Modeling of Nanostructured Heaters for Out-of-Oven Curing of Aerospace Composites

Abstract

Primary aerospace composite structures have traditionally been processed by applying vacuum, heat, and pressure to a laminate using an autoclave. More recently, aerospace secondary structures have been able to be processed without the need of an autoclave, but with just vacuum pressure in an oven. However, both of these methods are energy, space, and time intensive processes. A new composite manufacturing approach has recently emerged that utilizes carbon nanotube (CNT) based heaters to conductively cure the composite (termed out-of-oven, OoO curing) and nanoporous network (NPN) materials to replace the need for autoclave pressure. The OoO curing method uses CNT films which act as a thin-film heater to conductively process a composite structure. OoO curing is enabled by the advantageous thermal and electrical properties of CNT networks, which allow Joule heating to be used by applying a voltage to the CNT films. This approach was previously found to reduce the energy to cure a composite by ∼ 2 orders of magnitude when compared to conventional oven-based techniques and presents much greater flexibility for complex structures and curing configurations. This thesis models the composite cure process driven by CNT film heaters with ANSYS Composite Cure Simulation (ACCS) and particularly focuses on a curing configuration of two heaters with a non-heated gap in the middle, needed for both scaling of the OoO approach and for spatial cure tailoring. It is found that a minimum gap of 5 mm between two CNT film heaters is recommended for a maximum difference of 12 ∘C and 2.3% degree of cure (DoC) between the centers of the heated and the non-heated zones as a worst case scenario. Experimental verification of the computational temperature results is performed to verify the simulation results.