Tension Pull-off and Shear Test Methods to Characterize 3-D Textile Reinforced Bonded Composite Tee-Joints

摘要

Test methods, data acquisition, and data reduction techniques used to generate design properties for skin-to-spar composite bonded joints that are reinforced using shaped 3-D textiles are presented. These methods represent the culmination of lessons learned after execution of government Small Business Innovative Research (SBIR), Contracted Research and Development (CRAD), and company Independent Research and Development (IRAD) projects. Industry recognition of the poor in-terlaminar properties of laminated composite materials has limited applications to structures that primarily react to in-plane loads. However, under company IRAD, CRAD, and SBIR-funded Z-fiber programs, revolutionary tension-loaded bonded joints that utilize 3-D woven textile preforms have demonstrated vastly improved strength and damage tolerance capabilities. Characterization of failure modes and the onset of permanent damage for these novel joints are described. Test procedures involving stepped and fatigue type loading have been developed in order to distinguish between ultimate failure loads that are typically reported versus the service load capability of a particular joint. Overviews of the procedures used to conduct two specific types of element tests are presented. The methods are described as (1) tension web pull-off or tee-pull, and (2) horizontal joint shear.