Innovative Joining and Repair Methodologies Using Hybrid Textile Preforms

Strength, durability and reliability of commonly used bonded and bolted composite-to-metal structural joints suffer from sharp geometry variations, mismatch of elastic properties, coefficients of thermal expansion and thermal conductivity of the adherends, altogether causing high stress concentration and premature failure of adhesive bonded joints. The proposed work offers substantial enhancement of composite-to-metal bonded joints (including lap and butt joints, joints of composite skins and stiffeners, D-joint elements and other similar connectors) and metal repair with composite patches. The primary focus is on joining steel structural components to glass and carbon fiber 3-D woven and 3-D braided fabric preforms and composites. The two key features of this joining methodology are: (1) using hybrid preforms which incorporate metal filaments, multi-filament yarns, wires or cables and (2) welding or brazing such preforms to the metallic structures. The implementation of this new concept of composite-to-metal joining and metal repair 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 performed and supported by 3-D micromechanics modeling and predictive analysis of stress/strain fields, progressive failure, and fracture.