Polyamide-6/vegetal fiber composite prepared by extrusion and injection molding

The interest for the use of vegetal fibers as polymers reinforcement has recently increased because of their unique environmental and technological advantages. This work evaluated the use of Curauá fibers in polyamide-6 composites aiming at glass fiber replacement. Fiber content of 20, 30 or 40 wt% and fiber lengths of 0.1 or 10 mm were studied. Fibers were treated with N₂ plasma or washed with NaOH solution, to improve their adhesion to PA-6. Samples with 20 wt% of short or long fibers, with or without pre-treatment, were compounded in two different co-rotating intermeshing twin-screw extruders. These samples were submitted to mechanical and thermal tests. In conclusion, non-dried raw materials improved fiber/matrix interfacial adhesion. Tensile and flexural properties of this composite are better than unfilled, but lower than glass fiber reinforced polyamide-6. However, its impact resistance and heat deflection temperature are similar to the glass fiber reinforced polyamide-6 and its lower density, enable it to replace this latter in specific non-critical applications.     

Study of the effective parameters on mechanical and electrical properties of carbon black filled PP/PA6 microfibrillar composites

In this study the electrical and mechanical properties of microfibrillar polypropylene (PP)/polyamide6 (PA6) blend filled with super conductive carbon black (CB) have been investigated. In situ microfibrillar PP/PA6 composites filled with CB are produced using a single screw extruder equipped with a spinneret. Glycidyl methacrylate (GMA) grafted polypropylene (PP-g-GMA) is used as the compatibilizer. To investigate the effects of extensional flow on the microstructure, electrical and mechanical properties, three adaptors with various convergence angles were designed, prepared and applied between the extruder and the spinneret. To optimize the effects of processing and material parameters on the electrical and mechanical properties, the Taguchi method of experimental design is used. Material and processing factors which are studied include: concentration of PA6, compatibilizer level, CB concentration, drawing speed of melt spinning line, adaptor angle, order of mixing and temperature profile along the extruder. The results show an increase in DC conductivity of up to 10¹¹ times in comparison with pure PA6, by increasing the concentration of CB, drawing speed, adaptor angle and optimizing other parameters. By optimizing processing and material factors studied here, strength of microfibrillar structured composites is increased of up to 80% in comparison to pure PP.     

Multiresolution Representation of 2D CSG Models

Multiresolution is currently one of the main schemes used in CAD modeling for representing objects, particularly when large-scale geometric data must be transferred interactively over a network, as in the case of collaborative design. Increasingly complex products and growing competition have turned design into a collaborative team effort. Furthermore, the widespread development of Internet viewers has also necessitated the transfer and display of large-scale CAD models over networks. In order to reduce the volume of transferred data, efforts have been made to transfer CSG (Constructive Solid Geometry) models rather than those based on B_rep (Boundary Representation). This paper presents an original new method for speeding up data transfer by using multiresolution CSG models at different levels of details (LOD). The multiresolution CSG algorithm generates a hierarchy of multiresolution CSG trees; at each level, the shape is further approximated and represented by a smaller number of CSG primitives. The paper analyzes the proposed algorithm, and demonstrates its feasibility.     

Young’s modulus of crystalline C60 nanotubes studied by in situ transmission electron microscopy

Bending tests of crystalline nanotubes composed of fullerene C₆₀ molecules are performed inside a high-resolution transmission electron microscope. We fixed one side of a C₆₀ nanotube with a body-centered tetragonal structure with typical inner and outer diameters, i.e., 180 nm and 510 nm, respectively, and then applied concentrated forces on the other side using piezomanipulation of a silicon nanotip. The bending process was observed in situ by transmission electron microscopy with simultaneous measurements of the forces by an optical deflection method. It was found that the Young’s modulus of the nanotube was estimated to be 62–107 GPa, which was 1.1–3.3 times larger than that of C₆₀ nanowhiskers. The result concerning the increase in the Young’s modulus of the C₆₀ nanotube provided an experimental evidence for the structural model composed of an inner core and a surface shell for C₆₀ nanowhiskers.     

凯萨·布隆斯泰德和沃迪·凯威设计事务所

本文通过对主要设计成员凯萨·布隆斯泰德和沃迪·凯威的背景,以及对私人住宅、餐馆、办公楼、图书馆、精品屋等案例的阐释,向读者介绍了这家十分活跃的芬兰设计事务所,同时展现了北欧的室内设计风格。     

Manufacturing and structural safety evaluation of a composite train carbody

This paper explains the manufacturing process of a composite train carbody with a sandwich composite structure for bodyshell and a stainless steel structure for the under frame. In addition, the structural behavior and safety of the composite carbody of the Korean tilting train was investigated by the static load tests. From the test results, the stiffness of the composite carbody met the specified design. In the aspect of strength, the maximum stress of the composite bodyshell was of 12.2% of strength of CF1263 carbon/epoxy.     

Properties of Graphite‐Strengthened Magnesium

Mg was dispersion‐strengthened with graphite by powder metallurgy. The material was produced by ball milling Mg micropowder (median particle diameter 40 μm) with 3 vol.‐% graphite powder (median particle diameter 1–2 μm). After 8 h ball milling the product was consolidated by hot extrusion. Structural analysis revealed that a submicrocrystalline structure developed during ball milling. Tensile tests showed that the material was brittle even up to 300 °C and, therefore, most mechanical tests were carried out under compression. Under those conditions the reinforced material showed yield stresses of 270 MPa at ambient temperature, 170 MPa at 150 °C, and 125 MPa at 300 °C. Mg processed under the same conditions, but without graphite addition, had significantly lower yield stresses. The dispersion‐strengthened Mg showed a marked increase in creep resistance: at 200 °C and a stress, σ_c, of 100 MPa, the secondary creep rate, ?_s, was in the lower 10^–9 s^–1 range and at 300 °C and σ_c of 80 MPa, ?_s values of up to 1 × 10^–8 s^–1 were measured. The results are discussed.     

KEIO/72000/0.003型电抗器替代进口设计

本文通过分析电炉电极间短路电流，确定电抗器主要技术参数及设计依据。     

机械摆反馈机构的仿真设计

机械摆采用机械反馈机构，可以把系统的末端状态反馈到中间机构，通过调整框杆支点，实现机械摆随机同步跟踪。这里对该机械摆反馈机械进行了结构设计、解析计算和计算机仿真设计。这种设计现已成功地应用于某一工程机械设备的自动接货、供货装置上。