Effect of frozen conditions on dispersion morphologies of carbon nanotubes and electrical conductivity of carbon fiber/epoxy composites

Carbon nanotubes (CNTs) were introduced into three-dimensional carbon fiber fabric/epoxy composites with assistance of freeze-drying technique. Different frozen conditions, including slow-freezing, quick-freezing and unidirectional freezing, were utilized to affect CNT dispersion morphologies in fiber/CNTs preforms and composites. Electrical conductivity of composites was measured. The results demonstrated that: (1) frozen conditions had an obvious effect on dispersion morphologies of CNTs in preforms; (2) quick-freezing and unidirectional freezing were beneficial for CNTs to disperse in preforms and improve electrical conductivity of composites, compared to slow-freezing; (3) application of unidirectional freezing made the arrangement of CNTs possess certain orientation and, as consequence, electrical conductivity along freezing direction of composites was enhanced significantly. (C) 2014 Elsevier B.V. All rights reserved.