Novel Shape Memory Composite Substrate

The NASA Langley SMP was originally designed for smart active structures in morphing spacecraft and airfoils to provide noise reduction and increased stability. The technology may also have applications in self-deployable structures, smart armors, intelligent medical devices, and other various morphing structures. The incorporation of conductive fillers into the polymer matrix allows for a faster response time than that of typical SMPs due to a combined response from both Joule heating and dielectric loss. Joule heating is achieved by the application of a low-level current that is diffused uniformly across the polymer when an electric field is applied. The addition of an alternating field shortens the thermal response time due to dielectric loss. Voltage application is determined by the specific material dimensions. For a benchtop scale device, about 10-40V was required for activation of the material. Furthermore, the technologys variable stiffness polymer composite (VSPc) is laminated with highly elastic layers to provide additional stored elastic energy, resulting in a higher recovery force than that of similar materials currently on the market. The technology is being used in a laboratory setting at NASA and prototypes have been built, with durability and fatigue testing underway. The new polymer is patent pending, and NASA seeks companies to license the technology and develop it for commercial applications.

Shape memory alloys (SMAs) are metals that can return to their original shape following thermal input. They are commonly used as functional materials in sensors, actuators, clamping fixtures and release mechanisms across industries. SMAs can suffer from dimensional/thermal instability, creep, and/or low hardness, resulting in alloys with little to no work output in the long term. To combat these deficiencies, NASA has developed a process of incorporating nanoparticles of refractory materials (i.e., carbide, oxide, and nitride materials with high temperature resistance) into the alloys. Using various processing methods, the nanoparticles can be effectively mixed and dispersed into the metal alloys as shown in the figure below. In these processes the SMA and refractory material powder is mixed and the refractory nanoparticles incorporated through extrusions, melting, or directly used in additive manufacturing to create parts for applications across the aerospace, automotive, marine, or biomedical sectors. The nanoparticle dispersion is a controllable method to strengthen the SMAs, increasing the hardness of the alloys, reducing the impact of creep, and improving the overall dimensional and thermal stability of the alloys. The related patent is now available to license. Please note that NASA does not manufacture products itself for commercial sale.

Glenn researchers have optimized how shape memory alloys (SMAs) are trained by reconceptualizing the entire stabilization process. Whereas prior techniques stabilize SMAs during thermal cycling, under conditions of fixed stress (known as the isobaric response), what Glenn's innovators have done instead is to use mechanical cycling under conditions of fixed temperature (the isothermal response) to achieve stabilization rapidly and efficiently. This novel method uses the isobaric response to establish the stabilization point under conditions identical to those that will be used during service. Once the stabilization point is known, a set of isothermal mechanical cycling experiments is then performed using different levels of applied stress. Each of these mechanical cycling experiments is left to run until the strain response has stabilized. When the stress levels required to achieve stabilization under isothermal conditions are known, they can be used to train the material in a fraction of the time that would be required to train the material using only thermal cycling. As the strain state has been achieved isothermally, the material can be switched back under isobaric conditions, and will remain stabilized during service. In short, Glenn's method of training can be completed in a matter of minutes rather than in days or even weeks, and so SMAs become much more practical to use in a wide range of applications.

Shape memory alloys (SMAs) are metals that can return to their original shape following thermal input and are largely used as actuators for various applications across industries including space, aeronautics, automotive, and biomedical. These alloys can require long processing times to stabilize through repeated training cycles and suffer from loss of strength and stability during use. Precipitation strengthening (using heat treatments to grow small nanoscale regions of distinct metal phases within the base alloy) is one way to mitigate these issues. The NASA inventors have combined a modification of typical NiTi compositions by introducing Palladium (Pd) and small amounts of other metals and specific heat treatments to produce a novel SMA with improved properties. Specifically, the alloy is inherently stable, reducing both the need for extended processing times to stabilize the metal and the possibility of failure during high numbers of actuation cycles. Further, the SMA is specifically designed to have significantly lower hysteresis (the temperature difference between the heating and cooling) than current state of the art SMAs, i.e., at or below 10°C compared to 20°C or above. These properties combine for a SMA with enhanced properties usable across various industries and applications for reliable actuation. The related patent is now available to license. Please note that NASA does not manufacturer products itself for commercial sale.

A prototype device has been developed at Glenn for creating shapes from SMA wire. The apparatus uses material feedstock in spools made of alloys that exhibit the shape memory effect (temperature-induced activation), super elasticity (stress-induced activation), and to some extent, magnetism (magnetically-induced activation). The feedstock (e.g., wire spool) is routed and positioned around a series of modular pins to create a shape outline. Once the desired shape is formed, the wire ends are clipped from the feedstock and secured into a locking mechanism, then connected to a heating circuit (e.g., joule heating, hot plate, heat gun). The programmable prescribed circuit parameters, including current or temperature and training time, are set and confirmed using the apparatus control dials and indicators to ensure safe and accurate operation of the device. Before enabling the circuit, a plastic shield is placed over the modular array to protect the operator. The final product will be a desired shape that can be deformed and recovered numerous times through heat activation.