Abstract

Fused Filament Fabrication (FFF) technology is one of the most popular 3D printing processes and interest in direct manufacturing of functional parts is growing. For this reason, both techniques and feedstock materials require improvements to meet the mechanical requirements of load-bearing components. In this sense, this work is focused on the robotized FFF process of continuous carbon fiber thermoplastic composites. It includes an analysis and comparison of the developed FFF robotic 3D printing process with the conventional process, as well as the development of robotic 3D printing equipment for the manufacture of continuous fiber reinforced composites and the characterization of the printing process developed to print the new filaments based on the thermoplastic matrix and reinforced with continuous carbon fiber. The material was analysed by microscopic analysis, and the manufacturing specimens were characterized by mechanical tensile and flexural tests.

Abstract

Fibre breakeage in composite materials is usually a determining damage mechanism for its structural integrity due to the high energy associated, in comparison with matrix cracking. For this reason, the assessment of the translaminar fracture toughness is relevant for accurate numerical predictions of composite structures. However, there are scarce investigations related to this topic for additive manufactured composites reinforced with continuous fibres.  In this investigation, the translaminar fracture toughness of 3D-printed continuous fibre reinforced polymer (c-CFRP) composites was characterised using double-tapered compact tension (2TCT) specimens. The 2TCT geometric dimensions were obtained through a parametric study to prevent undesired failure modes. The results show a translaminar fracture toughness of 17.4 N/mm for the tested 0/90 laminates. The fracture toughness corresponding to the tensile failure of the 0° ply was derived using a rule-of-mixtures approach. Post-mortem micrographic and X-ray analysis indicated the presence of fibre pull-outs in the crack surface and confirmed the absence of any additional damage, validating the use of 2TCT geometry for the determination of the translaminar fracture toughness in additively manufactured c-CFRP composites. 

Abstract

In recent years, the aerospace industry has seen significant advancements thanks to the incorporation of composite materials, which enable the design of lighter structures with excellent mechanical properties. However, the manufacturing process of these composites remains difficult to monitor and still lacks proper standardization. This has led to the need for the development of intelligent control technologies that can be implemented to efficiently oversee the production cycle. In this work, a detailed analysis of the various stages involved in the infusion-based manufacturing process of composite parts has been carried out, identifying weaknesses and defects that may arise during production. The technology developed aims to implement a wireless monitoring system using ferromagnetic microwires embedded in structural composite components, with the goal of improving process control and reducing potential errors. Although the knowledge gained from this project is focused on a specific manufacturing process, the results obtained could be extrapolated to other sectors operating under similar conditions. In this way, the quality and added value of the parts produced with this technology are enhanced, ensuring compliance with the stringent demands of the market.

Abstract

The use of carbon fiber (CF) has increased in the last decade, shifting from the aeronautical sector to the leisure and automotive sectors. CF production requires high energy consumption and emits large amounts of CO₂. This increase in consumption generates a greater amount of CF composite waste, which must be properly managed to give it a second life. Deremco project aims to transfer and increase the TRL of different recycling technologies for composite from the wind and aeronautical sectors. The companies IDEC, BIRZIPLASTIK, and TECNALIA have focused on the recovery of post-production waste from the aeronautical sector to obtain recycled CF (rCF) through a thermochemical process. IDEC proposed the horizontal stabilizer  of an aircraft's as a use case. This secondary structure requires a lower level of mechanical properties, so the introduction of rCF has proven feasible. BIRZIPLASTIK proposes developing a thermoplastic formulation with high technical requirements for automotive applications. Two formulations have been developed that meet these requirements, one of which is 100% recycled material. To carry out these success use cases, TECNALIA has worked on optimized the rCF sizing processes and integrating it into the compounding and Resin Transfer Molding (RTM) processes.