Assessment of the Effect of Carbon Nanofibers on Matrix Cracking in Laminated Composites Using Lamb Wave Propagation

The main purpose of this study was to investigate the effect of carbon nanofiber (CNF) fillers on the matrix cracking behavior of cross-ply laminated glass/epoxy composites, evaluated by a nondestructive Lamb wave propagation method. Laminated composite specimens with stacking sequence of [02,906]s were fabricated and tested. The CNF fillers were added into the epoxy resin with a weight fraction of 0.25. This reinforced epoxy resin was used as the matrix of 90-degree layers of cross-ply laminated composite specimens. A tensile testing machine was used to induce different crack densities in composite specimens with and without CNF fillers. The same tensile machine was also used for the measurement of the mechanical properties of specimens. The results obtained from the Lamb wave propagation method were in good agreement with those obtained from the tensile tests and the predictions of the Hashin model and Andersons et al. semi-analytical model, proving the reliability of this method for nondestructive evaluation of composite structures. It was also shown that by adding CNF fillers into the composite specimens, smaller crack densities and stiffness reduction was observed at certain applied stress levels. Based on the analysis of the experimental data and the two micromechanical damage models, it was concluded that the most significant factor in decreasing the density of matrix cracking and stiffness reduction in the composite specimens by adding CNF fillers into their matrix, was the enhancement of tensile strength of the 90-degree layers.

Keywords:

Polymeric composites , Carbon nanofiber , Matrix cracking , Lamb wave , Elastic properties.