Impact behavior of glass and carbon fiber composites has been studied in some detail both with respect to methodology of testing and to interpretation of the influence of fiber orientation and viscoelastic resin properties on the measured fracture energies [14]. Most authors use some variation of the Charpy drop- weight test in which the impacted beam specimen is placed between two anvils. It is known that when the ratio of the span between the anvils to specimen thickness is small, e.g., less than 10, shear effects are very important. Most authors, therefore, test specimens at a larger span-to-thickness ratio, usually 16 and above. At these ratios the failure induced will be essentially a tensile fail- ure, dominated by fiber orientation and volume.