4.0 DISCUSSION The best composite materials for hockey sticks are Kevlar and carbon fiber. Different grades of Kevlar are available such as Kevlar K-24, Kevlar K-49, Kevlar K-100, Kevlar K-119, Kevlar K-129, Kevlar AP, and Kevlar KM2 for hockey sticks (DuPont, 2012). For example, Kevlar K-24: The mechanical properties of Kevlar K-24 based on the thermal effect on tensile strength, young age modulus, and tensile strain. The reason Kevlar has high tensile strength and high tensile modulus is that the bonding interface between fiber and matrix was not strong enough to transfer stress between fibers and matrix. The other was that the fibers were damaged when intentionally or accidentally exposed to thermal environments during the manufacturing process or during use, which caused degradation of the fiber properties (C,Y.Yue et al., 2000). The effects of thermal exposure on tensile properties have been noted by several researchers. Hindeleh and Abdo studied the effect of thermal exposure on Kevlar fibers when exposed to a controlled atmosphere of nitrogen gas at temperatures above 150°C for a duration of 15 minutes. Parimala and Vijayan extended the study on Kevlar-49 fibers in an uncontrolled atmosphere of air at temperatures up to 350°C for a heating duration of 0.5 to 260 hours. Figure 4.1: Average tensile strength of a single fiber for as received and heat treated Kevlar-29 fibers with different gauge lengths. The numbers on the columns indicate the gauge lengths. (CYYue et al., 2000). Figure 4.2: Average tensile strain of a single fiber for received and heat-treated Kevlar-29 fibers with different gauge lengths. The numbers on the columns indicate the gauge lengths. (CYYue et al., 2000).Figure 4.3: Ten single fiber media......half of paper......key stick. There are many types of grips used in field hockey, such as rubber composition grip, rope grips, synthetic grip, leather grip, elastomer grips and air cushion grip. Additionally, using chamois (suede) grip is the best material to encase the hockey stick handle. Why is leather grip use called “the best of the best” but almost extinct? This is due to the high costs and extended time required to produce it. Chamois is made from sheep or lambskin where the grain is removed and tanned with marine fish oil. What makes suede so special? As in daily life, leather is used to scrub foggy windshield on a cold day, clean and wax. Being a natural product, the pores can stretch and expand to adapt to water absorption and synthetic leather also replicates itself to make it the same as natural leather (Halpin, C. ,2010).