Abstract:This article reviews the influence of ultrasonic irradiation on polymers and their composites at the aspect of ultra-fine material dispersion, mechanical properties, physical and chemical properties and microstructure respectively. Developing direction of ultrasonic irradiation technology, including the processing of composite combined with other advanced technology, were put forwarded.

Abstract:In this paper, preparation process, performance, current situation and application of PMI foam are reviewed on helicopters for reference to the material researchers and helicopter composite structure selection.

Abstract:In this paper, as for the hot pressing process of polymer matrix composites, the two factors of the temperature field and the pressure field required for fabricating the components are taken as the main line, and from the aspect of finite element numerical simulation, the present research situation and the existing problems of hot pressing process forthe polymer matrix composites are reviewed.

Abstract:Bending problems of functionally graded rectangular plates were analyzed. In terms of Plevako function, assuming that the Yang's modulus of the material was distributed through a power function in the thickness direction, an exact solution of bending problem of simply supported functionally graded rectangular plates was obtained by variable separation method. Through numerical examples, the variations of displacement and stress components with different graded material distributions were analyzed and different graded parameters were found to have significant effects on the structural behavior. The research serves as theoretical basis for the development of numerical methods and simplified theories of functionally graded material structure.

Abstract:According to the demand of the gird structure skin and rib texture winding formantion,this article discuss the spiral curve and geodesic line of column and cone by means of the differential geometry method. The problem of the composite grid structure skin and rib texture winding formation was solved. The results show that the arc length and curvature calculation method of the spiral curve and geodesic line of column and cone can be used for the design and manufacture of the mold forming device of the composite grid structure and fiber winding.The calculation method of arc length and curvature of logarithmic spiral and archimedes spiral can be used for the design and production of the soft mold forming device of the cone composite grid structure and fiber winding.The condition for the automation manufacture of the composite trellis structure has created.At the same time, for engineering needs, different kinds of grid structure are selected for different processing and forming methods, which can greatly reduce the processing difficulty and realize low cost and fast mass production.

Abstract:O-o' methylene bridge is one of primary linkage among phenol-formaldehyde resins structure units. Pyrolysis mechanism of the 2BHM as a model compound was investigated by using density functional theory B3LYP methods at 6-311G(d,p) level in Gaussian 09 package. Six kinds of paths of pyrolysis reactions were designed, and the equilibrium geometries of the reactants, transition states and products of every reaction path were optimized, and the transition states were checked using IRC method. The standard kinetics parameters of every path were calculated. The calculation results show that Path3 are the major reaction channels and the corresponding products are phenol and o-cresol. Product of all path include phenol, and the CO₂ generates more easily than CO. Pyrolysis experiment results show that phenol content is the highest, and no CO is formed. This shows that the calculation results are basically identical to the experimental results, at the same time also shows that the application of quantum chemistry calculation theory to study the pyrolysis mechanism of phenolic resin is a kind of effective research method.

Abstract:Ultra-high temperature ceramic matrix composites were firstly made by eutectic method. The composites were made from ZrB₂ and flake graphite, ZrB₂, TaB₂, SiC and flake graphite,or ZrB₂, MoSi₂and flake graphite, respectively. Results shows that different phases distribute uniformly in these composites, and the graphite phases in the composites were highly ordered. The d₀₀₂ values of the graphite in the composites were 0.335 4, 0.335 9 and 0.337 7 nm, and the L_c values were 63.4, 51.5 and 68.7 nm, respectively. Boron had already doped into the carbon net, as indicated by the Raman analysis, and some amount of pores existed in the composites. Also, thermal conductivity coefficient of the composites were not very high. Eutectic method could be a promising method for making ultra-high temperature ceramic matrix composites.

Abstract:The pyrolysis mechanisms occurring during the conversion of polyborosilazane (PBSZ) into amorphous SiBCN ceramics have been investigated. TGA has been applied to investigate the mass loss behaviour during ceramization. Solid-state ¹¹B, ¹³C and ²⁹Si NMR spectroscopy has been applied to probe the local environment of all NMR active nuclei in the precursor, the thermolysis intermediates and the ceramic residue. IR spectroscopy has been performed to receive valuable information on the chemical bonding in all materials. At temperature below 400℃, NH₃ and H₂ are released via transamination and dehydrocoupling reaction involving N-H and Si-H units. It is followed by evolution of hydrocarbons due to the cleavage of bonds and formation of methane and hydrogen. Ceramization continues at temperature above 800℃. After heating to 1 000℃, ceramization complete and free carbon, BN₃ domains as well as Si-C-N units coexist(SiC_xN_4-x,x=0,1,2,3).

Abstract:Using the bisphenol E cyanate ester (BECE) and hydroxyl-terminated polyether sulfone (Mx) to co-modify novolac-cyanate ester (Novolac-CE) resin, and laminating with quartz cloth, a 400℃ temperature resistant and low dielectric loss supported structural adhesive film for bonding advanced radar radomes is developed. The results show that the impact toughness of Novolac-CE can be increased to 13 kJ/m², and the contact angel decrease to 72.8°with the addition of suitable amount of BECE and Mx in Novolac-CE resin. The adhesion strength between the disposed quartz cloth by the KH550/ethonal solution and Novolac-CE can be 70% higher than original quartz cloth, but the excessive KH550 is negative for the thermal resistance of film. The lap shear strength of the film is measured to be more than 5 MPa at 400℃, where it can be continuously used for 60 min, the dielectric loss is 0.014 (10 GHz). The adhesive film has a shelf life of more than 15 days at ambient temperature and suitable tackiness, which can be applied as high temperature transparent materials.

Abstract:The epoxy resin (F51) was modified by acrylonitrile butadiene rubber (CTBN) to improve its toughness. The structure and properties of the modified resin were characterized by SEM, FTIR, TG and mechanical facilities. The modified mechanism was discussed. The ablative properties of the low density material which made by the modified epoxy resin was checked by gas jet and wind tunnel experiments. The results show that after the modification of CTBN, the molecular chains have a certain degree of cross-linking. The tensile and bending properties of resin matrix decreased, but the toughness was enhanced. Thermal stability is greatly increased. At 800℃, the rate of the residual weight of the toughening F51 increased to 54% from 23%. The shear resistance and erosion resistance of low-density ablative materials have been enhanced, and the stability of the carbon layer has been improved, and the ablative properties have been improved.

Abstract:Self-deployable carbon fiber reinforced composite(CFRP) boom was prepared by CFRP hinge, CFRP tube and aluminium alloy mounts. The CFRP hinge was laminated from T300/epoxy thin prepreg with bi-lenticular configuration. Deploying moment, natural frequency and deployment properties were characterized. The deploying moment and power to weight ratio of the hinge were 372.8 N·mm and 13.3 W/kg respectively. The natural frequency and pointing accuracy were 4.25 Hz and 0.08°,respectively.

Abstract:In order to study the properties of TC4 coatings on TC4 alloys using cold spray technology, two kinds of technical parameters (gas materials and gas temperature) were used to analyze their effects on porosities, hardness and powder utilization ratio of TC4 coatings in this paper. Gas kinds (N₂ and He) and gas temperature (400℃, 500℃ and 600℃) were utlized and were adopted in experiment. The study indicates that the coatings are dense, more harder and utilization ratio is higher when gas temperatures become larger under the same gas materials. The coatings prepared using He are always dense, harder and utilization rate is higher than that of N₂ under the same gas temperature. In the end, the coatings with porosity 0.8%, hardness 440 HV_0.2 (improve 33% than that of TC4 alloys) and utilization ratio 88.2% are obtained under He gas (600℃, 0.9 MPa).

Abstract:A three-dimensional finite element model with different stitching diameter was established based on carbon fabric with 8/5 warp satin weave. The elastic modulus of the composites was predicted by the total damage and partial damage. The thicker stitch thread make the tensile modulus of the composites decrease, and the thinner stitch thread had little effect on the internal elastic modulus.Compared with unstitching,modulus variation of the different diameter is within 9.6%.The elastic modulus of the composites was verified.The results show that the experimental results were larger than the finite element prediction, and the experimental result agrees with prediction.

Abstract:The orthogonal test of two dimensional ultrasonic extrusion 7075 aluminum alloy were carried out. The comprehensive influence of process parameters on the surface roughness and micro hardness were studied with grey relational analysis. The prediction model of the grey relational degree was constructed with the multiple linear regression method.The optimal process parameters were determined based on the prediction model. The results indicate that the influence of the process parameters on the surface roughness, micro hardness and gray relational degree are different, and process parameters obtained by ranking the grey relational degree are not the optimal value. The prediction model of grey relational degree can accurately forecast the test results, and the optimal process parameters obtained by the nonlinear programming solver based on the model. When the static force is 220 N, the extrusion speed is 30 m/min and the feed-rate is 0.14 mm/r,the optimal surface quality may be obtained with the surface roughness of Ra 0.44 μm and the microhardness of 637 HL.

Abstract:Accelerated aging test for acrylonitrile-butadiene rubber was carried out with two compression ratios at four different temperatures in 10^# hydraulic oil. The molecular structure,Tg and thermal properties of nitrile butadiene rubber before and after storage were characterized by FTIR,DSC and TGA. The results showed that the reliability of the shelf-life deduced by accelerated aging test was high. The aging of acrylonitrile-butadiene rubber after 12 years was not obvious.

Abstract:The 3J53 steel wire was coiled into a spring and linear defect on the surface appeared after heat treatment. In this paper, the morphology of the linear defect of steel wire was analyzed by scanning electron microscopy. The linear defect was also analyzed by energy spectrum analysis, and the microstructure of the linear defect was observed by metallographic microscope. The results showed that the linear defect on the surface of steel wire was serrated and crack-type folding along the axial direction of steel wire. Folding defect was formed during the process of steel wire production, which was extended and stretched during the process of coiling and heat treatment, and eventually linear defect was formed.

Abstract:A carbide slotting cutter and a PCD slotting cutter were used for the slotting of the carbon-cloth CFRP, respectively. Then, the effect of the tool material on the machining quality was studied.The delamination of the slot was increased as the feed per tooth increased.It showed that utilizing the PCD slotting cutter one would achieve a stable machining quality of the slots. And an ideal machining quality of the slots will be achieved.

Abstract:According to the defects in the process of drilling carbon fiber reinforced plastic, the drilling experiment was carried out by self-designed bit-step drill. The drilling force, hole outlet quality and hole wall surface roughness of step drill drilling carbon fiber reinforced plastic under different cutting parameters were studied and were compared with twist drill. The experimental results show that the drilling axial force produced by stepped drill is about 1/2 of the axial force produced by twist drill, the surface roughness of hole wall is smaller, and the hole exit has no obvious defects. Step drill is suitable for drilling carbon fiber reinforced plastic.