raman mechanical spectroscopy was used to examine interfacial effects on the stress distribution in model polydiacetylene fiber/epoxy composites. epoxy release agents were coated on fiber surfaces to modify the interfacial adhesion properties. the modified fiber surfaces were then characterized by scanning electron microscopy and x-ray photoelectron spectroscopy as well as optical microscopy. no difference in the maximum stress value or stress distribution was observed for the two types of fibers, coated or uncoated, used in composites. this suggests that adhesion properties at the composite interface do not affect tensile stress transfer efficiency nor, therefore, the composite tensile modulus along the fiber axis direction in uniaxial composites. experimental data were also compared with theoretical calculations assuming perfect bonding between fiber and matrix, and idealized frictional force transfer mechanism at the fiber-matrix interface. (author abstract) 25 refs