Abstract: A computer model calculates a critical aspect ratio for a discontinuous fiber composite having fibers dispersed in a matrix. The critical aspect ratio is a function of the elastic modulus and the cohesive energy of the fiber and the matrix. The composite incorporates physical features such as fiber shape features or additives in the fiber or matrix which adjust the elastic modulus and/or cohesive energy of the fiber, of the matrix or both to a value different than the corresponding value for unmodified fiber material or matrix material. These adjustments are selected so that the critical aspect ratio for the material including the modifications will be less than the corresponding critical aspect ratio for the material without the modifications. The resulting composite provides enhanced load sharing between fiber and matrix.