591 pg592 v g2 7 27060 irwin schaffer 592 part iii iq

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Unformatted text preview: ong different direcLaminate composites can be designed A parameter employed in tions. Figure 14.3–7 shows thin sheets of unidirectionalat a given stress an arrangethe analysis of creep. It may be used composites stacked in to ment so that fibers are oriented along 0 , 90 , and 45 directions. The thin sheets, called determine how long the part will last at a given the laminae, can be stacked together in a regular arrangement to make up the laminate composite. If the fibersto determine the nd 90 directions only, the strength of the temperature or are stacked in the 0 a maximum allowable composite is high along these directions, but such composites have poor shear resistance. temperature for a fixed time duration. To obtain good shear resistance, the fibers must also be stacked along the 45 orientations. Such laminates are strong in all directions within the plane containing the fibers but lattice Three-dimensional space-filling repeating pattern are weak in the direction normal to the fiber planes. 591 pg592 [V] G2 7-27060 / IRWIN / Schaffer 592 Part III iq 12.01.98 plm QC2 rps MP Properties G L O S S FIGURE 14.3–8 v absorption coefficient A measure of the amount of light absorbed by a transparent material, expressed in units of reciprocal length. (a) (b) acceptor level The impurity level within the band gap ....................................................................................................................................... of a semiconductor associated with the electron holes DESIGN EXAMPLE 14.3–3 introduced by the incorporation of a Group II or III The lid of an electronic package is made from a glass-reinforced polymer composite. The corners element withstand minor impact semiconductor. of the lid must be able tointo a Group IV loads that may be applied in any direction during service. What fiber architecture would you recommend for this application? activation polarization A mechanism by which the Solution corrosion rate is reduced in some systems. It occurs when The corner regions will be subjected to multiaxial loads. Hence, the fiber architecture should consist one the steps in the corrosion process has a strength in all of plies in the 0 , of45 , and 90 directions. This will ensure nearly uniform highhigh directions in the plane of the composite (not in thethe whole process is common arrangeactivation barrier so that thickness direction). Another slowed ment in multiaxial applications is the 0, 30 , 60 , 90 stacking arrangement. considerably. ....................................................................................................................................... adhesive bonding Another type of fiber arrangementA process by which two parts areFigis a two-dimensional fabric, as shown in ure 14.3–8. It is possible to have three-dimensional weaves thatused in composites with joined by an adhesive. This process is result to join nearly isotropic properties. A three-dimensional network of fibers can also...
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