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

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.