When combining fiber and matrix to increase the toughness, not
only are their fundamental properties important, but interface characteristics
assume an added importance in the case of brittle matrix
composites, so the choice of the coating material is crucial in getting
the desired effect. Fracture in brittle matrix/brittle filament composite,
where the interfacial bond between fiber and matrix is strong, often
results in fast matrix crack propagation perpendicular to the filaments.
Usually such an energetic crack breaks through all filaments in the
path of the crack and complete brittle fracture ensues [25,26].