 | Interferometric Nondestructive Inspection |
| New MMPI Policy on Matching Funds |
| Hydrogen Bonded Polymer Complexes |
| Book Release |
| Fatigue Studies of Silicon Carbide Aluminum Matrix |
| Composite Applications for Computers |
| Fiber Electrophoretic Deposition Processing |
| Metal Matrix Composites II |
| Monitoring UV Initiated Cationic Photopolymerizations |
| Calendar of Events |
The Composite Materials and Structures Center is a multidisciplinary research facility located at Michigan State University's College of Engineering. Composite Materials are a new class of materials that combine two or more separate components into a form suitable for structural applications. While each component retains its identity, the new composite material displays macroscopic properties superior to its parent constituents, particularly in terms of mechanical properties and economic value. Research at the center provides fundamental scientific and engineering information about these new classes of materials. Faculty, students, and researchers from Agricultural Engineering, Biomechanics, Chemical Engineering, Civil Engineering, Computer Science, Electrical Engineering, Mechanical Engineering, Materials Science and Mechanics, and Packaging work together to develop lower cost and higher speed methods for composite processing and fabrication, as well as optimum design and manufacturing of composites for structural applications.
The newsletter will allow these individuals to share research articles, as well as inform of upcoming events, publications, and presentations. With the help of faculty and students, the newsletter will increase knowledge in the composites field of new technological developments and approaches to composite processing. Each issue of the newsletter will be distributed to companies interacting with the Composite Center, and most universities and institutions active in composites research in Michigan and abroad.
By James Nokes (Postdoctoral Research Associate, Materials Science and Mechanics), Dr. Gary L. Cloud (Professor, Materials Science and Mechanics)
An exciting approach to the nondestructive inspection (NDI) of composite materials is being persued in the Materials Science and Mechanics Department at Michigan State University. Researchers are using various interferometric techniques, such as Electronic Shearography (ES), and Laser Doppler Vibrometry (LDV) to detect and evaluate internal flaws within fiber reinforced composite materials. These interferometric techniques have a number of advantages over traditional NDI technologies. They are fast, non-invasive, and sensitive to a wide variety of flaws.
The operation of each of the interoferometric methods mentioned above is based on the coherence properties of laser illumination. Coherent light scattered from a specimen is captured using a video camera to form a speckle pattern representation on the specimen For example, each fringe formed by an ESPI system indicates a line of constant out-of-plane displacement, while the ES fringes represent lines of constant slope. The fringes are superimposed onto the specimen image providing easy visualization of the deformation . ESPI and ES are used for NDI by applying a small load to the specimen and evaluating the resulting fringe system. The fringes formed in the LDV system are utilized in a different manner than for either ESPI or ES. They are counted as they cross an optical detector to generate a time history of the out-of-plane displacement, or velocity. By using the velocity data, the dynamic properties of the target can be measured, specifically the damping and the resonant frequencies. The dynamic response information can be used for NDI applications separately or combined with the specimen mode shape properties available from either ESPI or ES.
A critical aspect for using interferometric techniques in NDI applications is finding appropriate specimen loading procedures. The loading should enhance the effect of the flaw on the resulting deformation. Investigations performed at Michigan State University have evaluated a number of alternative methods for loading the material. These alternatives included dynamic methods, such as acoustic and piezoelectric drivers, to quasistatic techniques, including thermal and mechanical loading. Fiber reinforced plates with internal delaminations were used to compare loading methods. The results showed that thermal loading generally provided the most sensitive indication of the delamination zone. Thermal procedures can require less than ten seconds to clearly indicate the delamination, while a mechanical creep test might require over five minutes to highlight the damaged area.
The work at Michigan State University has shown interferometric techniques to be a valuable alternative to traditional (NDI) technologies for the NDI of composite materials. Current research efforts are aimed at evaluating different methods of analyzing interferometric data. Improved analysis techniques will generate further improvements in the sensitivity of interferometric NDI procedures.
New Source for Matching Funds for Coposites Research.
The MMPI Board has approved awarding matching funds from its Michigan Strategic Fund (MSF) allocation for individual research proposals on polymer matrix composites authored by MMPI members (includes MSU faculty) if the following conditions are met:
The primary financial sponsor (industrial or federal government) agrees to share all results with the industrial members of MMPI (this now inludes 22 companies).
MMPI is focussed on the application of polymer composite materials and their application to the durable goods industries. The 3 technical committees of MMPI are charged with soliciting, funding and monitoring research in structural aspects of polymer composite materials; processing of composite materials; and recycling of polymer composite materials. Any project asking for matching funds would to be of high quality and would have to fit within this scope as determined by the appropriate technical committee.
Once the primary sponsor agrees to provide support, the same proposal would be sent to the appropriate MMPI technical committee for action on the matching request. The state of Michigan will only allow a match for cash support. In-kind contributions, equipment, etc. are not acceptable. The primary sponsors funds have to be sent first to MMPI which would provide the match and then send them to the PI.
There are a few issues that are under discussion such as the requirement for waiver of overhead on the state portion of the funds, maximum amount requested, etc. The recent MMPI/NSF format is preferred. There is no deadline date and requests may be made at any time. For further information please contact: L.T. Drzal at x35466.
By Carl L. Aronson (Graduate Assistant, Chemical Engineering), Alec B. Scranton (Professor, Chemical Engineering)
The use of macromolecular complexation for the development of novel polymeric materials is an area of unexplored potential. The specificity and reversibility of polymer complexes make them useful for providing some control of a material's structure and properties. We are investigating the use of macromolecular complexation for developing materials which exhibit an enhanced glass transition temperature, greater toughness, and increased solvent resistance relative to the individual constituents.
We have considered a model system of poly(4-vinyl phenol) (PVPh) with poly (N,N-dimethylacrylamide) (PDMA). In this system, PVPh is a proton donor, PDMA is a proton acceptor, and the two form relatively strong hydrogen bonded complexes. The PVPh/PDMA complex was synthesized by precipitation from alcohol solutions with yields over 95 mass percent under ideal conditions. The complex was characterized in solution and in solid polymer blends. The composition of the complex was determined by high resolution proton NMR spectroscopy as well as elemental analysis, and was correlated to feed composition. The glass transition temperature as determined by differential scanning calorimetry was found to be higher than either of the two constituent homopolymers. The solubility of the complex and the constituent homopolymers were characterized in a wide variety of solvents. Many of the solvents dissolved both constituent and homopolymers, but would not dissolve the complex.
Only strong hydrogen bonding solvents such as N,N dimethylformamide, pyridine and dimethyl sulfoxide dissolved the complex. However, the complex appears to be broken during dissolution in these solvents. In any case, the complex precipitate was observed to form at concentrations as low as 0.01 weight percent polymer in methanol. The complex has been further characterized by refractive index measurements. The refractive index of the complex varied linearly with the composition.
Future work in this area includes characterization of the mechanical properties of the complex as well as using infrared spectroscopy to examine the underlying complexation process. Several synthetic schemes for incorporating both polymer constituents within the same material are also being investigated, including random and graft copolymers. The final effort in this study will be to generalize this technique for other complimentary polymer systems.
This research received partial support from the State of Michigan Research Excellence Funds.
This work will be presented at the 8th Annual ASM/ ESD Advanced Composites Conference and Expo in Chicago, Illinois on November 5, 1992.
A paper has also been accepted for publication in the ASM/ ESD conference proceedings.
By Dr. M.V. Gandhi (Professor, Mechanical Engineering), Dr. B.S. Thompson (Professor, Mechancial Engineering)
The text, Smart Materials and Structures, is the first book dedicated exclusively to the embryonic eclectic field of smart materials and adaptive structures. This new generation of synthetic materials mimic biological materials, which are considered to be the ultimate class of materials. Consequently, they typically feature sensing, actuating, and processing functions at the material's macroscopic level. The text provides a comprehensive introduction to this new and rapidly evolving topic prior to presenting a state-of-the-art review of the sub-disciplines of the field. Electrorheological fluids, piezoelectric materials, shape-memory materials and fibre-optics receive particular attention.
Readers are appraised of the technical challenges to the commercialization of products incorporating these materials technologies, and in addition, readers are appraised of the potential applications of these technologies in virtually every segment of the international marketplace. Furthermore, the multi-disciplinary nature of the field of smart materials is expounded and the impact of the evolution of these materials on many scientific and technologically diverse fields is enunciated. Examples of these classes of materials include aircraft wings that can detect ice build-up, composite materials with embedded sensors to ensure optimal manufacture, tennis racquets with variable stiffness and energy-dissipative characteristics, submarines with sonar-sensitive skins, and wrapping materials for the food packaging industry to ensure that fruit and vegetables mature in a controlled manner for optimal consumption by the consumer.
The final chapter presents a treatment of the blue-sky research issues currently confronting researchers in the field of smart materials, and a comprehensive bibliography completes the book.
Smart Materials and Structures, Intelligent Materials and Structures Laboratory
Chapman & Hall, London, ISBN 0-412-37010-7
Co-Published in U.S.A. with Van Nostrand Reinhold, Inc., New York, ISBN 0-442-30876-0 (U.S.A. only)
By Dr. Gary L. Cloud (Professor, Materials Science and Mechanics), Sean Flemming (Research Assistant, Materials Science and Mechaics), Lan Meng (Research Assistant, Materials Science and Mechanics)
Metal-Matrix Composites (MMC) are rapidly becoming a material of choice for load- bearing applications even though minimal testing of such materials has been performed, especially in the area of fatigue or reliability. This lack of research or literature required that a simple and valid reliability investigation be undertaken. A fixture was designed and fabricated for fatigue testing. Fracture surfaces were evaluated for the fatigue test specimens. Testing was performed for both the axial extrusion direction and the transverse direction.
The material evaluated was a SiC/Al MMC with 15 v/o whiskers. A 3-point-cyclic-bending test was chosen. The controlled variable was deflection, which was measured with an extensometer mounted mid-span in a deflection mechanism. The specimens were approximately 1/4" x 1/4" (6..35mm x 6..35 mm ) with a 2'" (50.8mm) span. A computer program was written to interface with the testing machine, which captured the loads and displacements at designated intervals. The 3-point bending test was compression-compression and the waveform was sinusoidal. The maximum deflection ranged from 0.10 mm to 0.30 mm, with a 0.05 mm increment. The R (amplitude) ratio was set at 0.1 in order to maximize the cyclic range while maintaining a compressive load throughout the entire cycle, thus reducing the chance of impacting the specimen. The cyclic frequency ranged from 1 hertz to 20 hertz depending on the deflection level.
The cyclic-bending study illustrated that the fatigue life of the axial specimen was two-ten times greater than that of the transverse specimen for the same deflection level. Initially, cyclic stiffening occurred. Then, during 50% to 75% of the specimen's fatigue life, the material began to soften; possible due to microcracking, and ultimately failure occured. Finally, the fracture surfaces were observed. The transverse specimen failed similarly to a single-phase metal, that being parallel to the loading plane in bending. Most of the transverse fracture surfaces were smooth and clean. The axial specimen demonstrated that the SiC whiskers resist much of the load; and the rupture resembled that of shear failure, creating very jagged fracture surfaces. Both specimen orientations exhibited fatigue striations, or beach marks, similar to those observed in aluminum fatigue studies.
The results of this study indicated the need for additional quantitative research in the area of MMC's. This would allow for precise determination of the elastic and plastic fatigue constants and coefficients. Knowledge from this study would allow for implementing a fatigue model to accurately predict fatigue life of such MMC's.
Researchers in the Case Center for Computer-Aided Engineering and Manufacturing, under the direction of Professor Erik Goodman, have developed a number of modules which have potential for use in applications regarding composite materials. Such tools include a simulator to assist in programming robot spray coatings onto sculptured surfaces. The first simulator developed is empirically paramaterizable from measurements made on a single test pattern. The technology used in the simulator may be extendable, for example, to stimulation of spraying of chopped fibers for composites. The routines used in writing the simulator are from a Case-Center developed library for dealing with CAD geometry and robot programs, including routines for reading and discretizing IGES input files, producing color- coded shaded images of CAD geometry, etc. The research team has many years of experience in dealing with complex geometric problems in CAD and CAM. Dr. Goodman plans to enhance the utility and modularity of this technology by implementing its modules within an Object-Orientated Programming (OOP) framework.
By C.J. Suydam (Graduate Assistant, Materials Science and Mechanics), B.A. Wilson (Graduate Assistant, Materials Science and Mechanics), Dr. Melissa J. Crimp (Professor, Materials Science and Mechanics), Dr. Martin A. Crimp (Professor, Materials Science and Mechanics)
Currently, a research project is underway to develop a process to produce a fiber- reinforced intermetallic-matrix composite material. Intermetallic aluminides represent a new-age of high-strength, low density materials suitable for high temperature applications. Traditionally, intermetallic aluminides are known for their ability to sustain high temperature strength. Recently, it has been discovered that this is not always true. Therefore, it has become necessary to provide some means by which the intermetallic can retain its strength and toughness while subsequently being resistant to creep at high temperatures. In order to accomplish this, several types of reinforcements have been introduced into an intermetallic matrix to form what is now commonly known as intermetallic matrix composites or IMC's.
During this research project, an IMC will be produced using FeAl powder as the matrix material and alumina filament to provide for the continuous fiber reinforcement. The driving force for this fiber winding process is to take advantage of already existing principles unique to colloid science and apply these to traditional powder metallurgy techniques. The continuous fiber will be drawn through a slurry of powder dispersed in an aqueous solution. By controlling the parameters which apply to the existing attractive forces between the FeAl particles and the alumina fiber, the particles will adhere or "coat" the fiber. Once the fiber has been drawn through the dispersion, it is wound on a teflon mandrel whereby the plys for composite can be cut and stacked at desired orientations. Several consolidation techniques such as cold-isostatic pressing, sintering, and/or hot-isostatic pressing (HIPing) will then be employed to provide the composite material with an optimum density. The major difference between this process and other fiber winding processes is that no binder is required to adhere the matrix particles to the fiber prior to consolidation. Traditionally encountered problems from binder usage include detrimental contamination and an increase in the production cost of the composite material. It is the elimination of these problems which make this process very appealing.
Currently, the major focus of this project includes designing and constructing a suitable fiber-winding system to produce the composite. Research has already been completed which determined the necessary parameters for providing optimum conditions for coating of the fibers by the matrix particles. By employing this knowledge, a laboratory-scale prototype winding system has been developed. The major parameters considered in the design of this system include producing a dispersion bath that was both adequate in size and easily removable for purposes of cleaning and refilling. Also, consideration had to be given to the methods by which the particles in the solution could be kept suspended, and at the rate at which the filament tow is drawn through the powder solution. In addition to monitoring the rate at which the fiber tow proceeded through the bath, specific attention had to be given to the winding of the impregnated tow onto the teflon mandrel. It is very important to provide a means by which the impregnated tow can be accurately placed on the mandrel, so as to provide consistent placement of the tow and furthermore, be able to produce a composite that has uniform fiber placement and uniform density. By implementing this new process, it is anticipated that a contaminate-free IMC can be produced with optimal characteristics required for usage in high-temperature aircraft applications.
MS Fall Meeting, Chicago, Illinois, November 1992 By Dr. K.N. Subramanian (Professor, Materials Science and Mechanics)
Dr. K.N. Subramanian will chair the Metallurgical Society's fall meeting this month, where he will present and discuss a variety of papers on composite related topics. Dr. Subramanian has published these materials, and many have appeared in the press. Here is a listing of papers that will be discussed at the conference:
"Effect of Surface Oxidation on the Thermal Expansion Behavior and Mechanical Properties of a Metallic Glass Ribbon Reinforced Glass-Ceramic Matrix Composite," 94th Annual Meeting of American Cancer Society, Minneapolis, MN, April 1992 (coauthored with R.V. Vaidya and K.K. Chawla).
"A Theoretical and Experimental Analysis of Ductile Ribbon Pull-out from the Brittle Matrix," 94th Annual Meeting of American Cancer Society, Minneapolis, MN, April 1992 (coauthored with T.K. Lee).
"Load Transfer Mechanism in a Continuous Metallic-Glass Ribbon Reinforced Glass-Ceramic Matrix Composite," Composites Science and Technology, 43, 245 (1992) (coauthored with R. Vaidya).
"Studies on a Metallic-Glass/Glass-Ceramic Interface," SAMPE Journal, 28, 19 (1992) (coauthored with R. Vaidya).
"Interfacial Effects in a Metallic-Glass Ribbon Reinforced Glass-Ceramic Matrix Composite," J.Mater Sci. (in press) (coauthored with C. Norris and R. Vaidya).
"Failure Behavior of Particulate Reinforced Aluminum Alloy Composites Under Uniaxial Tension," J. Mater Sci. (in press) (coauthored with J.C. Lee).
"Effect of Cold Rolling on the Tensile Properties of (Al2O3) P/Al Composites," Materials Science and Engineering (in press) (coauthored with J.C. Lee).
"Effect of Cold Rolling on the Elastic Properties of (Al2O3) P/Al Composites," J. Mater Sci. (in press) (coauthored with J.C. Lee).
"Interface in Al2O3 Particulate Reinforced Aluminum Alloy Composite and its Role on the Tensile Properties," TMS Fall Meeting, Chicago, IL., November 1992 (coauthored with J.C. Lee).
"Comparison of Resultant elastic Properties of Cold and Hot Rolled (Al2O3) P/Al Composites," TMS Fall Meeting, Chicago, IL., November 1992 (coauthored with J.C. Lee).
"Effect of Cold Rolling on the Tensile Properties of (Al2O3) P/Al Composites," TMS Fall Meeting, Chicago, IL., November 1992 (coauthored with J.C. Lee).
"Interfacial Effects on Fracture Toughness of Glass Reinforced with Metallic Ribbons," TMS Fall Meeting, Chicago, IL., November 1992 (coauthored with T. K. Lee).
By E.W. Nelson (Research Assistant, Chemical Engineering), A.B. Scranton (Professor, Chemical Engineering)
Cationic photopolymerizations of epoxies and vinyl ethers have considerable potential for the high-speed, low-cost, pollution free production of polymer composites. These reactions exhibit extremely rapid curing rates at room temperature with a fraction of the energy requirements of traditional thermal systems. Furthermore, the reactions proceed to completion in less than a minute when exposed to ultraviolet (UV) light. However, fully formulated mixtures containing monomer and initiator are completely stable in the absence of UV light, eliminating the need for mixing immediately before use. Despite the promise of cationic photpolymerizations, these reactions have received little consideration for the production of composites in part because appropriate initiators have developed only very recently.
This research project is providing a fundamental investigation of UV-initiated cationic photopolymerizations of diepoxies and vinyl ethers. Detailed, time resolved temperature profiles have been obtained by fast monitoring thermal couples, and will also be confirmed by florescence techniques. The rapid reaction rates exhibited by UV initiated cationic photopolymerization of bis(vinyl ethers) make kinetic measurements particularly challenging. Because the reaction may proceed to completion in a few seconds, there are few experimental techniques with sufficient time resolution to characterize these polymerizations. Florescence spectroscopy is particularly attractive as a time-resolved, in situ technique for monitoring the extent of cure in these high speed polymerizations.
Three different fluorescence techniques have been attempted for following the rate of reaction. One technique involves the use of intrinsic florescence of the reactive functionalities, while the others involve the use of reactive or non-reactive probe molecules. Infrared and Raman spectroscopy are also being used as independent verifications of the cure rate. The temperature and cure profiles are leading to a detailed kinetic picture of the photopolymerization reaction. The thermal and mechanical properties of the resulting highly crosslinked polymers and composites are then thoroughly characterized using the instruments available at the Composite Materials and Structures Center. This fundamental research could help to establish cationic photopolymerizations as a viable option for the production of epoxy composites.
This project received partial support from the State of Michigan Research Excellence Funds.
November
November 2-5: Advanced Composites Conference and Exposition 8th Annual, Chicago, IL. Held concurrently with the ASM-TMS Materials Week '92. Contact: Clare B. Ellis, (313)995-4440.
November 2-5: Eigth Annual ASM/EDS Advanced Composites Conference/Exposition, SM International and Engineering Society of Detroit, Detroit, MI. Contact: ASM, (216)338-5151.
November 16-17: Compression Response of Composite Sturctures, Miami, FL. Contact: Scott E. Grove, Lawerence Livermore National Laboratory, P.O. Box 808, L-342, Livermore, CA, 94550.
November 16-17: Cyclic Deformation, Fracture, and Nondestructive Evaluation of Advanced Materials, Miami, FL. Contact: Dr. M.R. Mitchell, Rockwell International Science Center, 1049 Camino Dos Rios, Thousand Oaks, CA, 91360.
Composite Materials and Structures Center
College of Engineering
Michigan State University
East Lansing, MI 48824-1326
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