Thermal protection of high temperature polymer-material-carbon fiber composites

Abstract

Two evaporative-cooling materials were studied which are (i) salt hydrates and (ii) polyacrylic acid for the purpose showing proof of concept of being able to put evaporative-cooling materials into a composite with the Air Force polyimide AFR-PEPAN. The salt hydrates were observed to absorb water and then evaporate water, but due to having a collapsible lattice, made them incapable of reabsorbing water. Polyacrylic acid was mixed into an epoxy sheet at polacrylic acid weight percentages of 5, 10, 12.5. For each weight percentage there was a hydrated epoxy specimen and a dry epoxy specimen. All specimens were individually shot with a hot air stream (temperature approximately 1300C). Temperature readings were taken for each sheet. The hydrated specimen exhibited greater evaporative cooling over its dry counterpart. 12.5 wt% was shown to have the best evaporative cooling mechanism. Experiments were repeated to show that the polyacrylic could reabsorb water. This study illustrates proof of concept utilizing polyacrylic acid as an evaporative cooling material.