碳纤维复合材料振动钻孔初探

本文对碳纤维复合材料超声波振动钻孔进行了初步探索和试验分析,提出了旋转超声刀切剁概念。     

Fabrication of artificial defects and their effect on the mechanical properties of C/C-SiC

Determining the effect of defects in fiber-reinforced materials, such as polymer matrix composites (PMCs), can be studied by creating artificial flaws in these materials, for example by introducing artificial PTFE foil to induce material delaminations. For fiber-reinforced ceramics (CMCs), this approach is more difficult due to the more complicated production routes of CMCs, which involve several processing steps at elevated temperatures. This work deals with the fabrication and introduction of defined defects in carbon fiber reinforced silicon carbide (C/C-SiC) composites in a way, which allows their detection by non-destructive material testing methods during and after each production step of the composite. It was shown that the defects produced using boron nitride (BN) and alumina fiber roving were stable over the entire manufacturing process and could be detected by ultrasound and x-ray tomography techniques. To determine any possible effects, an initial sampling of bending samples with artificial defects was manufactured, tested and compared with defect-free reference materials. These tests showed a lower bending strength and failure strain for the defect samples compared to samples without defects.     

Stress distribution in carbon-post applied with different composite core materials: a three-dimensional finite element analysis

The aim of this study was to investigate, using three-dimensional finite element analysis [3D-FEA], the stress and/or strain distribution of five different resin composites used in combination with carbon fibre posts. FEA models of five different light-cured composites were employed. The stress distribution of composite in combination with carbon fibre post was analysed under two different loading conditions: (i) polymerization shrinkage and (ii) load of 150 N with a 35° tilt to the long axis of the tooth. The Material Fatigue Rate [MFR%] of composite materials, dentin and fibre post was calculated. The highest stress values were recorded for Heliomolar and Clearfil-Photo P. The lowest stresses and MFR% values were attained when using Diamond Crown. High MFR% value [>45%] for carbon posts were found in all the tested cases under load. Composite materials with a Young’s modulus similar to that of dentin should be selected for the restoration of endodontically-treated teeth when using carbon fibre posts. The peak of the polymerization stress of the composite core is localized at the ferrule level. This might induce an open margin with higher risk of coronal leakage.     

碳纤维毫米波天线的应用研究

介绍了毫米波天线技术在军用领域的发展方向,具体对作战监视雷达、直升机防撞雷达和星载天线进行了说明;对碳纤维天线成型模具、铺层设计、成型工艺等关键技术进行了讨论,提出了该制造技术中的一些先进方案;最后,对国内外先进材料做了分析、比较。     

Effect of carbon-fibre powder on friction and wear properties of copper-matrix composites

ABSTRACT

The copper-matrix composite contains carbon-fibre powder which is prepared using a powder metallurgy sintering process in an effort to examine the effects of 50-mesh (270?μm) carbon-fibre powder on the microstructure and, friction and wear properties of copper matrix composites at high speed. When carbon-fibre powder is added within a certain range, the friction coefficient of the composite material is increased and the amount of wear is greatly reduced, When the content of carbon-fibre powder is 0.2wt-%, the hardness, density, friction and wear properties of the copper-based composite material has the best combination.     

An investigation into the damage development and residual strengths of open-hole specimens in fatigue

An extensive experimental program was carried out to investigate and understand the sequence of damage development throughout the life of open-hole composite laminates loaded in tension–tension fatigue. Quasi-isotropic carbon/epoxy laminates, with stacking sequence [45₂/90₂/−45₂/0₂]_S, [45/90/−45/0]_2S and [45/90/−45/0]_4S were examined. These were selected on the basis that under quasi-static loading the [45₂/90₂/−45₂/0₂]_S configuration exhibited a delamination dominated mode of failure whilst the [45/90/−45/0]_2S and [45/90/−45/0]_4S configurations showed a fibre dominated failure mode, previously described as “pull-out” and “brittle” respectively. Specimens were fatigue loaded to 1 × 10⁶ cycles or catastrophic failure, which ever occurred first. A number of tests were interrupted at various points as the stiffness dropped with increasing cycles, which were inspected using X-ray computed tomography (CT) scanning. A static residual strength program was carried out for run-out specimens of each configuration.     

碳纤维／聚丙烯复合材料的研究

主要研究了碳纤维／聚丙烯复合材料的热性能，流动性，力学性能和导电性能。实验表明：随着ＣＦ含量的增加，复合材料的熔点和结晶度稍有提高，拉伸强度有着明显的提高，当ＣＦ含量在（２５－３５）％时，复合材料的增强效果为最佳；复合材料的导电性能随ＣＦ含量增加而提高；但ＣＦＲ含量增加使复合材料的流动性能有明显的下降，冲击性能亦有所下降。     

LARGE VOLUME IONIZATION CHAMBER USED AS LABORATORY REFERENCE FOR LOW ENERGY X－RAY MEASUREMENT

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Towards a programming culture in the design arts

In his introduction to this issue of AD, guest-editor Mike Silver celebrates ‘the flexible language of commands and logical procedures’ of computers whose creative potential has until now been undervalued in architecture. He explains how the ‘happy accident’ of late 1990s blob architecture is now giving way to a focus on programming and composing new code, which promises ‘to generate new and unprecedented modes of expression’. Copyright © 2006 John Wiley & Sons, Ltd.     

防护水平低能X射线次级标准电离室的研制

用具有优良导电性能的碳纤维材料经环氧树脂固化制成壁厚０．３６ｍｇ／ｃｍ￣２、直径为１９５ｍｍ的大体积球形电离室。电离室机械强度好、体积稳定、对低能Ｘ射线能量响应好、灵敏度高，它不仅可作为防护水平低能Ｘ射线次级标准实验室的参考电离室，而且也适用于照射量率的现场测量。