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Tham khảo tài liệu 'plastics technology handbook 2011 part 6', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 2-56 Plastics Technology Handbook A woven glass fabric cloth might be used in place of the mat or in combination with it. In this case there will be a variation in strength with the angle between the axis of the fibers and the direction of stress. Twisted yarns are generally woven into fabrics of varying thickness and with tight or loose weaves depending upon the application. Most are balanced weaves i.e. equal amounts of yarn in each direction although some are unidirectional more fibers running in one direction . Although costlier they offer a high degree of strength. Rovings can also be woven into a fabric that is less costly than the woven yearn fabrics coarser heavier and easier to drape. For optimum adhesion at the interface between the fiber surface stationary phase and the resin matrix continuous phase the glass fibers must be treated with coupling agents to improve the interfacial adhesion. The pioneer coupling agent linking agent was methacrylatochromic chloride Volan . This has been supplanted by organosilanes organotitanates and organozirconates. These coupling agents contain functional groups one of which is attracted to the fiber surface and the other to the resin Figure 2.51 . 2.13.2.2 Graphite Carbon Fibers Graphite carbon fibers are the predominant high-strength high-modulus reinforcing agent used in the fabrication of high-performance polymer composites. In general the term graphite fiber refers to fibers that have been treated above 1 700 C 3 092 F and have tensile moduli of elasticity of 5X105psi 3 450 MPa or greater. Carbon fibers are those products that have been processed below 1 700 C 3092 F and consequently exhibit elastic moduli up to 5X105 psi 3 450 MPa 25 . A further distinction is that the carbon content of carbon fibers is 80 -95 and that of graphite above 99 . However the industry has universally adopted the term graphite. It will therefore be used to describe both product forms in this section. Graphite fibers were first utilized by
