“VISCOELASTIC PROPERTIES OF FIBER REINFORCED EPOXY RESIN WITH RANDOM-PLANAR ORIENTATION OF SHORT FIBERS”

Abstract

Viscoelastic properties of epoxy resins reinforced with random-planar orientation of short glass and carbon fibers were studied in relation to the dependence on the fiber length, fiber content in the composites, and the mixing ratio of a particulate to the glass fiber.Although the composites reinforced with glass fiber of 0.05mm in length shows only one dispersion (α) corresponding to the primary transition of matrix resin, those reinforced with 3 and 10mm glass fibers show an additional dispersion (α′) which appears above the α dispersion temperature. The composite reinforced with 3mm carbon fiber (resinous pitch) does not show the α′ dispersion. Intensity of the α′ dispersion increases with fiber content. The α′ dispersion is considered to arise from friction or slippage among fibers and/or appears more evidently for composite having stronger interaction between fiber and matrix resin. For the composites reinforced with mixture of 10mm glass fiber and particulate (milled glass fiber), the negative slope of the doubly logarithmic plot of relaxation spectrum and activation energy of relaxation increase with the content of particulate. From these facts it is concluded that the interaction between reinforcing material and matrix resin decreases with increase of the content of particulate for the composite reinforced with mixture of particulate and short fiber.