Protective Helmet Types with Materials and Methods of Construction

Journal of Recent Trends in Mechanics Volume 4 Issue 2

Dr. Nemailal Tarafder* EX-Emeritus Professor, Department of Textile Engineering, Hooghly Engineering and Technology College, West Bengal, India Email: [email protected]

Abstract Any motorcycle helmet is a type of helmet that is worn by the motorcycle riders and is at high risk in traffic crashes. Wearing helmet protects against cervical spine injury of the motorcycle rider. Motorcycle helmets are basically of five types. There are two main protective components in the conventional motorcycle helmets. Many countries have made compulsion for the motorcycle riders to wear helmet as per the laws of the respective countries. Throughout the world, most of the countries have their own standards to assess the effectiveness of quality of the helmets from the view point of safety. In conventional helmet, there are three basic components, namely the shell, a foam layer and the padding material. It is observed that modern helmets have not changed significantly since the introduction of Styrofoam impact absorption in 1960 for the construction of helmets. In any helmet, the liner is the most important part, the foam layer where the energy of the crash is managed. In the design construction, the most important consideration is the survival impact.

Keywords: Ballistic thread, bead, cervical spine, fatigue, foam, safety right, shell

INTRODUCTION bicycling was thrown over the handlebars Safety of the motorcycle rider is the and died in the hospital. He was not primary object of the protection of head wearing any helmet. Lawrence death led to against any injury from impact or collision the conclusion that the unnecessary loss of and ultimately to save the life of the life by motorcycle despatched riders motorcyclist [1]. The report says that through head injuries. Cairns’ research led wearing helmets reduces the chances of to the increased use of crash helmets by head injury by 69% and death by 42% [2]. both military and civilian motorcyclists The origin of the helmet date backs to the [4]. Brook Lands Racetrack in early 1914, when a medical officer Dr. Eric Gardner There are five basic types of helmets observed that a motorcyclist found in intended for motorcycling and others not injured condition about every two weeks intended for motorcycling but which are [3]. He along with Mr. Moss of Bethnal caused by some riders. All types of Green made a canvas and shellac helmet helmets are secured by a chin strap, and stiff enough to stand heavy blow and their protective benefits are greatly smooth enough to glance off any reached, if not eliminated if the chin strap projections it encountered. Dr. Gardner is not securely fastened so as to maintain a received a letter from the Isle of Man snug fit. The Snell Memorial Foundation Medical Officer stating that after the TT recently certified a flip-up helmet for the races, they normally had several first time. ECE, 22.05 allows certification interesting concussion cases but that in of modular helmet with or chain bar tests 1914 there were none. In 1935, when T. E. [5]. A novelty helmet can protect the scalp Lawrence lost control in a narrow road against sunburn while riding and if it stay

Journal of Recent Trends in Mechanics Volume 4 Issue 2

on during crash might protect the scalp the shell. In contrast, a wide variety of against abrasion, but it has no capability to helmets will employ very similar foam protect the skull or brain from an impact layers. In EPS foam, the stuff is stiff and [6]. To understand the action of a helmet, light weight but also perfectly crushable the first necessary thing is to understand during impact [11]. Modern helmets with the mechanism of head injury. Skull new constructions and methods are fracture is not life-threatening unless the improving safety, in some cases absorbing fracture is depressed and impinges on the 30% more energy than their Styrofoam brain beneath and bone fractures usually equivalent. Motorcycle or bicycle helmets heal over a relatively short period. Brain or other helmets use in the sports absorb injuries are much more serious. Therefore, impact energy using expanded the primary purpose of a helmet is to Polystyrene, the same material used to prevent traumatic brain injury while skull deliver varying densities to accommodate and face injuries are significant secondary different deceleration rates for different concern [7]. weight heads [12]. The main benefit is that it is cheaper and there is no measurable Motorcycle helmets greatly reduce injuries difference in safety provided by more and fatalities in motorcycle accidents thus expensive helmets versus crappy helmets. many countries have laws requiring Bicycle helmet liners are mostly moulded acceptable helmets to be worn by the in expanded Polystyrene (EPS) foam. motorcyclists [8]. These laws vary Granules of EPS known as bead are placed considerably, often exempting mopeds and in a mould and expanded with steam and other small-displacement bikes. In USA pressure into the familiar picnic colour and India, there is some opposition to foam. Still with EPS world, the top end compulsory helmet use. Many other helmets require internal reinforcement, countries have their own sets of standards usually to open up larger vents and the that are used to judge the effectiveness of a techniques for including the reinforcement motorcycle helmet in an accident. Some of in the mould and getting them to line up the specified standards are like, ACU Gold correctly are critical to the manufacturing or Silver badge, BSI 6658, CMVSS, processes [13]. Manufacturers use a CRASH, CSA CAN 3-D 230-M 85, variety of materials such as nylon, DOTFMVSS 218 USA [9] and many polypropylene or even metal or metal more. The standards also describe how mesh for reinforcement. EPS can be made helmets must be labelled, including such in layers with different densities to tune information as how to wear and clean the impact management, permitting softer helmet, its size and mass and warnings to layers to crush in lesser impacts and harder replace the helmet after a violent impact layers to handle the reality the bad hits. [10]. The most important design consideration Any motorcycle helmet consists of a foam for helmets is to survive impacts. These layer, shell and padding. The shell impacts can vary from falling objects to disperses the impact across wide area, head-on collision. The helmets lessen the while also preventing anything from impacts by absorbing energy, but it turns piercing the helmet. Mean while, the foam out that the best way of doing this and the absorbs as much as impact as possible, so materials depends on the type of impact. as the head does not have to. The soft Helmets have existed since early times to padding ensures a good fit against the protect people in battle. Before the head. The basic difference between introduction of steel and aluminium they ordinary advanced helmets normally lies in were made of iron and beaten into shape

Journal of Recent Trends in Mechanics Volume 4 Issue 2

[14]. The present day use of helmets are obstructed his view of two boys on not restricted to only for police and army bicycles shivering to avoid them, but there has been a wide application of Lawrence lost control and was thrown over helmets in the common purposes like the handlebars. He had no helmet and persons in the construction works, cycling, suffered serious head injuries which left horse riding, snowboarding, boxing, etc. him in a coma, he died after six months in The past 20th century technical and the hospital. One of the doctors attending material design for bicycle at times him was Hugh Cairns, a neurosurgeon, increased greater than automobile design. who after Lawrence’s death began a long Now in the 21st century even the said low- study of what he saw the unnecessary loss class bicycles are pushing boundaries of of life by motorcycle despatch riders light weight, efficient, functional and high- through head injuries. Cairn’s research led performance needs of the cyclists [15]. to the increased use of crash helmets by both military and civilians [1]. Today technology has advanced the ballistic threat to human has increased There are five basic types of motorcycle significantly. As well as every civilians helmets and other types are not intended who are exposed to these threats as part of for motorcycling, although those are used their every day work requires adequate by some riders. All of these helmets are equipment. This increasing demand for secured by a chin strap and their protective body armour and ballistic helmets are benefits are greatly reduced if not driving the equipment industry to create eliminated, when chin strap is not securely light weight, reliable protection adequate fastened so as to maintain a snug fit. A full for specific application and to a wide range face helmet covers the entire head with a of customer [16]. The head is a very rear that covers the base of the skull and a delicate part of the body and one which we protective section over the front of the rely on every day. Injuries of head can be chin. Such helmets have an open cut out in very serious which is why head protection a bane across the eyes and nose and often is so important. According to the U.K include a clear or tinted transparent plastic Health and Safety Executive’s statistics face shield, known as a visor that generally 2015−16, 15 people were killed in the swivels up and down to allow access to the U.K. when being hit by a moving, falling face. The motor cross or off-road helmet or flying object. Six out of these were in has already elongated the chin and visor the construction industry. Head injuries portions, a chin bar and partially open face also accounted for one in ten reported non- to give rider extra protection while fatal injuries which can still have life wearing goggles and to allow the changing effects. Even after a minor head unhindered flow of air during the physical injury, brain function can be temporarily exertion typical of this riding. A hybrid impaired, something often referred to as between full face and open face helmets concussion. This can lead to difficulties for street use is the modular or flip-up such as dizziness, fatigue, depression, helmet, also sometimes termed convertible irritability and memory problems [17]. or flip-face. When fully assembled and closed, that resemble full face helmet by MOTORCYCLE HELMETS bearing a chin bar for absorbing face In May 1935, T. E. Lawrence, known as impacts. Its chin bar may be pivoted Lawrence of Arabia had a crash on upwards by a special lever to allow access Borough Superior SS 100 on a narrow to most of the face, as in an open face road near his cottage at Wareham. The helmet. Open face or three quarters accident occurred because a dip in the road helmets cover the ears, cheeks and back of

Journal of Recent Trends in Mechanics Volume 4 Issue 2

the head, but lack the lower chin bar of the mechanism of head injury. The common full face helmet. Many offer snap-or visors perception that helmet’s purpose is to save that may be used by the rider to reduce the rider’s head from splitting often sunlight glare. An open face helmet misleading. Skull fractures are usually not provides the same rear protection as a full life threatening unless the fracture is helmet, but little protection to the face, depressed and impinges on the brain even from non-crash events. The half beneath and bone fracture usually heal helmet also referred to as a shorty in the over a relatively short period. Brain USA and Pudding basin or TT helmet in injuries are much more serious. They UK and popular with rockers and road frequently result in death, permanently racers of the 1960s in the British Isles. It disability or personality change and unlike has essentially the same front design as an bone, neurological tissues have very open face helmet but without a lowered limited ability to recover after an injury. rear in the shape of a bowl. There are other Therefore, the primary purpose of a helmet types of head wears often called beanies is to prevent traumatic brain injury while brain buckets or novelty helmets. A skull and face injuries are a significant novelty helmet can protect scalp against secondary concern [7]. It is important that sunburn while riding and if it stays on the liner in a motorcycle helmet is soft and during a crash, might protect the scalp thick so that the head decelerates at a again abrasion, but it has no capability to gentle rate as it sinks into it. The helmet protect the scalp or brain from impact [6]. becomes quickly impractical if the liner is more than 2.5−5.1 cm thick. An ideal liner Black helmets are popular among is stiff enough to decelerate the impacting motorcyclists but a study reports that they head to an abrupt stop in a smooth uniform offer the least visibility to motorists. manner just before it completely crushes Riders wearing a plain helmet (white) the liner and no stiffer. rather than a black helmet were associated with 24% lower risk of suffering from an Many countries have their own laws and accident injury or death. It is also reported standards for the motorcycle riders to wear that riders wearing high-visibility clothing helmet in order to avoid accidents [8]. and white helmets are likely to be more These laws vary considerably often safety conscious that other riders. Modern exempting mopeds and other small helmets are constructed from plastics and premium price helmets are made with fibre displacement bikes. Countries like USA glass reinforced with Kevlar or Carbon and India, they have introduced fibre. They usually have fabric and foam compulsory helmet wearing for the riders interiors for both comfort and protection. of moped and small slow speed two- Helmets are constructed from EPS foam wheelers. Similarly, throughout the world, and an outer shell to protect EPS. The many countries have made it compulsion density and thickness of EPS is designed for the quality standards of the helmets to to offer better protection. Fibre glass or avoid accidents. Among them are: ACU fibre shells will crash on impact offering gold or silver badge, AS/NZS 1698, BSI better protection. Kevlar or Carbon fibres 6658, CMVSS, CRAHS DOT FMVSS 218 help to reduce the amount of fibre glass (USA) [9], ECE regulations 22, ICC, IS but in the process it reduces the helmet 4151, SHARP (UK), etc. Most motorcycle weight and offer more protection from standards use impacts at speeds between 4- penetration but still crushing on impact. 7 m/s (9-16 mph). Since the surface of the road is almost parallel to the direction a To understand the action of a helmet it is motorcyclist moves while driving on a first necessary to understand the small component of their velocity is

Journal of Recent Trends in Mechanics Volume 4 Issue 2

directed perpendicularly. The severity of Since the adoption of Styrofoam impact an accident impact is also influenced by absorption in 1960, there has not been any the nature of the track. There is a wide significant change in the construction of range of severity in the impacts that could modern helmets. With the introduction of happen in a motorcycle accident, some new materials along with the methods of will be more severe than the impacts used construction, lots of improvements are in the standards texts and some will be less taking place in the safety area of the [10]. helmets and in some cases, helmets are absorbing 30% more energy than the MATERIALS FOR HELMETS Styrofoam at the time of impacts [12]. It is A motorcycle helmet consists of a shell, actually pretty good at absorbing impacts, foam layer and padding. The difference given its extremely basic nature and is between basic and advanced helmets easily accommodating different normally lie in the shell in contrast, a wide deceleration rates for different weight variety of helmets will employ very similar heads. Its main benefit is that it is cheaper foam layers. Most use some variation of and that is why there is little to no EPS—Expanded Polystyrene foam layer. measurable difference in safety provided This stuff is stiff and light weight but also by the more expensive helmets versus perfectly crushable during impact. Some of crappy varieties. The purpose of the advanced helmets will use multiple introducing Enter Koroyd, a new material densities of EPS in various layers and for the construction of helmets and the locations. This creates a smarter helmet purpose of which is to crush on impact which can absorb the crash differently thereby absorbing energy in a measurable depending on the severity and location of and effective way. The appearance of the impact. Thermoplastic is usually some material is like a honeycomb and each of form of Polycarbonate which is not the its tubes is made of a co-polymer created hardest material. These helmets require through the extrusion process. The more foam padding to meet the safety function of the thick inner layer is to standards. Thermoplastic helmets are provide energy and strength, while the larger and heavier than more advanced outer layer looks like a thin membrane of lids. Fibreglass shells are more expensive just a few microns thick. Its ability to than plastic mainly as they are is a pain in absorb varying levels of energy can be the butt to make. They have a shell that is tailored by the thickness of the tube walls. harder and lighter in weight than plastic. Smith is the first helmet brand to adopt the Fibreglass is quite brittle and prone to material and Sours explained that it brings cracking. They do not require as much benefits beyond just safety. Koroyd is foam padding, making them smaller and lighter than Styrofoam. Cyclists lighter than plastic lids. Advanced universally love Koroyd’s next benefit the fibreglass shells are made from advanced ventilation. Hollow tube all over the areas fibres that have already been mixed with means ventilation all over. Areas on a resin or some other substances. Kevlar helmet that were once solid Styrofoam is composite shells can be about 20% lighter now have all vents. The Sun’s rays are than fibreglass shells. Kevlar and Carbon blocked by the contour of the helmet’s composite shells always combine Kevlar curves meaning riders bare scalp would with some other materials to make up not burnt on long rides. The combination shortcomings. It is very expensive. It of two layers in the Multi-directional achieves the safety standards of fibreglass Impact Systems having a slippery layer to and plastic helmets with much less size act as helmet’s impact absorption and and weight [11]. comfort offering effect, as well as to

Journal of Recent Trends in Mechanics Volume 4 Issue 2

separate heat from the rotational force quality of fabric, surface finish, weave and created during an accident. other subtle characteristics. Straps are put on to the helmet after it comes out of the BICYCLE HELMETS mould. The buckle is the last major piece The most important part of a helmet is its of the helmets and it is attached when liner and it is the foam layer where the straps are put into the helmet. Bike helmets energy of the crash is managed. Helmet made with ring fit arrangement are fitted liners in the bicycles are mostly moulded with an adjustable ring of some kind in EPS foam. For the cheaper helmets that inside. The next step is the assembly of the make up the largest part of sales in the U. parts in the complete helmet. It is usually S market, the techniques are standards done by hand labour. Once the assembly is used in the industry’s foam shops or complete, it is finished off with the making all sorts of EPS parts. Granules of application of graphics in the form of EPS known as bead are placed in a mould stickers. Many other accessories can be and expanded with steam and pressure into added during the manufacturing or the familiar cooler foam. Among the EPS assembly process. helmets, the top end varieties require internal reinforcements, usually to open up In the design construction, the most larger vents and the techniques for important consideration is to give more including the reinforcements in the mould stress on to the ability to survive impacts. and getting them to line up correctly are These impacts are related to falling body critical to the manufacturing process. The to head-on collisions. The helmets lessen first bicycle helmet to use this technique the impacts by absorbing energy and to was the Pro Tec Mirage, a late 1980’s obtain it the best material must be selected model and had used a nylon mesh [13]. [14]. In order to prevent injury from small The reinforcement is normally buried in falling objects, workers in the factories or the foam and the user may not even be in the building construction, a hard hat is aware that it is there but it is essential to recommended. Here also the key keep the models with larger vents from requirement is that the helmet must not splitting on impact. break under the impact. The properties of the material should of such type that it The shell for less expensive helmets are must have good toughness so that they do made usually glued into the liner, then not fracture/crack and enough strength to taped around the edge for appearance, take the maximum load without any although some use glue and others have no deformation. The selection criteria for the tape. In case of expensive helmets, the materials in making the helmets should be shells are included in the mould when the of such that materials have high toughness liner is expanded from the beads, and must and sufficient strength. Composites, most therefore be polycarbonate or any other metals and many polymers are the best higher quality plastics which can withstand choices. the heat of the mould. In a more sophisticated helmet more than one section A case study has been reported by the of shells are moulded and up to five pieces author [15] on the material science of can provide shell protection for lower part bicycle wheels, frame, components and of a helmet or even the interior. Skate-style helmets. The idea behind this was to helmets and a few bicycle-style helmets enhance the knowledge of the readers as have hard shells made of ABS or well as the author to expertise the Polypropylene. They all look very similar, knowhow regarding bicycle materials and but actually vary considerably in the to possible improvement on them by

Journal of Recent Trends in Mechanics Volume 4 Issue 2

innovations. It also helps in understanding In the U. K, they have the Personal the application analysis and material Protective Equipment (PPE) at Work selection. In any motorcycle, the major Regulations 1992, which replaced the overall requirements are speed, comfort previous Construction Regulations 1989 and endurance. Bicycle helmets are related and brought into action the 1992 U. K to comfort and safety of the riders. In this regulations. PPE must have to follow study, the helmet materials considered was certain requirements while supplying as a separate type as compared to other well as wearers also to follow certain bicycle types. The design of a standard requirements. Self-employed individuals helmet is basically crushable foam. Foe should provide their own hard hats and any helmet design, the considerations are ensure they wear them. All forms of related to its weight, cost and safety. The protective gears must be suitable, correctly helmet materials lie in the separate fitted and have an easily adjustable head category-crushable foam, and crushable band, nape and chin strap where foams are ideal for helmet design for one appropriate. Related standards are BSEN hard impact. Some foam used is EPS, EPP 397 and BSEN 14052 and these are and EPU. EPS is the most available, cheap worldwide accepted standards. Bump caps and efficient, thus it is the most common are not tested for lateral deformation and helmet material selection. will not protect from severe impact or crushing injuries. These are suitable for a INDUSTRIAL GUIDE LINES FOR wide range of working environment SAFETY HELMETS because of the range of hazards they It is known to all of us that when we protect against. There are various other undertake certain activities, we have to design features which can be selected to protect our head. It is not always true that ensure that the safety helmet is fit for the all the time we have to use bowler hats, purpose. which we had in the earlier days to protect our head. Today, the market for head There was a longstanding issue regarding protection has moved on. Modern day use of helmets with chin straps, but now head protection offers a wide range of the manufacturers have moved towards a options and can be selected based on the more user-friendly ratchet wheel. A particular activities being undertaken [17]. suspension type model and shell structure In our body head is a very delicate part and has been designed for use in industrial, we rely the most on it. Protection of head mountaineering rescue and leisure is very important and essential because any activities. Tested to mountaineering injury to head can cause serious damage. If standards in addition to industrial after a minor head injury, brain function standards they provide protection to those can be temporarily impaired and as a result activities where a greater range of hazards of that many problems like headaches, may be present and still allow the dizziness, fatigue, depression, irritability connection of accessories that may be and memory loss may arise. For the required in an industrial setting as protection of head Personal Protection mentioned earlier. Sometimes a hard hat Equipment can be used. It can be used to comes off after an impact and thus the prevent or lessen damage caused on the purpose of wearing it fails. Therefore, all skull by any impact from falling or flying hard hats should have a fixing to attach a object and many more. Using head chin strap if needed. It is evident that chin protective gear it generally protects the straps is an effective tool in reducing head scalp and sometimes the jaw and nape on injuries. The purpose of using ratchet the neck. wheel is to remove the additional hazards

Journal of Recent Trends in Mechanics Volume 4 Issue 2

of attached chin strap which cause REFERENCES strangulation when the hard hat becomes 1. Motorcycle Helmet-Wikipedia. caught and releasing an early force to get 2. Lie, B. C, Ivers, R, Norton, R, rid of it. It is therefore suggested that the Boufous, S, Blows, S, Lo, S. K, Liu, solution for the protection of head against Bette, C (ed), (2008), “Helmets for injury is to select the right form of a preventing injury in motorcycle helmet. riders”,https://dro.deakin.edu.au/eserv/ DU CONCLUSION 3. “How the crash helmet originated?”, Wearing helmets reduce the risk of head Motorcycle Magazine, June 22nd, 1922. injury and death from such injuries. The 4. “Motorcycle Helmets Help Protect primary object of wearing helmets is to Against Spine Injury: Study, protect the head from injury. A novelty Researchers debunk myth that weight helmet can protect the scalp against of head protection puts neck at risk in sunburn while riding, but it has no crash”, capability to protect the skull or brain from http://healthusnews.com/healthnews/fa impact. To understand the mechanism of a mily-health---- 5. “ECE 22.05 Motorcycle Helmet head injury it is very much essential to Standard, revision 2”, know the action of a helmet. Most of the http://www.ulece.org/trans/main/wp29/ countries in the world have set their own -- standards with enforcing laws to judge the 6. Turner, P. A, Hagelin, C. A., (2000), quality parameters of the helmets to be “Novelty Helmet by motorcycle riders worn by the motorcycle riders to protect in Florida”, pp. 69−76. themselves from accidental injuries with 7. “Helmets: a road safety manual for minimal possibilities. The severity of an decision makers and practitioners”, impact in an accident is also influenced by http://www.int/roadsafety/projects/man the nature of the surface track. Advanced uals/helmet_manual/em/ materials in the construction of helmets do 8. “The effect of the 1992 California not imply advance safety. Modern helmets Motorcycle Helmet Use Law on always combine Kevlar with some other Motorcycle Crash fatalities and materials to make up for its shortcomings. Injuries”, Jess F. Kraus, MPH, Ph D; Multi-directional Impact System means Corinne Peek, MPH; David L. Mc which can have a slippery layer between a Arther, Ph D, MPH Allan Williams, Ph helmet’s impact absorption layer and its D, JAMA. comfort liner separating the head from 9. Standard No 218; Motorcycle helmets rotational forces created by an impact. http://edocket.access.gpo.gov/cfr- ABS or polycarbonate plastics have been 2007/octqtr/49efr571.218.pdf 10. “The United Nations Motorcycle introduced in the Skate-style helmets along Helmet Study, ECE/TRANS/252”, with some of the bicycle helmets to create http://www.unece.org/fileaddmin/DA hard shell. Modern helmets are mostly of M/trans/publications/WP29/United_M polymer construction but their design otorcycle_Helmet_Study.pdf varies depending on the selection of 11. “Materials Used in Motorcycle material and design will have a leading Helmets”, Fort Nine. role in terms of technology. Choosing the 12. “The New Materials That Are right form of head protective gear is the Revolutionizing Helmet Safety Right only choice for the selection of helmets to Now”, Wes Siler, 03/18/15, protect head from injuries. Registration No S/1L/9509 of 2002.

Journal of Recent Trends in Mechanics Volume 4 Issue 2

13. ”Bicycle Helmet Safety Institute-How 16. “Materials and design Issues for Bicycle Helmets are Made”, military helmets”, National Defence Helmets.org,consumer-funded, University, Malaysia (PDF). volunteer staff. 17. ”Types of Safety Helmets, an 14. “Helmets”, PDF format. Industrial Guide”, -H S Magazine. 15. “Bicycle Materials Case Study”, Andrew Cantrell & Professor Tom Stoebe, Project Advisor.