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NIA Seminar by Michael Philen |
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Date: November 3, 2006
Time: 9:00am
Location: NIA, Rm 137
Semi-Active and Active Tuning of Variable Stiffness Adaptive Structures Based on Hydraulically Pressurized Flexible Matrix Composites
Michael Philen, Virginia Tech
Recently, a variable stiffness adaptive structure idea that has the potential to achieve orders of magnitude change in stiffness has been proposed [1]. The new adaptive system is a multicellular structure composing many small-diameter fluidic flexible matrix composite (F2MC) tubes integrated into supporting matrix materials. The F2MC tubes are fluid-filled composite tubes where the tubes consist of multiple layers of oriented, high performance fibers such as carbon in a flexible matrix. Due to the internal fluid having a high bulk modulus (e.g. water, oil), significant changes in stiffness can be obtained by simply opening or closing an inlet valve to the F2MC cells. With an open valve, the new adaptive structure can be very flexible. On the other hand, when the valve is closed, the fluid resists volume change due to its high bulk modulus, and because of the fiber reinforcement, the constrained F2MC structures will develop very high stiffness. In other words, the variable stiffness adaptive structure has the flexibility to easily deform when desired (open valve) and possesses the high stiffness required under loading conditions when deformation is not desired (closed valve – locked state). Through semi-active control of the valve (open/closed), the system is able to switch between the two stiffness modes of operation with very little power. However, by adding feedback control of a variable orifice, the adaptive system has the potential to follow a desired stiffness trajectory, thus making the stiffness truly variable.
[1] Philen, M., Shan, Y., Bakis, C. E., Wang, K. W, and Rahn, C. D., “Variable Stiffness Adaptive Structures utilizing Flexible Matrix Composites with Hydraulic Pressurization and Valve Control,” 14th AIAA/ASME/AHS Adaptive Structures Conference, May 1-4, 2006.
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