确定层状复合材料界面结合强度的新模型

本文提出了一个确定层状复合材料界面结合强度的新模型,即由两种材料交替完全粘结在一起的复合梁。利用材料力学方法对这种梁进行了应力分析,包括正应力分析和剪应力分析。研究了两种情况:一种情况假设两种材料均是线弹性材料;另一种情况假设其中一种材料是纯线弹性材料。而另一种材料是理想弹塑性材料。本文给出的复合梁剪应力的计算公式为复合材料界面剪切强度的测定提供了比较精确的计算公式。     

某复合材料π接头的强度估算

复合材料胶结接头是复合材料整体化成型技术的关键,其承载能力的大小直接关系到整体结构的力学性能.本文基于通用有限元分析软件ABAQUS采用实体单元建立某复合材料π形接头的三维有限元分析模型,参考最大正轴应力准则根据各铺层应力分析结果判定了接头结构的初始损伤部位.在此基础上,采用局部消刚模型对损伤部位进行刚度修正并进行重新计算,直至给出接头结构的极限载荷.与实验结果相比,初始损伤载荷计算误差小于6.1%,极限载荷计算值误差小于5%.损伤位置与试验基本吻合.     

Time-Dependent Compressive Strength of Unidirectional Viscoelastic Composite Materials

The strength of unidirectional composites is often lower in compressionthan in tension, making compressive strength an especially importantdesign criterion. Compressive strength in the fiber direction depends onthe stiffness of the matrix material, which softens over time due toviscoelastic effects, and thus lowers the strength of the composite.This reduction must be accounted for in assessing the long-termdurability of composite structures.The dependence of compressive strength on time and temperature hasbeen investigated for a unidirectional carbon/epoxy composite material.Experimental results for strength versus time are compared withanalytical predictions based on a one-dimensional fiber microbucklingmodel and numerical results from finite element analysis.     

Micromechanical Characterization of Tensile Strength of Fiber Composite Materials

A micromechanical model is proposed to predict the tensile strength of unidirectional composite materials that have a fiber breakage. It is assumed that the load carried by the broken fiber is transferred eccentrically to the adjacent ones, which leads to a stress increase that would cause a reduction in the overall composite material tensile strength. The behavior of the model is investigated by a simulation approach using the SAP-90 computer program, where the composite material was simulated by two types of available elements in SAP-90. These elements are the FRAME element to represent the fibers as two-dimensional truss elements and the ASOLID element to represent the matrix as two-dimensional plane stress elements. Several combinations of fibers and matrices were used to perform the composite materials that have been used in this study, such as boron, graphite, Kevlar and glass fibers, and epoxy, polyamide, and polyester matrices. The results obtained from the proposed model are tabulated and plotted, and compared with those obtained from the SAP-90 computer program, which is found to work very reasonably. The influence of key parameters that are thought to effect the amount of reduction in tensile strength of composite materials due to fiber breakage has been considered in the model formulation. These parameters are specimen (lamina) length-to-width ratio, fiber volume fraction, applied tensile load, shear modulus of the matrix, and elastic modulus of the fiber.     

Acoustic-Emission Criteria for Rapid Analysis of Internal Defects in Composite Materials

We present the results of acoustic-emission investigation of volume damage of composite materials with various types of stacking of carbon fibers. All 16 layers of fibers placed in the same matrix give different contributions to the strength properties of the material with varying acoustic-emission activity in the process of loading. We established criteria for the quantitative estimation of volume damage of composite materials with regard for the specific character of changes in amplitudes of acoustic-emission signals at various stages of loading. The analysis of spectral characteristics of acoustic-emission pulses passed through original and damaged materials of the specimen confirms the efficiency of the proposed criteria. We give values of criterional parameters for the investigated types of specimens of composite materials.     

On The Use Of Vector J-Integral In Crack Growth Criteria For Brittle Solids

In this paper the criterion for crack-growth in solids is investigated on the basis of the concept of potential energy release rate. The expressions for path-independent vector integral J_i (i = 1,2) are derived for brittle crack growth. The relationship is then established between the value of the path-independent vector integral J_i and the potential energy release rate for crack growth in an arbitrary orientation. This allows the prediction of crack re-orientation angles on the basis of the maximum energy release rate (MERR) criterion. The crack growth angle is determined analytically as a function of (). This result is compared with other theoretical formulations of crack growth criteria, as well as with experimental results reported in the literature, and good agreement is found. The formulation provides a rigorous basis for numerical modelling of the processes of crack initiation and propagation.     

商品包装材料的现状和趋势

主要描述商品用包装材料的现状并就其国内外发展趋势进行预测。     

On the Practice of Strength Estimation for Nonmetallic Fibrous Composite Materials at High Temperatures

We present experimental data on the effect of temperature on tensile, compression, bending, and shear strength characteristics of a carbon-reinforced plastic. It is shown that experimental shear strength values differ for various bending loading schemes.     

Strength Analysis and Process Simulation of Subway Contact Rail Support Bracket of Composite Materials

An application of composites for construction of subway brackets is a very effective approach to extend their lifetime. However, this approach involves the necessity to prevent process-induced distortions of the bracket due to thermal deformation and chemical shrinkage. At present study, a process simulation has been carried out to support the design of the production tooling. The simulation was based on the application of viscoelastic model for the resin. Simulation results were verified by comparison with results of manufacturing experiments. To optimize the bracket structure the strength analysis was carried out as well.     

可调式螺杆制冷压缩机噪声问题的探讨

通过对一台存在问题的可调式螺杆制冷压缩机的详细测试和分析,对进一步降低可调式螺杆压缩机的噪声起到推动作用.     

Analysis Of Repeatability For Measurements Of Veiling Glare Index

Various factors that affect the repeatability of an apparatusfor the measurement of veiling glare index of a long focal length opticalsystem are discussed,which include the errors influencing the radianceuniformity of the extended bright field,positions of the detector,measuring aperture,and the black patch.The results can be used in thedesign of any veiling glare measurement apparatus.     

聚合物基复合材料废弃物几种处理方法概述

本文简述了聚合物基复合材料特点及应用情况,随着时间推移其数量日益增多,外加上环保要求的提高,使得其后续废弃物的处理压力也随之增大。通过分析其废弃物特点,并结合相关处理经验,对其废弃物处理提出了几种方法,并对处理工序等加以详细阐述。     

New Developments Of Materials

Materials Research Innovations -     

Some Problems of Nonlinear Mechanics in Geophysics, Planetology, and Strength of Materials

We generalize results of investigations in nonlinear mechanics as applied to the phenomena at the interface between strength of materials, stability of discrete-continuous complex systems, and physicoengineering problems of verifying the unified theories of fundamental fields. The principle of a fundamental triad is formulated. In this case, systems analysis can be useful for simulating the dynamics of complex discrete-continuous mechanical systems of different dimentional scales.     

Failure of Composite Materials

Abstract:  An overview is given of the state of the art of theories and procedures for predicting and analysing failure in composite materials. Of the scores of failure theories available, only those representative of each of the following categories are discussed: limit or noninteractive, interactive, and failure mode-based theories. The validity and applicability of the various theories are evaluated from the point of view of convenience of application and agreement with experimental results. Both lamina and laminate failures are discussed. In the case of ultimate laminate failure, a progressive damage scheme coupled with a failure mode-discriminating criterion is discussed. Special attention is given to textile composites where new three-dimensional experimental results are reported and a new interlaminar failure theory is proposed.     

Strength of Materials and Structures

Book reviewAll engineering structures designed according to modern principles have to be strong and sufficiently rigid. Scientists and engineers have long recognized the importance of the strength ofmaterials and structures, and dedicated much their efforts to bothfundamental and industrial research into the theory for vast engineering materials and various structures. A lot of engineers needto be familiar with the fundamental principles of strength in materials and structures in order to desi…     

Similarity Criteria for Dusting of Plastic Materials

We propose a system of similarity criteria and criteria formulas that have made it possible to generalize the available experimental data on the erosion of plastic materials (metals) by particles, impacting with them at a right angle, with a rootmeansquare error of 30%. The experimental data analyzed have been obtained under the following conditions: velocity of the particles, 10–300 m/sec; temperature of the obstacle, room temperature–0.8T _m ; ratio between the densities of the particle flux and the obstacle material, 0.3–3; diameter of the particles, 40–3000 m. A formula for generalizing experimental data on the erosion of materials by particles incident on their surface at different angles has been obtained.     

Strength of Structural Carbon Materials

The effect of microstructure on the strength of various carbon materials is analyzed. The strength of structural carbon materials is shown to decrease upon oxidation and to rise during neutron irradiation.__________Translated from Neorganicheskie Materialy, Vol. 41, No. 5, 2005, pp. 523–530.Original Russian Text Copyright © 2005 by Virgilev.