Composite materials have been widely used in the sports industry. In this report, some of the key aspects of the composite materials are going to be discussed. The aspects are an example of sports equipment, the characteristics of the material, the key properties that the sporting equipment should possess and the influence on the game performance.
1.0 ICE HOCKEY STICK
Recently, the importance composite material has since become more evident especially in sports equipment. Composite materials are used in the manufacturing field to give unusual combinations of stiffness, strength, weight, hardness and sports related performance to name a few(Askeland & Phule, 2006). Those were the days when almost all of the sports equipment was made up from wood. Wood is unique because it is a natural composite material. It can be easily accessible. One of the examples is ice hockey stick. Ice hockey is a sport similar to field hockey. There is a difference between both sports, where the ice hockey is played on an ice surface while the field hockey is played on the pitch. There was a period where all the ice hockey sticks were made up from wood. However, the ice hockey sports as well as other sports have gone through a small revolution where the current technology has helped to bring more advancement to the sports industries. According to Matson (2009), in the last ten years, the ice hockey sticks made up from composite materials has gradually replaced the wooden ice hockey sticks.
The ice hockey stick that has been discussed in this report is a stick which consists of some composite materials. Based on an academic publication by Deleris and Destra (1991), some notable materials such as polyvinylchloride, glass fibers, carbon fibers, aramid fibers and resin were used to make a composite ice hockey stick.
The composite hockey stick includes an expanded polyvinylchloride foam core, fiberglass mesh, carbon fiber mesh, epoxy type resin, a mesh of aramid fibers and wood (Deleris and Destra, 1991). The composite hockey stick is made up from structural composite which can be further explained as a laminar composite. According to Callister (2001), structural composite can be composed with both heterogeneous and homogeneous materials. It doesn't depend only on the properties of the material, the geometrical design of each materials play a vital role in producing high end composite materials. Callister (2001) also stated that a laminar composite is composed of 2 layers of material. Moreover, those can be different materials to increase the mechanical or physical properties of the composite material. In contrast, by using the same material, where the materials are staked together in a different direction can result in increment in mechanical or physical properties.
First step is to get the basement, which in this case is the expanded polyvinylchloride foam core. Polyvinylchloride is also known as PVC in short. PVC is a stable polymer and can sustain modifications under the normal usage. PVC foam has the resistance to penetration which is between 50 and 100kg/cm2. This is one of the characteristics that important for the invention of an ice hockey stick. PVC is thermoplastic which can be re-softened by heating (Pvc.org, 2009). The material is heated and molded to a general shape of an ice hockey stick shape.
Later, a mesh of fiberglass is used to cover the entire one piece of PVC based ice hockey stick. Fiberglass mesh can be explained as the fibers of the glass material in treads form are woven together to produce a cloth like sheet. The weaving initial angle and the final weaving angle of the mesh are varying. This sheet is placed on top and fully covered the PVS basement. The Fiberglass mesh is pressed and solidly affixed to the PVC core. Fiberglass mesh provides a good elasticity property to the material. It has a weight per meter of 115 to 130g, diameter of 40 to 50mm, number of threads of 550 to 600,weaving angle of 30° to 45° with respect to the longitudinal of the core (Deleris and Destra, 1991).
2.3 CARBON FIBER
Next, a mesh of carbon fiber is used cover the stick which is already covered by fiberglass mesh. Carbon fiber mesh is the threads made up from carbon woven together as a sheet. The carbon fiber mesh is placed and covered the entire PVC core and fiberglass assembly at a different weaving angle with respect to the longitudinal axis between its original and final position. The deference of weaving angles of both meshes in the final position creates an offsetting of the threads of one mesh to another. In result, it has the effect of reinforcing the structure (Deleris and Destra, 1991). The exterior carbon fiber mesh provides a higher stiffness in the composite material. It has a weight per meter of 55 to 65g, diameter of 40 to 50mm, number of threads of 40 to 50, weaving angle of 20° to 30° with respect to the longitudinal of the core (Deleris and Destra, 1991).
After that, a reinforcement of aramid or Kevlar mesh is used at the bending part of the stick and the blade section due to the parts which undergoes a great stress. With the weaving angle of 20° to 30° in position in the assembly, number of thread of 185 to 200.
Moreover, all the meshes used are affixed together with an epoxy type resin. The resin helps to obtain a perfect bonding of the assembly in the stick (Deleris and Destra, 1991). The resin will be become hard after the polymerization occurred. The polymerization can be accelerated by heating process. Resin compresses the stick thus produce a good surface condition.
Lastly, a layer of wood is affixed to the handle section of the stick to provide the grip for the hockey player. The same epoxy resin is used here as a glue function.
There are a lot of characteristics of the ice hockey stick have to be taken into consideration. For example, the stiffness, elasticity, strength-to-weight ratio, deficiencies, good flexibility, better restoration of lunging power, mechanical resistance to shock and resistance of deformation. However, according to Deleris and Destra (1991), stiffness and strength-to-weight ratio have been identified as the most vital characteristics of the sports equipment, ice hockey stick.
Stiffness is defined as the resistance to withstand the elastic deformation when a force is applied to the body of a material (Askeland & Phule, 2006). When a force is applied to a material body, it will undergo a stress thus the material will deform to a certain degree. The deformation sizes of different materials are different due to the different stiffness of the material. When a stress of 100MPa is applied on material A and material B, material A could deforms 1cm while the material B can undergo deformation at about 5cm. The results define that material A is a higher stiffness material. This is because it has the higher resistance to deform. However the material B is less stiff than the material A and is a lower stiffness material due to its tendency to deform more easily.
An ice hockey stick must be rigid but at the same time must have some flexibility to able to make the perfect shots. While ice hockey sticks made up from wood are prone to wear and tear in a low temperature condition such as ice, it is necessary to invent an ice hockey stick made up from composite materials. The stick should be able to resist the huge stress applied when taking a shot. As a result, the stick should comprise of high stiffness materials. However, it must also have the elasticity as a very brittle stick is very vulnerable to break easily. With decent ductility ability, the stick should able to should able to withstand a high stress without deform or break.
A mesh of carbon fibers has its resistant to pulling and a mesh of fiberglass gives good elasticity (Deleris and Destra, 1991). The first mesh is the fiberglass which is located in between the PVC core and the second mesh consists of carbon fiber. With the embodiment of fiberglass located inside while the embodiment carbon fiber surrounded exteriorly, consequently giving a good elasticity and a great stiffness to the overall assembly.
3.2 STRENGTH-TO-WEIGHT RATIO
Strength-to-weight ratio is also known as specific strength. Specific strength can be defined as the ratio of the ultimate stress to the specific weight of the material (Nash, 1998). The material with higher specific strength is the material with a higher strength as well as a lower weight.
The shape of an ice hockey stick can be explained as a straight long shaft bending to the end of the shaft to join with a blade. According to Deleris and Destra (1991), the section where the shaft and the blade are joining will undergo a huge stress during the game, when the player is taking a shot. To overcome this, a material has to be identified to add the strength to the stick. An ice hockey stick should weigh around 440g per stick (Tradekey.com, 2009).Weight is vital to the players as heavy sports equipment can impede the performance in a game. In order not to exceed the weight of the stick, a high strength material with a high strength-to-weight ratio will be a perfect material.
Aramid fibers or Kevlar, the commercial name is type of polymer fibers, formed from polyamides has a five times the strength of the steel and offers less weight (Bakerjian & Mitchell, 1992). It is also cost effective. The assembly of the ice hockey stick is reinforced with Kevlar which offers a higher strength at the section where it can absorb a huge stress in a game.
A mesh of Kevlar is placed and fully covered the assembly which is already reinforced with fiberglass and carbon fibers. The Kevlar mesh is then affixed to the assembly and covered with an epoxy type resin to help the bonding and offer a smooth finish. This subsequently enables the ice hockey sticks to withstand a huge stress without breaking the stick. Besides that, it also been done without adding a significant weight to the overall assembly.
The composite materials have an edge over the traditional wood ice hockey stick. Deleris and Destra (1991) stressed that the ice hockey stick made up form composite materials are much lighter than their wooden counterpart. This subsequently enables the players to take more shots in a game. With a lighter ice hockey stick, a player able to skate on the ice more easily with the feather weight composite ice hockey stick. The composite ice hockey stick makes the players take more time to adapt to the stick compare to the wooden one. Most of the people would complain that the composite stick doesn't provide the same ‘feel' as the traditional wooden stick. The composite ice hockey stick that has been discussed throughout the report has overcome the problem. This has been done by adding an extra layer of wooden sheet which makes it the hybrid stick due to the presence of the traditional material. The wooden sheet is to give the players the same ‘feel' and experience as playing with the wooden sticks.
Icehockeysource.com (2009) stated that at the moment, about 85% of players in the National Hockey League use one-piece composite ice hockey sticks. The online article also stated that the fiberglass and the carbon fiber elements with the addition of Kevlar mesh made the stick very strong. The overall wear and tear of a composite ice hockey stick blade will last much longer than a wood ice hockey stick. With the composite stick neither brittle nor very ductile, it has the characteristic where a player can make shots with worrying that the stick would break. Those wooden sticks are more vulnerable than the composite sticks. According to Jordan (2009), are more consistent from stick to stick and they have been engineered to provide player with a quicker shots. The quicker shot comes from the lower kick points in composite sticks. The kick point is taking part on the hockey shaft where the stick bends without breaking when the player hit the puck. With wood shafts the bend tends to be where you place your lower hand. This causes a larger and slower loading and release cycle. Low kick point composite sticks place the bend point at the bottom of the shaft near the blade. This provides a shorter loading and release cycle and the net result is a quicker shot. Hence, improving the overall performance and giving the players the opportunity to take the game to the next level.