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Polymer-metal hybrid structures have excellent comprehensive properties and have been widely used in aerospace, automotive industry, biomedicine, and other fields. There exists a strong dissimilar metal-plastic joints requirement in lightweight design in various engineering fields. As a highly efficient processing technology, laser welding has been proved to be a new welding technology with a sound potential in joining hybrid structures compared with traditional adhesives, mechanical and other bonding methods. This review focuses on the technology of laser joining of metal and polymer. The difficulties and main problems of metal to polymer laser joining are analyzed in five aspects: joining mechanism, temperature field simulation, defect identification and suppression, factors affecting joint strength, and process monitoring and inspection for weld quality. Meanwhile, the current status of some crucial issues such as prediction and control of weld defects, improving joints quality methods, and the future trends in the field are also discussed.

Typical effects of coarse and fine aggregates on the long-term properties of sea sand recycled aggregate concrete (SSRAC) are analyzed by a series of axial compression tests. Two different types of fine (coarse) aggregates are considered: sea sand and river sand (natural and recycled coarse aggregates). Variations in SSRAC properties at different ages are investigated. A novel test system is developed via axial compression experiments and the digital image correlation method to obtain the deformation field and crack development of concrete. Supportive results show that the compressive strength of SSRAC increase with decreasing recycled coarse aggregate replacement percentage and increasing sea sand chloride ion content. The elastic modulus of SSRAC increases with age. However, the Poisson’s ratio reduces after 2 years. Typical axial stress-strain curves of SSRAC vary with age. Generally, the effect of coarse aggregates on the axial deformation of SSRAC is clear; however, the deformation differences between coarse aggregate and cement mortar reduce by adopting sea sand. The aggregate type changes the crack characteristics and propagation of SSRAC. Finally, an analytical expression is suggested to construct the long-term stress-strain curve of SSRAC.

DNA-based hydrogels are exceptional materials for biological applications because of their numerous advantages such as biodegradability, biocompatibility, hydrophilicity, super absorbency, porosity, and swelling. Among these advantages, the ability of DNA-based hydrogels to respond to specific physical and chemical triggers and undergo reversible phase transitions has garnered significant attention in the fields of disease diagnosis (biosensors) and treatment (drug delivery). This article focuses on the recent advancements in the research of DNA-based hydrogels and discusses the different types of these hydrogels, the synthetic methods, their unique properties, and their applications in biosensors and drug delivery. The types of DNA hydrogels are categorized based on their building blocks, and the process of synthesis as well as the unique characteristics of DNA-based hydrogels are described. Then, DNA-based responsive hydrogels utilized as intelligent materials for the development of biosensors are reviewed. Furthermore, this article also presents the current status of DNA-based responsive hydrogels in drug delivery for cancer treatment, wound healing, and other therapeutic applications. Ultimately, this paper discusses the current challenges in expanding the practical application of DNA-based hydrogels.

ABSTRACTBattery-casing sealing is the key factor for secure travel of new energy vehicles. We constructed a relatively accurate mechanical-simulation model by selecting a constitutive model, analyzing the influence of thermal elongation, verifying the grid-independence and comparing numerically by the pressure-measurement film on the basis of studying the physical performance of a certain type of sealing material that had been used in battery-casings after aging. Based on a porous-media model and combined with changes of macroscopic and microscopic contact characteristics of materials at different times after aging, the evolution rule of sealing performance with time was analyzed quantitatively by calculating the leakage. By analyzing the structure of circular arc bulge on the surface of sealing material, the radius of circular arc bulge with better sealing performance was obtained, which could reduce the leakage of sealing structure during the material’s lifecycle.

We established a method for calculating and analyzing the static leakage rate based on a porous media model for foamed silicone rubber materials. The mechanical properties of the foamed silicone rubber material under macroscopic compression were described by the Ogden third (foam) model in the finite-element hyperelastic model. It solved the problem of difficult convergence of large compressible and volume compressible cell materials. The size and distribution of the cells on the surface of the foamed material were obtained by a white-light interferometer and mathematical fitting. The boundary conditions for solving the porous medium model were obtained by the coupling of the macroscopic contact pressure and the microscopic cell contact pressure. For the unique cell structure and contact state of the surface of the foamed material, the flow state of the fluid at the sealing interface was described by a porous medium model, and the leak rate was obtained. In addition, this article analyzed the effect of different compression and the relative pressure of the sealing end face on the leakage.

The study on the deformation distribution and crack propagation of concrete under axial compression was conducted by the digital image correlation (DIC) method. The main parameter in this test is the water-cement (W/C) ratio. The novel analysis process and numerical program for DIC method were established. The displacements and strains of coarse aggregate, and cement mortar and interface transition zone (ITZ) were obtained and verified by experimental results. It was found that the axial displacement distributed non-uniformly during the loading stage, and the axial displacements of ITZs and cement mortar were larger than that of coarse aggregates before the occurrence of macrocracks. The effect of W/Con the horizontal displacement was not obvious. Test results also showed that the transverse and shear deformation concentration areas (DCAs) were formed when stress reached 30%–40% of the peak stress. The transverse and shear DCAs crossed the cement mortar, and ITZs and coarse aggregates. However, the axial DCA mainly surrounded the coarse aggregate. Generally, the higher W/Cwas, the more size and number of DCAs were. The crack propagations of specimens varied with the variation of W/C. The micro-crack of concrete mainly initiated in the ITZs, irrespective of the W/C. The number and distribution range of cracks in concrete with high W/Cwere larger than those of cracks in specimen adopting low W/C. However, the value and width of cracks in high W/Cspecimen were relatively small. The W/Chad an obvious effect on the characteristics of concrete deterioration. Finally, the characteristics of crack was also evaluated by comparing the calculated results.

In this study, the properties of seawater volcanic scoria aggregate concrete (SVAC)-filled circular stainless steel (SFCST) and glass fibre-reinforced plastic (GFRP) tubes (SFCGT) were investigated. Ten groups were considered and 30 specimens were prepared, including four different parameters: the concrete type (SVAC and ordinary concrete [OC]), outer tube type (GFRP and stainless steel tubes), concrete strength (C30 and C40), and tube thickness (0, 3, and 4 mm). The typical influences of the SVAC and outer tube on the mechanical properties of specimens were then analysed. The research findings show that the strength and ductility of the SFCGT and SFCST are significantly higher than those of plain SVAC. The peak strain and strength enhancement factor of the SFCGT and SFCST increase with an increase in the tube thickness, and the concrete strength has a detrimental impact on the toughness of the specimen. Unlike in the confined OC specimens, a sudden decrease is observed in the stress–strain curves of the SFCGT and SFCST owing to the changes in the deformability of the SVAC. Generally, the strengths of the SFCGT and SFCST specimens are 10.3% lower and 4.1% higher than those of the confined OC specimens, respectively. Finally, analytical models of the strength and stress–strain curves considering the influences of the SVAC and passive confinement were established, and numerical simulations were performed to provide a basis for the practical application of the SFCGT and SFCST.

In theoretical research pertaining to sealing, a contact model must be used to obtain the leakage channel. However, for elastoplastic contact, current numerical methods require a long calculation time. Hyperelastic contact is typically simplified to a linear elastic contact problem, which must be improved in terms of calculation accuracy. Based on the fast Fourier transform, a numerical method suitable for elastoplastic and hyperelastic frictionless contact that can be used for solving two-dimensional and three-dimensional (3D) contact problems is proposed herein. The nonlinear elastic contact problem is converted into a linear elastic contact problem considering residual deformation (or the equivalent residual deformation). Results from numerical simulations for elastic, elastoplastic, and hyperelastic contact between a hemisphere and a rigid plane are compared with those obtained using the finite element method to verify the accuracy of the numerical method. Compared with the existing elastoplastic contact numerical methods, the proposed method achieves a higher calculation efficiency while ensuring a certain calculation accuracy (i.e., the pressure error does not exceed 15%, whereas the calculation time does not exceed 10 min in a 64 × 64 grid). For hyperelastic contact, the proposed method reduces the dependence of the approximation result on the load, as in a linear elastic approximation. Finally, using the sealing application as an example, the contact and leakage rates between complicated 3D rough surfaces are calculated. Despite a certain error, the simplified numerical method yields a better approximation result than the linear elastic contact approximation. Additionally, the result can be used as fast solutions in engineering applications.

This study systematically investigated the mechanical properties of marine volcanic-scoria concrete (MVSC) under the coupled effects of the mix components. Six groups and 408 specimens were used, including four different experimental parameters: types of coarse and fine aggregates (volcanic-scoria aggregate and natural aggregate), types of mixing water (seawater and freshwater), and age (days 7, 14, and 28). The macro-mechanical properties, mechanism, and microstructure of MVSC were analysed using a novel test system, including an axial compression test, digital image correlation (DIC) method, and scanning-electron microscopy (SEM). Variations in the failure pattern, stress–strain curve, deformation field distribution, crack initiation, and propagation of MVSC were studied. Generally, the failure of MVSC is brittle compared to that of ordinary concrete (OC). The cubic compressive strengths of MVSC at day 7 and 14 were 82.7% and 91.7% of the cubic compressive strength at day 28, respectively. The splitting tensile strength of MVSC was 7.3% higher on average than that of OC. The mix components changed the strength of MVSC. Seawater and sea sand accelerated the development of compressive strength, volcanic-scoria fine, and coarse aggregates (VSFA and VSCA, respectively) enhanced the tensile strength. After using volcanic-scoria aggregates, the curvature of the concrete stress–strain curve decreased; however, the curve declined sharply after the peak stress (σmax). Compared with OC, the ductility of MVSC decreased by an average of 17.2%, whereas the peak strain increased by 6.9%. Furthermore, VSCA significantly changed the displacement distributions of the specimen, whereas the impacts of the mixing water and fine aggregate were small. The crack initiation and propagation of MVSC were different from those of OC; that is, microcracks first appeared in VSCA, and their characteristics propagated slowly before σmax. Finally, a theoretical model of the MVSC stress–strain curve involving the coupled impacts of the mix components was established, which can prompt the practical application of MVSC structures.