Mechanical behavior of sintered submicron glass fiber mats

Abstract

The mechanical behavior of sintered glass fiber mats of two different types with fiber diameters in the submicrometer range is studied experimentally and theoretically. Microscopically-entangled and macroscopically-oriented glass fibers in the mats were mutually sintered during heat treatment at different temperatures and their mechanical properties explored by tensile testing. Here, we report for the first time that the mechanical behavior of ultra-thin glass fiber mats after sintering can be maintained or even enhanced, contrary to the conventional belief derived from the experience with thick glass fiber mats. For one type of the mats explored in the present work, a more than 120% increase in the value of Young's modulus after heat treatment at the annealing temperature of 500 °C was observed. The friction forces and unique percolative skeleton structure of the present glass fiber mats after sintering are presumably enhanced, which facilitate the enhanced mechanical properties while the annealing temperature increases. The mechanical behavior is clearly affected by the detailed microstructure and architecture of each type of the glass fiber mats. The macroscopic glass fibers embedded in the mats of one type diminished the thermal expansion, which manifested itself by practically constant mechanical properties independent of heat-treatment temperature. These bundled fibers also were the sites where multiple minor fractures before the catastrophic specimen fracture originated, which enhanced brittleness and, accordingly, diminished the fracture toughness in comparison with that of the mats without such bundled fibers. Furthermore, a theoretical mode developed here to evaluate the sintering time of macro - and microscopic glass fibers, agrees well with the experimental results with the viscosity of glass fibers ranging from 1010.6 to 1011.6 Pa s.