Transverse Elastic Deformation Behavior of Aligned Fiber Bundles under Bulk Compressive Pressure and Longitudinal Stress

Abstract

Advanced composite materials generally use fiber in very high volume fraction, compression of textile/perform is adopted in manufacture processes. The major role of the compaction process is to obtain high fiber volume fraction in final parts. During the compaction process, transverse compaction of textile/perform is the main deformation form, where the compaction behavior of a fiber bundle is the most basis issue. In this paper, a micromechanical model of aligned fiber bundle with high fiber volume fraction was developed to investigate elastic deformation behavior under bulk compressive pressure and longitudinal stress. Bending characteristics of a waved fiber was established to describe the transverse bulk compression and the longitudinal deformations of a bundle. A wave amplitude was introduced to describe initial distance between fibers, which affects the initial fiber volume fraction and the transverse deformation feature. An improved representative fiber cell was present to get the deflection of a bending fiber under transverse and axial force. Randomly distributed directions of waved fibers lead to a more reasonable representative fiber cell, which influences initial fiber volume fraction and leads to logical deformation explanation and symmetric constitutive relation for aligned fiber bundle with high volume fraction. Analytical formulae to describe the constitutive relationship of fiber bundle under transverse and longitudinal stress were present. Numerical results show that the transverse bulk compressive stress and its deformation are related to wave amplitude and available fiber volume fraction. The comparison to present literatures was given to show the improvement of the model.