Micromechanical Characterization Parameters for a New Failure Criterion for Composite Structures

Abstract

Strain Invariant Failure Theory (SIFT) is a newly-developed failure criterion for composite structures [8, 9]. SIFT comprises two main features, namely micromechanical finite element modification and critical strain invariant parameters. Micromechanical finite element modification is performed to incorporate residual strains between fibers and matrix into homogenized finite element lamina solution. The presence of residual strains takes into account the mechanical and thermal (environmental) effects. Critical strain invariant parameters can be obtained from simple tensile test by carefully observing the occurrence of damage initiation in composite constituent. Strain tensors extracted from experiment are substituted into strain invariant parameters of J1i (first invariant of strain; i = f, m - fiber, matrix) and εvmi (equivalent strain or von Mises strain; subscript vm stands for von Mises). As noted in [8, 9], three critical strain invariants were found to be the onset of composite failure for carbon-fiber/epoxy system; they are J1-crm, ε vm-crf and εvm-crm. Micromechanical characterization parameters aim to provide general insight on the critical state of strains in which damage initiation locus may be determined by using SIFT critical parameters. Micromechanical model was subjected to six different loading conditions (three normal deformations and three shear deformations) and strain tensors (ε1, ε 2, ε3, ε12, ε13, ε23) were extracted from finite element analysis. Micromechanical characterization parameters were obtained by normalizing the strain invariants of micromechanics analysis with respect to critical strain invariant. Important issues such as effect of fiber volume fraction and fiber packing arrangement are briefly discussed.

Department(s)

Mechanical and Aerospace Engineering

Keywords and Phrases

Composite structures; Damage initiation; Micromechanical characterization parameters; Strain invariant failure theory

International Standard Serial Number (ISSN)

1662-9795; 1013-9826

Document Type

Article - Conference proceedings

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 2025 Trans Tech Publications, All rights reserved.

Publication Date

01 Jan 2006

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