Multiple studies have revealed that the prevalent cost element for manufacturing composite components is the cost of operating an autoclave. Traditional laminates are cured under vacuum, pressure, and heat in an autoclave to flow, consolidate, and cure the resin. However, there are many drawbacks to using an autoclave; most notably, they are very inefficient in delivering heat to composite parts, thereby consuming excessive power. Autoclaves heat convectively, meaning they resistively heat air through a blower, which in-turn heats the surface of the composite. Since autoclaves contain a fixed volume of air, the cost to produce the heat remains fixed regardless of the size of composite part being cured, yielding the potential for much waste. MDC has demonstrated the use of CNT appliques to conductively cure composite components not only without an autoclave, but out-of-oven entirely. Conductive curing costs scales with part surface area rather than autoclave volume, thus providing a path for reducing composite acquisition costs by up to 50%, while providing more uniform properties and removing autoclave-induced geometric constraints.
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Multifunctional Structures
A core expertise at MDC has been the development of novel multifunctional structures. By exploiting the exotic properties of unique materials MDC has engineered structures that can efficiently serve multiple functions. These properties include piezoelectric, piezoresistive, pyroelectric, shape memory alloys, and electroactive polymers. Most commonly carbon nanotubes (CNT) have been employed due to their exceptional and tailorable electrical and thermal properties. CNT have been considered as possible durable replacements for traditional copper wire, ESD/EMI/lightning-strike protection and heat sinks, and MDC has also demonstrated their ability to be used as key elements within embedded sensors for monitoring strain and damage, as well as in actuators and morphing structures. The greatest maturity has been achieved for establishing CNT as lightweight heaters for applications such as deicing/anti-icing and low-cost manufacturing of composite materials.
Deicing/Anti-Icing
Reliable Ice Protection Systems (IPS) are flight-critical for aircraft, from fixed-wing to rotorcraft and unmanned vehicles (UAV/RPA). They provide anti-icing capabilities to prevent the formation of ice and/or de-icing to remove ice build-up from aerosurfaces. Traditional de-icing fluid used in commercial applications is not environmentally friendly and is impractical for most military platforms. While purely passive solutions are attractive, none have proven sufficiently reliable and durable. MDC has demonstrated that carbon nanotube (CNT) multifunctional appliques can be integrated into both composite laminates and metallic assemblies to be used as an efficient and effective means for electrothermal ice protection. They can provide equivalent performance at a fraction of weight (as little as 1% compared to metal-based heaters) and have the potential to operate with significant power savings. MDC has participated in several hundred ice-tunnel tests and successfully completed both dry and wet-air flight test campaigns.