Depends on the material. Matrixes are certainly a proven value. horse hair in plaster, carbon fiber or glass fiber in resin, rebar in concrete, are all better

Depends on the material. Matrixes are certainly a proven value. horse hair in plaster, carbon fiber or glass fiber in resin, rebar in concrete, are all better than either of their individual components. A supporting filler could increase the toughness, supporting the filaments against buckling, or there could be other values like filling the space to prevent moisture or oxygen from getting in there, etc.