Robb Winter, PhD

The overall goal of our research is to provide an understanding of how molecular level chemical phenomena influence bulk material properties in composite systems. Our basic research is directed at understanding the relationship between chemical changes in the interphase and the nanomechanical properties derived from those changes. Our applied research takes this knowledge to solve problems relevant to industry. The interphase is the region between the surface of the reinforcement or filler and the polymer matrix. The chemistry of the interphase is different than that of the bulk matrix and the mechanical properties are expected to also differ from those of the bulk in relation to the chemical variations. The level of adhesion between the polymeric material and the reinforcement/filler surface also influences mechanical properties of a composite system. It is recognized that the stress transfer between the polymer matrix and the reinforcement takes place across the interphase and hence the interphase and interface adhesion are critical for composite performance. This work is supported by the National Science Foundation, the Department of Energy, NASA, and the Department of Defense.

Current fundamental research efforts include: 

1. Through the support of the NSF and the Department of Energy (DOE) we are utilizing FT-IR evanescent wave fiber optic spectroscopy to investigate the interphase chemical kinetics in model fiber-epoxy composites. We have clearly demonstrated the power of the fiber optical sensor in obtaining data for chemical kinetic analysis within the interphase region and potential long-term chemical analysis of composite structures.
    

2. Through the support of the DOE and NSF, we are developing and utilizing the interfacial force microscope (IFM) to investigate the relationships between interphase chemistry, mechanical properties and adhesion in polymer matrix glass fiber reinforced composites and filled systems.
    

3. Supported by NASA, FT-IR evanescent wave spectroscopy has been used to investigate the chemical kinetics in high performance polyimide (PMR-15)-carbon fiber composites. The goal of this research was to improve part reproducibility and quality by understanding the relationship between chemical kinetics and final mechanical properties as a function of process variables for the Civil High-Speed Transport project.
    

4. We are investigating the effect of novel surface treatments of fibers and fillers found in polymer matrix composites on the processing characteristics of the composites systems. In this case, diffuse reflectance and ATR spectroscopy is used to obtain the nature of the adsorbed species. Torque and capillary rheometery is used to investigate the impact of a surface treatment on processability. Macro-mechanical test (e.g. tensile and three point bend) are used to understand the relationship between surface treatment chemistry and the mechanical strength and toughness of test specimen.
    

5. With NSF support we (Dr. Jenkins and Dr. Vinogradov at MSU) are studying the creep behavior of polymers and polymer matrix composites when subjected to cyclic loading, a phenomenon called vibrocreep. FT-IR Raman spectroscopy are used to investigate the chemical and structural changes of the material adjacent to crazes and cracks, which result from long-term cyclic loading typical of aerospace and automotive applications. Interfacial force and atomic force microscopy are utilized to reveal nanomechanical properties and morphology of the stressed specimen. This fundamental information will be used in developing predictive models for the occurrence of the vibrocreep phenomena.
    

6. In collaboration with Drs. K.M. Liechti and J.M. White (U of Texas - Austin) we have initiated an NSF supported investigation of the fundamental relations between interphase chemistry and fracture mechanics in composite-substrate systems. The focus of the work is to investigate the stress-strain behavior of the polymeric interphase region, cohesive zone/crack tip region, and pre- and post fracture to link the interphase properties to traction-separation laws from cohesive zone models. To accomplish this objective IFM and FT-IR ATR are being employed. The long-term goal is to be able to predict fracture reliably and develop fracture resistance composites.
    

7. The Department of Defense is funding our (with Dr. Jenkins) work on the investigation of adhesive joints for nano-engineering and modeling. Our overall objective is to address problems of predicting the long-term durability of nano-engineered adhesive joints. We are establishing the design space for nano-engineering adhesive joints through the application of Raman and Fourier Transform Infrared spectroscopies, interfacial force microscopy and infrared radiometery.
    

8. With collaborators, Dr. S. Khanna (University of MO-Columbia) and Dr. J. Stoffer (University of MO-Rolla), we are developing and manufacturing highly damage resistant fiber glass reinforced window panels for buildings in hurricane analysis of the proposed multiply glass-fiber glass reinforced polyester-glass composite are currently under way. A hurricane projectile simulator will be used in the final testing stage of the optimized system.
    

9. We have initiated a study of nano composites properties and processing requirements which is currently funded through the Camille and Henry Scholar/Fellow program. We are investigating the relationship between interphase chemistry and nanomechanical properties in nanocomposites as revealed by vibrational spectroscopy and interfacial force microscopy.

Publications

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