Under Navy funding, MDC has been working to develop an integrated system capable of reliable ice-detection, de-icing and anti-icing, in addition to structural diagnostics for fixed-wing leading-edges and rotorcraft blades. The basis for this system is structured Carbon Nanotube (CNT) enhancements that can either be embedded within the composite laminates during manufacturing, or applied as a separate surface layer in a secondary process. The aligned CNTs are sufficiently long (20-30 um) to span interply matrix regions, improving electrical conductivity by a factor of a million and thermal conductivity by orders of magnitude. Overall, this system offers many benefits over current Ice Protection Systems (IPS), allowing conformal, uniform, and structurally integral heating and sensing elements, and enabling closed-loop operation, all of which contribute to a reliable, robust and durable system design. Compared to the conventional resistive heating blanket approach for de-icing, the CNT-enhanced system is more efficient, lighter weight, lower profile, and provides integral damage detection feedback.
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Multi-Disciplinary Systems
Propulsion Systems
Over the last 100 years of powered flight, the performance of aircraft has almost universally been constrained by the performance of the available propulsion systems. The imagination and ambition of aircraft designers has always been tempered by the low thrust-to-weight ratio, large size and poor fuel consumption of available propulsion systems. The introduction of the turbofan has completely transformed large scale aviation by providing an engine with improved thrust-to-weight ratio, low fuel consumption and excellent reliability. However, small and light weight aircraft are still restricted by their use of low performance reciprocating engines. The Propulsion Systems group at MDC is developing innovative and cost effective propulsion technologies that will make the higher thrust-to-weight ratio, low noise, low fuel consumption and reliable turbofan engine available to designers and operators of light aircraft.
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Ice Protection Systems
Under Navy funding, MDC has been working to develop an integrated system capable of reliable ice-detection, de-icing and anti-icing, in addition to structural diagnostics for fixed-wing leading-edges and rotorcraft blades. The basis for this system is structured Carbon Nanotube (CNT) enhancements that can either be embedded within the composite laminates during manufacturing, or applied as a separate surface layer in a secondary process. The aligned CNTs are sufficiently long (20-30 um) to span interply matrix regions, improving electrical conductivity by a factor of a million and thermal conductivity by orders of magnitude. Overall, this system offers many benefits over current Ice Protection Systems (IPS), allowing conformal, uniform, and structurally integral heating and sensing elements, and enabling closed-loop operation, all of which contribute to a reliable, robust and durable system design. Compared to the conventional resistive heating blanket approach for de-icing, the CNT-enhanced system is more efficient, lighter weight, lower profile, and provides integral damage detection feedback.
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CNT Deicing
For de-icing, or melting of ice, a resistive heating principal is used. A controlled voltage is applied across the Carbon Nanotube (CNT) network through conformal or embedded electrodes, and heat is rapidly generated due to the small but finite resistance of the CNTs. A uniformly-distributed surface-temperature rise can be achieved as result of the aligned structure of the CNT network and their good thermal conductivity. This approach is much more convenient and environmentally friendly than the traditional practice of applying de-icing fluid. It is also considerably more efficient than conventional internally-mounted ceramic heating blankets, which must conduct all the way through the cross section of a material (such as an aerosurface) to reach the boundary layer of the ice. CNTs are typically stronger than their host material, thus would also have a tremendous durability advantage over proposed ultrasonic-based de-icing, or other methods that make use of moving parts.
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CNT Anti-icing
Similar to de-icing, anti-icing, or the prevention of ice-formation, is also achieved using a resistive heating principle, where heat is generated by applying a voltage across the small but finite resistance of the Carbon Nanotube (CNT) network. Anti-icing essentially amounts to maintaining the surface temperature of a material to above freezing levels such that ice cannot begin to form. When anti-icing follows de-icing, anti-icing prevents refreezing of melted ice left on a surface after de-icing. Since most of the energy in the de-icing process goes to the ice-water phase change, anti-icing can be achieved at considerably lower power levels, however that power would need to be applied for a longer period of time to maintain the elevated surface temperature in a cold ambient environment. There are several applications where this is a favorable trade-off, particularly in performance critical applications such as wind turbines.
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CNT Ice Detection
Ice-detection with a Carbon Nanotube (CNT) network is achieved using an effective heat-capacity approach. The CNT-enhanced host-material has a simple thermodynamic relationship with ambient conditions, thus it is easy to calculate the time to reach equilibrium given an induced heat within the CNT-network. Calculating equilibrium for the same system with the addition of a layer of ice between the host-material and ambient conditions is a similarly simple model except that the time constant is now dependent on the thickness of that ice layer. Therefore, if power is briefly applied to the CNT-network to induce a calibrated resistive heat level, the slope of the temperature rise can be well correlated to the thickness of ice present. Since this approach uses the same enhanced materials and electrical network as the proposed CNT de-icing and anti-icing methods, it provides an efficient, reliable and durable means for providing closed-loop automated feedback control of these elements.
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Electro-Mechanical Design
In parallel with internal programs developing propulsion and ice-protection systems, MDC has been providing outsourced technical consulting services for electro-mechanical design for nearly a decade. Much of this derives from the expertise of MDC engineers in specific niche competencies, such as piezoelectric transducers, shape memory alloys, ultrasonic methods, energy-harvesting and power-transfer techniques, pattern and image recognition; composite, hybrid and nano-engineered materials; and general non-linear multi-physics simulation and modeling. MDC has extensive experience in the design, simulation, fabrication and evaluation of these types of complex electro-mechanical systems. The focus of this consulting service has been elevating the technical maturity of customer concepts by validating fundamental aspects through proof-of-concept experiments and embodying client innovations in prototype demonstration units. Through a trusted network of vendors and partner companies, MDC can facilitate the fabrication, assembly and testing of nearly any type of device in any conceivable range of conditions, including consumer, military and space environments.
