Novel Shape Memory Composite Substrate

The new SMC substrate has four components: a shape memory polymer separately developed at NASA Langley; a stack of thin-ply carbon fiber sheets; a custom heater and heat spreader between the SMC layers; and integrated sensors (temperature and strain). The shape memory polymer allows the as-fabricated substrate to be programmed into a temporary shape through applied force and internal heating. In the programmed shape, the deformed structure is in a frozen state remaining dormant without external constraints. Upon heating once more, the substrate will return slowly (several to tens of seconds) to the original shape (shown below). The thin carbon fiber laminate and in situ heating solve three major pitfalls of shape memory polymers: low actuation forces, low stiffness and strength limiting use as structural components, and relatively poor heat transfer. The key benefit of the technology is enabling efficient actuation and control of the structure while being a structural component in the load path. Once the SMC substrate is heated and releases its frozen strain energy to return to its original shape, it cools down and rigidizes into a standard polymer composite part. Entire structures can be fabricated from the SMC or it can be a component in the system used for moving between stowed and deployed states (example on the right). These capabilities enable many uses for the technology in-space and terrestrially. Shape memory polymers, like shape memory alloys, have the capability to return to their original shape from a temporary (or programmed) shape when some external stimulus is applied (e.g., temperature, electric field). However, shape memory polymers have not seen the same level of implementation as the alloys because (1) they do not have high actuation forces (i.e., the force of the shape change) and (2) the polymers do not spread stimuli well, as such, the actuation is not constant across the material. NASA inventors have developed a novel shape memory polymer composite (SMC) substrate by combining a shape memory polymer with thin carbon fiber sheets and an in-situ heating mechanism. The in-situ heating and a carbon fiber layer result in heat being spread evenly across the polymer and significantly higher actuation forces compared to the polymer alone. The capabilities of the composite substrate will enable deployable systems across various industries.