Showing results: 1 - 5 of 5 items found.
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Material Sensing & Instrumentation
Microwave cavity characterization complements TDR Dielectric Spectroscopy in low-loss materials, providing high-resolution permittivity and loss data at specific single frequencies. Since measurements do not change significantly with frequency in low-loss materials (Kramer-Kronig relation) cavity measurement at select frequencies provides a full characterization across the RF/microwave range.
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Material Sensing & Instrumentation
MSI Time-Domain-Reflectometry (TDR) Structural-Health Monitoring probes the structural health of a composite part by propagating a fast electrical pulse along a distributed linear sensor which has been fabricated directly in the laminate. The sensor is formed from the native graphite fibers already used in composite manufacture, and constitutes zero defect. Fibers are patterned into a microwave waveguide geometry, or transmission line, and interrogated by a rapid pulse as shown below. Structural faults along the line cause distortions in waveguide geometry, producing reflected pulses similar to radar. Cracking, delamination, disbonds, moisture penetration, marcelling, and strain are all detected by propagation delay, for sensor lengths up to several meters.
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Material Sensing & Instrumentation
Broadband Dielectric Spectroscopy is a powerful tool for investigating a variety of dielectric processes for both electrical and non-electrical applications. Also called Impedance Spectroscopy, the measurement separates molecular process on the basis of response time, providing a unique relaxation frequency along with a signature variation with frequency.
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Material Sensing & Instrumentation
MSI Time-Domain-Reflectometry (TDR) Concrete Cure Monitoring provides a new approach to cure monitoring in concrete and cementitious materials [1-7]. Using an ultrafast pulse and inexpensive capacitance sensor, our TDR system follows rotation of individual chemical states of water participating in the hydration reaction. The system monitors formation of bound-water hydration products, as well as unreacted free-water to form the hydrated state.
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Material Sensing & Instrumentation
MSI Time-Domain-Reflectometry (TDR) Composite Cure Monitoring [1-4] provides a new approach to cure monitoring of advanced polymer composites. Using a high-speed pulse and inexpensive microwave sensor, our TDR system follows rotation of a polar resin molecule, providing real-time information on viscosity and percent cure. Operating in the microwave frequency range, TDR Cure Monitoring provides an alternative between high-frequency fiber-optic methods and low-frequency dielectric methods, combining optical-style precision and miniaturization with electrode-based simplicity and robustness.
