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With the use of natural fibers as a substitute for synthetic reinforcements, a significant contribution towards advanced ecological and efficient lightweight structures can be made. Within this article, the polyurethane (PUR) spray coat method is used for the manufacture of natural fiber-reinforced composites based on the fiber materials linen and hemp. Both the investigation of the mechanical properties and the yarn impregnation, as a reference for the composite quality, are of major interest and help to evaluate the potential of these bio-based materials as a contribution towards advanced lightweight components.

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Over the last decade, carbon fibre-reinforced composites (CFRP) are increasingly used as lightweight material for various industrial applications. Due to the anisotropic material structure and its corresponding properties, novel design concepts and processing technologies were developed to further harness the material inherent lightweight potential. However, the material degradation in long-term use and failure behaviour is still considered a challenging issue for material scientists and engineers in particular. Therefore, concepts for structural health monitoring and their suitable implementation is still a major research topic. Among others, one solution uses the conductivity of carbon fibre yarns and their suitability to act as in-situ strain sensors. In the present work, the measurement principle bases on the usage of the piezo-resistive effect, meaning that every mechanical strain of the roving filaments causes a correlative change of the measurable electrical resistance. Since, these sensory elements need shielding from their surrounding carbon filaments of the composite structure, suitable fibre-based dielectric jackets have been developed with a wide range of suitable materials and textile processing technologies. In this contribution, the influence of the integrated carbon fibre sensors on the resulting mechanical performance of the composite structure is evaluated using an analysis of variances approach. Beyond that, the local composite morphology is analysed to evaluate the composite microstructure.