To address the drag reduction requirements of superhydrophobic surface coatings for underwater vehicle hulls, this study designed a synthesis method based on resin substrate modification and filler modification according to superhydrophobic coating synthesis techniques. Three types of superhydrophobic microstructured surface coatings were prepared: polyurethane resin, silicone resin, and fluororesin. The coatings were fabricated by incorporating fluorine-modified SiO₂ nanoparticles into the modified resin matrices to construct hierarchical micro/nanostructures. The main components and synthesis processes for each coating were determined. Performance tests were conducted to evaluate mechanical properties (thickness, hardness, adhesion, wear resistance), functional characteristics (surface morphology, static/dynamic hydrophobic angles), and environmental resistance (seawater immersion, salt spray stability, thermal stability). Five surface coating test plans for underwater vehicle hull models were proposed, and drag reduction experiments were carried out to compare total drag, drag coefficient, and drag reduction rate across coating plans. Experimental results indicated that the silicone resin superhydrophobic coating with F660 + 8% SiO₂ exhibited the best comprehensive performance, while the PU + 6% SiO₂ superhydrophobic coating achieved optimal drag reduction at speeds below 9 m/s, meeting the performance criteria for underwater vehicle hull applications.

This paper studied the Moisture absorption behaviors, DMTA temperature spectrum, Infra-red spectrogram, Quasi-static characters of the dry and hygrothermal UHMWPE composites. The material was UHMWPE fiber reinforced polyurethane matrix composite manufactured by hot press method, which was firstly kept in a heating oven, and then put in a beaker of distilled 70°C water bath for 24 days and 60 days. The results show that there were two plateaus for the moisture absorption curve of the UHMWPE composites. The coupled effects of moisture and temperature reduce the composite glass transition temperature(Tg) by matrix plasticization and degrades the fiber/matrix interface. The storage modulus and loss modulus of dry and 24 days hygrothermal were gradually decreased in the initiatory calefaction, which drop sharply in Tg. The tensile strength was lossing in the beginning, and comeback to the initial at last in the hygrothermal environment. The quasi-static compressive strength is reduced by about 8% after 24 days treatment. Hygrothermal treatment has no effects on the quasi-static characters.

Dynamic properties of high strain rate and absorbing energy for laminate composites in the marine environment were studied in this paper. The high strain rate dynamic compressive tests were carried out on Split Hopkinson Pressure Bar(SHPB) experimental facility at strain rate 1800/s, 1530/s, 1230/s and 950/s. The front surface failure modes were Analyzed by optical micrographs. A fractured fibres mode was discussed in high rate compression. The stress-strain rate curves showed that, the specimen dynamic properties were better for the samples immersed in marine environment for 12 days. The energy absorption properties were test by ballistic trajectory experiment. Experimental results and penetration faces showed that, the ballistic trajectory properties with 60days of hygrothermal environment was better.

To address the issues of color cast, insufficient contrast, and detail loss in underwater optical images, this paper proposes an underwater image enhancement method based on multi-scale fusion and detail sharpening. The algorithm first applies an improved Gray World White Balance method with color compensation to perform color correction on the original underwater image. Subsequently, two processed images are generated for fusion: the first image is obtained by applying a Particle Swarm Optimization-enhanced Contrast Limited Adaptive Histogram Equalization (CLAHE) algorithm to the color-corrected image to enhance contrast; the second image is produced by applying an adaptive gamma correction algorithm to improve uneven illumination regions. These two images are then fused using a multi-scale fusion strategy. Finally, a weighted multi-scale detail sharpening technique is employed to further enhance the texture details of the fused image, yielding the final enhanced result. The performance of the proposed method is evaluated using no-reference underwater image quality metrics: the Underwater Image Quality Measure (UIQM) and the Patch-based Contrast Quality Index (PCQI), and tested on the open-source dataset from Nanyang Technological University. Experimental results demonstrate that the proposed method leads to an improvement in underwater image quality in both qualitative and quantitative assessments.