In recent years, the composites industry has experienced a major shift from autoclave to out-of-autoclave (OoA) processing methods. This shift has been motivated by the high capital and operating costs of autoclaves as well as the long cycle times. As the demand for composites in commercial aircraft increases, autoclave processing will not be able to satisfy the required production rates. While there are advantages to OoA processing, a major disadvantage is the increased susceptibility to defect formation due to the absence of compaction pressure provided by an autoclave. Therefore, one major focus of the M. C. Gill Composites Center is defect reduction in composite parts made from OoA prepregs. The Composites Center has access to a wide variety of characterization, fabrication and processing techniques that enable comprehensive analysis of OoA prepregs. Our efforts have led to new insights into defect sources and mitigation strategies. Recent contributions to this field are noted below.
“The Effect of Processing Parameters on Volatile Release for a Benzoxazine/Epoxy Blended RTM Resin; J. Lo, M. Anders, T. Centea, and S.R. Nutt, Compos. A Feb (2016) (Download from USC Composites or ScienceDirect)
“Multifunctional Superhydrophobic Composite Films from a Synergistic Self-Organization Process” H. Lu, and M. Fang, Z. Tang, and S. Nutt J. Mater. Chem. 22 (2012) 109-114. (Download from USC Composites or RSC)
As exemplified by wind turbine blades and components of oil platforms, the use of polymers and polymer composites for civil infrastructure is accelerating. In such applications, long-term durability is critical, as structures are generally expected to provide decades of service with minimal inspection or maintenance. Understanding the effects of aging on the mechanical performance of polymers and polymer composites are essential to mitigation strategies as well as lifetime prediction. The M. C. Gill Composites Center at USC has been actively studying the effects of exposure to aging environments on the mechanical and thermal properties of composite materials. Studies have focused on thermal, oxidative, hygrothermal, and radiation aging effects. Research from this topic has led to several publications in the leading journals of the field; the most recent papers are listed below.
The performance of conventional materials can be enhanced by introducing nano-sized reinforcing phases. This reinforcing phase can be in the form of particles (ceramic particles), sheets (e.g. graphene microsheets), or fibers (e.g. carbon nanotubes). Understanding the mechanism responsible for improved mechanical properties is crucial to further development of processing techniques and improvement of properties. The M.C. Gill Composites Center at USC has extensive experience in studying different aspects of nano-composites, including correlating processing parameters with mechanical properties of such materials. Our group has worked with a range of nano-inclusions, including carbon nanotubes, graphene, and nano-structured aluminum alloys. Below are some of our group’s publications, presenting our recent contributions to the field.
“Assembly of layered monetite-chitosan nanocomposite and its transition to organized hydroxyapatite: An alternative to bone substitute material”J. Moradian-Oldak,Q.Ruan, D. Liberman, Y. Zhang, D. Ren, Y. Zhang, and S. Nutt, ACS Biomaterials Sci & Engrg 2 1049-58(2016)(Download from USC Composites or ACS)
“Two-Step SPD Processing of a Trimodal Al-Based Nanocomposite”Yuzheng Zhang, S Sabbaghianrad, H. Yang, T.D. Topping, T.G. Langdon, E.J. Lavernia, J.M. Schoenung, and S.R. Nutt, Metall Trans Sept (2015) (Download from USC Composites or Springer)
Creating a material that is lightweight and yet strong is the ultimate goal of many material scientists. Lightweight metals such as aluminum, magnesium, titanium and their alloys are light and tough, resulting in extensive adoption for widespread use in aerospace, automobile, and other industries. The M.C. Gill Composites Center at USC has a broad background in exploring and developing novel processing techniques and unique microstructures for such materials. Two highlights are manufacturing and production of aluminum and syntactic steel foams. Research from this topic has led to publications in the leading journals of the field; the most recent papers are listed below.
Carbon fiber composites are increasingly used in high-temperature applications, driving the development of new resin systems such as benzoxazines and polyimides. These resins can be used to fabricate fan blades, ducts, or casings for jet and rocket engines, where service temperatures can reach several hundred degrees Celsius. Manufacturing techniques include compression molding and resin transfer molding (RTM). Due to the complex chemistry of these resins, the processing is significantly more challenging than for traditional epoxies. Research at the M.C. Gill Composites Center focuses on comprehensive materials characterization and the development of optimized manufacturing procedures. Through a combination of experiments and modeling, we demonstrate defect formation mechanisms and prevention strategies, and establish process windows and manufacturing guidelines as deliverables for our industrial sponsors.
“Hypervelocity Impact of Bulk Metallic Glasses and Composites" L. Hamill, S. Roberts, M. Davidson, W.L. Johnson, S. Nutt, and D.C. Hofmann, Adv. Engrg. Matls, 15  1-9 (2013) (Download from USC Composites or Wiley)
"Investigating Amorphous Metal Composite Architectures as Spacecraft Shielding” M Davidson, S Roberts, G Castro, RP Dillon, A Kunz, H Kozachkov, MD Demetriou, WL Johnson, S Nutt, DC Hofmann, Adv Engrg Matls (2012) (Download from USC Composites or Wiley)
The composites industry is always looking to develop stronger composite systems to push the limits of various performance metrics; but before composites incorporating new material systems or processing techniques are deployed, it is important to have a full and reliable understanding of their mechanical properties. Additionally, a complementary understanding of failure mechanisms can inform designers of how to avoid the loading conditions under which failure can be anticipated. The M. C. Gill Composites Center has made considerable investments in developing and maintaining the infrastructure necessary for a full battery of mechanical tests. Our facilities boast four load frames and an impact drop tower, allowing us to conduct quasi-static, dynamic, and fatigue testing. Additional analysis can be conducted using the available light and electron microscopes. Below are some of our group’s most recent publications, highlighting work in which our mechanical testing infrastructure was integral.
“All-printed Strain Sensors:Builidng Blocks of the Aircraft Structural Health Monitoring System” Y. Zhang, N. Anderson, S. Bland,S. Nutt, G. Jursich, and Shiv. Hoshi, Sensors and Actuators A, Oct(2016) (Download from USC Composites or ScienceDirect)
“Bio-Inspired Impact Resistant Composites” L. Grunenfelder, N. Suksangpanya, C. Slinas, G. Milliron, N. Yaraghi, S. Herrera, I. Evans-Lutterodt, S.R. Nutt, P. Zavattieri, D. Kisailus, Acta Biomaterialia Apr (2014). (Download from USC Composites or ScienceDirect)
“Effects of Fabric Target Shape and Size on the V50 Ballistic Impact Response of Soft Body Armor Composite Structures” G. Nilakantan and S. Nutt, Compos. Structures 116 661-669(2014) (Download from USC Compositesor ScienceDirect)
The composites industry is looking for solutions for recycling and reusing composites. During manufacturing processes, there are several scrap products which could be reused in other applications. Furthermore, recovering resin and fibers from finished products would promote composite recycling. The M.C. Gill Composites Center at USC has been investigating recycling and reusing composites. We have work on using pretreatment and acid digestion to break down cured composites to recover fibers. We have the capability to analyze the components of these chemical processes to optimize procedures. Below are selected publications highlighting our work in this area.
The composites industry is constantly looking for new resins to increase the variety of applications. New formulations can allow for more sustainable materials, stronger structures, and application in more challenging environments. The M.C. Gill Composites center has experience working with novel resins. We have the analytical capability to analyze resins and the mechanical testing capability to characterize them. Below are selected publications highlighting our work in this area.
“Thermosetting Polymer Based Flexible Synthetic Cement for Successful Zonal Isolation in Thermal Wells-A New Approach” R. Shanbhag, Z. Melrose, S.R. Nutt,M.Cleveland,and R.Keese, Soc Petrol Engrs July(2015)(Download from USC Composites or Soc Petrol Engrs )
“Amelogenin-Chitosan Matrix for Human Enamel Regrowth: Effects of viscosity and Supersaturation Degree” Q. Ruan, N. Siddiqah, X. Li, S. Nutt, and J. Oldak, Connective Tissue Research, 55 [S1] 150-154 (2014) (Download from USC Composites or Taylor & Francis Online)
“Poly(phenylene oxide) modified cyanate ester resin for self-healing” L. Yuan, S. Huang, Y. Hu, A. Gu, G. Liang, G Chen, Y Gao, and, S. Nutt, Polymers for Advanced Technologies (2104) (Download from USC Composites or Wiley)
“Blends of Polystyrene and Poly (n-Butyl Methacrylate) Mediated by Perfluorocarbon End Groups” Jingguo Shen, Victoria A. Piunova, Steven Nutt and Thieo E. Hogen-Esch, Polymer 215790-5800 (2013) (Download from USC Composites or ScienceDirect)
“Synthesis of poly(urea-formaldehyde) encapsulated dibutyltin dilaurate through the self-catalysis of core materials” L. Yuan, F. Chen, A. Gu, G. Liang, C. Lin, S. Huang, and S. Nutt, Polymer Bulletin Sept (2013) (Download from USC Composites or Springer)
“A cyanate ester/microcapsule system with low cure temperature and self-healing” L. Yuan, S. Huang, A. Gu, G. Liang, F. Chen, Y. Hui, and S. Nutt, Compos Sci & Tech 87 (2013) 111-117 (Download from USC Composites or ScienceDirect)
“Novel polytphenylene oxide microcapsules filled with epoxy resins” L. Yuan, A Gu, S. Nutt, J. Wu, C. Lin, F. Chen, and G. Liang, Polymers Adv. Tech. 24  81-89 (2012)(Download from USC Composites or Wiley)
Because the study of composite materials requires a cross-disciplinary perspective as well as a wide array of laboratory instrumentation, we recruit members from diverse backgrounds—including physics, chemical engineering, mechanical engineering, and, of course, materials science. This diversity in our infrastructure and the technical breadth of our staff puts us in the unique position to take on a broad range of projects sometimes only tangentially related to our primary areas of focus. Below are our recent publications that reflect that diversity of backgrounds and training.
“Amelogenin affects brushite crystal morphology and promotes its phase transformation to monetite” Ren, Dongni;Ruan, Qichao; Tao, Jinhui;Lo, Jonathan;Nutt, Steven;Moradian-Oldak,Janet. Crystal Growth & Design Aug 164981-90 (2016)(Download from USC Composites or Wiley)