Accurate flow measurement is a ubiquitous task in fields such as industry, medical technology, or chemistry; it remains however challenging due to small measurement ranges or erosive flows. Inspiration for possible measurement methods can come from nature, for example from the lateral line organ of fish, which is comprised of hair cells embedded in a gelatinous cupula. When the cupula is deflected by water movement, the hair cells generate neural signals from which the fish gains an accurate representation of its environment. We built a flow sensor mimicking a hair cell, but coupled it with an optical detection method. Light is coupled into a PDMS waveguide that consists of a core and a cladding with a low refractive index contrast to ensure high bending sensitivity. Fluid flow bends the waveguide; this leads to a measurable light loss. The design of our sensory system allows flow measurement in opaque and corrosive fluids while keeping production costs low. To prove the measurement concept, we evaluated the light loss while (a) reproducibly bending the fiber with masses, and (b) exposing the fiber to air flow. The results demonstrate the applicability of an optical fiber as a flow sensor.

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Due to their potential of decreasing weight and emission, the importance of lightweight designs with carbon fibre reinforced polymers (CFRP) in the aeronautic and automotive industry is increasing constantly. However, the formation of cracks and delaminations is one of the most prominent failure mechanisms during mechanical loading of CFRP, significantly influencing the material’s behaviour. The effects range from no effect on the structure up to complete failure of the part. In order to assess the severity of the effects, a profound knowledge of the origin of delamination initiation, its evolution and dimension of delaminations is indispensable. To display the inner structures of the specimen, X-ray computed tomography (XCT) leads to three-dimensional images of the specimen under investigation. In a multiscale XCT approach, beginning with a lower resolution, a visualization of the position and, to a lesser extent, the dimension of the delamination can be obtained over the entire volume of the specimen. A detailed visualization of the initiation and propagation of delamination at stepwise increased loadings of the specimen is obtained with higher resolution measurements. With the aid of a simple wooden in situ loading setup, the whole process of delamination initiation and growth over a certain displacement can be monitored. These two approaches in combination with certain loading stages allows a detailed description of the performance of the specimen under load.