Reclaimed Timber and Timber Composites are becoming vital for complex building applications. Traditionally, high-volume timber production relies on uniform timber grades. However, previous consortium projects have demonstrated the potential of using the unique properties of individual timber pieces to manage the hygroscopic behavior of building elements or to broaden the range of wood qualities suitable for timber beams. This approach strategically places materials based on local performance requirements, allowing for the inclusion of large quantities of low-quality timber typically discarded or burned.
A key obstacle is the accurate identification of individual timber qualities through nondestructive technologies. Traditional grading often categorizes timber into broad classes with significant variations in properties, primarily focusing on strength due to its high unpredictability, rather than stiffness, which is more crucial for timber construction. In response, RAW is developing methods to utilize reclaimed timber for innovative Glue Laminated Timber (GLT) assemblies. These methods leverage specific material data obtained via non-destructive testing and incorporate performance predictions from our resource-driven, non-prescriptive design model to optimize the use of diverse timber grades effectively.
Among the diverse group of fast-growing fibers, flax and hemp stand out as successful raw materials for creating composite semi-finished products and yarns. Hemp, in particular, is one of the fastest-growing plants globally, capable of reaching heights of 4 meters within just 100 days. It is also highly efficient at sequestering carbon, with a single hectare of hemp able to absorb between 8 to 22 tonnes of CO2 annually. The quality of the extracted hemp fiber is influenced by several factors including the cultivation location and type, variety of hemp, timing of the harvest, processing methods, and the weather conditions throughout the growing season.
Hemp has several advantages over flax; it is simpler to cultivate organically, yields more biomass per hectare, and does not compete with food production—instead, it produces both nutritious seeds and fibers. Given its widespread cultivation across Europe, there is significant variability in hemp's raw material quality, which is further influenced by farming practices, particularly in pesticide-free and fertilizer-free organic agriculture. This variability impacts not only the fiber's quality but also its availability, as hemp cannot be repeatedly grown on the same plot each year without degrading the soil.
Traditional methods like single fiber tensile testing in a dry state often fail to provide accurate results due to the high variance in fiber characteristics, as demonstrated by preliminary experiments by UIBK in the Alpenhanf 360° network. Conversely, tensile testing and advanced imaging techniques such as CT and X-ray scans of embedded fibers (in composites or yarn) have produced more reliable data, allowing these characteristics to be effectively correlated with initial growth and processing conditions.
Fiber winding systems, which create composites from fibers and binders or rely solely on fiber-friction mechanisms, are highly efficient in resource utilization. Advances in computational design and fabrication have transformed traditional homogeneous textile systems into additively fabricated, graded systems. This innovation allows for variations in fiber density, type, and interfaces to be tailored to local requirements for optimal performance. For instance, the Coreless Fiber Winding technique developed by ICD/ITKE showcases this method's capabilities. However, these systems face challenges when transitioning from synthetic, high-performance fibers and fossil-based resins to bio-based materials. For example, the livMatS Pavilion demonstrated that each batch of fibers requires manual adaptation, often necessitating double the material usage to compensate for variability and uncertainties in fiber strength. RAW aims to innovate on-the-fly adaptations for fiber-based fabrication processes, integrating novel strain sensors in fiber winding machines and fiber-optic sensors (FOS) in the wound structures. This setup allows for high-resolution strain data assessment at the scale of individual fiber bundles, correlating this data with the stress distributions of the designed structure to optimize material stiffness through non-destructive testing methods.
Agricultural Waste - Biopolymer 3D Printing. Biopolymer composites, derived from biodegradable waste materials, are being explored for their potential in robotic 3D printing for architectural uses, as demonstrated in prior work by the applicants. Although multi-material printheads can blend different biopolymer mixes during extrusion, the performance of these mixes greatly depends on the consistency of the source materials, typically limiting use to highly refined inputs from food (like collagen) or agricultural products (like fibers).
To overcome this challenge, RAW is developing a 3D printing system designed to accommodate the variability of waste-sourced biopolymers. This system will feature continuous in-line monitoring to assess the rheological performance of the feed mixture, enabling adjustments in real-time to ensure optimal printing outcomes.
Coordinator: Martin Tamke, martin.tamke@kglakademi.dk
Media: Wendy Wuyts, wendy@omtre.no
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Funded by the European Union (Project Number 101161441). Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or the European Innovation Council (EIC). Neither the European Union nor the granting authority can be held responsible for them.
