Reclaimed Carbon and Flax Fibre Composites: Manufacturing and Mechanical Properties

Abstract

The feasibility of using the HiPerDiF (high performance discontinuous fibre) method to manufacture highly aligned discontinuous fibres intermingled hybrid composites with flax and reclaimed carbon fibres (rCF), and the potential benefits of so doing, are investigated in this paper. It is demonstrated that, despite their hydrophilic nature, flax fibres are not affected by this water-based process. Intermingled flax/rCF hybrid composites are characterised in terms of their tensile and vibrational response. It is concluded that natural/rCF fibre hybrid composites can be a viable solution for those applications where a reduction in primary mechanical properties, e.g., stiffness and strength, is an acceptable trade-off for the enhancement of secondary properties, e.g., noise, vibration, and harshness (NVH) mitigation, and the reduction of monetary costs.

Review on Hybrid Carbon/Flax Composites and Their Properties

“…The strength and stiffness of hybrid composites increases with the increase of carbon fiber content. This tendency seems to be independent, whether carbon fiber textile [13,17,18] or short recycled carbon fibers [23] are used. As example, the replacement of one flax ply with a carbon ply in a composite with 6 plies leads to increase of the tensile modulus of about 262.0% and tensile strength of 266.4% [12].…”

“…However, the increase of carbon fiber content in textile carbon/flax composites leads to the decrease of strain to failure [13]. At the same time, in the case of short fibers, the strain to failure is nearly independent of the carbon content [23].…”

“…Finally, two studies report the use of short fibers. In the former study, the carbon fibers are recycled from pyrolysis [23], and in the latter one, the recycled carbon fibers from production waste are used, e.g., from trimming or from cured carbon composite products [26].…”

“…Specially developed techniques are used for the manufacture of carbon/flax short fiber-epoxy composites. These methods are presented in Table 4, including the fiber preparation steps [23,26]. The basic information regarding the techniques used for the fiber-reinforced composite manufacture is described extensively in the literature [29,34].…”

“…In the case of hand lay-up combined with pressure moulding, the curing varies quite considerably from onestep curing at 20°C for at least 7 h to curing in 4 steps, with a temperature range from 80°C to 150°C, which takes around 30 h. The curing during a single-step vacuum bagging, which is also known as a vacuum infusion process, commonly takes place in 2 steps with a maximum temperature of 90°C. In the case of short fiber carbon/flax composites, at the beginning of the composite manufacture, the fibers are in the form of prepreg with mixed aligned carbon and flax fibers preimpregnated with epoxy resin [23] or mixed and compressed carbon and flax fibers [26]. Consequently, in the former case, the short fibers are processed similarly as typical prepregs via curing in autoclave.…”