Football helmet
A football helmet is a type of protective headgear used mainly in gridiron football, although a structural variation has occasional use in Australian rules football. It consists of a hard plastic shell with thick padding on the inside, a face mask made of one or more plastic-coated metal bars, and a chinstrap. Each position has a different type of face mask to balance protection and visibility, and some players add polycarbonate visors to their helmets, which are used to protect their eyes from glare and impacts. Helmets are a requirement at all levels of organized football, except for non-tackle variations such as flag football. Although they are protective, players can and do still suffer head injuries such as concussions.
Football helmets have changed dramatically with the modernization of the sport to facilitate technological changes and to improve the safety of the game. Despite lower rates of some injuries, serious traumas to the head are still common, and determining the consequences of these traumas is an active area of research. In addition to the acute concern about traumatic brain injuries, such as concussions, studies have found players increase their risk for long-term problems such as chronic traumatic encephalopathy. Football helmets present a unique design challenge because, unlike bicycle helmets, which are thrown out after a single hit, football helmets need to withstand multiple impacts. A recent focus on improving player safety through better helmet designs has started reducing the total number of concussions.
History
Invention
One of the first instances of football headgear dates to 1896 when George "Rose" Barclay, a halfback at Lafayette College in Easton, Pennsylvania, began to use straps and earpieces to protect his ears. It is not certain who invented the football helmet. Many sources give credit for the creation of the helmet to James Naismith, while other sources credit U.S. Naval Academy Midshipman Joseph M. Reeves, who had a protective device for his head made out of mole pelts to allow him to play in the 1893 Army–Navy game. Reeves had been advised by a Navy doctor that another kick to his head would result in "instant insanity" or even death, so he commissioned an Annapolis shoemaker to make him a helmet out of leather. Later, helmets were made of padded leather and resembled aviators' helmets or modern day scrum caps. At least in professional football, they were optional. Some National Football League players, notably Hall-of-Famer Bill Hewitt, played all or most of their careers without a helmet.Early years
One innovation from the early 1900s period was hardened leather. In 1917, the first helmets were raised above the head in an attempt to direct blows away from the top of the head. Ear flaps also had their downfall during this period as they had little ventilation and made it difficult for players to hear. The 1920s marked the first time that helmets were widely used in the sport of football. These helmets were made of leather and had some padding on the inside, but the padding was insufficient and provided little protection. In addition, they lacked face masks. As a result, injuries were very common. Early helmets also absorbed a lot of heat, making them very uncomfortable to wear.In 1939, the Riddell Company of Chicago, Illinois started manufacturing plastic helmets because it felt that plastic helmets would be safer than those made of leather. Plastic was found to be more effective because it held its shape when full collision contact occurred on a play. These helmets were also much more comfortable and had more padding to cushion the head in an impact. Included with the plastic helmet came plastic face mask, which allowed the helmet to protect the entire head. By the mid-1940s, helmets were required in the NFL. They were still made of leather, but with improved manufacturing techniques had assumed their more familiar spherical shape. The NFL initially allowed either plastic or leather helmets, but in 1948 the league outlawed the plastic helmet, considering the hard-plastic material to be an injury risk. The NFL lifted the plastic helmet ban after just one year in 1949, and by 1950, the plastic helmet had become universal in that league.
Introduction of advanced materials
By the 1950s, the introduction of polymers ended the leather helmet era. The last leather helmet manufacturer, MacGregor, ceased production of leather helmets in the mid-1960s. The NFL also recommended face masks for players in 1955, reducing the number of broken noses and teeth, but also necessitating new rules prohibiting opposing players from grabbing the face mask. By varying accounts, either Pat Studstill or Garo Yepremian was the last to forgo the facemask; among non-kickers, Tommy McDonald was the last to do so.Recent designs
In 2002, American football equipment manufacturer Riddell released a new design of helmet called the Revolution in response to a study of concussions. In addition, Riddell has recently come out with a new design of helmets, the Riddell Speed Flex. This helmet came out in 2014. This new helmet uses elements of Riddell's older helmets, the 360 and the Revolution, such as Side Impact Protection and All Points Quick Release face mask attachment system.Demand for a safer helmet prompted Schutt Sports to announce the arrival of a next generation helmet, the ION 4D, which included an integrated face guard. This new face guard design features shock-absorbing "Energy Wedges" that reduce the force of impacts to the face guard. College teams wearing the helmet include Air Force, Penn State and Virginia. Schutt has also distinguished between their varsity helmets and youth helmets. The varsity helmets from Schutt are made with polycarbonate, which is a very strong polymer designed to take bigger hits. The Schutt youth helmets are made from ABS, which is a lighter material, meant for children who do not take such powerful hits.
The newest model Schutt has released is the Schutt F7. Schutt came out with the Schutt F7 in 2017 and it was released into the NFL in the same year. The F7 expands on F7 technologies such as TPU cushioning and 3-Dimensional Tectonic Plate Technology. Schutt engineers improved the F7 LTD's shell design to boost performance and impact absorption in high-impact sections of the helmet. The helmet now incorporates Anti-Friction faceguard attachment points, as well.
Recently, a brand new type of helmet has come into play. Vicis is a new company that is producing helmets that have a softer outer layer. The softer layer absorbs more energy from impacts. In addition, the inside of the helmet also has a foam-like substance that absorbs energy and improves comfort.
In the summer of 2022, the National Football League had offensive and defensive linemen, linebackers and tight ends wear a Guardian Cap, a protective cover worn on top of head. Players who wore the Caps had more than 50% fewer concussions than players who did not. Starting in the 2024 season players are allowed to wear a Guardian Cap during games, though its use is not mandatory.
Modern helmet components
Outer shell
The outer shell of helmets have changed appreciably throughout the history of the NFL. In the 1920s, football helmets had soft leather exteriors, whereas today they have polycarbonate exteriors. The first molded polycarbonate helmet appeared in the NFL in 1986. Today's helmets typically have polycarbonate shells on the order of 3.35mm. The hard outer shell protects the head from local impacts by delocalizing the force, so the load can be absorbed by the other elements.Polycarbonates are ideal materials for outer shells because they are lightweight, tough and exhibit good impact strength, even in extreme temperatures. Polycarbonates refer to a family of thermoset polymers that are wIdely used in manufacturing, for their mechanical performance and ease in manufacturing.
The aesthetic design of the outer shell has become central to teams' uniform and image.
Energy absorbing elements
The performance of a football helmet is based on its ability to decrease the force to the head from an impact. A helmet reduces the peak force transferred to the head by temporarily storing or dissipating impact energy.The primary energy absorbing elements are the compression shock and shock bonnets, while the secondary elements are comfort pads. The materials used to build these components and their dimensions vary within the helmet. The design takes account of a player's comfort and specific position, as well as the goal of protecting the most sensitive regions of the head and areas where big hits are most common.
Because football helmets need to withstand multiple collisions, the helmet materials need to return to their original form after each hit. Padding materials need to be low density to make the helmet comfortable and practical without sacrificing energy absorption. Most football helmets are made from polyurethane or nitrile foams, because they keep the force peak under the load recommended for head health without deforming, while being relatively lightweight and easy to manufacture.
The polyurethane or nitrile foams are all be broadly categorized as viscoelastic foams. When a stress is applied to these types of materials, there are three main regions of deformation: linear elastic, plateau and densification. In the linear elastic region a material deforms reversibly in proportion to its young's modulus, or stiffness. In the plateau region the foam begins to collapse, and this is also a type of recoverable deformation. When the material reaches its densification region it begins to change its internal structure permanently and cannot return to its original shape. Because football helmets are used repeatedly, they needed to be designed, so the strain stays in the elastic or plateau region. The area under the curve in stress strain curve represents the energy absorbed. Foams should be strained a precise amount, so they absorb energy without permanent densification.
In viscoelastic materials, the elastic region changes its shape depending on the strain rate, meaning the speed at which the material is deformed, or more practically, the velocity of the hit. In general, when the material is strained more quickly it is stiffer, so it deforms less. The degree of protection provided by the helmet depends on the velocity of the hit, and performance is poor for the fastest and slowest hits. Air pockets, while absorbing some energy themselves, also help the helmets perform better in very high and low velocity hits. Air chambers have venting systems so the volume and geometry of air chambers is dynamic, helping dampen the viscoelastic effect.
The inception for air pockets came from Vin Ferrara, a former Harvard quarterback. One night, Ferrara was looking for an aspirin when he saw a squirt bottle in his medicine cabinet. As he pumped it and then punched it, he realized that the bottle withstood the blows of different forces. Ferrara came up with the idea to encase football helmets with a number of inflatable pockets in order to cushion the blows a football player receives and reduce concussions.
The foams in football helmets break down over time, and this process is often overlooked in safety modeling. Especially for youth teams, helmets are reused over the course of many years, putting players at risk since they are less protected than otherwise anticipated.