Abstract

Debonding between plies, or delamination, is a critical failure mechanism for laminated composite materials and has been analysed in several scientific investigation. Usually in real applications delamination initiates and propagates between interface layers with different reinforcement orientation. However, most of the experimental works are carried out using unidirectional specimens for determining the interlaminar fracture toughness because in laboratory conditions it is difficult to propagate the crack between multidirectional interface layers without other failure mechanisms that invalidate the test. Among these failure mechanisms, crack plane migration and crack branching at several planes are the most common. In this communication it will be detailed and analyzed the experimental characterization of the interlaminar fracture toughness in multidirectional interfaces of 3D-printed composite materials is detailed, including the manufacturing process of the Double Cantilever Beam (DCB) specimens that warranty crack propagation under pure mode I loading and without plane migration. Finally, a quantitative comparison is carried out between multidirectional interlaminar fracture toughness and the unidirectional one and a fractography analysis is reported.

Abstract

Carbon fibre matrix composites are consolidated in high-demanding industries such as aeronautics and aerospace. Nowadays, thermoset composites are fully integrated on several new aircrafts in production. However, thermoplastic composites are progressively emerging as a better solution due to their end-of-life recyclability and optimized manufacturing process. One of the processes used to manufacture final parts from thermoplastic composite materials is press-moulding, in which a high-temperature heating system is combined with the application of pressure at high speeds. This article studies the optimization of press-moulding process in combination with an Additive Manufacturing (AM) produced metallic mould core. The aim of this study is the manufacturing of a thermoplastic aeronautical part, that would be submitted to real-world performance test. For the press-moulding process, a high-temperature infrared heating system was designed, supported by thermal oil mould heating, this heating system was combined with a mould-pressing process by integrating the system in a commercial injection machine. Regarding the AM tooling, produced by Wire Arc Additive Manufacturing (WAAM) process, was designed to reduce tooling weight, and optimise thermal cycle. Moreover, manufacturing data from WAAM tooling was recorded and compared with that obtained from a symmetrical conventional manufacturing made mould. The analysis shows savings in terms of material and energy consumption, as well as cycle times reduction. The final part metrology study shows indistinguishable results between the press-moulding process carried out using the WAAM tooling and that manufactured through conventional methods.

Abstract

Guided wave-based structural health monitoring (SHM) systems using piezoelectric sensors for composite parts face challenges due to the weight of copper wiring. This study developed lightweight, 3D-printed conductive paths using silver ink (Dycotec Materials) and epoxy (Epolam 8052) doped with carbon nanotubes (CNTs) and graphene nanoplatelets (GNPs). The inks were characterized for their weight and conductivity with a Keithley 2410. Following which they were evaluated for signal transmission of guided waves and easy integration with induction heating. Nanoparticle-doped epoxy inks demonstrated increased viscosity and controlled circuit dimensions, though dispersion issues led to voids and agglomerates. Unmodified silver inks did not show good printing quality; however, the quality was improved significantly with the adding of GNPs. Circuits from both inks were evaluated for conductivity and signal transmission. Silver inks achieved conductivity levels comparable to copper and effective signal transmission, while nanoparticle-doped epoxy had significantly lower conductivity and signal loss (2-3 times), even at its best formulation. A lightweight film integrating silver circuits was successfully bonded to a composite panel using induction heating, demonstrating a rapid integration method for SHM systems. These findings highlight the potential of metallic and nanoparticle-doped inks to replace traditional copper wiring, offering significant weight reduction, and easier integration capabilities for SHM applications.

Abstract

One of the most critical challenges in the aerospace industry is the mismatch in the coefficient of thermal expansion (CTE) between optical components in satellites and their metallic supports, which limits system reliability and performance. Ceramic materials, due to their superior thermal properties, offer a potential solution; however, their adoption has been limited by the complexity of their geometries and conventional manufacturing constraints. Additive manufacturing has opened new opportunities for the development of advanced ceramics, including ceramic matrix composites (CMCs). Within the framework of the AERORECORD-3D project, funded by the Spanish Ministry of Science and Innovation, ceramic cordierite-based supports reinforced with reduced graphene oxide (rGO) have been developed for aerospace applications. In this study, cordierite nanocomposites with varying rGO contents were successfully fabricated via 3D printing. Their thermal, electrical, and mechanical properties were evaluated to assess their performance, exploring their potential as advanced materials for demanding space applications. This work represents a significant step toward the implementation of 3D-printed ceramic nanocomposites by combining innovative materials with advanced additive manufacturing technologies.

Abstract

Thanks to the wide range of available cores and skins, the design and manufacture of sandwich structures allows for many variations, but conventional manufacturing processes limit design freedom when it comes to geometries. In recent years, interest in sustainable materials, such as plant-based resins and natural fibres, has grown. Furthermore, recent advances in 3D printing have opened up new design possibilities, including the use of biodegradable foams and functionally graded structures. This study presents the development of a 1:6 scale car bonnet, where the skin is made of bio-epoxy resin reinforced with flax fibre and the core is a PLA foam produced via additive manufacturing. Two variants were considered: in the first, the core was distributed homogeneously across the entire bonnet surface, and in the second, it was distributed in areas selected through topological optimisation simulations. As both bonnets have the same mass, the density of the homogeneous bonnet had to be lower. This was achieved by programming different 3D printing parameters. Quasi-static load test results show that the bonnet with the optimised distribution is 25% stiffer. The study's main conclusion is that manufacturing cores using 3D-printed foamed PLA enables a wide range of densities and design possibilities that are not feasible with conventional materials and manufacturing processes.

 

Abstract

By 2050, 68% of people will live in urban areas, which will create increasing pressure on the mobility infrastructure, increasing certain problematic aspects of cities. As cities get bigger, efficient, and sustainable urban mobility will become a major challenge. To address this problem, it is fundamental to be able to design cities taking into account the 3 possible dimensions, and to develop technologies that allow the air mobility of both goods and people. Drones are seen as a medium-term solution to these problems.

A drone has been manufactured using a Composites 3D printer. The design of the unmanned aerial vehicle (UAV) has been carried out and the manufacture of the different elements using long and short carbon fiber, looking for the configuration that provides the best combination of mechanical properties with a lower weight of the drone.

Extensiometric gauges are designed and printed on a flexible substrate using a combination of conductive and dielectric inks and the gauges are embedded in the composite during the manufacture of the pieces. These embedded gauges allow monitoring the flexion produced in flight of the drone frame, monitor bumps and defects during the useful life of the drone and increase the functionalities of the UAV without increasing the weight of the same and the number of elements.

Likewise, the conventional wiring has been replaced by printed wiring making the connections between the motors and the speed controllers.

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

The manufacture of curing tools for composite materials using 3D printing represents an innovative, rapid, and economical solution, especially for small production runs. It is an efficient alternative to traditional machining, although its influence on the mold must be known. A method for manufacturing high-temperature laminating tools is proposed, based on a 3D printed model and short fiberglass-reinforced epoxy resin, which allows its use at temperatures up to 160 °C. The influence of the tool will be studied through a dimensional analysis of the geometric variations of the model throughout each stage, from 3D printing to the post-curing required for working at high temperatures. The results of this analysis will be discussed and will allow the development of compensation techniques to minimize deviations between the final part and the nominal geometry and the reduction of residual stresses to improve the precision and repeatability of the process.