Fail-safe light transmitting SiC fiber-reinforced spinel matrix optomechanical composite

A light transmitting "Optomechanical Composite" was fabricated by incorporating SiC (SCS-6) fibers into optically transparent MgAl2O4 ceramics. The fibers were aligned unidirectionally in the matrix with a spacing of 1 to 4 mm to allow light transmittance between the fibers: resulting fiber volume content was from 0.75 to 0.19 vol%. The total and in-line light transmittance of the matrix and the composite was measured in the visible/near-IR wavelength region. The light transmittance of the composite was found to be decreasing with increasing fiber volume fraction, however, even the composite with the highest fiber volume fraction has a light transmittance of 25-50% in the visible wavelength region. Although the optical transparency of the matrix becomes slightly lower by the incorporation of the opaque fibers, its catastrophic failure is prevented by the bridging effect of the intact fibers, introducing the fail-safe nature to the brittle ceramic material. To obtain this fail-safe mechanism, the minimum fiber volume fraction was similar to0.37 vol% in the present material system. (C) 2002 Kluwer Academic Publishers.