Composite-Constituent Failure Analysis

摘要

A majority of structural failure criteria developed for composite materials to date can be classified as macromechanical because the criteria attempt to predict failure using composite stress-strain data. A key element of macromechanics is the combining of constituent properties into a homogeneous set of composite lamina properties and possibly combining lamina properties into homogeneous laminate properties. In contrast, micromechanical failure analyses retain the individual identities of the lamina and their constituents. Micromechanical failure models have seen limited application in structural analyses due to the difficulty in acquiring information at the constituent level. In this paper, we develop a nonlinear progressive failure analysis for composite structural laminates based on constituent (phase averaged) stress fields. Damage in a composite material typically begins at the constituent level and may, in fact, be limited to only one constituent in some situations. An accurate prediction of constituent failure at sampling points throughout a laminate provides a genesis for progressively analyzing damage propagation in a composite structure. A constituent based failure model also allows one to identify intermediate damage modes. The failure analysis approach presented utilizes the classic strain decomposition put forth by Hill to extract constituent stress and strain fields during a routine finite element analysis at the structural level. We refer to this approach as a multicontinuum theory in recognition of the continuum nature of the constituent stress and strains. Constituent-based, quadratic, stress-interactive, failure criteria are developed to take advantage of the micro-scale information provided by multicontinuum theory. The criteria are fully three-dimensional and require a minimum number of experimentally derived constants. A finite element implementation utilizing the proposed failure criteria was used to generate one- dimensional stress-strain curves and two-dimensional failure surfaces for a variety of composite laminates under uniaxial and biaxial loads. The results were shown to be superior to comparable single continuum failure analyses and in good agreement with experimentally determined failure loads.