Accession Number : ADA306381

Title :   High-Performance Composite Materials for Vehicle Construction. An Elastoplastic Analysis of Crack Propagation in a Unidirectional Composite.

Corporate Author : RAND CORP SANTA MONICA CA

Personal Author(s) : Adams, Donald F.

PDF Url : ADA306381

Report Date : MAR 1973

Pagination or Media Count : 108

Abstract : The behavior of materials under mechanical stress can be divided into three distinct regimes: (1) linear elastic response up to the elastic limit, (2) inelastic behavior beyond the elastic limit and up to that loading at which first failure occurs locally, and (3) subsequent crack propagation and total composite failure. The crack initiation and its subsequent propagation, described above as the third regime, is the subject of the present study. A method has been developed for predicting the strength of a unidirectional composite material in terms of its micromechanical response to an applied stress. It includes elastoplastic material behavior, local failure that initiates a crack, and propagation of the crack to cause total failure of the composite. Although the basic methodology is applicable to the general problem, a specific loading condition--transverse normal loading--has been selected for detailed analysis. This loading condition is of particular interest to composite materials technology because of the inherently low transverse strength of most high-performance composites. The basic principles of the theory of plasticity have been combined with a finite element numerical analysis technique. The result is a rigorous analysis procedure capable of accurately modeling the complex boundary value problem being considered. A complete digital computer program has been developed as part of the investigation, Because the primary goal of the study was to develop a method of analysis and to write an associated computer program, only limited numerical results have been obtained to date. These are discussed in detail. Problem areas for research range from improving the accuracy of the basic finite element solution technique to developing a more representative model of the propagating crack.

Descriptors :   *FIBER REINFORCED COMPOSITES, *CRACK PROPAGATION, *ELASTOPLASTICITY, STRESS STRAIN RELATIONS, COMPUTER PROGRAMS, STRESS ANALYSIS, COMPOSITE MATERIALS, LAMINATES, FINITE ELEMENT ANALYSIS, STIFFNESS, CRACKING(FRACTURING), DISPLACEMENT, ELASTIC PROPERTIES, MODULUS OF ELASTICITY, FAILURE, ACCURACY, STRAIN(MECHANICS), STRENGTH(MECHANICS), BOUNDARY VALUE PROBLEMS, PLASTIC PROPERTIES, FAILURE(MECHANICS), MICROMECHANICS, DIGITAL COMPUTERS, TRANSVERSE, UNIDIRECTIONAL.

Subject Categories : Laminates and Composite Materials
      Mechanics

Distribution Statement : APPROVED FOR PUBLIC RELEASE