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DESIGN OF STRUCTURE WITH COMPOSITES 31 F.J. Schwan 31.1 INTRODUCTION Composite materials are finding more uses each year across a wide spechum of applica- tions. Designers of structural components, in particular, continue to find new applications for reinforced composite materials. The most suc- cessful structural applications are those where the innate advantages of reinforced materials can be translated into performance advantages for the manufactured part. These advantages include stiffness-to-density ratios, strength-to- density ratios, low thermal expansion characteristics, and occasionally others, such as resistance to specific environments, thermal conductivity, and fatigue characteristics. This section focuses on the design of com- ponents determined by mechanical performance requirements such as stiffness, durability, or strength. The importance of establishing and articulating design require- ments cannot be overstated. The extent to which design requirements are isolated and quantified determines the degree of certainty associated with trade studies and material selection decisions. Unsuccessful applications are quite often the result of unclear or poorly defined design requirements. Two terms which will be used extensively throughout this chapter are 'material proper- ties', and 'design allowables'. Since there are no universally accepted definitions of each of these terms, it is necessary to adopt definitions Handbook of Composites. Edited by S.T. Peters. Published in 1998 by Chapman & Hall, London. ISBN 0 412 54020 7 to avoid confusion in this chapter. The term 'material properties' is used generally to include extensional and compressive moduli of elasticity, Poisson ratios, inplane shear mod- ulus, coefficients of thermal expansion and coefficients of moisture expansion. 'Design allowables' refer to material strengths, specifi- cally tension, compression, inplane shear, interlaminar shear and bearing. This distinc- tion between material properties and strengths is established because of the significant differ- ences which exist in our ability to predict and measure each group, and because of the differ- ent treatment which properties and strengths receive in all phases of the design process. 31.2 DESIGN PROCESS A general comment concerning the contents of this section, and the chapter in general, is that the perspective represented throughout the chapter is that of a designer within a large organization, operating as part of a large design team, a situation typical of aerospace projects. However, the process is the same for all sizes of projects involved with design of composite structure. The primary differences are in the formality associated with each step in the process. In large organizations, extensive documentation tends to occur at each step, while in one-man teams little informal, and usually no formal documentation is required.
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This note was uploaded on 03/16/2010 for the course MECHANICAL ME765401 taught by Professor Prof.sulis during the Spring '10 term at Institut Teknologi Bandung.

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