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 introduces several novel design concepts of bonded lap joints, butt joints, integral composite D-joint elements and other similar connectors, all based on the use of 3-D woven and 3-D braided fabric preforms. Unique manufacturing processes used in production of such preforms enable to split them into two or more thinner sheets or branches, hybridize different fiber types within 3-D architectures, continuously vary cross-sectional shapes. Using complex shape 3-D textile preforms with gradual variation of thermo-mechanical properties for composite joints of interest will allow, as anticipated, to significantly reduce stress peaks and mitigate the negative effects of joining dissimilar materials. Design and manufacturing of special fabric preforms, fabrication of experimental composite joints samples and their experimental evaluation will be supported by 3-D micromechanics modeling and predictive analysis of stress/strain fields, crack propagation and thermo-mechanical response. The combined experimental and theoretical effort will be used to validate the efficiency of proposed joining concepts.