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Thermal Deformations and Stresses in Composite Materials

  • I. M. Daniel

Abstract

Composite materials are highly anisotropic thermally with the coefficient of thermal expansion in the fiber direction much lower than that in the transverse to the fiber direction. Coefficients of thermal expansion in unidirectional and multidirectional laminates can be calculated by using the properties of the constituents and lamination theory. Residual stresses are introduced in multidirectional laminates during curing as a result of thermal anisotropy. These stresses have been investigated analytically and experimentally It was found that the significant strains recorded during the cooling stage of curing correspond to thermal expansion of the laminate. Residual or restraint strains are computed from measured restrained and unrestrained thermal expansions. Residual stresses are computed using appropriate orthotropic constitutive relations. Results have been obtained from a variety of materials including boron, graphite, Xevlar, S-glass and hybrids with epoxy or polyimide matrices, for a variety of lamination angles. It was found that residual stresses do not relax appreciably with time. Results show that, for graphite and Kevlar laminates, residual stresses at room temperature are high enough to have caused damage in the transverse to the fiber direction.

Keywords

Residual Stress Residual Strain Fiber Direction Thermal Deformation Hybrid Laminate 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Plenum Press, New York 1980

Authors and Affiliations

  • I. M. Daniel
    • 1
  1. 1.IIT Research InstituteChicagoUSA

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