A. Krishnamurthy, A. Forster, D. Hunston
National Institute of Standards and Technology,
Keywords: fuzzy fiber composites, hygrothermal degradation, MWCNTs
Summary:Polymer composites are often prone to degradation when exposed to hygrothermal conditions. The physical, chemical and the mechanical properties of polymer matrices deteriorate reversibly/irreversibly based on the time/temperature of exposure. Further, the damage to the fibers is another aspect of the degradation process that can affect the mechanical properties of composite materials over prolonged exposure. With the increasing use of nanomaterials for composite processing, the effect of hygrothermal exposure on their mechanical properties has not yet been fully understood. In the current study, MWCNTs (“fuzzy fiber”) based composites were manufactured by exposing woven alumina fibers to high temperatures in the presence of carbon precursors at atmospheric pressures. After the chemical vapor deposition (CVD) process, the radially aligned MWCNT-alumina fibers are stacked up and are infiltrated with high glass transition temperature (Tg), RTM6 resin. The direct deposition of MWCNTs on the alumina surface offers advantages such as better nanofiller stability and alignment within the polymer matrix. The composites manufactured by this process improve both the electrical and thermal properties in addition to the mechanical properties by forming a conductive network (CNT-percolation) within the resin. These properties can exploited in many applications such as piezoelectric sensing for damage assessment, self-healing, energy dissipation, electromagnetic shielding etc. The manufactured composite materials are then characterized for their mechanical, chemical and microstructural properties before and after a ~3 month distilled water immersion at high temperature (~60C).