Nanoparticle-Based Mitigation of Fiber Print-Through in Composite Mirrors

摘要

A composite mirror based on carbon fiber reinforced polymer would have significant weight savings over a conventional mirror because of its lower density. However, it has been difficult to achieve a surface quality comparable to that of a conventional mirror because of fiber print-through. The heterogeneity inherent in composite manifests itself in the form of undulations on the mirror surface.The present paper describes how the surface quality of a composite mirror can be improved through the addition of nanoparticles. As fiber print-through is a result of difference in shrinkage between matrix and fibers during curing, providing a resin-rich region near the surface can annihilate uneven shrinkage. However, maintaining a resin-rich surface is not easy because the extra resin can easily be squeezed out during curing. Fortunately, the addition of alumina nanoparticles into the resin layer has been found to preserve the resin-rich surface region. Atomic force microscopy (AFM) results show a substantial decrease in surface roughness as 1 vol% of nanoparticles is dispersed into the surface resin layer. With 2 vol% addition of nanoparticles, the resulting mirror surface is already of the same smoothness as the glass mandrel surface itself. Thus, no further improvement is observed as more nanoparticles are added. Finite element analyses of the observed cross sections also indicate the disappearance of fiber print-through with the formation of a resin-rich region near the surface.