Abstract

El avance de la tecnología de impresión 3D ha permitido la creación de estructuras complejas con formas únicas, como los diseños basados en kirigami, inspirados en el arte de cortar papel para formar estructuras tridimensionales. Estas estructuras ofrecen beneficios significativos, como una construcción ligera, despliegue rápido y la capacidad de soportar cargas mecánicas y absorber energía de deformación. Sin embargo, existe una investigación limitada sobre el comportamiento de estas estructuras y sus conexiones críticas cuando se fabrican con materiales compuestos mediante técnicas de impresión 3D.

Este estudio examina las propiedades mecánicas de estructuras kirigami impresas en 3D y sus conexiones, centrándose en mejorar el comportamiento de unión y optimizar el uso del material. Se emplea el marco Space Mapping para abordar la anisotropía inherente de los compuestos impresos en 3D, transformando el comportamiento direccional complejo del material en un dominio isotrópico equivalente. Este enfoque permite aplicar modelos no lineales isotrópicos ya consolidados, mejorando la precisión de la simulación y reduciendo el coste computacional.

Se utilizan simulaciones por elementos finitos para modelar el comportamiento de las estructuras kirigami, prestando especial atención a las propiedades del material, la adhesión entre capas, la dirección de impresión y la orientación de las fibras en el material compuesto. Se llevan a cabo ensayos mecánicos para validar las simulaciones, centrándose en la rigidez y resistencia de los pliegues y uniones bajo diferentes condiciones de carga. Mediante la mejora de los mecanismos de plegado y la optimización de la distribución del material en las zonas críticas, esta investigación busca demostrar cómo se comparan las estructuras kirigami frente a los diseños sólidos tradicionales en aplicaciones que requieren tanto resistencia como adaptabilidad.

Estos resultados son especialmente relevantes para sectores donde se necesitan diseños ligeros y flexibles, como la aeronáutica, la automoción, el transporte marítimo y la ingeniería civil. Combinando análisis numérico con validación experimental, el estudio ofrece aportaciones valiosas para la optimización de los puntos de plegado y conexión en estructuras kirigami impresas en 3D, con vistas a su aplicación en la ingeniería avanzada.

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

Thermoplastic composites are becoming increasingly important in the automotive industry due to their high strength-to-weight ratio, recyclability and cost-effectiveness. Within these composites, continuous fibre-reinforced composites offer superior mechanical properties than discontinuous fibre-reinforced composites, but their design flexibility is limited. In contrast, discontinuous fibre composites allow more complex geometries. A promising approach to overcome these limitations and improve composite components is hybrid manufacturing, which integrates multiple manufacturing techniques. In this work, we have studied the feasibility of combining the additive manufacturing of composites with continuous glass fibre (cAM) and the forging of thermoplastic materials reinforced with discontinuous fibre (GMT). A topologically optimised cAM reinforcement has been inserted into forged GMT omega profiles. The results of microscopic analysis have confirmed that there is adequate compaction between the hybridised materials. Furthermore, the results of numerical simulations replicating a three-point bending test have demonstrated the potential of cAM as a local reinforcement in forged components, as the specific stiffness of the hybrid beams was increased by up to 42%. This hybridisation technique represents a significant advancement towards the development of innovative solutions in thermoplastic composite processes, with the potential to produce lighter, stronger components adapted to complex geometries.

Abstract

Manufacturing composite materials by conventional methods is known to be costly as it requires many steps, equipment and tooling. The challenge this presents can benefit from the moldless approach and rapid, automated prototyping enabled by additive manufacturing. Today, additive technologies are changing the manufacturing processes of plastics and composites, allowing short series to be automated and scalable for adaptation to long series, always oriented to final part production. In addition, the mechanical limitations presented by 3D printing processes of polymeric materials have been enhanced by the reinforcement of short or continuous carbon and glass fibers, mainly. Moreover, the hybridization of additive technologies with conventional processes makes it possible to overcome their current limitations, taking advantage of many of their benefits and increasing the fields of application.

In this context, the idea of developing a technology that allows obtaining intermediate parts or preforms with high geometric complexity, which require a subsequent process, such as resin transfer molding (RTM), that confers mechanical performance similar to that of composites. In this work, an alternative method of manufacturing carbon fiber reinforced preforms using an additive process based on Fused Fusion Deposition Modeling (FDM) is detailed, as well as the production of composites from these preforms. Thus, the 3D preform is manufactured from fiber filaments coated with a thermoplastic binder. Then, this preform is subjected to a thermosetting resin injection process in a mold to obtain the final composite. In summary, a new method of additive preforming in combined with RTM is proposed to manufacture carbon fiber reinforced polymer composites (CFRPC).