Damage tolerance of glass mat/epoxy laminates hybridized with flexible resin under static and impact loading

This study deals with the impact property and damage tolerance of matrix hybrid composite laminates with different laminate constitution. The matrix hybrid composite laminates consisted of the laminae with a conventional epoxy resin and the laminae with a flexible epoxy resin modified from the conventional resin to avoid the interlaminar delamination. The impact energy absorption ratio greatly depended on the matrix resin placed at the impact face. The energy absorption was almost constant if the conventional resin was placed at the impact surface layer, while it increased exponentially with the increasing fraction of the flexible resin if the flexible resin was placed at the impact face. The impact energy was absorbed by the damage development and propagation in the laminate with conventional resin laminae as the impacted face, while it was absorbed by both the recoverable deformation of the flexible resin and the damage propagation in the laminate with flexible resin laminae as the impacted face.     

Interfacial reaction between CO2-CO gas and molten iron oxide containing P2O5

The interfacial reaction between CO₂-CO gas and molten iron oxide containing P₂O₅ was investigated by the ¹³CO₂-CO isotope exchange technique at 1773 K with CO₂/CO=1.0. The apparent rate constant rapidly decreased with the addition of P₂O₅ up to 2.86 mol pct PO_2.5 and the Fe³⁺/Fe²⁺ ratio kept constant at approximately 0.2. By the classic site blockage model, in which the reaction only occurs on the vacant sites, and the modified site blockage model, in which the reaction occurs on the vacant sites and the sites occupied by phosphorus simultaneously, the effect of the addition of P₂O₅ was analyzed and the reaction mechanism of CO₂ dissociation was discussed. It may be concluded that the dissociation of the adsorbed CO₂ molecule is reasonable as a rate-determining step and that the effect of phosphorus on the interfacial reaction is caused by the decrease in the number of active sites with the increase of phosphorus content as a surface active element in molten iron oxide.     

Recovery retardation in equal channel angular pressed Al–Zr alloy during friction stir welding

The effect of Zr on reduction of hardness and microstructure in an FS weld of equal channel angular-pressed Al alloy was investigated. Zr addition to Al suppressed dynamic recovery in the thermomechanically affected zone and enabled retention of the high hardness of the ECA-pressed material throughout the weld.     

Superconductivity in W-containing diamond-like nanocomposite films

Superconductivity in a tungsten-containing carbon-oxide film was reported. The film with 500 nm thickness was deposited onto polycrystalline silicon oxides using chemical vapor deposition and the co-sputtering of a tungsten metal target. The bonding state of the carbon atoms and the macroscopic and microscopic crystal structure of the film were investigated by Raman spectroscopy, X-ray diffraction and transmission electron microscopy measurements. From the experimental results, we determined that this film essentially had an amorphous structure. The temperature dependence on resistivity was measured in the temperature range of 2–300 K. Resistive superconducting transition was observed at 3.8 K. The dc magnetizations were measured in the temperature range of 1.8–6.5 K. The diamagnetism resulting from a superconductive state was observed below 3.75 K, which is consistent with a resistive superconducting transition. It is thought that the finite sized clusters of the different superconductive transition temperatures cooperatively produce a macroscopic superconducting phenomenon.     

水平管气力输送数值模拟

本文采用粒子追踪理论对水平管中粒子流动状态进行了数值模拟.文中提出了一种新的粒子碰撞模型,并忽略粒子的旋转和扬力,仅考虑气流阻力和重力对粒子的影响,在输送量为9.13×10~3kg/s,混合比约0.3的条件下,通过数值计算得知:由于粒子间的碰撞,使得异径粒子的速度趋向平均化;粒子间的碰撞是粒子悬浮的原因之一;粒子的浓度沿管轴向是随时间而发生变化的.     

Design of electrofusion joints and evaluation of fusion strength using fusion simulation technology

Fusion simulation is one of the key techniques in designing and producing electrofusion (EF) joints for gas distribution and in evaluating fusion joint integrity. This paper describes the result of a numerical simulation of a thermal fusion process, using the finite element method. A nonlinear heat transfer computer program was used to obtain the temperature profile of a large electrofusion joint at fusion. The effects of applied voltage, heating time, wire pitch, and ambient temperature were examined for designing a 150-mm EF joint. A method to shorten the cooling time was also investigated. The fusion condition range suitable for a 150-mm EF joint was found to be slightly narrower than that suitable for a 50-mm EF joint. Examination of the effect of wire pitch revealed that if the pitch is extremely large, thermal degradation starts in the resin close to the wire before the fusion-interface strength reaches the maximum value. We have developed a program to simulate the process of closing the gap between the pipe and the joint due to resin expansion and melting after the power is supplied.     

High-performance polymer alloys of polybenzoxazine and bismaleimide

Two series of high-performance polymer alloys were prepared by mixing typical benzoxine monomers, 3-phenyl-3,4-dihydro-2H-1,3-benzoxazine (P-a) or 6,6-(1-methylethyliden)-bis-(3,4-dihydro-3-phenyl-2H-1,3-benzoxazine) (B-a), with a typical bismaleimide, 4,4-bismaleimidodiphenyl methane by various ratios followed by thermal treatment up to 240 °C. DSC and IR of the alloys were examined to follow the curing reaction. These analyses showed that the obtained polymer alloys are AB co-cross-linked polymer networks through the formation of ether linkage between the hydroxyl group of polybenoxazine and the double bond of bismaleimide. Viscoelastic analysis and softening temperature measurement revealed that the polymer alloys have much higher glass transition temperatures than those of each homopolymer. The thermal stability also increased with the increase of bismaleimide content as evidenced by TGA.     

Heat Generation in Multilayer Piezoelectric Actuators

Multilayer piezoelectric actuators when driven under high frequency, generate significant heat, which influences the reliability and other piezoelectric properties. In this paper, heat generation in various types of multilayer PZT-based actuators was studied. Experimental results showed that heat generation is mainly caused by ferroelectric hysteresis loss in the stress-free state. A simplified analytic method was established to evaluate the temperature rise, which is useful for the design of multilayer and other high-power actuators.     

Ideal crosslinked-polymers and their characterization in free-radical monovinyl-divinyl copolymerizations

The critical conditions in which the classical Flory-Stockmayer gelation theory (F-S theory) is applicable to monovinyl-divinyl copolymerizations were pursued in detail. The resulting prepolymers or precursors of ideal crosslinked-polymers were characterized as standard polymers for the discussion of network formation in free-radical monovinyl-divinyl copolymerizations. Methyl methacrylate was copolymerized with a small amount of ethylene dimethacrylate, butylene dimethacrylate or nonapropyleneglycol dimethacrylate in the presence of lauryl mercaptan, a chain transfer agent to reduce the occurrence of a thermodynamic excluded volume effect and intramolecular crosslinking as the primary and secondary factors, respectively, for the greatly delayed gelation in the free-radical monovinyl-divinyl copolymerizations and, moreover, to keep the primary chain length constant by inhibiting a gel effect. The ratio of the actual gel point to the theoretical one reached 1.1, supporting the validity of F-S theory. The resulting prepolymers were subjected to SEC-MALLS analysis to determine the molecular weights, the molecular-weight distributions and the radii of gyration; the correlations of molecular weight vs. elution volume and radius of gyration vs. molecular weight were useful for the characterization of the precursors of ideal network-polymers.