Novel Structural Joining Concepts Using 3-D Textile Preforms and Composites

Strength and durability of commonly used bonded and bolted composite-to-composite and composite-to-metal structural joints suffer from sharp geometry variations, mismatch of elastic moduli, Poisson’s ratios, coefficients of thermal expansion and thermal conductivity of the adherends, altogether causing high stress concentration and premature joint failure. The proposed work is focused on development of several novel design concepts and manufacturing methods for composite-to-composite and composite-to-metal joints, including lap and butt joints, joints of composite skins and stiffeners, Ð-joint elements and other similar connectors. All of them are based on the use of hybrid 3-D woven and 3-D braided fabric preforms which incorporate metal filaments, multi-filament yarns, or wires. Dry preforms or composites that include these metal elements on specified surface(s) can be welded or brazed to another preforms or composites of a similar nature, or to solid metal elements. Using this new concept of joining will allow, as anticipated, to significantly increase strength and durability of dissimilar material joints. Design and manufacturing of special fabric preforms, fabrication of experimental joints samples and their experimental evaluation will be supported by 3-D micromechanics modeling and predictive analysis of stress/strain fields, progressive failure, and fracture phenomena. The combined experimental and theoretical effort will be used to validate the efficiency of proposed joining concepts.