Carbon fiber-reinforced gelatin composites. I. Preparation and mechanical properties

Composites were made from carbon fibers and gelatin using a solvent-casting or solution-impregnation technique. Relationships between the fiber volume fraction (Vf), glycerol (plasticizer) content, gelatin content, fiber form , and mechanical properties (tensile strength and modulus, elongation at br eak, and shear strength) of the composites were investigated. In long carbo n fiber gelatin composite (C-L/Gel), tensile strength, modulus, and shear s trength increased steadily with the Vf. In the case of a short carbon fiber gelatin composite (C-S/Gel), an initial improvement in tensile strength an d modulus was followed by a reduction, whereas the shear strength improved with the Vf and then reached a constant value. The elongation decreased wit h the Vf for both composites. It is shown that C-L/Gel had higher values of strength, modulus, and elongation than did C-S/Gel at any Vf level. The ef fects of glycerol and gelatin contents on the mechanical properties of the composites were found to be much less significant as compared to the Vf. Ac cording to scanning electron microscopic observation of the fracture surfac es, the fibers were uniformly distributed in the gelatin matrix, but the in terfacial adhesion between the gelatin matrix and the carbon fibers was not very good for both composites. Fiber surface modification would be necessa ry to further improve the mechanical properties of the two composites. (C) 2000 John Wiley & Sons, Inc.