Suchergebnisse

Different polycarbonate materials have been reinforced with carbon nanotubes to tune electrical conductivity and to induce piezoresistive self-sensing capabilities. Further, the composites were processed by solvent casting and fused deposition modelling (filament for 3D printing) methods. An electrical conductivity percolation threshold of ≈0.3 wt.% has been found for solvent casted films, whereas samples processed by 3D printing show higher thresholds, ≈2 wt.%, presenting all samples a similar maximum electrical conductivity (σ ≈ 1 × 10−3 S m−1), thermal and chemical properties. Overall mechanical properties are larger for the solvent cast films concerning the 3D printed ones, particularly the elongation at break. The piezoresistive sensitivity, obtained after four-point-bending and uniaxial strain experiments, shows gauge factors up to 1.7, independently of the processing method. The functionality of the materials has been demonstrated by the implementation of an airplane wing section model with self-sensing capabilities. Two implemented strategies showed the suitability of the developed materials for real-time monitoring of the wing mechanical deformation. ; Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Funding UID/FIS/04650/2020 and projects UIDB/05549/2020 and TSSiPRO-NORTE-01-0145-FEDER000015. The authors thank the FCT for financial support under SFRH/BPD/110914/2015 (P. C.) and SFRH/BD/121780/2016 (B.F. G.) grants. Financial support from the Basque Government Industry and Education Departments under the ELKARTEK, HAZITEK and PIBA (PIBA-2018-06) ...

Lightweight and strong structural materials attract much attention due to their strategic applications in sports, transportation, aerospace, and biomedical industries. Nacre exhibits high strength and toughness from the brick-and-mortar–like structure. Here, we present a route to build nacre-inspired hierarchical structures with complex three-dimensional (3D) shapes by electrically assisted 3D printing. Graphene nanoplatelets (GNs) are aligned by the electric field (433 V/cm) during 3D printing and act as bricks with the polymer matrix in between as mortar. The 3D-printed nacre with aligned GNs (2 weight %) shows lightweight property (1.06 g/cm(3)) while exhibiting comparable specific toughness and strength to the natural nacre. In addition, the 3D-printed lightweight smart armor with aligned GNs can sense its damage with a hesitated resistance change. This study highlights interesting possibilities for bioinspired structures, with integrated mechanical reinforcement and electrical self-sensing capabilities for biomedical applications, aerospace engineering, as well as military and sports armors.

Self-injection locked oscillators have been recently proposed for motion sensing applications demonstrating a good experimental performance. Here a detailed investigation of the system dynamics is presented using a realistic model of the oscillator circuit under the injection of the reflected signal, which is phase modulated due to the target motion. The instability effects observed for some distance values are studied by means of a perturbation method and the results are validated through comparison with full circuit-level simulations and with measurements. The regular operation ranges are efficiently determined through a bifurcation analysis in terms of the distance to the target and the antenna gain. The modulation effect is analyzed with a reduced-order envelope transient formulation that copes with the accuracy problems associated with the small values of the modulation frequency. Very good agreement has been obtained with the experimental results. ; The authors would like to thank to Spanish Ministry of Economy and Competitiveness for their financial support under the research project TEC2014-60283-C3-1-R and Juan de la Cierva Research Program IJCI-2014-19141 and the Parliament of Cantabria for financial support under the project Cantabria Explora 12.JP02.64069.

This is the final version of the article. Available from the publisher via the DOI in this record. ; This paper presents an envisaged autonomous strain sensor device, which is dedicated to structural health monitoring applications. The paper introduces the ASIC approach that replaces the discrete approach of some of the main modules ; The SMARTER project is supported by European Union under the ERA-Net funding scheme of the FP7 (CHIST-ERA), and in the case of the spaniard partner through MINECO, reference PCIN-2013- 069.