The Fracture Toughness of Epoxy-glass Bead Composites
Title:
The Fracture Toughness of Epoxy-glass Bead Composites
Author:
Dibenedetto, A. T. Wambach, A. D.
Appeared in:
International journal of polymeric materials
Paging:
Volume 1 (1972) nr. 2 pages 159-173
Year:
1972-01-01
Contents:
The plane strain fracture toughness of epoxy resins and glass bead filled epoxy composites has been investigated. It was found that the energy required for fracture depended primarily on the ability to dissipate energy in the polymer phase. At low temperatures, where the epoxy was relatively brittle, the addition of glass beads increased the fracture energy and induced roughness in the otherwise smooth fracture surface. At higher temperatures and/or increased catalyst concentration, the unfilled epoxy became more ductile, its fracture surface became rougher, and its fracture energy was increased. When the epoxy was ductile, the addition of beads tended to decrease the fracture energy because of a reduction of the amount of polymer on the fracture surface. Adhesion of the matrix to the glass beads was only important when the polymer was ductile. Improved adhesion permitted the beads to constrain polymer flow and decrease the fracture energy. Poor adhesion permitted flow around the beads which required additional energy for crack propagation. At low temperatures, where the matrix was brittle, the additional constraints caused by adhesion appeared to make little difference. Water absorption resulted in plasticizing the polymer, destroying the interface, and probably destroying the polymer near the interface. Short term immersion increased the toughness because of the additional ductility. Long term immersion tended to reduce the toughness. An effective coupling agent minimized this reduction, thereby showing that improved adhesion can improve the environmental stability and extend the useful life of the material.
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