On the elastic stress transfer and longitudinal modulus of unidirectional multi-short-fiber composites

An analysis is presented on the elastic stress transfer and longitudinal mo dulus of unidirectional multi-short-fiber composites. The analysis involves a three-cylinder model consisting of fiber, matrix and composite medium. T he fiber axial stress and the interface shear stress are derived as functio ns of the fiber axial position. The effects of fiber-aspect ratio, fiber-vo lume fraction, fiber-to-matrix modulus ratio and inter-fiber separation (or fiber end gap) on stress transfer are studied in detail. The influence of neighbouring fibers on stress transfer is considered in a global manner by including the effect of the composite medium. The significance of the influ ence is clearly shown by comparing the stress transfer in multi-short-fiber composites with that in single-short-fiber composites. The composite modul us can be expressed by a modified rule of mixtures equation by introducing a fiber-length factor. Then, the effects of fiber-aspect ratio, fiber-volum e fraction, fiber-to-matrix modulus ratio and inter-fiber separation (or fi ber end gap) on the fiber-length factor are investigated. Some interesting findings are obtained. Finally, the present theory is compared with several existing theories. (C) 2000 Elsevier Science Ltd. All rights reserved.