Figure 1: Good and poor-quality adhesive bond-lines.
The M.C. Gill Composites Center at USC, directed by Steven Nutt, M.C. Gill Professor of Chemical Engineering and Materials Science, has been awarded a major four-year research contract from the National Aeronautics and Space Administration (NASA). The project, to be carried out in collaboration with the Center for Composite Materials at the University of Delaware (UD), will focus on the development of a physics-based model for the co-cure of honeycomb core sandwich structures.
Composites used in aerospace are engineered combinations of strong, stiff carbon fibers and a polymer resin matrix. Such materials typically begin as plies of “prepreg”, or pre-impregnated fiber bed layers, which are stacked on a tool to form a laminate and cured in large, pressurized ovens called autoclaves. For some applications, composites are also bonded to a honeycomb core material to produce stiff, lightweight “sandwich structures.” The co-cure of sandwich structures, during which the laminate cure and bonding processes occur simultaneously, is an efficient route for manufacturing load-bearing aerospace parts. However, the complex physical and chemical phenomena that take place during co-cure can lead to defects, and render process optimization challenging.
The USC team and their UD counterparts (led by Prof. Suresh Advani) will receive $1.5 million over four years to investigate the governing physics of co-cure processing, and to develop an accurate and reliable methodology for predicting the quality of co-cured sandwich structures. The ability to simulate processing and determine part quality based on material and processing inputs will allow NASA and aerospace companies to quickly optimize production cycles, identify the root causes of defects, and reduce the number of experiments required for certifying composite structures.
Prof. Steven Nutt, Director of the M.C. Gill Composites Center, has carried out research on composites for thirty years. “We must be more efficient with our use of materials and our manufacturing processes so we waste less,” he says. “Sandwich panels are among the most efficient load-bearing structures and are used throughout aerostructures. However, we must control the distribution of adhesive at the bond-line to maximize performance and ensure reproducibility. We are fortunate to have a talented team working on this project, including Dr. Timotei Centea, Co-Investigator at USC, and Prof. Advani.”
Figure 2: Honeycomb core sandwich structures.
This NASA project builds upon USC’s research on the advanced manufacturing of composite materials, with particular emphasis on defect reduction and process efficiency. The Composites Center recently completed a three-year, multi-national program funded by the NSF on sustainable manufacturing, and is engaged in collaborative projects with industry partners on topics including high-temperature polymer composites, out-of-autoclave/vacuum bag-only prepregs, and polymer concrete. The expert personnel and exceptional facilities of the Center, assembled partly through a generous endowment from Merwyn C. Gill and The Gill Corporation, have made USC a leading research institution in composite materials.