Abstract

Abstract

Our latest generation aircraft are more efficient by design, lighter and emit on average 25% less CO2 than previous generation aircrafts. Lightweight materials like composites have contributed significantly to reach the current emissions levels, like the A350 with more than 50% of structural weight made of composites. However, composites drive also the environmental footprint of the aircraft life-cycle without considering the operational phase, involving currently important drawbacks in terms of energy consumption and waste recycling. The transition towards a composite circular economy needs to be anticipated due to the aviation sector de-carbonization challenge as well as the regulation evolution. This transition will be leveraged by several elements, being the composite recycling one of the most important, due to the need to transform the composite waste from production and end of life into new added value materials. For this, the development of efficient composite recycling technologies to not only recover energy during incineration but also high value recycled carbon fibers and semi-products are needed. This project was focused on the recycling of dry carbon fiber scrap, which can proceed from part production by infusion technologies (e.g. RTM) or from pyrolysis of end of life composite part. The approach was to obtain a non-woven mat from the dry fiber scrap, following a mechanical process, which was, then, fully characterized to identify potential applications in aeronautical field. Different approaches of hybridization of the recycled non-woven fabric with virgin fabric were also evaluated.

Abstract

This paper focuses on the impact of processing parameters on the joint quality of carbon fiber-reinforced thermoplastic (CFRTP) materials in a continuous ultrasonic consolidation process, with the purpose of optimizing the performance of this process. Parameters such as joining speed and ultrasonic amplitude are examined through porosity and shear strength. Optical microscopy was employed to analyse the interface morphology, and the shear strength of the joints was measured. The results showed that a joining speed of 1 mm/s resulted in the highest shear strength. Additionally, samples with less than 2% porosity were achieved, indicating that this process can produce high-quality joints with respect to porosity and mechanical properties.

Abstract

One of the main areas of study within composite materials, and more specifically within the aerospace sector, is their recycling. Currently, most composite waste management techniques involve the disposal of these materials without the possibility of reuse. This work presents the use of a hydrothermal process that enables the recovery of carbon fiber fabrics from a composite laminate in a condition suitable for use in new manufacturing processes.

In this study, different types of carbon fiber reinforcements (dry fabric, non-crimp fabric and prepregs) were used to manufacture laminates, which were subsequently subjected to a hydrothermal recycling process. The treatment conditions were optimized for each material studied, achieving resin removal rates above 90% for several of them. Moreover, the fibers obtained from the hydrothermal process preserved their original structure, allowing them to be handled and reused for the manufacture of new laminates. It was also verified that the process did not remove the fiber sizing.

A testing campaign was carried out to evaluate the mechanical properties of the recycled material, and the results were compared with those obtained from the original samples. The findings show that the recycled fibers could be reused. Although their application in primary aircraft structures may be debatable, they could be employed in other components with lower performance requirements. An example of such use is their application in drone manufacturing, as demonstrated in the final phase of the RECICOM project.

The work presented in this abstract is part of the RECICOM project, funded by the European Union through Next Generation funds and by CDTI under its PTA2022 program – SME Category.

Abstract

Abstract