Advanced Materials Research Vols. 652-654

Abstract: In this paper, propagation of flexural vibration in phononic crystal thin plates with straight, bending or branching linear defects are explored using finite element method. The plate is composed of an array of circular crystalline Al₂O₃ cylinders embedded periodically in the epoxy matrix with a square lattice. The numerical results showed that accurate band structures and transmission response curves could be obtained by finite element method compared with that of improved plane wave expansion method. The exploration indicated that finite element method is efficient and suitable in dealing with the wave propagation in phononic crystal, and displays potential abilities in dealing with complex structures.

Abstract: Delaminating of composite is one of keys for composite structures. An energy method was used to analyze the fundamental frequency of HT3/5224 carbon fiber reinforced laminated plate in this paper. Different delaminated situations are considered in analysis on vibration of composite based on Kirchhoff theory. The results show that delaminations have a great influence on the fundamental frequency of laminated plate. The discussion shows inner delaminations have more influence on composite laminates than surface delaminations. Different kinds of delaminations can interact each other and the interaction can increase the influence on frequency.

Abstract: Carbon nanotubes (CNTs) selective dispersion and electrical properties of one kind of thermoplastic/thermosetting polymer composite consisting of polyetherimide (PEI) and epoxy resin (EP) were investigated. The results showed that, in the CNTs/EP/PEI composite, under control of thermodynamics, CNTs are preferably dispersed in PEI-rich phase, and an inverted phase structure is obtained with continuous PEI-rich phase and separated EP phase as globular shapes. And this microstructure helps to achieve a very low percolation threshold of 0.3wt% CNTs in the composite. The composites at CNTs contents over the percolation threshold, have a high dielectric constant of around 100, which first decreases slightly and the drop rapidly into a platform with increasing frequency from beginning.

Abstract: The WC-Fe bulk composites were prepared by means of the plasma jet metallurgy using WO₃, C and Fe-based alloy powder as raw materials. Phases of the composites were mainly WC, W₂C, M₆C, M₇C₃ and (Fe, Ni).The WC grains formed in situ had rectangular or triangular shapes with size of 30-70μm. The growth morphology of Fe₃W₃C was faceted polygon and herringbone. The formation of the unique composite microstructure was attributed to the incomplete peritectic reaction between W₂C and Fe₃W₃C.

Abstract: In-situ production of (Fe,Cr)₇C₃ particulate bundles-reinforced iron matrix composites were prepared by infiltration casting between Cr wires and white cast iron at 1200°C plus subsequent heat treatment. The composites prepared under different heat treatment time were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), macrohardness test and pin-on-disc wear resistance test. The results show that the composite is mainly consist of (Fe,Cr)₇C₃ carbides and γ-Fe. The area of the particulate bundles gradually increases with the increase of heat treatment time, the microstructure evolved from eutectic to hypoeutectic, and the morphologies of the reinforcements present chrysanthemum-shaped, granular and intercrystalline eutectics, respectively. The (Fe,Cr)₇C₃ particulate bundles reinforced composite has high macrohardness and excellent wear resistance under dry sliding wear testing conditons.

Abstract: In this paper, the high-filled talcum masterbatches with four different talcum contents (60%, 65%, 70% and 75%) were prepared. The effect of two addition methods (masterbatch method and direct method) on the performance of the PP composite was studied. The burning residual of all four high-filled masterbatches was above 95%. The analysis on the mechanical properties of PP/talcum composites indicated that the talcum masterbatch with 70% content possessed better application effect than others. Based on the microstructure observation and comparison with direct addition method, the PP composite made through masterbatch method achieved more even distribution of talcum in the matrix, better stable quality and smaller performance difference among different batches of products, and improved the technological process.

Abstract: Selective dispersion of carbon black (CB) in three kinds of epoxy resin (EP)/ thermoplastic multiphase conductive polymer composites were investigated. The thermoplastics involved polystyrene (PS), polyethersulfone (PES) and polyetherimide (PEI). The results showed that the selective location of CB particles are mainly controlled by thermodynamics as indicated by consistency of wetting coefficient prediction and real microstructure. For CB/EP/PS, with co-continuous phase structure, CB particles are not selectively located in one polymer but located in both EP-rich phase and PS-rich phase. For CB/EP/PES, with not perfect inverted phase structure, CB particles are selectively located in PES-rich phase. For CB/EP/PEI, with perfect inverted phase structure, CB particles are selectively located in PEI-rich phase.

Abstract: This paper presents the thermal analysis on fiber-reinforced composites containing inhomogeneous interphase subjected to a uniform temperature change. Based on the assumption of generalized plane strain, the deformations and thermal stresses of the composites subjected to a radial constraint are obtained by using iterative technique. The material properties of the interphase are assumed to be linear variation along radial direction. The effects of different volume fractions of the interphase on the stresses in the composites subjected to applied radial stress/strain are investigated.

Abstract: By modifying O-cresol Formaldehyde epoxy resin with DOPO and Diethanolamine, and then neutralized by acetic acid, phosphorous-containing epoxy emulsion with excellent flame retardancy can be obtained under strong agitation. Diethanolamine opening rate and neutralized degree to the formation of epoxy emulsion were optimized. The flame-retardant property of the cured phosphorous-containing epoxy resin was test by UL-94, LOI and TGA method. The result shows that when the opening rate of Diethanolamine is 25.0% and the neutralized degree is 95.0%, stable epoxy emulsion can be obtained. When phosphorus content of the epoxy resin was 3.0wt%, the LOI value of the resin can be reach to 39.2 and pass the UL-94 test，the 700°C char remaining is 30.0wt%. The result shows that the flame retardant mechanism of the phosphorous-containing epoxy resin is mainly through a condensed- phase mechanism.

Abstract: Al foam is an advanced engineering material with many outstanding properties, such as very low density, high specific strength and stiffness, and large energy absorption. In the present study, pure Al foams were mixed with either cenosphere or precipitator fly ash particles of various contents. Fly ash particles are used in Al foams as reinforcement and stabilising materials which enable the foams with large expansion. It is found that Al foams with precipitator fly ash particles of various contents exhibited larger expansions than the foams with cenosphere fly ash particles. The quantitative analysis also revealed that more stable foam structure was obtained in Al foams with precipitator fly ash addition.