In this study, silica glass, optical fiber Bragg gratings (FBGs) are used for torque-induced strain monitoring in carbon fiber reinforced polymer (CFRP) hollow shafts toward the development of a methodology for structural load monitoring. Optical fibers with gratings are embedded during shaft manufacturing, by an industrial filament winding process, along different orientations with respect to its central axis and surface mounted after production. Experimental results are supported by numerical modeling of the shaft with appropriate boundary conditions and homogenized material properties. For an applied torque up to 800 Nm, the strain sensitivity of an embedded grating positioned along the reinforcing fibers’ direction winded under 55° is in the order of 3.6 pm/Nm, while this value is more than 4× times higher than the other examined orientations. The study also shows that surface-mounted optical fiber Bragg gratings along the reinforcing carbon fibers’ direction perform equally well in monitoring strains in composite shafts under torque.

Combining additive manufacturing (AM) with carbon fiber reinforced polymer patched composites unlocks potentials in the design of individualized, lightweight biomedical structures. Arising design opportunities are geometrical individualization of structures using the design freedom of AM and the patient-individual design of the load-bearing components employing carbon fiber patch placement. To date, however, full exploitation of these opportunities is a complex recurring task, which requires a high amount of knowledge and engineering effort for design, optimization, and manufacturing. The goal of this study is to make this complexity manageable by introducing a suitable manufacturing strategy for individualized lightweight structures and by developing a digitized end-to-end design process chain, which provides a high degree of task automation. The approach to achieve full individualization uses a parametric model of the structure which is adapted to patients’ 3D scans. Moreover, patient data is used to define individual load cases and perform structural optimization. The potentials of the approach are demonstrated on an exoskeleton hip structure. A significant reduction of weight compared to a standard design suggests that the design and manufacturing chain is promising for the realization of individualized high-performance structures.

We present a ZnO out-cladding, overlaid optical fiber Bragg grating sensor, for the detection of vapors of common alcohols and acetone at concentrations lower than 25ppm, while operating at room temperature. The optical fiber sensing results indicate a chemostriction effect occurring in the ZnO layer when exposed to volatile organic compounds, which effect in turn induces shifts in the cladding, and most importantly, in the core confined, Bragg mode. The sensor exhibits maximum sensitivity of ~1pm/ppm to ethanol vapors, with exposure to other alcohol vapors (isopropanol and methanol) showing lower sensitivities; also, response to acetone vapors was traced at ~0.5pm/ppm. X-ray diffraction measurements of the ZnO nanolayer revealed that, in saturated ethanol vapors atmosphere, the poly-crystalline ZnO film undergoes a contraction by 0.6% of the interplanar distance corresponding to the (002) crystalline direction, denoting the chemostrictive effect through an underlying piezotronic mechanism. X-ray diffraction measurements and optical fiber sensing data are further correlated by numerical simulations carried out, so to study the strain interactions of the ZnO layer with the silica glass optical fiber.

Despite continuous efforts to improve the robustness of cardiac valve implants, neither bioprosthetic nor mechanical valves fulfill both hemodynamic and durability requirements. This study discussed novel flexible leaflet designs, focusing on polymeric materials with proven hemocompatibility, such as polyether ether ketone, of much higher stiffness than native tissue, aiming at optimal valve implants. A biomimetic valve with a single-curvature belly-curve (B-C) was used as a reference for new design variants with a double-curvature B-C with varying radii. Soft (13.2 MPa) and stiff (2.4 GPa) leaflet materials and different thicknesses were studied using lean simulations and in vitro experiments under physiologic hemodynamic conditions. The performance was assessed using opening pressure (OP) and orifice area (OA). The latter was determined by a newly developed automatized image processing tool. Experimental trends are in agreement with simulations and demonstrated that a buckling-inspired double-curvature leaflet design significantly enhances the trileaflet valve opening behavior, which is particularly advantageous for stiffer leaflet materials. Compared to the reference, the best-performing variant showed an OP improvement of 47% and 44% based on simulations and experiments, respectively. In contrast, the achieved mean pressure differential was directly comparable to state-of-the-art bioprosthetic valves. The OA was slightly reduced for new variants but still in the satisfying range. Graphic abstract