In an effort to understand the implications of the fiber/matrix interphase on the performance of aerospace grade composite materials, a study was performed to examine the properties of the interphase region on the micro-scale. An epoxy resin was cured with several curing agent systems to evaluate the material based variations in experimental detection of glass transitions with scanning thermal microscopy (SThM). After an appropriate material was selected, glass fibers with different finishes were impregnated with an epoxy/amine resin system, and the properties of the interphase regions were examined using scanning thermal microscopy.