Parametric study of piezoresistive structures in continuous fiber reinforced additive manufacturing

• Published in: Composites Part C: Open Access
• Main Authors: Tim Heitkamp, Marijn Goutier, Karl Hilbig, Simon Girnth, Nils Waldt, Günter Klawitter, Thomas Vietor
• Format: Article
• Language: English
• Published: Elsevier 2024-03-01
• Subjects: Continuous fiber; Fiber reinforced additive manufacturing; 3D printing; Design for additive manufacturing; Resistive sensors; Material extrusion
• Online Access: http://www.sciencedirect.com/science/article/pii/S2666682024000021

Recent advancements in fiber reinforced additive manufacturing leverage the piezoresistivity of continuous carbon fibers. This effect enables the fabrication of structural components with inherent piezoresistive properties suitable for load measurement or structural monitoring. These are achieved without necessitating additional manufacturing or assembly procedures. However, there remain unexplored variables within the domain of continuous fiber-reinforced additive manufacturing. Crucially, the roles of fiber curvature radii and sensing fiber bundle counts have yet to be comprehensively addressed. Additionally, the compression-sensitive nature of printed carbon fiber-reinforced specimens remains a largely unexplored research area. To address these gaps, this study presents experimental analyses on tensile and three-point flexural specimens incorporating sensing carbon fiber strands. All specimens were fabricated with three distinct curvature radii. For the tensile specimens, the number of layers was also varied. Sensing fiber bundles were embedded on both tensile and compression sides of the flexural specimens. Mechanical testing revealed a linear-elastic behavior in the specimens. It was observed that carbon fibers supported the majority of the load, leading to brittle fractures. The resistance measurements showed a dependence on both the number of sensing layers and the radius of curvature, and exhibited a slight decreasing trend in the cyclic tests. Compared with the sensors subjected to tensile stress, the sensors embedded on the compression side showed a lower gauge factor.