hybridising helmet constructions in this
 way, using often incompatible materials is considered.
 
 The two most common helmet manufacturing processes are
 also outlined, and the paper discusses how careful selection of processing
 parameters is key to realise the full potential of the materials used: how the
 increased use of ultra-high molecular weight polyethylene in ballistic helmets
 has led to the use of new manufacturing processes, such as deep draw, for the
 manufacture of fibre reinforced composite helmets rather than the traditional
 compression moulding. 
 
 These preferences and the experience gained during the
 development initiatives are considered to provide insight and guidance to those
 specifying requirements for their own helmets, such as the technical
 representatives of international Ministries of Defence.
 

Designing safer composite helmets to reduce rotational accelerations during oblique impacts.

Oblique impact is the most common accident situation that occupants in traffic accidents or athletes in professional sports experience. During oblique impact, the human head is subjected to a combination of linear and rotational accelerations. Rotational movement is known to be responsible for traumatic brain injuries. In this article, composite foam with a column/matrix composite configuration is proposed for head protection applications to replace single-layer uniform foam, to better attenuate rotational movement of the head during oblique impacts. The ability of composite foam in the mitigation of rotational head movement is studied by performing finite element (FE) simulations of oblique impact on flat and helmet shape specimens. The performance of composite foam with respect to parameters such as compliance of the matrix foam and the number, size and cross-sectional shape of the foam columns is explored in detail, and subsequently an optimized structure is proposed. The simulation results show that using composite foam instead of single-layer foam, the rotational acceleration and velocity of the headform can be significantly reduced. The parametric study indicates that using a more compliant matrix foam and by increasing the number of columns in the composite foam configuration, the rotation can be further mitigated. This was confirmed by experimental results. The simulation results were also analyzed based on global head injury criteria such as head injury criterion, rotational injury criterion, brain injury criterion and generalized acceleration model for brain injury threshold which further confirmed the superior performance of composite foam versus single-layer homogeneous expanded polystyrene foam. The findings of simulations give invaluable information for design of protective helmets or, for instance, headliners for the automotive industry.

Mechanical analysis of thermo-hydroforming of a fiber-reinforced thermoplastic composite helmet using preferred fiber orientation model

The composite thermo-hydroforming process, utilizing heated and pressurized fluid, was used to form an advanced helmet with the Spectra Shield. Experimental results obtained from the forming process show that thermo-hydroforming is a feasible process for manufacturing thermoplastic composite materials. Concurrent to the forming experiments, the forming process was numerically modeled using ABAQUS/CAE. The behavior of the fiber reinforced polymer composite was modeled using the Preferred Fiber Orientation model, which was implemented into the explicit finite element code ABAQUS by writing a User Material Subroutine. The preferred fiber orientation model was further adapted to work with a composite laminate consisting of multiple layers. Numerical results were compared with experimental data to validate the method in terms of predicting the deformed geometry of the multilayer composite, wrinkling, as well as the punch force–displacement curve. Overall, the deformed shape of the fiber-reinforced thermoplastic composite helmet, including the distribution of wrinkles were predicted accurately.

Thermoforming and Structural Analysis of Combat Helmets

To reduce combat casualties, military helmets are designed to provide protection against projectiles. Modern combat helmets are constructed of relatively lightweight composite materials that provide ballistic protection to the soldier. The manufacture of most composite helmets is labor intensive and involves the manual application and smoothing of individual layers of reinforcement to a concave mold surface. The recently developed double diaphragm deep drawing thermoforming process turns as-purchased, flat-form composite materials into structurally efficient three-dimensional shapes. Using this process, prototype shells have been produced and subsequently tested structurally. The success of the outcome has been greatly assisted through the use of specialized virtual prototyping techniques to provide insight into the thermoforming process of the shells and subsequently their structural performance by accounting for the actual fiber orientations of those finished shells.