Advanced Materials Research Vols. 194-196

Abstract: Composites made from yarns perform better than composites made from random nonwoven mats. However, the twist structure of conventional ring spun yarns prevents the full utilization of fiber mechanical properties in the final composites. We produced flax/pp wrap yarns in which all flax fibers were twistless. Composites made from the wrap yarn gave a significant improvement of flexural properties. Most natural fibers, such as decorticated hemp, cannot be efficiently made into yarns because of their lack of cohesion. Adding pp fibers to decorticated hemp improved textile processing performance. The pp fibers served as a carrier for the natural fibers during processing and became the polymer matrix in the final composites.

Abstract: Lignin have been blended with low density polyethylene (LDPE). Maleic anhydride grafted polypropylene (PP-g-MAH) has been added as compatibilizing agent. The weight ratio of LDPE, ligin and PP-a-MAH were 75:25:5, 75:25:7.5 and 75:25:10, respectively. The mechanical properties of the blends were investigated according to Chinese standard GB/1447-2005 and compared with those of lignin/LDPE composites without compatibilizing agent. Scanning electron microscopy (SEM) was used to investigate the dispersion of the lignin and LDPE and the compatibilizing mechanism was analyzed. The results reveal that addition of compatibilizing agent increased the interfacial bonding strength of the composites, improved the mechanical properties and obtained the better dispersion of the lignin and LDPE.

Abstract: Nano-TiO₂/Micron size Cu composite particles were prepared in ambient conditions by bio-inspired method. Observation by field emission scanning electronic microscope shows TiO₂ particles of 3-5 nm covers on copper powder surfaces to form nanometer/micron composite particles. XPS analysis shows that the element C, O, Ti, Sn and Cu existed on the surfaces of the composite particles. UV-vis spectra show a red shift of the absorption edge and a significant increase of absorption intensity in the visible region. The degradation experiment taking methyl orange demonstrates the photocatalysis activation of powder with good body made. At the same time, the apparent kinetics model for degradation reaction was established.

Abstract: The composite material has high strength-to-weight, stiffness-to-weight ratios and it has the layer designing property to satisfy special mechanical requirement. Nowadays, the marine produce industry makes efforts to use composites for marine propeller to improve the hydrodynamic and structural performance. In this paper, the authors use FEA coupled CFD to design the layer sequence of composite propeller and develop ANSYS subroutine to simulate resin flow in the mould. The composite propeller is produced by RTM (resin transfer molding) and tested to measure the performance of composite propeller. Compared to the same size aluminum propeller, the composite propeller saves 39% weight and has less noise.

Abstract: In response to the problem for non-washable and poor taking comfortable characterizations of smart electronic fabrics at present, two different organizational structures of fabric sensors with plain weave and double weave are designed. The basic principle of design of fabric sensor is: the core-spun yarn made of metal wire is used as core wire, the structural unit with capacitor function is built by interweaving warp with weft, and the induction of fabric to external pressure is reflected by testing changes in capacitance of fabric. The models of equivalent electronic circuits of two fabric sensors with plain weave and double weave are analyzed, and the relationships between area and capacitance characteristics of fabric sensor are discussed. The results show that: the larger the fabric area, the greater the capacitance, and the capacitance of 36cm² fabric is maximum with 100Hz test frequency; under the condition of the same area and test frequency, the capacitance of plain weave fabric is greater than that of double-layer fabric under no pressure, but the increasing rate of capacitance of double-layer fabric is larger than that of plain weave fabric under the same pressure.

Abstract: In the state space framework, a separable K-canonical formulation of rectangular element and explicit symplectic schemes for the static responses analysis of three-dimensional (3D) laminated plates are proposed in this paper. Firstly, the modified Hellinger-Reissner (H-R) variational principle for linear elastic solid is simply mentioned. Secondly, the separable J-canonical system with Hamiltonian H and the separable K-canonical formulation of rectangular element are constructed. Thirdly, on the basis of the symplectic difference schemes, the explicit symplectic schemes are employed to solve the separable K-canonical governing equation for a single plate. Then, to obtain the high accurate numerical results, a multi-scale iterative technique is also presented. Finally, based on the interlaminar compatibility condition (displacements and stresses), the excellent performance of the method presented in this paper is demonstrated by several numerical experiments of the static responses of laminated plates.

Abstract: The polypropylene (PP)/ poly(phenylene sulfide) (PPS) in-situ microfibrillar composites were prepared by the melt blending technology using a single screw extruder. Maleic anhydride grafted polypropylene (PP-g-MAH) is used as the compatibilizer. The rheology was characterized on capillary rheometer, and thermal behaviors of the PP/PPS were investigated by DSC. The experiment results reveal that the melting PP/PPS composites conform to the law of Non-Newton and show typical shear-thinning behavior. The viscosity of PP/PPS composites is nearly independent of the PPS concentration at 270°С and 280°С , respectively. However, the contents of PPS have an influence on shear viscosity of the PP/PPS at 290С and 300°С . The DSC results exhibit that the crystallization temperatures (T_C) of PP in the composites are higher than that of the pure PP, and the T_C of PP increases slightly with increasing PP content in the composites. Moreover, the melting temperature of PPS in the composites decreases slightly with increasing PP content.

Abstract: Dodecyl benzene sulfonic acid (DBSA) doped polyaniline (PANI) grafted MWNTs (PANI-g-MWNTs)/Epoxy composite were prepared by aniline in situ polymerization in the presence of phenylamine groups contained MWNTs followed by solution blending and mould casting. Phenylamine groups grafted on the surface of MWNTs via amide bond join in the in situ polymerization and MWNTs are encapsulated by PANI coatings forming a core (MWNTs)-shell (PANI) nano-structure. DBSA doped PANI coatings swell in tetrahydrofuran (THF) and core-shell nano-structures are stabilized in epoxy solution, which is in favor of MWNTs dispersion in epoxy resin and formation of a homogenous MWNTs/Epoxy composite. After DBSA doped PANI-g-MWNTs are introduced in Epoxy, initial curing and exothermic peak temperatures as well as curing reaction enthalpy decrease, which indicates addition of DBSA doped PANI-g-MWNTs promotes curing reaction of Epoxy. Tensile strength, Young’s modulus, elongation at break, flexural strength and flexural modulus of the composite are improved by 71.7%, 42.3%, 99.8%, 55.01% and 39.86% compared with Epoxy, respectively.

Abstract: Formation conditions of the condensed phases (Si₃N₄ and Si) in CVD process of SiCl₄-NH₃-H₂ precursors have been investigated in detail with thermodynamic analyses by using the FactSage code and its embedded database (44 species being involved). The productions have been examined at different SiCl₄/(SiCl₄+NH₃) ratios, H₂/(SiCl₄+NH₃) ratios, temperatures and pressures. The results showed that the condensed phase composition was quite sensitive to the ratios and temperature whereas it was insensitive to pressure. The ideal conditions for the deposition of Si₃N₄ were listed as followed: the ratio of SiCl₄/(SiCl₄+NH₃) and H₂/(SiCl₄+NH₃) was 0.44 and in the scope of 10^0.6-10^5.2, respectively. Temperature ranged from 1200 to 1300 K with lower pressure. Si was formed in the H₂/(SiCl₄+NH₃) ratio of 10³~10⁵ and SiCl₄/(SiCl₄+NH₃) ratio of 0.44-1.0. The formation of single-phase Si₃N₄ or Si would be easily controlled by changing the ratios of SiCl₄/(SiCl₄+NH₃) and H₂/(ZrCl₄+BCl₃). SiHCl₃, SiCl₃ and SiH₂Cl₂ should be the crucial intermediates in the process of CVD Si₃N₄ and could participate in the competition in deposition process. The results in this work were instructive for further investigation on the experiments under different conditions.

Abstract: By means of matching filling of five kinds of spherical silica with the particle size of 2μm, 3μm, 5μm, 10μm, 20μm respectively, the epoxy molding compounds(EMC) for integrated circuits(IC) were manufactured. Using classical particle accumulation theory, the particle distribution according with Dinger-Funk-Alfred equation was calculated by Matlab simulation software, and then the optimal particle size formulations were obtained. Adding the mixed silica according to the above optimal formulations into epoxy resin, the EMCs were manufactured by twin-roll compounding at 95~105°С . The melt viscosities of varied EMCs were measured by Rotating Rheometer. The results showed that the matching filling of different silica with different particle size can improve the flowability of EMC greatly.