Abstract

In this work the development of a profile manufactured by pultrusion and thereafter curved by thermoforming is presented. The pultrusion profile is based on a new thermostable epoxy resin with dynamic bonds capable of being reprocessed, repaired and recycled thanks to the incorporation of reversible links within its reticulated structure (3R Technology). Being a resin that contains dynamic bonds, the cured composite shows unexpected properties for thermosetting materials.

In a first phase, a new resin/hardener formulation processable by pultrusion with a viscosity, adhesion to the fibre and speed of curing similar to a conventional formulation have been developed and in a second phase, taking into account the properties of the new composite material, the parameters of the thermoforming process (pressure, temperature or speed of thermoforming) have been analysed and optimized.

Thanks to the combination of pultrusion and thermoforming processes, longitudinal 3R composite profiles acquire a new curved geometry defined by the design of a mould. In this way, the thermoforming of the straight profiles will allow manufacturing curved parts from profiles of thermostable composites with high mechanical performance manufactured by pultrusion in medium-high rates, typical of the automotive sector. Additionally, it will be shown that the profiles manufactured using these composites can be recycled, reducing the amount of waste generated and offering these materials a second useful life.

Abstract

The demand for lightweight and high-strength materials across various industries has driven research into hybrid structures that combine the mechanical advantages of metals with the low weight and strength of carbon fiber-reinforced composites. The use of thermoplastic composites additionally enables disassembly and reuse at the end of the service life. Furthermore, the metal-composite joining process and the thermoplastic CFRP processing could potentially be achieved in a single step, resulting in reduced manufacturing cycle times and overall higher productivity.

However, several challenges must be addressed, such as differences in the coefficients of thermal expansion, the influence of the composite processing parameters on the metallic material and its surface treatment, and the potential formation of galvanic couples.

This study investigates different manufacturing methods for dissimilar or multi-material joints: automated fiber placement (AFP) and thermoforming. A comparison is presented based on the manufacturing parameters, which were adjusted to maximize joint strength for each process.

A cross-sectional optical microscopy analysis was carried out to evaluate the joint interface and the interaction between the surface treatment and the thermoplastic resin matrix layer, which is responsible for the adhesive bond between both components.

In addition, mechanical testing was conducted to assess the influence of processing parameters, establishing a joint design route for optimized performance evaluation.

The conclusions demonstrate that the polymer layer at the interface plays a key role in compensating for differences in thermal expansion coefficients, leading to enhanced mechanical performance of the joint. The advantages and limitations of each manufacturing method are discussed in this work.

Abstract

El futuro del sector aeronáutico está orientado a fabricar estructuras y componentes más ligeros y rentables, empleando materiales y tecnologías más ecológicos que permitan reducir costes, peso y consumo de combustible con ciclos de fabricación más cortos, a la vez que se aumenta la eficiencia energética en la fabricación. En este contexto surge el proyecto AEROPLAS, con el objetivo de contribuir al proceso de fabricación avanzada de composites termoplásticos utilizando tecnologías de bajo coste para la industria aeronáutica. En el presente estudio se abarca la sustitución de piezas aeronáuticas fabricadas actualmente en composite termoestable por composite termoplástico, en dos componentes reales: panel de cubierta y puerta de acceso del carenado ventral del A350, empleando dos materiales de distinta calidad: un semipreg de LM-PAEK/CF (TenCate Cetex® TC1225) y un prepreg de PC/CF (ePreg245CHT/PC40). Mediante diseño y cálculo, se han obtenido los apilados y espesores de pieza necesarios para cubrir los requerimientos estructurales de ambos componentes, a partir de los datos obtenidos de la caracterización de los materiales de partida. Se han estudiado y comparado dos procesos de fabricación para la obtención de las nuevas piezas, seleccionando el termoformado y la estampación como los más prometedores. Por último, se ha llevado a cabo la caracterización de las piezas obtenidas mediante ensayos no destructivos (inspección visual, verificación por ultrasonidos, inspección dimensional mediante laser tracker) y destructivos (tracción en sentido plano [AITM1-0066], resistencia al aplastamiento [AITM1-0009], resistencia a tracción del laminado [AITM1-0007], resistencia a tracción de unión atornillada [AITM1-0067]).