Experiments on fiber-break progression and local load transfer in a model graphite/glass/epoxy microcomposite
A review of the experimental literature on the probabilistic/micromechanical theory of failure of continuous unidirectional composites indicates that crack propagation in the transverse and longitudinal direction depends primarily on the load transfer between the fiber and matrix, and on the strength of the fibers. Currently, neither the matrix constitutive behavior nor the fiber strength at small gauge lengths, {approx} 0.5 mm, are known with sufficient detail to evaluate micromechanical models. This investigation focused on the independent and concurrent determination of the graphite/epoxy load transfer and the graphite fiber strength distribution. The method consisted of the fabrication and observed tensile loading of a three-fiber, microcomposite tape containing a closely spaced planar array of a glass/graphite/glass fiber in an epoxy matrix. The load transfer was modeled using shear lag assumptions, where the epoxy shear behavior was best described by an elastic, plastic, and debond zone. The Weibull parameters for the strength of filaments within a sample were estimated by an approximate model for the number of breaks as a function of strain. The model assumed the flaws were distributed according to a Poisson process such that the resulting distribution for the strength of a single fiber had Weibull form.
- Research Organization:
- Cornell Univ., Ithaca, NY (USA)
- OSTI ID:
- 5210979
- Resource Relation:
- Other Information: Thesis (Ph. D.)
- Country of Publication:
- United States
- Language:
- English
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