Preliminary visual characterization of the effects of thermal cycling on the surface structure of Kevlar®/Epoxy tubular braided composites using scanning electron microscopy

Thermal cycling is a hazardous condition that satellites in low Earth orbit (LEO) are regularly exposed to, as it causes the development of thermal stress in materials with non-zero coefficients of thermal expansion (CTE). Tubular braided composites (TBCs) combine high strength fibers with polymer matrices into a cylindrical structure suitable for load bearing applications. Their high customizability can allow for the creation of TBCs with near zero CTEs. In the author’s prior investigation, the effects of low amounts of thermal cycling on the mechanical performance of Kevlar®/Epoxy TBCs was investigated to assess the viability of these materials in satellite structures. In this work, scanning electron microscopy (SEM) was used to analyze the surfaces of Kevlar®/Epoxy TBCs exposed to thermal cycling to identify signs of material degradation. Samples were manufactured with one of three braid angles (35°,45°, and 55°) and exposed to 0, 5, or 10 thermal cycles between −50℃ and 120℃. Images of the samples were then taken using scanning electron microscopy and then digitally filtered to improve visibility of damage, which included microcracking, fiber-matrix debonding, and fiber breakage. At five cycles of exposure, samples manufactured at 35 and 55 degrees began to display signs of degradation, while the 45 degree samples did not. At 10 cycles of exposure, samples at all three braid angles displayed an increased presence of material damage. The development of thermally induced damage may be prevented through varying the material components or the introduction of nanoparticles to the epoxy resin.