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Showing papers on "Micromechanics published in 1973"


Book
21 Feb 1973

81 citations


01 Jan 1973
TL;DR: In this article, the authors presented a set of matrix properties that can be used a priori to select matrices to yield composite composites with improved unidirectional strength, including matrix properties such as ultimate strength, ultimate elongation, toughness and fracture toughness.
Abstract: Criteria are presented which can be used a priori to select matrices to yield composites with improved unidirectional strength. The criteria evolved from an investigation including both theoretical and experimental efforts. Composite micromechanics were used in conjunction with suitable experiments and reference data to identify those matrix properties which influence composite strength properties. Composites of graphite fibers and low, intermediate and high-modulus resins were investigated. It was found that the area under the matrix stress/strain diagram limited to one percent strain is a good index for an a priori assessment of the matrix contribution to composite strength. The corresponding initial modulus is a useful parameter in translating matrix properties to composite properties. Matrix properties such as ultimate strength, ultimate elongation, toughness, and fracture toughness are misleading in translating matrix properties to composite strength.

11 citations


01 Jan 1973
TL;DR: In this article, a method has been developed for predicting the strength of a unidirectional composite material in terms of its micromechanical response to an applied stress, including elastoplastic material behavior, local failure that initiates a crack, and propagation of the crack to cause total failure of the composite.
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.

7 citations


Journal ArticleDOI
TL;DR: A FORTRAN IV computer code for the micromechanics, macromechanical, and laminate analysis of multilayered fiber composite structural components is described in this article.

3 citations


Journal ArticleDOI
TL;DR: A summary of the state-of-the-art in the mechanics of fiber reinforced composite materials is presented in this paper, where particular emphasis is placed on concepts of lamination theory and application of composite mechanics to the analysis of test methods for characterizing the mechanical properties of fibrous composites.
Abstract: A summary of the state-of-the-art in the mechanics of fiber reinforced composite materials is presented. Micromechanics and macromechanics are both examined although particular emphasis is placed on concepts of lamination theory. Application of composite mechanics to the analysis of test methods for characterizing the mechanical properties of fibrous composites is also covered. Equations which represent some of the more important concepts in composite mechanics are summarized. It is shown that the state-of-the-art in the mechanics of composite materials has reached a plateau where it can be used in structural design.

3 citations


Journal ArticleDOI
TL;DR: Several analytical techniques have been used to investigate molecular bond rupture in materials as mentioned in this paper, and these are compared and discussed in terms of suggested molecular models of fracture in highly orientated polymer fibers and films.
Abstract: Several analytical techniques have recently been used to investigate molecular bond rupture in materials. These are compared and discussed in terms of suggested molecular models of fracture in highly orientated polymer fibers and films.

3 citations