CMMS research incorporates advanced manufacturing concepts into the fiber reinforced composite materials arena through automated process development. A broad spectrum of composite materials is studied with applications ranging from wind turbines to high temperature engine components.
Process Induced Warpage: Prediction, Measurement, Control
Composite component distortion during manufacture is a critical problem for the industry. This area of research continues to be a prime focus area for the Composite Materials, Manufacture and Structures Laboratory researchers.
Viscoelastic Properties Determination
With the advent of “designed damping” in composite materials, and modern computer design tools, accurate three-dimensional material properties information is critically important. Further, design of advanced composite structures often requires knowledge of material properties over a range of temperatures. Conventional testing approaches for the determination of material properties present difficulties related to specimen preparation, fixturing and test apparatus. Consequently, engineers frequently make use of micromechanics generated properties. Unfortunately, micromechanics approaches do not usually account for manufacturing and temperature variations, which affect material properties. This research focuses on developing approaches to allow experimental characterization of elastic and viscoelastic properties of fiber reinforced composite laminae, over a range of temperatures. In addition to investigating the temperature dependence of the three-dimensional material properties, for the viscoelastic characterization, the effect of loading frequency is also addressed. A technique for the determination of the three-dimensional elastic coefficients of transversely isotropic laminae has been developed, using a combination of laminate coefficient of thermal expansion (CTE) measurements and two elastic properties measured from a standard tensile test. The CTE measurements have been conducted in a laboratory thermo mechanical analyzer (TMA), using samples of simple geometry. PEEK/IM7 laminae were used to verify this approach and the computed room temperature elastic properties are in good agreement with quoted elastic material properties measured by standard techniques.
Composite Design and Fabrication
Many projects related to design and fabrication of composites have been undertaken at the Composite Materials, Manufacture and Structures Laboratory. These projects have ranged from the composites hardware for student design competition projects, such as Solar Car, Formula SAE and Walking Machine, to redesigns of industrial equipment.
Ultra-Lightweight EMI Shielding Materials
A family of materials has been developed which are compatible with structural composites and have attenuations in excess of 100 dB at frequencies above 0.1 GHz. These tailorable materials have been produced with densities lower than 0.6 gm/cm3. They can be cast to shape or co-processed with a structural composite. The approach makes use of metallized hollow microsphere fillers and has investigated varying filler fraction as well as effects of various types and sizes of filler particle.
Advanced Polymer Processing
Damage Assessment and Repair Strategies
Chemical Vapor Infiltration of Carbon/Carbon
Process modifications for the infiltration of carbon into carbon fiber preforms is the principal focus. Graduate research has investigated the effects of using pulsed chemical vapor infiltration rather than conventional constant flow (batch mode) to densify fiberous preforms. This work generated curves of the varying level of densification through the preform thickness related to changes in pulsing parameters. Results indicate that some reduction in time to densify can be obtained, but most importantly it was found that substantially less precursor gas was used during pulsing to obtain similar levels of densification.