Nautical Applications Research Articles

Robust superhydrophobic composite fabricated by a dual-sized particle design

Superhydrophobic surfaces have shown great potential in various areas such as self-cleaning, anti-icing, drag reduction and biomedical applications. However, it is still challenging to prepare robust superhydrophobic surfaces for real applications. Here, a facile, low-cost dual-sized particle strategy is proposed to fabricate the robust superhydrophobic composite with an “armoured” micro-/nanostructure. As a proof-of-concept, the intrinsically hard quartz sand microparticles (QS MPs) and the epoxy (EP) adhesive are adopted to construct a firm surface frame (EP@QS) as an “armour” to provide mechanical durability while modified superhydrophobic SiO2 nanoparticles (msSiO2 NPs) are confined within the cavities among the QS MPs, forming a nanostructure to impart liquid repellency. Benefitting from the strong “armour”, the EP@QS@msSiO2 composite can reserve excellent water repellency after different kinds of environmental test such as cycled mechanical abrasion, ultraviolet radiation treatment, outdoor exposure damage, tape-stripping test, acid-base treatment and NaCl salt solution immersion, temperature treatment and knife scratching. Furthermore, the substrate versatility and nanoparticle versatility of our strategy are explored and verified. By virtue of the structural advantages, these EP@QS@msSiO2 composite manifest superior self-cleaning property and efficiently directional oil adsorption ability even after mechanochemical damage. Together with robustness and universality, the design strategy of the robust superhydrophobic composite is expected to extend the application scope in harsh nautical applications.

Effects of anodizing surface treatment on the mechanical strength of aluminum alloy 5083 to fibre reinforced composites adhesive joints

In this study, the anodizing process based on the use of tartaric sulfuric acid solution (TSA) was carried out on metal substrate to evaluate for the first time its effect on the adhesion strength and corrosion resistance of aluminium alloy (i.e., AA5083) to fibre (i.e., basalt or glass) reinforced composite adhesive joints for nautical applications. Furthermore, some TSA anodized samples were soaked in a NaOH solution to investigate the influence of this post-immersion step on the joint performances. With the aim to improve the fibre-matrix adhesion in the composite substrate thus further increasing the overall mechanical response of the joint, glass and basalt fibres were treated with a silane coupling agent solution. The corrosion behaviour of the aluminium alloy was studied by electrochemical techniques. Samples morphology was analysed by scanning electron microscopy, while the interaction between aluminium alloy substrate and epoxy resin was studied through contact angle analysis and resin uptake tests. The effectiveness of the silane treatment was examined by means of Fourier transform infrared spectroscopy and quasi-static tensile tests carried out on dry glass and basalt fabrics. The mechanical response of the resulting joints was evaluated by means of quasi-static tensile tests in accordance to ASTM D3528 standard.

Effect of Superhydrophobic Composite Coatings on Drag Reduction in Laminar Flow

In this work, the drag reduction (DR) performance of superhydrophobic composite coatings was investigated. The DR behavior for both short-term and long-term use was studied using a parallel-plate rheometer, and the morphology of the composite interface was studied by fluorescence staining. For short-term performance, the DR increased with higher silica NP content in the composition up to 40% by weight. The composite interface played a governing role in the DR of superhydrophobic coatings except for a very high particle loading sample. The surface topography effect on this composite interface was also studied. The increase in autocorrelation length was found to be related to the increased distance between wetted asperities and the decreased solid fraction. Furthermore, it was found that the reduced peak height also increased with autocorrelation length, providing a larger distance for meniscus sag and explaining the reason for increased DR with a larger autocorrelation length. Investigation of the long-term DR showed that sustainable DR can be provided by superhydrophobic coatings. In the case of the higher silica-loaded samples, the air plastron remained throughout the experiments and DR performance was retained. This has important implications for superhydrophobic coatings in DR for nautical applications.

Using Lighting Smart Grids in Nautical applications

Using Lighting Smart Grids in Nautical applications

On Nautical Observation Errors Evaluation

Mathematical Theory of Evidence (MTE) enables upgrading models and solving crucial problems in many disciplines. MTE delivers new unique opportunity once one engages possibilistic concept. Since fuzziness is widely perceived as something that enables encoding knowledge thus models build upon fuzzy platforms accepts ones skill within given field. At the same time evidence combining scheme is a mechanism enabling enrichment initial data informative context. Therefore it can be exploited in many cases where uncertainty and lack of precision prevail. In nautical applications, for example, it can be used in order to handle data feature systematic and random deflections. Theoretical background was discussed and computer application was successfully implemented in order to cope with erroneous and uncertain data. Output of the application resulted in making a fix and a posteriori evaluating its quality. It was also proven that it can be useful for calibrating measurement appliances. Unique feature of the combination scheme proven by the author in his previous paper, enables identifying measurement systematic deflection. Based on the theorem the paper aims at further exploration of practical aspects of the problem. It concentrates on reduction of hypothesis frame reduction and random along with systematic errors identifications.

Systematic Errors Handling with MTE

Mathematical Theory of Evidence (MTE)1,2 extended for possibilistic platform3,4 enables modelling and processing uncertainty. It enables upgrading new models and solving crucial problems in many disciplines. Evidence combining scheme as mechanism enriching initial data informative context is useful in many cases. In nautical applications, for example, it can be exploited in order to make a fix and evaluate its accuracy. MTE delivers new unique opportunity once one engages possibilistic concept. Approaches towards theoretical evaluation of tasks including imprecise nautical data were already proposed. Nevertheless one of important issue that is indication and evaluation of a measurement systematic error remain unexplored. In nautical practice in order to calculate fixed correction one has to know directions or distances to a landmarks. Engaging MTE apparatus in order to cope with random and systematic errors is the main topic of the paper.

Strain monitoring with embedded Fiber Bragg Gratings in advanced composite structures for nautical applications

Methods to effectively and reliably embed Fiber Bragg Grating sensors in the composite material have been investigated in this work, with particular regard to a sailing boat mast manufacturing process by means of bagging technique in autoclave.Small samples were produced in order to investigate the effect of the curing process parameters on the light transmission characteristics of the embedded optical fibers. Polyimide and acrylate coated optical fibers were tested measuring the relative coefficient of attenuation by Optical Time Domain Reflectometry. In particular, carbon fiber reinforced epoxy laminas with embedded FBGs were manufactured and specimens for tensile tests extracted from the laminas. Each specimen was instrumented with FBG and conventional electrical strain gage bonded on the surface. The comparison between the FBG and SG measurements recorded during static tensile tests permitted to assess the strain monitoring capability of the FBGs and their sensitivity and accuracy.

Mechanical behaviour and failure modes of metal to composite adhesive joints for nautical applications

In this paper, the influence of several parameters on the mechanical behaviour and failure modes of hybrid bonded joints aluminium/composite was investigated. Particularly, the effects of metallic surface condition, adhesive properties and thickness on single-lap joint resistance were analysed. To these aims, two adhesives were used and, for each adhesive, two different adhesive thicknesses (0.5 and 1.5 mm) have been investigated. Furthermore, two sets of joints for each adhesive kind and thickness were investigated: the former was obtained using aluminium blanks which were previously mechanically treated with sandpaper (P60) and the latter using aluminium treated with sandpaper and with presence of fillets in the ends of the overlap area. In order to improve the adhesion strength between polymeric adhesive and aluminium, two metal surface treatments have also been performed using a silane coupling agent, γ-glycidoxypropyltrimethoxysilane (γ-GPS). The mechanical performances and failure modes were found to be significantly increased using the chemical pre-treatments with γ-GPS silane coupling agent unlike other parameters investigated. As regard the thickness of the adhesive layer, the better value is found to be equal to 0.5 mm, for both adhesives investigated.

Performance analysis of a digital compass for the heading estimation in nautical application

This paper deals with the calibration of a magnetic digital compass for measuring the heading angle of a vessel. The main source of error in the heading measurement is the distortion caused by the presence of ferrous materials nearby the instrument that produces a local magnetic field interfering with the earth magnetic field. This distortion generally changes as the vessel moves around and, for this reason, it is generally difficult to compensate. Tuning the calibration algorithm based on data collected dynamically rather than at a fix location, as it is the standard practice, allows to account for this time-varying characteristics, while avoiding at the same time to discontinue the vessel operation. The accuracy achieved by different calibration algorithms tuned on data collected on a car ferry performing a round trip in the Venetian lagoon is analysed. In particular, a calibration algorithm combining the elliptical model of the magnetic distortion with a neural network is proposed.

Repeated impact response of hand lay-up and vacuum infusion thick glass reinforced laminates

Vacuum infusion (VI) is being considered as a viable alternative to more traditional hand lay-up (HL). Main reason in favor of the more costly technique is the cleaner and friendlier work environment. Moreover, VI potentially offers another important benefit over HL in that prepreg levels of resin may be achieved, resulting in stronger and lighter laminates. The present paper compares the two manufacturing techniques on the basis of the response to repeated impact loading. The laminate is a thick non-symmetric glass-fiber-reinforced plastics intended for nautical application. Four impact velocities (1.5, 2.2, 3.1 and 3.8 m/s) were considered, and a minimum of four specimens for any given velocity were subjected to 40 repeated impacts or up to perforation. The impact response was evaluated in terms of damage progression by visual observation of the impacted specimens, evolution of the peak force and of the bending stiffness with the number of impacts and by calculating the Damage Index (DI), a damage variable recently proposed by the authors to monitor the penetration process in thick laminates. Results point out that for impact velocities for which no perforation occurs within test duration, the experimental data essentially overlap. On the contrary, for perforation tests, HL specimens survived more impacts before perforating absorbing more total energy than VI specimens. Plots of the DI variable against the number of impacts were observed to exhibit an initial linear portion, owing to a stable process of damage accumulation within the laminate, and to undergo an unstable growth a few impacts before perforation. When comparing the VI and HL specimens it was observed that, given an impact energy, the level of damage at first impact as well as the rate of stable damage accumulation is alike for the two sets of specimens. On the contrary, it is the number of impacts of the stable damage accumulation region which is lower for VI specimens.

A graphical system for geographical data processing in a minicomputer environment

In this paper a minicomputer system for geographical data processing for computer cartography applications is described. The main features of the system are: capability of processing irregularly distributed data points; interactive facility during the editing and map refinement steps; modular organization; use of minicomputer systems with standard display devices. At present the system is used to produce isarithmic maps for nautical applications.