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Based on the rubber vulcanization kinetics equation and the mechanical constitutive model, the effect of vulcanization degree and residual stress on the fabric rubber composites and Ω-shaped fabric rubber seal molding are investigated. First, the three-dimensional homogeneous vulcanization constitutive equations of rubber materials are derived, and the thermal conduction and the rubber vulcanization kinetics are simulated by finite element method with UMATHT and UMAT subroutines. Second, the vulcanization kinetics process is analyzed and optimized which is verified by rubber seal formulation vulcanization experiments. Finally, the vulcanization degree and the residual stress of fabric rubber during the vulcanization process are analyzed, which indicates that the maximum residual stress of fabric rubber composite is ten times that of the pure rubber. The investigation on the vulcanization degree and the residual stress distribution during the vulcanization process will provide a theoretical guidance for optimizing the parameters and evaluating the properties of fabric rubber composites.

In this paper, the method of designing a drive shaft with a 3D 4-Directional braided composite structure is proposed. First, the tubular unit cell model of 3D 4-Directional braided composite is established for obtaining the engineering elastic constants and the strength values of the tubular braided composite. Also, the relationship among the shear modulus , the braided angles and the fiber volume fraction is analyzed. Second, an orthogonal anisotropic tubular model with a fiber volume fraction of 50% and a braided angle of 45° is established to predict the torsional strength, torsional stiffness and virbration modes of the 3D braided composite drive shaft. Finally, the parameterized design with the thickness of the tubular is used to calculate the ultimate torque of the drive shaft, also the optimal drive shaft size is given and the 60.18% weight loss is achieved. This work will play an important role in the lightweight design of the 3D 4-Directional braided composite drive shaft.

Liposomes (LPs) as commonly used mRNA delivery systems remain to be rationally designed and optimized to ameliorate the antigen expression of mRNA vaccine in dendritic cells (DCs). In this study, we synthesized mannose-cholesterol conjugates (MPn-CHs) by click reaction using different PEG units (PEG100, PEG1000, and PEG2000) as linker molecules. MPn-CHs were fully characterized and subsequently used to prepare DC-targeting liposomes (MPn-LPs) by a thin-film dispersion method. MPn-LPs loaded with mRNA (MPn-LPX) were finally prepared by a simple self-assembly method. MPn-LPX displayed bigger diameter (about 135 nm) and lower zeta potential (about 40 mV) compared to MPn-LPs. The in vitro transfection experiment on DC2.4 cells demonstrated that the PEG length of mannose derivatives had significant effect on the expression of GFP-encoding mRNA. MP1000-LPX containing MP1000-CH can achieve the highest transfection efficiency (52.09 ± 4.85%), which was significantly superior to the commercial transfection reagent Lipo 3K (11.47 ± 2.31%). The optimal DC-targeting MP1000-LPX showed an average size of 132.93 ± 4.93 nm and zeta potential of 37.93 ± 2.95 mV with nearly spherical shape. Moreover, MP1000-LPX can protect mRNA against degradation in serum with high efficacy. The uptake study indicated that MP1000-LPX enhanced mRNA expression mainly through the over-expressing mannose receptor (CD206) on the surface of DCs. In conclusion, mannose modified LPs might be a potential DC-targeting delivery system for mRNA vaccine after rational design and deserve further study on the in vivo delivery profile and anti-tumor efficacy.