Enabling damage detection: manufacturing composite laminates doped with dispersed triboluminescent materials

Abstract

Triboluminescent materials are being harnessed to address the gaps in current structural health monitoring systems. Their innate ability to emit light when stressed or broken makes them ideal candidates for the ubiquitous and in situ monitoring of structures. The increasing use of advanced composites in critical structures, where subsurface damage initiation may go unnoticed, further highlights the urgency in developing efficient online monitoring technologies. This work looked at the manufacturing of composite laminates that have been doped with various concentrations (0 to 10 %wt.) of a triboluminescent material (ZnS:Mn). Laminates were manufactured using a vacuum infusion process. Dispersing the ZnS:Mn particulates was cumbersome because their density was higher than the resin that caused settling during resin infusion. The dispersion of ZnS:Mn is critical to their use in the health monitoring of the host structure. As such, a method for mechanical agitation using a rotational vacuum infusion apparatus was developed employing centrifugal motion. The degree of dispersion in the resulting laminates was determined using scanning electron microscopy and the energy dispersive scanning feature of the electron microscope for elemental mapping. A quantitative metric was established by computations of the Euclidean distance of EDS mapping. Studies of the effect of ZnS:Mn concentration on the tensile strength of laminates showed that increasing the ZnS:Mn concentration reduced the tensile strength. Key processing parameters were studied, and determined that curing kinetics were not altered by ZnS:Mn inclusion.