天然纤维增强塑料之门

在一项公开推出的项目中开发了一个天然纤维增强塑料的参数与知识数据库。该数据库会从各个方面给用户提供有关原料生产,增强塑料的制备与加工直至构件的计算与结构方面的信息。     

Twin screw reinforced plastics compounding

Co-rotating, self-wiping twin-screw equipment has been developed which incorporates fiber glass or fillers into various plastics to form compounds with superior mechanical properties. Fiber glass bundles are folded into the plastic melt in such a fashion that each glass strand is wetted out with minimum breakage of the strand. The intensity of compounding is controlled externally to condition the basic polymer for optimum filler incorporation. The external control permits compounding a wide variety of plastics over a range of throughputs. The degree of mixing can be varied while the machine is in operation. The fiber resin blend passes through an independently controlled extruder for pelletizing with a hot die face cutter. Either air or water quench systems can be used for cooling the pellets. The gentle handling of the fiber resin blend through compounding and extrusion not only minimizes glass breakage, but also minimizes wear on the equipment. Retention of glass fiber length and good strand bonding impart superior properties to the fiber resin product.     

纤维强化复合材料特性的发展

前 言复合材料为目前世界各国竞相发展研究的材料,其优点多且能符合许多工程上的要求。随着科技的日新月异,对产品性能要求日益提高,而其中最为基本的,不外乎对材料性能之了解与选用。近年来材料科技高度发展,许多可用于特殊状况(如较高温、低低温、较高压力或较高负荷…)之材料不断地被开发出来,复合材料便是其中一种颇具发展性的材料。复合材料就广义而言,仅利用两种或两种以上不同材料,以各种不同的加工法,结合在一起,撷取原材料的特性与优点,发挥协同作用,制成性能优异并能满足需求的新材料。就狭义而言,以复合材料的基材型态可分为 3 …     

塑料超声波扫描焊接技术

超声波扫描焊接是连续、高速地超声波焊接在固定超声波焊头或旋转焊头与砧座下方传送的平直工件的方法。该方法适用于至少有一个平面便于焊头接触的硬质热塑性塑料工件。某些织物或薄膜也适用于这种方法。无论是大型的还是小型的热塑性塑料工件都可以超声波扫描焊接。本文简述了超声波扫描焊接原理、分类、接头设计、特点及应用。     

Molding by reactive injection of reinforced plastics

A model for the molding by reactive injection of reinforced plastics for systems in which fiber glass reinforcements are placed into the molds, is proposed. It allows for the determination of processing parameters and their influence on dependent variables: conversion, temperature, and pressure. Moldability areas, where premature gelling is avoided, are defined. Operating conditions are selected to reduce cycle time, produce small load losses, and provide a fairly uniform curing stage throughout the product.     

Processing of reinforced plastics using multi-screw compounders

Polymer modification by addition of reinforcing agents represents a popular means of increasing physical property values. The polymer matrix has been forced to accept up to 55 percent by weight of fibrous reinforcement and 80 percent by weight of powdered types in order to meet application requirements. These materials demand sophisticated mixing equipment which must provide extensive intake and conveying capabilities, polymer wetting of reinforcement, and dispersion of reinforcement. This process must also be conducted with controlled shear intensity and excellent temperature and residence time control in order to respect polymer thermal sensitivity and product requirements. The extrusion process is a proven economical method for incorporating reinforcements into polymer resins. Co-rotating intermeshing twin-screw extruders are particularly suited for these tasks. Positive conveying, self-wiping, and shear intensive mixing characteristics provided by the screw mechanism satisfy requirements of reinforcement compounding. This mechanism allows interruption of streamline flow which is needed to disperse both high and low aspect ratio reinforcing agents into a polymer matrix. Mathematical representation of the benefits of twin-screw extrusion (relative to single-screw) related to pumping and mixing capability have been developed based on the classical pressure flow continuity equation with proper selection of boundary conditions.     

Fatigue crack growth in fiber reinforced plastics

Crack extension during fatigue loading is one of the primary causes of failure in engineering materials. While the fatigue crack resistance of homogeneous and even adhesive systems has received detailed study and characterization, relatively few and scattered results are available for fiber composites. One difficulty with obtaining such data for composites is their tendency to develop complex patterns of intra- and interlaminar damage which expand in a stable manner during fatigue. Such damage usually does not severely reduce the load carrying capacity of a structure but the complexity of the damage geometry has so far frustrated efforts to apply any unifying theories of growth. Measurement of the rate of macroscopic crack growth, through thickness crack extension, has been possible for certain composites and crack direction where the stable damage is constrained. These include cracks in 0°/90° laminates, woven fabric laminates, chopped strand mat laminates, sheet molding (SMC) materials, and short fiber reinforced thermoplastics. Macroscopic interlaminar cracks in continuous fiber systems have also received some recent attention. Fatigue crack growth in glass fiber composites for which most data are available, involves significant contributions from both static and cyclic load effects. A simple model for predicting fatigue crack growth rates from traditional S-N curve and fracture toughness data has proven useful for certain well behaved systems. Limited study has also been made of the effects of moisture and salt water on the fatigue crack growth rate.     

Studies on a fiber reinforced plastics honeycomb structure

Based on an adhesive and fabric screening program, a rubber-modified resole adhesive and a flexible grade plain weave glass fabric were found appropriate for the fabrication of a glass-reinforced plastics honeycomb core material. Sandwich structures of different densities were fabricated. A linear regression analysis was performed to correlate the mechanical properties (S) with the density (p) for a wide range of sandwich structures based on honeycomb and cellular plastic core materials. An analytical model of the form S = Kρⁿ was derived, with two empirical constants K and n. The density exponent n was between 1 ≤ n ≤ 2 in all cases. An equation was also derived to relate density with thermal conductivity. The dynamic mechanical analysis (DMA) results revealed that the glass transition temperature of the resin matrix associated with the sandwich structure was higher than that of the corresponding facing laminate or near resin casting.     

玻纤增强塑料的回收解决方案

人们一直在寻求价格低廉、质轻的新型材料,以取代玻璃纤维,或天然纤维用于加工增强性塑料部件。德国Fraunholer高聚物应用研究所的Hans-PeterFink发现,当今流行采用注塑或挤出的玻纤增强聚丙烯（GFR-PP）制件具有相当高的强度,但缺点是比重大,而且回收处理相当困难。他在对汽车轮胎的研究工作中取得重大突破,采用纤维素轮胎子午线代替玻纤增强商品化聚合物,取得理想的效果。