Through capturing spectral data from a wide frequency range along with the spatial information, hyperspectral imaging (HSI) can detect minor differences in terms of temperature, moisture and chemical composition. Therefore, HSI has been successfully applied in various applications, including remote sensing for security and defense, precision agriculture for vegetation and crop monitoring, food/drink, and pharmaceuticals quality control. However, for condition monitoring and damage detection in carbon fibre reinforced polymer (CFRP), the use of HSI is a relatively untouched area, as existing non-destructive testing (NDT) techniques focus mainly on delivering information about physical integrity of structures but not on material composition. To this end, HSI can provide a unique way to tackle this challenge. In this paper, with the use of a near-infrared HSI camera, applications of HSI for the non-destructive inspection of CFRP products are introduced, taking the EU H2020 FibreEUse project as the background. Technical challenges and solutions on three case studies are presented in detail, including adhesive residues detection, surface damage detection and Cobot based automated inspection. Experimental results have fully demonstrated the great potential of HSI and related vision techniques for NDT of CFRP, especially the potential to satisfy the industrial manufacturing environment. Index Terms-Hyperspectral imaging (HSI); non-destructive inspection; carbon fibre reinforced polymer (CFRP); H2020. I. INTRODUCTIONMany sectors, including aerospace, maritime transportation, sports, and civil engineering, use carbon fiber-reinforced polymer composites (CFRP) as structural materials because of its unique properties of lightweight, high stiffness/strength and damping resistance [1, 2], as illustrated in Fig. 1(a). Components and products based on composites often have a lifespan of fewer than 20 to 30 years, e.g. 20-25 years for a wind turbine [3], and 10 years on average for recreational boats and vehicle bodies [4]. End-of-life (EoL) CFRP waste management is becoming increasingly important due to the rapidly developing demand for composites in industrial manufacturing. Nowadays, landfilling is still the most common waste management technique, which is reasonably inexpensive,
Fiber‐plastic composites with a thermosetting matrix are considered to have only limited recyclability. Either the high density‐specific mechanical properties of the material are lost in the recycling process or the recycling processes are associated with very high costs, so that implementation is not economically worthwhile. A new approach is the reuse of continuous fiber reinforced laminate layers separated from a composite. In the present work, the extent to which laminate layers can be made separable from a thermosetting fiber‐plastic composite was investigated. The separation is based on the volume increase mechanism of thermally expanding particles (TEP) introduced into the polymeric matrix of a laminate layer. Heating leads to expansion of the particles. As a result, the laminates can be separated. Glass fiber reinforced epoxy resin laminates with TEP in the separating matrix layer were fabricated and tested using hand lay‐up techniques. Using the double cantilever beam test, it was determined that the force required for separation is drastically reduced with increasing TEP mass fraction. In addition, the extent to which the thermally expanding particles affect the mechanical properties of the laminates was tested. Through the 45° tensile test, it was determined that loads not parallel to one of the fiber directions have a negative effect on tensile strength and tensile stiffness.
For the reuse of components and structures made of fiber composite materials, a complete remanufacturing process chain is necessary to prepare the parts for a further life cycle. The first step is to dismantle the parts to be reused. Fiber composite components are mostly joined using adhesive technology, so that solution techniques are required for adhesive connections. One possibility is the separation of the adhesive layer by means of thermally expanding particles. Adhesive residues are removed by laser so that the components can be glued again after reprocessing. The decisive factor for which process is used for the remanufacturing of the components is the state at the end of the life cycle. Non-destructive testing methods offer a very good option for detecting damage, planning necessary repairs and direct reuse of damage-free components. Repairs to fiber composite structures have been carried out in aviation for a long time and are accordingly established. These processes can be transferred to the repair of automotive fiber composite components. Many technical solutions were developed and tested as part of the project. Future research work is aimed at further development, particularly with regard to the automation of the technologies in order to enable an industrial application of the recycling of automobile components made of fiber composites.
Cars designed for reuse are a novelty. The disassembly and remanufacturing of major vehicle structures is not an established process yet. This means new tasks and within that, new business models must be found to close the loop. New facilities and logistics are part of the process chain. In this chapter the processes will be outlined on basis of a car-sharing vehicle as an example of a fleet ownership. The reusable platform and the seat structure are the basis of this model-based consideration. The technical issues and obstacles will be discussed as well as economic and ecologic questions.
The design of reusable composite structures for cars needs high constructional effort. The car must be divided into separable modules meeting ecologic and economic requirements. Here, a battery containing platform and a seating structure were selected as large components with high potential for reuse. In a first step the desired car is described setting the basic scenario. A carsharing vehicle shows perfect conditions due to low logistics effort and the business model of the owner. This sets the boundary conditions for the design of the platform. Two different approaches were tested and merged into a concept ready for reuse. Simulations of the stiffness and the crash performance show good values. First large CFRP profiles were produced in a complex pultrusion process. An associated seating structure following similar design principles was constructed using profiles and nods. All load-cases that can occur during the utilization phase could be beared. Both modules together can form the basis of a reusable car. The design principles like detachable joints—in particular the utilization of detachable adhesive connections—can be adapted for any other technical composite product.
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