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Residual Stresses in Ceramic Fiber Composites: Effect of Non-Uniform Fiber Distribution

  • Bent Fruergaard Sørensen
  • Ramesh Talreja
  • Ole Toft Sørensen
Chapter

Abstract

Residual stresses evolve in ceramic fiber composites during cool down from a stress free state. These stresses play a very important role in the overall mechanical behaviour of the composites, and may lead to microcracking by themselves or when aided by thermomechanical loadings. In this paper, the residual stresses in unidirectional fiber composites are computed by the three dimensional finite element analysis. We investigate the effect of fiber volume fraction and fiber distribution effects such as fibers touching and fibers enclosing matrix (short range effects) as well as matrix and fiber rich domains (long range effects). The effect of thermal expansion mismatch is studied by examining two ceramic composite systems: SiC fibers (Nicalon) reinforced by LithiumAluminumSilicate (LAS) and CalciumAluminumSilicate (CAS) glass-ceramics. It is shown that the residual stress state varies with fiber distribution: The analysis of small range effects shows that the local stresses may differ considerably from the average stresses. The analysis of long range effects shows that the residual stress states are affected both inside and outside the domains. Due to differences in the thermal expansion mismatch, the residual stress state in SiClLAS and Sic/CAS are very different. Therefore, different damage modes are expected in the two systems. Partial debonding is likely in SiC/LAS at locations where fibers are in contact, whereas matrix cracks may initiate in Sic/CAS.

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Copyright information

© Elsevier Science Publishers Ltd and MPA Stuttgart 1992

Authors and Affiliations

  • Bent Fruergaard Sørensen
    • 1
  • Ramesh Talreja
    • 2
  • Ole Toft Sørensen
    • 1
  1. 1.Materials DepartmentRisø National LaboratoryRoskildeDenmark
  2. 2.Department of Solid MechanicsTechnical University of DenmarkLyngbyDenmark

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