This paper discusses the effects of different rotor sizes and epoxy systems on the process-induced residual strains accumulated within multi-ring composite rotors. Thick composite cylinders were manufactured with wet impregnation of E-glass and graphite fibers in the epoxy resin systems. The radial stiffness and strength and the coefficients of thermal expansion were first measured. Hybrid two-ring composite rotors of glass and graphite fibers with equal thickness were manufactured for three different inner to outer radius ratios, i.e., 1.5, 2.0 and 2.5. A split ring method was then used to measure the radial and circumferential residual strains, following liquid penetration tests to detect delaminations on the surfaces. The measured residual strains are estimated using a two-dimensional stress analysis with an effective temperature drop. It is shown that the middle temperature-cured rotor attains as high strength as the high temperature-cured rotor while reducing significantly the residual strains.
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