Abstract

The present document describes a new concept of composite fuselages manufacture, oriented towards the minimization of manufacturing costs through the generation of a monocoque fuselage structure, that allows to reduce the number of rivets and also the components joining operations, by means in addition of a process that avoids the use of molds, finally producing a lightweight and adaptable structure. The process in turn facilitates a high level of automation in the manufacture of composite fuselages and opens the door to a greater acceptance of this application in the aeronautical sector. The document outlines the design of the manufacturing process and the implementation of that particular production process for the manufacture of a real-scale concept demonstrator within the MTorres facilities, showing the reduction of the production cycle and the general manufacturing costs based on the simplification of the structural design and the integration of components into just one piece. Other additional variables that can benefit the reduction of costs and cycle times of the production process are also evaluated.

Abstract

Carbon fibre reinforced composite materials show potential as energy storage components, due to the high electric conductivity of the carbon fibre. Supercapacitors store electrostatic energy over the electrode surface. Increasing the surface area of electrodes based on carbon fibre could lead to an increase in storage capacitance.

Different methods to increase surface area of carbon fibre are studied with the aim of increasing energy storage capacitance of the fibres working as electrodes for structural electrochemical capacitors. Surface modification was carried out by the deposition of carbon nanoparticles (GNP) and porous carbon (CAG). Effectiveness of the different methods was analysed by measurements of BET surface area and microscopy characterisation. The effect on mechanical properties of individual fibres was analysed and storage capacitance was measured by electrochemical characterisation.

Abstract

Reducing the environmental impact of composite materials by using new matrices and fibres, as well as a manufacturing process that allows obtaining high-quality standards, is on the strategic agenda of academia and industry. Replacing thermosetting matrices with thermoplastics is a challenging vector for improvement, facilitating recycling. Regarding the fibres, natural fibres of mineral origin, such as basalt, reduce the ecological footprint in the raw material extraction phase. Characterising the impact behaviour of these new composites is necessary to identify potential applications. Otherwise, direct comparison with reference materials is essential since differences in the manufacturing process, fibre content, or test conditions make it impossible to put the new material in context. In this paper, we compared the impact properties of two thermoplastic-matrix (pCBT) composites manufactured using resin transfer moulding (RTM). On the one hand, as a reference material, the pCBT is reinforced with carbon fibres, and on the other hand, with basalt fibres. The results are better for the composite reinforced with basalt fibres, regardless of whether the properties are compared in absolute terms (×2.2), in weight reduction (×1.8) or in reduction of energy consumed during the primary production of the fibres (×4.4). 

Abstract

Many manufacturing processes for composite material structures are based on large and expensive facilities that result in slow, expensive, and energy-inefficient processes. The preforming of dry fiber fabrics, for example, is carried out in large hot drape forming facilities, where conventional heating sources based on infrared lamps are not very efficient, since much of the heat supplied is transferred to the heavy aluminum molds in which the preforming process is carried out. In the current context in which it is essential to reduce the carbon footprint of each component, it is essential to reduce the energy needed in production processes and at the same time achieve competitive cycle times. 

In this context, Tecnalia has been working for years on the direct resistive heating technology in order to accelerate and optimize composite material manufacturing processes. The direct application of a current to the carbon fiber material to be processed has the advantage of avoiding the heating and cooling of the molds or other adjacent tools, obtaining the results much more quickly and efficiently than with the methods used until now. In the case, for example, of the preforming process of carbon fabrics, applying heat only to the preform allows reducing cycle times and energy consumption by more than 60% and 80% respectively. This means reducing the cost of the process related to lower energy consumption and shorter cycle time. The quality of the preforms obtained through resistive preforming is the same to that obtained through conventional hot drape forming technology and, in addition, it is a repetitive process that has been validated in industrial manufacturing environment.

The article also indicates that this direct resistive heating technology is not only applicable in carbon fiber preforming processes but could also be used in other manufacturing processes for composite material components.

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

An analytical and experimental study of flexural testing on laminates formed by layers of unidirectional carbon-fibres pre-impregnated with an epoxy resin is presented. Among other stacking sequences, the configuration comprised by groups of ±45° is of interest in the transport industry in which often there are structural parts subjected simultaneously to bending moments and shear forces. Having as a reference the three-point flexural testing, the work is focused on taking into account the different response of the material under tensile and compressive loads. From the experimental point of view, the damage initiation and evolution of the material are proposed to be visualized by means of optical methods and microscopy techniques, comparing the experimental observations with the analytical estimations. The analytical model used is based on the technique of homogenized section and it allows to predict the initial failure mode that will occur experimentally depending on the thickness of the specimen.

Abstract

Thermostable matrix are extensively used in structural components because of their good mechanical properties [1]. The region of stability of these polymers is defined by the glass transition temperature (Tg) [2]. The typical service temperature of these materials should be lower than Tg but in some cases operating temperatures can exceed Tg which causes a variation in the properties of the polymer and consequently, modifies the mechanical properties of the composite material [3]. Therefore, it is important to understand the effect of temperature on the failure mechanisms that occur in the material in order to ensure stability and durability [4,5]. The objective of this work was to evaluate the effect of temperature and time of exposure on the mechanical properties of carbon/epoxy composites. For that purpose, samples were aged at different temperatures and periods of time and then, impact and flexural tests have been performed. It was observed that thermal ageing caused notable variations in the glass transition temperature of the epoxy resin. In consequence, two different effects were observed: in most cases, thermal ageing causes a reduction on the mechanical properties of the composites due to the thermo-oxidation of the epoxy resin and the loss of adhesion in the matrix/fibre interface, especially at higher temperatures; however, at temperatures below the Tg, there is an increase of the maximum strength because of a post-curing effect. [1] E. Selver, P. Potluri, C. Soutis, Impact damage tolerance of thermoset composites reinforced with hybrid commingled yarns, Compos. Part B 91 (2016) 522-538. [2] E. Ernault, E. Richaud and B. Fayolle, Origin of epoxies embrittlement during oxidative ageing, Polymer Testing 63 (2017) 448-454 [3] A. Mlyniec, J. Korta, R. Kudelski and T. Uhl, The influence of the laminate thickness, stacking sequence and thermal ageing on the static and dynamic behaviour of carbon/epoxy composites, Composite Structures 118 (2018) 208-216 [4] A. P. C. Barbosa, A. P. P. Fulco, E. S. S. Guerra, F. k. Arakaki, M. Tosatto, M. C. B. Costa and J. D. D. Melo, Accelerated ageing effect son carbon fibre/epoxy composites, Composites Part B, 110 (2017) 298-306 [5] S. Marouani, L. Curtil and P. Hamelin, Ageing of carbon/epoxy and carbon/vinylester composites used in the reinforcement and/or the repair of civil engineering structures, Composites Part B, 43 (2012) 2020-2030

Abstract

El proyecto ECO-CLIP se basa en una combinación de actividades de innovación orientadas a lograr piezas estructurales más ligeras a partir de los residuos de fábrica de TPC´s (Thermoplastic Composites), para la próxima generación de demostradores de fuselaje de aviación, que se lleva a cabo como parte de Clean Sky 2. En el proyecto se ha desarrollado un material polimérico compuesto de LMPAEK reforzado con un 40% en peso de fibra de carbono corta para la producción de Brackets. Con el fin de seleccionar la tecnología más ventajosa para la fabricación de estos, se ha llevado a cabo la comparativa de un método de fabricación convencional, como es la inyección, con una tecnología emergente, como es el FGF (Fused Granulated Fabrication). Para su comparativa se han llevado a cabo estudios de longitud y distribución de fibra, caracterización térmica y ensayos mecánicos, tanto para las probetas de inyección como en FGF. En esta última tecnología, además se ha llevado a cabo un estudio de parametrización de diámetros de boquillas con el fin de obtener la influencia que tiene en la adhesión entre capas, la longitud de la fibra, la microestructura de la pieza y la calidad final de las piezas.

Gracias a estos resultados se ha podido establecer una relación entre la naturaleza del refuerzo, las propiedades térmicas y los parámetros de fabricación, con las propiedades mecánicas en pieza final.

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.