Materials Program

Composite Materials

Activities at UT-CEM involve both basic research of composite materials and application of this developed technology to ongoing programs at UT-CEM. UT-CEM's involvement with advanced composite materials began in the early 1980's with the need for more robust, higher strength armature winding structures for compulsators. Work has continued in this area through the development of improved Resin Transfer Molding (RTM) techniques with fiber reinforcement.

Over the years, UT-CEM's use of composites has expanded with the need for higher performance air core compulsators. Primary structure for these newer compulsators consists of multiple, high strength graphite composite cylinders which are press fit together. Recent applications for composite rotors are high speed energy storage devices for electric vehicles and locomotives.

Commercial finite element codes and in-house codes are maintained to support analytical and fabrication needs for composite materials research. Composite testing is primarily conducted in-house with arrangements for contract testing for additional tests. Existing facilities permit fabrication and assembly of small to large structures.

Composite Materials Analysis and Testing Capabilities

  • Commercial Finite Element Codes

  • ABAQUS General finite element code

  • COSMOS/M General finite element code

  • PDA/PATRAN Pre- and post-processor for finite element codes

In-house Codes

  • TEMPEST Nested ring code for 2D axi-symmetric analysis

  • LAMPAT* Specialized code for analyzing and designing thick laminated composite structures.

  • * Developed by the U.S. Army Research Laboratory

Testing Capabilities for Composite Structures:

  • Fiber direction and transverse-to-fiber properties of hoop wound structures

  • Hydraburst fixture

  • Split "D" fixture

  • Transverse tensile fixture mounted in a MTS tensile machine

  • High strain rate, dynamic properties

  • Composite material impact tower

  • Fatigue

  • High cycle fatigue fixture capable of testing samples to millions of cycles

  • Fracture toughness

  • Interlaminar shear

  • Creep

  • Glass Transition Temperature

Composite Fabrication and Assembly Facilities:

McClean Anderson Filament Winding Machine
Winding machine can fabricate structures using a variety of available fibers. This is a 4 axis NC machine capable of diameters up to 1.7 m. UT-CEM uses this machine to wind composite structures with specialized laminate designs tailored to program needs.

500° F Curing Oven
Composite filament wound rings and hand laid-up structures are cured in 500° F curing oven. The 10 ft high x 17 ft deep x 12 ft wide oven is programmable with emergency backup power.

500 Ton Assembly Press
Composite rotors are assembled by tapered press fits. UT-CEM built a 500 ton hydraulic press specifically for composite rotor fabrication. The press platform has about 40 ft of vertical travel adjustment with 40 in. of hydraulic ram stroke.

Ongoing UT-CEM Programs Utilizing Specialized Composite Structures

Compulsators for Electric Gun Programs
Air core compulsators, using little ferrous material, are primarily constructed with composites. The result is a significant increase in operating speed, delivered power, and reduction in weight.

To build these high strength, robust structures, UT-CEM has developed a proprietary tow-preg system that facilitates the use of toughening agents and 0° axial fibers to increase bending strength and reduce the propensity to radial cracking. This system, developed over years of research and testing, has proven to be a superior composite system in terms of strength and reliability.

Past air core compulsator programs include the Small Caliber and 9 MJ Range Gun programs. Current programs include the Cannon Caliber and Focused Technology programs. Composite rotor for the Cannon Caliber program is pictured.

Composite Flywheels for Electric Vehicle Programs
UT-CEM's high performance composite rotor technology has been leveraged for flywheel battery applications. UT-CEM has two flywheel battery programs utilizing high speed composite flywheels for load leveling and regenerative braking. One application is for a locomotive and the other is for a transit bus. The flywheels on both programs will be fabricated using high strength, graphite composites and operate at tip speeds over 1,000 m/s.

A composite flywheel, similar in design to the flywheel for the transit bus flywheel battery, is shown above. This flywheel consists of seven intermediate modulus graphite rings of equal length. The rings are sized to nest together coaxially, each one slightly larger in diameter than the previous with the smallest ring fitting over an annealed 6 Al-4V titanium hub. Rings were pressed together with interference fits engineered to maintain acceptable stress levels during all phases of operation. This flywheel stores 2.0 kW-hr of energy at the operating speed of 40,000 rpm.

Sponsors
This work was sponsored by U.S. Army ARDEC, U.S. Army Research Laboratories, DARPA, Houston Metropolitan Transit Authority, and the State of Texas.

See Also: Composite Rotor Testing

For further information please contact:
Richard C. Thompson
Research Engineer Associate
(512) 232-1615