An overview of the polymer matrix composites research with a focus on stitched composites is presented. Reinforcing composite materials in the thickness direction using techniques such as stitching, z-pinning, needling, tufting, and 3D weaving has increased in recent years. Through-thickness stitching of dry composite preforms, followed by resin infusion using vacuum-assisted resin transfer molding (VARTM), is an effective way to fabricate unitized structures with seamless co-cured interfaces. While stitching reduces in-plane mechanical properties, transverse stitching increases the interlaminar tensile and shear strengths of composites. Stitching parameters such as stitch density, seam angle, thread density, and pre-tension can greatly impact the in-plane and out-of-plane properties of the composite. Research in stitched composites is a multi-scale approach where the influence of stitching parameters is investigated from a micro-mechanical level to full-scale structures. Damage propagation within stitched composites is studied for cryogenic thermo-mechanical fatigue, Mode I/II or mixed-mode tests, in-plane biaxial tests, and impact tests. Stitched composites are used in the fabrication and testing of a T38-Talon strut door and an X-33-based multi-lobed cryogenic tank.
Dr. Rani W. Sullivan
Department Head of Aerospace Engineering (ASE) at Mississippi State University (MSU) and holds the Bill and Carolyn Cobb Endowed Chair. Her professional experience includes faculty fellowships at NASA Glenn Research Center and the Wright Patterson AFB. She is an associate fellow of AIAA. Her research interests include structural health monitoring, composite manufacturing, mechanical and non-destructive characterization of polymer matrix composite materials and large-scale structures for aerospace applications, and engineering education. She is the recipient of the 2019 Hermann Oberth Award for advancement in aeronautical sciences. In 2014, she was named the Diversity Educator of Mississippi and received the SAE International Ralph R. Teetor Educational Award. She is a member of the MSU Bagley College of Engineering Academy of Distinguished Teachers.