This dataset includes microscopic image data of cross-sectional cuts prepared from fiber-composite samples composed of carbon fiber and epoxy matrix, coated with a polymer. The fiber composite did not undergo compaction during curing of the matrix, and the polymer coating was applied after curing. The cuts were made orthogonal to the fiber orientation. The cut surfaces were not polished after sawing. Multiple specimen were sampled at random positions. The images were acquired using a digital microscope and stored in TIF file format. The files are numbered to avoid duplicate filenames, but the numbering order is random. Each image includes an embedded scale bar.