Search

The interlaminar repairing behavior and thermoforming capacity of new carbon fiber reinforced Vitrimer epoxy resin (V-CFRP) composite and corresponding mechanisms were studied. The results reveal that the glass transition temperature (Tg) of the new Vitrimer epoxy resin is 92.8 ℃, and it exhibits significant stress relaxation behavior at temperatures higher than Tg. The stress relaxation time exhibits a linear relationship with temperature; The hot-press repair behavior and thermoplastic molding ability of V-CFRP composites were studied using a three-point bending experiment. The hot-press repair study shows that hot pressing at 180-220 ℃ for 1.5-2.0 h and 5 MPa can achieve nearly 100% repair of interlaminar damage in the composite; The bending modulus and bending strength of V-CFRP composites is decreased by more than 80% after pre-heating at 180-220 ℃ for 5-30 min. The significant decrease of bending modulus means that V-CFRP composite is suitable for thermoforming process. Moreover, a V-CFRP part with three-dimensional structure is successfully prepared by thermoforming process under the conditions of 200 ℃, 5 MPa and 2 h, which confirms the thermoforming capacity of V-CFRP composites.

In view of the limitation that the existing theoretical methods cannot reflect the influence of fiber wettability on permeability, the analytical expression of capillary pressure and the calculation formula of lateral dynamic permeability of fiber tow impregnation process were derived. The numerical simulation of the process of resin impregnated fiber tows was carried out by using a phase field method. The simulation results indicated that the numerical solution of the capillary pressure obtained by the phase field method was consistent with the analytical solution obtained from this paper. This proved the reliability of the developed method. The effects of fiber volume fraction and contact angle on the dynamic permeability were studied. The results indicated that this method could better characterize the effect of fiber wettability on the permeability and realize the dynamic prediction of the permeability at different impregnation radii. Compared to the existing permeability calculation methods, the developed method is more applicable and the calculation results are more accurate. [ABSTRACT FROM AUTHOR]

Environmental stress cracking(ESC) behavior of silicone coated polycarbonate (PC) in ethanol was studied. Stress relaxation of PC and PC/silicone coating under a combined action of ethanol and stress was measured by self-made three point bending equipment. After stress relaxation testing, crack morphology was observed by polarizing microscope. The results indicate that silicone coating is able to improve the stress cracking resistance of PC parts in ethanol. The coated PC shows slower stress relaxation rate and less number of cracks than pristine PC. It is mainly attributed to that the silicone coating can provide barrier effect to the absorption and diffusion of ethanol in PC substrate. Furthermore, the mechanical properties of flexible silicone coating matched fairly well with that of PC, so that the coating is uneasy to peel off from PC substrate during the ESC testing. The silicone coating has a favorable effect to protect PC substrate from ESC under the combined action of solvent and stress.

The Box dimension of a class of Weierstrass function ... is discussed. Under the help of the λ-ary expansions, the Box dimension of Γ(f) is 2 when the sequence satisfies ..., where 1<λ is an integer and {an} is a summable sequence with positive terms. [ABSTRACT FROM AUTHOR]