Patch repair of composites using Dielectric Barrier Discharge-induced heating and curing

Here, we demonstrate a novel methodology of repairing cracks or damage points in carbon fiber reinforced composites (CFRCs) using Dielectric Barrier Discharge (DBD) generated plasma induced heating and curing. We observed that conductive carbon fibers heat up when exposed to DBD-generated plasma. This study involves the use of an epoxy-impregnated carbon fiber patch which is applied on the cracked or affected area of a composite to mitigate the damage. The DBD applicator generates an electric field plasma; when conductive carbon fibers are exposed to this plasma, an electric current is induced which leads to heating in the fibers. This heat from the fibers is transferred to the surrounding epoxy, thus curing the patch. This cured patch acts as a structural additive to the damaged part, significantly improving its mechanical properties and extending the part`s lifetime. We investigated the heating response of bare fibers when exposed to DBD as a function of their electrical conductivity. X-ray Photoelectron Spectroscopy (XPS) was used to study the effect of plasma on the surface functionality of carbon fibers. Differential Scanning Calorimetry (DSC) experiments show that the glass transition temperature and degree of cure of the exposed patch can be controlled by adjusting the target temperature and residence time of the DBD generated plasma induced heating process. Furthermore, the mechanical properties of damaged and repaired samples were compared using tensile testing; a ∼78% increase in ultimate tensile strength of the DBD-repaired sample was observed compared to the damaged sample. This study establishes Dielectric Barrier Discharge as an energy-efficient, out-of-oven methodology for damage repair in carbon fiber composites.