A team of researchers from the Brightlands Material Centre in the Netherlands have created self-sensing 3D printed composite parts which are able to monitor critical structures.
Self-sensing is the ability of a material to sense its own condition which means you don’t need an implanted or attached sensor system reducing costs while increasing durability and sensor coverage.
Polymer-matrix composites, containing continuous carbon fibre, are known materials that have self-sensing capabilities based on measurable changes in electrical resistance of the continuous fibres. For example, a self-sensing composite was used for damage detection in a cylinder made by filament winding. The practical importance of such products can potentially be found in structural health monitoring in aeroplanes or critical parts of constructions like bridges.
Brightlands Materials Center is combining the self-sensing properties of continuous fibre reinforced thermoplastics with fabrication by additive manufacturing. Additive manufacturing with continuous fibres enables very precise positioning and orientation of carbon fibres. The carbon fibres are placed at chosen locations inside the product that forms an integral part of the structure. That means that the carbon fibre “sensors” are located where they are needed, and multiple fibres could form a range of sensors throughout the part.
The concept was proven by Brightlands Materials Center by monitoring deformation in a simple bending beam and in a scale model of a pedestrian composite bridge. Both were printed with an Anisoprint A4 Composer which allows full freedom of the carbon fibre layout and material choice. This is specifically important for sensing because carbon fibre has to stick out of the part to be able to make connections to the monitoring electronic hardware.
Damage detection by self-sensing in 3D printed bike frame lugs is part of the “100% Limburg Bike” project in which the centre collaborates with amongst others Eurocarbon, CeraCarbon, Brightlands Chemelot Campus and Belgian Cycling Factory – known from racing bike brands like Ridley and Eddy Merkcx – and which is supported by the European Fund for Regional Development and the Province of Limburg in the OPZuid framework.
Self-sensing can also play a role in the design and prototype phase of new products or in replacing spare parts that are not available anymore. 3D printed self-sensing fibre reinforced thermoplastics can help to gather information about the real use circumstances. During a testing period, the self-sensing 3D printed part registers the real dynamics and forces that a product needs to withstand. This gives designers and engineers a clearer understanding of what requirements the 3D printed parts will have to meet. As a diagnosis tool, 3D printed self-sensing orthoses or protheses might guide patients and provide valuable information to doctors, regarding stress distribution and movement patterns.