Monitoring structural information in 3D printed parts and products.
Self-sensing is the ability of a material to sense its own condition. The material itself is used as a sensor. Advantage is that you don’t need an implanted or attached sensor system. The costs are lower, the durability is higher, the sensing volume is bigger and the mechanical property loss is lower.
Polymer-matrix composites, containing continuous carbon fiber, are known materials that have self-sensing capabilities based on measurable changes in electrical resistance of the continuous fibers. For example, a self-sensing composite was used for damage detection in a cylinder made by filament winding. A standard continuous fiber composite manufacturing technique . The practical importance of such products can potentially be found in structural health monitoring in airplanes or critical parts of constructions like bridges.
Combining Additive Manufacturing and self-sensing
Brightlands Materials Center is combining the self-sensing of continuous fiber reinforced thermoplastics with fabrication by additive manufacturing. Additive manufacturing with continuous fibers enables very precise positioning and orientation of carbon fibers. The carbon fibers are placed at chosen locations inside the product that form an integral part of the structure. That means that the carbon fiber “sensors” are located where they are needed, and multiple fibers 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 fiber layout and material choice. This is specifically important for sensing, because carbon fiber has to stick out of the part to be able to make connections to the monitoring electronic hardware.
100% Limburg Bike Project
Damage detection by self-sensing in 3D printed bike frame lugs is part of the “100% Limburg Bike” project in which Brightlands Materials Center 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 fiber reinforced thermoplastics can help gather important information
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 fober 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.
Brightlands Materials Center
Brightlands Materials Center is an independent research center founded by TNO and Province of Limburg. It supports innovation in industry and has a strong application focus. We offer dedicated contract research and participation in our research roadmap on 3D printed self-sensing fiber reinforced thermoplastics.
 Journal of Intelligent Material Systems and Structures, vol 17, 57, 2006.
 More info on 100% Limburg Bike Project .