A novel marine composite structure (experimental tidal turbine blade) made up of a polyurethane (PU) foam/glass fiber/epoxy resin composite with multiwall carbon nanotubes (MWCNTs) is proposed herein to self-sense its strain under a structural test scenario. To achieve this, MWCNTs were deposited onto glass fiber fabric by spray-coating technique in order to form an effective electrical percolation network onto the external skin surface of the tidal turbine blade which enables piezoresistive capability. After MWCNT deposition, the blade was manufactured by means of one-shot resin transfer molding (RTM) in a closed and heated metallic mold specially designed with a blade geometry of 67 cm length. The results confirm that the spray coating technique is a viable method to deposit MWCNTs onto glass fiber surface and form electrical networks into the blade at a relatively low MWCNT concentration. Finite element analysis (FEA) predicted a suitable structural blade design with a maximum failure index value of 0.9 attained in the blade shear web. The measured longitudinal strains of the tidal turbine blade were in good agreement with the numerical strain values predicted with FEA. Electromechanical tests carried out on a structural test rig designed and instrumented for tidal turbine blades showed that the electrical resistance change response of carbon nanotube (CNT) network integrated into the blade was capable of following the mechanical curve response up to the blade limit load, confirming its ability to self-sense its strain in real time.

Optimization of the energy consumption of a Dorna 1 commercial robot was carried out by replacing the original materials of the links (aluminum) with a lighter and more resistant material (carbon fiber) with the aim of lowering the operating costs of the robot. For this reason, a reduction in the total mass of the robot of 11.08% was achieved by replacing the original materials. In addition, simulations were carried out using finite element analysis to verify that the mechanical resistance of the optimized parts was adequate according to the level of demand that occurs during the operation of the robot. Subsequently, a comparison of the energy consumption of the original robot and the robot with the optimized parts was carried out using the Internet-of-Things device. The tests were carried out at three different speeds—1000, 3000, and 9000 deg/min—for 15 min by executing a pre-established routine starting from home. The results showed that at all test speeds, there were energy savings, but the greatest energy savings occurred at the speed of 3000 degrees/min in the range of 3.66%. With this result, it has been shown that the integration of light materials in robots can achieve energy savings.

The main objective of this research was to evaluate the piezoresistive response and mechanical performance of seawater-aged blades manufactured with glass fiber/epoxy resin incorporating multi-walled carbon nanotubes (MWCNTs). MWCNTs content was 0.75 wt. %, which was sufficient to form an electric percolation network. MWCNTs were dispersed in the fiber using the spray-coating method, allowing the entire blade outer surface to gain strain self-sensing capability. Exposure of the blades with and without MWCNT to seawater caused a moisture absorption of 1.67% and 1.56%, respectively. This caused damage such as matrix cracking, and fiber/matrix interfacial debonding. These effects were manifested by an increase in tip displacement of 13% and 1.43% in the blades with and without MWCNTs, also local deformations on the blade increased. The MWCNTs induced a positive effect on piezoresistive capability, resulting in the development of sensitivity to deformation. This showed that MWCNTs in the specified content is efficient for damage detection in complex structural components even after seawater aging while retaining maximum electrical resistance change of 0.45% and 0.26% on the tensile and compressive side, respectively. With acoustic emission (AE), it was confirmed that the presence of MWCNTs acts as toughening mechanisms reducing damage such as micro-cracks in the matrix.