Significant Properties of Epoxy Resins as Matrices in Graphite Composites.

The objective of the work being reported was to determine experimentally what properties of the matrix resins most significantly affected the mechanical properties of the unidirectional graphite fiberepoxy resin composites evaluated. Five different epoxy resin systems were used as matrix resins. They were selected to provide wide ranges of the properties expected to be significant modulus, strength, and elongation. The composites fabricated with these five resins were tested in four different modes. Tensile and compressive loading were made longitudinally, in the fiber direction. Transverse loading produced principal tensile stresses at 90 degrees to the fiber direction tensile test and at 45 degrees to the fiber direction torsional test. The load-strain behavior of all specimens in each loading mode was recorded. Initial modulus, proportional limit, and ultimate strength were calculated from the loading curve of each specimen. Stiffness, strength, and toughness properties of the five matrix resins, as cast solids without reinforcing fibers, were also measured. P.S.-PL