Investigation of EMI Shielding in Carbon Black-Doped PLA Cellular Structures for Additive Manufacturing in UAV Applications

Sammanfattning

Recent years have shown an increasing need for low-cost, lightweight aerial systems across many sectors. As electromagnetic pollution and weaponized electromagnetic interference become more common, the ability to effectively shield onboard electronics against such disturbances has also become increasingly important. Many industries are becoming more dependent on 3D-printed solutions due to their cost-effective materials and rapid deployment capabilities. Different material types can be utilized to enhance structural strength or to tailor components for specific functional requirements. In particular, Carbon Black (CB)-infused filaments are used to make an otherwise non-conductive material, such as PLA, electrically conductive. This thesis aims to investigate whether this type of filament and production method can serve as a reliable solution for shielding against electromagnetic interference at 1,46 GHz, 1,60 GHz, and 1,73 GHz in Unmanned Aerial Vehicles (UAVs). To answer the research questions, an experimental study was conducted comparing standard PLA, CB-PLA, and PLA coated with galvanizing zinc spray. These materials were manufactured in two different thicknesses (3 mm and 6 mm) and with two infill patterns (gyroid and rectilinear). The results show that CB-PLA achieved the highest shielding effectiveness (SE), reaching nearly -20 dB at 1,46 GHz at 6 mm thickness. This corresponded to a specific shielding effectiveness (SSE) of up to -24 dB cm3g−1 or a SSE/thickness of up to -62 dB cm2g−1. The galvanizing zinc spray did not produce a measurable improvement over uncoated PLA, which could be attributed to its coating chemistry and application. The practical value of CB-PLA is dependent on the use case. In low-interference environments, simply using CB-PLA could pose to be a viable option to protect internal electrical components. However, in more demanding environments, CB-PLA as a standalone solution falls short. As a result, future work may explore alternative metal or EMI shielding coatings, different material compositions, and varied infill structures. Additionally, combining conductive filaments such as CB-PLA with conductive coatings may offer improved shielding performance, as suggested by previous research. The main contribution is a controlled comparison of three shielding strategies based on Commercial Off-The-Shelf (COTS) products in a UAV-relevant frequency band on standard FDM hardware, together with a documented negative result for galvanizing zinc spray and an independent confirmation of published SSE values for the same filament.