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COMPOSITE

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Figure 16.1 Some examples of composite materials: (a) plywood is a laminar composite of layers of wood veneer, (b) fiberglass is a fiber-reinforced composite containing stiff, strong glass fibers in a softer polymer matrix ( 175), and (c) concrete is a particulate composite containing coarse sand or gravel in a cement matrix (reduced 50%).

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Figure 16.7 Microstructure of an aluminum casting alloy reinforced with silicon carbide particles. In this case, the reinforcing particles have segregated to interdendritic regions of the casting ( 125). (Courtesy of David Kennedy, Lester B. Knight Cost Metals Inc.)

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Figure 16.16 Scanning electron micrograph of the fracture surface of a silver-copper alloy reinforced with carbon fibers. Poor bonding causes much of the fracture surface to follow the interface between the metal matrix and the carbon tows ( 3000). (From Metals Handbook, American Society for Metals, Vol. 9, 9th Ed., 1985.)

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Figure 16.9 The influence of volume percent boron-coated SiC (Borsic) fibers on the properties of Borsic-reinforced aluminum parallel to the fibers (for Example 16.7).

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Figure 16.12 (a) Tapes containing aligned fibers can be joined to produce a multi-layered different orientations to produce a quasi-isotropic composite. In this case, a 0°/+45°/90° composite is formed.

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Figure 16.13 A three-dimensional weave for fiber-reinforced composites.

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Figure 16.17 Methods for producing (a) boron and (b) carbon fibers.

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Figure 16.21 Production of fiber tapes by encasing fibers between metal cover sheets by diffusion bonding.

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©2003 Brooks/Cole, a division of Thomson Learning, Inc. Thomson Learning™ is a trademark used herein under license.

Figure 16.22 Producing composite shapes in dies by (a) hand lay-up, (b) pressure bag molding, and (c) matched die molding.

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Figure 16.23 Producing composite shapes by filament winding.

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©2003 Brooks/Cole, a division of Thomson Learning, Inc. Thomson Learning™ is a trademark used herein under license.

Figure 16.24 Producing composite shapes by pultrusion.

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Section 16.6 Fiber-Reinforced Systems and

Applications Advanced Composites - The advanced composites

normally are polymer–matrix composites reinforced with high-strength polymer, metal, or ceramic fibers.

Metal-Matrix Composites - These materials, strengthened by metal or ceramic fibers, provide high-temperature resistance.

Ceramic-Matrix Composites - Composites containing ceramic fibers in a ceramic matrix are also finding applications.

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Figure 16.27 The manufacturer of composite super-conductor wires: (a) Niobium wire is surrounded with copper during forming. (b) Tim is plated onto Nb-Cu composite wired. (c) Tin diffuses to niobium to produce the Nb3Sn-Cu composite.

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Section 16.7 Laminar Composite Materials

Rule of Mixtures - Some properties of the laminar composite materials parallel to the lamellae are estimated from the rule of mixtures.

Producing Laminar Composites - (a) roll bonding, (b) explosive bonding, (c) coextrusion, and (d) brazing.

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Figure 16.30 Techniques for producing laminar composites: (a) roll bonding, (b) explosive bonding, and (c) coextrusion, and (d) brazing.

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Section 16.8 Examples and Applications of

Laminar Composites

Laminates - Laminates are layers of materials joined by an organic adhesive.

Cladding - A laminar composite produced when a corrosion-resistant or high-hardness layer of a laminar composite formed onto a less expensive or higher-strength backing.

Bimetallic - A laminar composite material produced by joining two strips of metal with different thermal expansion coefficients, making the material sensitive to temperature changes.

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Figure 16.31 Schematic diagram of an aramid-aluminum laminate, Arall, which has potential for aerospace applications.

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Section 16.9 Sandwich Structures

Sandwich - A composite material constructed of a lightweight, low-density material surrounded by dense, solid layers. The sandwich combines overall light weight with excellent stiffness.

Honeycomb - A lightweight but stiff assembly of aluminum strip joined and expanded to form the core of a sandwich structure.

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Figure 16.32 (a) A hexagonal cell honeycomb core, (b) can be joined to two face sheets by means of adhesive sheets, (c) producing an exceptionally lightweight yet stiff, strong honeycomb sandwich structure.

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Figure 16.33 In the corrugation method for producing a honeycomb core, the material (such as aluminum) is corrugated between two rolls. The corrugated sheets are joined together with adhesive and then cut to the desired thickness.

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