Carbon nanofibers for strain and impact damage sensing in glass fiber reinforced composites based on an unsaturated polyester resin

Abstract

AbstractIn this article, a successful employment of carbon nanofibers (CNFs) as a filler in the unsaturated polyester (UP) matrix of a glass fiber reinforced polymer (GFRP) is reported. Because of the high aspect ratio of carbon nanofibers, very small amount of these particles were sufficient to significantly modify the electrical properties of the obtained glass fiber composites: for this reason, nanocomposite matrices were produced using no more than 1 wt% of these nanoparticles. The goal of this work was to investigate the possibility to correlate the presence of a mechanical stress, or the onset of damage, in the composite produced, with the variation of electrical resistance. Following this goal, the electrical resistance of the samples was constantly measured during their mechanical testing. Two different kinds of load were applied: flexural and impact. It was possible to show that a systematic variation in the electrical resistance of the composite takes place in correspondence of both the growth of a flexural state of stress, and the creation of an impact damage. In the case of the flexural load, the electrical resistance versus strain curves provides information on the growth of damage well before such damage affects the stress–strain curve. In the case of the impact damage, electric resistance measurements were able to monitor the loss of mechanical integrity before the complete failure. SEM pictures of the crack surface have confirmed the role of the carbon nanofibers in the sensing process. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers