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Tham khảo tài liệu 'mil-hdbk-17-4 - composite materials handbook vol4 [us dod 1999] 4ah episode 4', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | MIL-HDBK-17-4 1.2.4.2 Role of reinforcement The role of the reinforcement varies with its type in structural MMCs. In particulate and whisker reinforced MMCs the matrix is the major load bearing constituent. The role of the reinforcement is to strengthen and stiffen the composite by preventing matrix deformation by mechanical restraint. This restraint is generally a function of the interparticle spacing-to-diameter ratio. In continuous fiber reinforced MMCs the reinforcement is the principal load bearing constituent the metallic matrix serves to bond the reinforcement and transfer and distributes the load. Discontinuous fiber reinforced MMCs display characteristics between that of continuous fiber and particulate reinforced composites. Typically reinforcement increases the strength stiffness and temperature capability of MMCs. When combined with a metallic matrix of higher density the reinforcement also serves to reduce the density of the composite thus enhancing properties such as specific strength. 1.2.5 REINFORCEMENT COATINGS 1.2.5.1 Role of coatings In many MMCs it is necessary to apply a thin coating on the reinforcements prior to their incorporation into the metal matrix. In general coatings on the fibers offer the following advantages 1. Protection of fiber from reaction and diffusion with the matrix by serving as a diffusion barrier 2. Prevention of direct fiber-fiber contact 3. Promotion of wetting and bonding between the fiber and the matrix 4. Relief of thermal stresses or strain concentrations between the fiber and the matrix 5. Protection of fiber during handling In some instances particulates are coated to enhance composite processing by enhancing wetting and reducing interfacial reactions. 1.2.5.2 Types of coatings Given the major role of coatings there are several techniques available for the deposition of thin coatings on long fibers and to a much lesser extent on short fiber and particulate reinforcement. One such process is chemical vapor .
