The paper considers a fiber composite, the fibers of which on the surface contain special layers formed by whiskers. The presence of whiskers leads to an increase in the strength of the composite material during longitudinal shear. Traditionally, such a composite consists of three phases: a fiber, an interfacial whiskerized layer, and a matrix. There are investigated the modified composites consisting of two phases – fiber and an interfacial whiskerized layer acting as a binder. Two types of fiber composites with an epoxy binder are considered, in the first, the base fiber is IM7 carbon fiber with a whiskerized zinc oxide layer, and in the second, the base fiber is T650 carbon fiber with a whiskerized CNT layer. In both cases, the length and diameter of the whiskers are selected in such a way as to ensure the maximum volumetric content of whiskers in the whiskerized layer. For a modified composite loaded with longitudinal shear, calculations of the stress-strain state in each of the phases and calculations of effective properties are carried out. The deformed state in the whiskerized layer and the matrix is investigated, and a comparative analysis with the deformed state of a similar classical composite is carried out. The deformation fields of the modified and classical composites were determined under the conditions of the equivalence of force loading. The results of the study showed that the modified composites are able to withstand the load significantly exceeding the load that can be withstood by similar classical composites. This makes it possible to judge the increase in the strength of modified composites with whiskerized fibers in comparison with similar classical composites in the case of pure shear along the fibers. At the same time, it was shown in the work that from the point of view of strength and effective properties, the whiskering of the composite by microfibers made of zinc oxide is more preferable than the whiskering of the composite by the more rigid CNTs.