On the initiation and growth of kink bands in fiber composites. Part II: analysis

Motivated by the experimental findings in Part I, the growth of a kink band in a uniaxial composite is investigated using two- and three-dimensional m icromechanical models. The models include both a local and a global imperfe ction and were preloaded in compression and then sheared under displacement control. An inclined kink band initiates from the local imperfection and g rows across the specimen. Similar results were obtained for pure compressio n loading. The simulated kink bands are quite similar to those observed exp erimentally; though, when J(2) plasticity is used to model the inelastic ma trix, their inclination is lower than in experiments. The calculated band i nclination is shown to be insensitive to many model parameters including im perfection characteristics, fiber diameter, volume fraction, and matrix yie ld stress. However, it is quite sensitive to the dilatancy of the matrix as demonstrated by the use of the Drucker-Prager constitutive model for the m atrix. It was found that the ability of the matrix to deform in the directi on transverse to the fibers plays an important role in allowing larger, mor e realistic kink band inclinations to be obtained. (C) 2001 Elsevier Scienc e Ltd. All rights reserved.