Effect of moisture content on the properties of silanized jute-epoxy composites

The composites investigated in this article were epoxy resins reinforced with jute-fibers. The jute-fibers were modified with an epoxyfunctional-gamma-glycidoxypropyltrimethoxy-silane (A-187 from Osi-Specialtis GmbH, Germany), which works as a coupling agent between fiber and matrix. The introduction of the coupling agent distinctly influences the mechanical properties of the composite: Dynamic modulus was doubled, damping was reduced by about 50%, and the Wohler curves showed fatigue limits increased by about 20%. The investigations pointed out further that the moisture uptake of composites with silanized fibers was reduced by about 10-20%. Moisture at equilibrium and kinetics of absorption increase with increasing fiber content. Finally, the application of the coupling agent caused a reduction of moisture effects on mechanical properties. Tensile strength, tensile modulus, and fatigue strength under repeated tensile stress were reduced up to 30%. This tendency was not duplicated in the results for flexural strength and flexural modulus.