Yasmine Abdin

Stress distribution around a broken carbon fibre and how it is affected by carbon nanotubes in the interface region

ABSTRACT We performed a numerical study to evaluate the influence of carbon nanotubes (CNTs) on the stress build-up in and around a broken fibre in a single carbon fibre/epoxy composite loaded longitudinally. The CNTs were located in the interface region and mimicked one of the two deposition techniques: 1) direct growth on the fibre or 2) dispersion in the fibre sizing. These techniques are known to produce different alignment, orientation and concentration of CNTs in a composite, which affect stress redistribution upon the fibre failure. The study was performed using a two-scale finite element model based on the embedded regions technique. The most significant effect on the stress build-up was found for CNTs aligned in the fibre direction. In this case, the crack opening displacement and the ineffective length were reduced by 15% and 28%, respectively, thus making the stress recovery in the broken fibre faster. In addition, the shear stress at the fibre-matrix interface decreased by a factor of two. These results indicate that hybridization of microscopic fibres with nanotubes aligned in the fibre direction is a promising strategy to influence the process of fibre fragmentation in a composite. Graphical Abstract

Fatigue analysis of carbon, glass and other fibres

Abstract The fatigue behaviour of fibres is an important knowledge, fibres being the main load-bearing elements in fibre-reinforced composites. The fatigue strength of composites largely depends on the fatigue behaviour of fibres. While the static strength of reinforcing fibres has been extensively investigated, there are very few data available on their fatigue properties. The main reason is the difficulty of conducting fatigue tests on unimpregnated fibres. The scope of this chapter is to provide insight on the fatigue properties of different types of reinforcing fibres, with a focus on the high-performance glass and carbon fibres. Moreover, some data on the fatigue behaviour of natural fibres, aramid fibres, optical fibres and steel fibres is mentioned. Experimental characterization methods, as well as modelling approaches for the fatigue strength of single fibres and fibre bundles, are addressed.