Composite baseball bats incorporate a recent advancement in the technology of aluminum baseball bats for high school and collegiate players. In general, composite bats are constructed with the same aluminum exterior as standard aluminum baseball bats, but have a "woven" graphite wall on the inside.[1] Composite bats provide an advantageous swing weight, an improved trampoline effect, a lower bending stiffness, and a higher damping rate. Recently, composite baseball bats have come under scrutiny because tests performed by the NCAA during the 2009 NCAA Division I Baseball Tournament showed that the majority of composite bats used during the championship failed the BESR test.[2]
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Even though the composite bat is a new technology in baseball, composite type bats have been around as early as the '80s in slow-pitch softball. This ground breaking bat did not have a long stay though due to the better performance of all aluminum bats. With advances in the composite bat technology over the years, these bats have regained strength. Most notably, Louisville Slugger developed a slow-pitch bat that was awarded best performance at the 2001 Bat Wars. Miken responded in 2002 by developing their own composite softball bat.[3] Even though composite material has only been historically used in slow-pitch and softball, this technology has been emerging in high school and collegiate baseball over the past few years.
Even though composite baseball bats have a different design compared to standard aluminum bats, they still must meet the same specifications as the standard aluminum baseball bat. To be suitable for high school and collegiate play, they must meet weight, dimension, and rebound rate requirements. The composite bat must have a -3 drop, which means that the bat must weigh 3 ounces less than the length (i.e. 33in 30oz). Also, the baseball bat must have a barrel that is 2 5/8” in diameter (except Little League Division's Majors and below use a 2 1/4" diameter bat). Finally, composite bats for high school and college play were required to meet a specific BESR (Ball Exit Speed Ratio) through 2010. Composite bats will be required to meet BBCOR (Bat-Ball Coefficient of Restitution) standards for 2011 college[4] and high school play.[5][6] Little League International has not officially endorsed BBCOR standards as of this date but currently has in place a similar moratorium on composite bats.
There are very few disadvantages in the use of a composite bat. The most notable concern is the use in cold temperatures. All aluminum bats have a warning sticker stating that the bat cannot be used below a certain temperature. A batter can often get away with using a standard aluminum bat below the stated temperature, but for composite bats, it is more pivotal to abide by the listed temperature.[7] Poor use of a composite baseball bat can lead to cracking of the barrel. Ball speed coming off an aluminum bat is much greater compared to wood bats, this could be a concern for the pitcher safety.
Another disadvantage is that composite bats sound differently than aluminum bats. Where aluminum bats make a "ping" sound, composite bats make a sound more similar to wooden bats.[3] Many players therefore feel that composite bats don't have the pop that they are accustomed to with their aluminum bats because of the different sound.[7]
In December 2010, Little League Baseball announced a moratorium on the use of composite bats, presumably due to concerns about safety of young players. The increased batted ball speed introduced increased risk to the fielding players. But that is when they introduced the idea of the composite handle and the alloy barrel. In the Little League you cannot have a comp. barrel although they do allow you to have a comp. handle. What does this do you might ask. Well the compostite handle bends at connection of the ball. when the ball's energy is transferred from itself to the bat and back again the bat bends itself back to a straight line therefore causing the trampoline effect of the bat with the composite handle.
Another disadvantage is that composite bats can bend so much that they can break.
There are many advantages to using composite baseball bats. As has been chronicled in slow-pitch softball recently, composite bats have out performed standard aluminum bats.[8] There are five main advantages for using composite bats: swing weight, trampoline effect, bending stiffness, bending vibrations, and sound.[3]
The swing weight of a baseball bat deals with how heavy the bat "feels" when swinging, and is therefore different than the actual listed weight of the baseball bat. Ball players might swing two different bats that weight exactly 30oz, but one might feel lighter than the other. How is that possible? In order decrease the swing weight and allow the hitter to swing the bat quicker and easier, the center of mass is designed closer to the handle of the bat.[7] A smaller moment of inertia will also decrease the swing weight. Composite bats maximize the effect of swing weight by having both a lower moment of inertia as well as a center of mass closer to the handle. Manufacturers are able to achieve both factors because the graphite material composite bats are made out of is lighter than aluminum. This allows the manufacturers to move the weight around the bat to achieve an optimal center of mass close to the handle.[3]
The trampoline effect, which is common terminology for baseball players, is the phenomenon when the baseball "jumps" off the bat at contact. The bat-ball collision can be demonstrated from the physics of elastic collisions. The stiffer the barrel of the bat, the slower the baseball comes off the bat because it loses energy in the collision. The softer the barrel of the bat, the faster the baseball comes off the bat because it retains its energy applied by the pitcher. The trampoline effect has been experimentally tested, and results show that composite bats outperform all aluminum bats.[3] The reason why composite bats outperform other aluminum bats is that the trampoline effect can essentially be "tuned." Composite materials have properties that are different in all directions, or anisotropy,[9] which allows the bat manufacturer to design the bat stiff longitudinally (along the handle) and softer circumstantially (around the barrel). This softer barrel allows the ball to come off with small losses in energy while maintaining the stiffness of the bat in the handle.[3]
Ball players often experience a "sting"[7] in their hands caused by vibrations when the ball does not come in contact with the sweet spot of the bat. The frequency of these vibrations throughout the bat is related to the bending stiffness. Daniel A. Russell of Kettering University has shown that standard aluminum bats have a high bending stiffness that produces vibrational frequencies in the range where most hands are sensitive; therefore, causing a sting. He also has shown that composite materials can lower this bending stiffness without compromising other advantages.[3]
Including the lower bending stiffness, composite baseball bats have a higher damping rate. The damping rate corresponds to how quickly the material lessens the vibrations it is experiencing. Russell also states that composite bats have a damping rate anywhere from 2 to 10 times more than standard aluminum bat.[3] Many ball players therefore refer to composite bats as more forgiving because if they do not make contact with the ball on the sweet spot, they will not feel the vibrations (sting) from the miss hit.[7]
For a time, the future of composite baseball bats at the collegiate level was in question. On July 22, 2009, the NCAA reported that the rules committee had requested to ban the use of composite bats. The NCAA Playing Rules Oversight Panel found that 20 out of the 25 composite bats tested during the 2009 NCAA Division I Baseball Tournament failed the BESR (Ball Exit Speed Ratio) test. The tests showed that the balls were actually coming off the bat much quicker than what the specifications state. Since bats must pass the BESR specification inside the factory before reaching the market, there are two possible hypotheses. One suggests that the performance of composite bats increases with repeated use, and the other states that players can intentionally alter the composite bat.[2] The most common method of altering composite bats is through bat rolling, where a large amount of pressure is applied by various means while rolling the bat back and forth.[10] The rules committee met on August 17, 2009, to discuss their proposal with manufacturers, and on August 24, the NCAA Playing Rules Oversight Panel approved the temporary ban on composite bats. During this temporary ban, the rules committee will continue testing the bats to determine if the performance is enhanced through repetitive use, or if intentional alteration seems more plausible.[11] Currently, the NCAA is requiring that all composite bats meet BBCOR standards. See the Design section above for details.
On December 30, 2010, Little League officials announced a moratorium on using the bats in all divisions and during the Little League World Series.[12][13] Several manufacturers of composite bats have subsequently obtained Little League International approval for specific composite bats. Persons interested in using composite bats should periodically check the Little League International Equipment web page for links to lists of approved bats.