A Parametric Study of Variables That Affect Fiber Microbuckling Initiation in Composite Laminates: Part 1-Analyses

Abstract

The objectives of this research focus on the effects of nonlinear matrix constitutive behavior, initial fiber waviness, and fiber/matrix interfacial bond strength on fiber microbuckling initiation in thermoplastic composites. Nonlinear geometric and non linear material two-dimensional finite element analysis is used to model the initiation of fiber microbuckling of an initially wavy fiber. Results show that reductions in the resin shear tangent modulus, larger amplitudes of initial fiber wavinesses, and debonds each cause increases in the localized matrix shear strains; these increases lead to premature fiber microbuckling initiation. These numerical results are compared with experimental data obtained during this investigation. These experimental results and comparisons are presented in a companion paper [1] .

Internal instability as a possible failure mechanism for layered composites

“…We have intentionally chosen to present the computations for model generic material systems only. Some comparisons with available experimental data were discussed earlier [10,[22][23][24]. The applicability of the method to practical materials, e.g.…”

“…From the early literature on compressive fracture, it was easy to get the impression that fibre instability (microbuckling) and kinking are competing mechanisms. However, it is now accepted that a kink band is an outcome of the microbuckling failure of actual fibres, as observed experimentally [23,24]. Fibre microbuckling occurs first, followed by propagation of this local damage to form a kink band.…”

The effect of fibre volume fraction on the onset of fracture in laminar materials with an array of coplanar interface cracks

“…Hence, it was implicitly assumed that fibre distribution within the matrix is uniform (no resin rich regions were considered). For resin rich regions, distribution of strain/stresses is disturbed, thus it may trigger premature fibre microbuckling and subsequent kink band formation [15,22].…”

A mechanics model for the compressive response of fiber reinforced composites

“…Following Rosen [3] and many other investigators we employ the Cartesian two dimensional model shown in Figure 1 behavior of the resin but did not explicitly address the variation of the matrix shear strain parallel to the fiber direction, which is incorporated herein. On the other hand, it appears that the finite element method employed by Guynn et al [10] and the iterative numerical scheme utilized by Highsmith et al…”

“…The probability density distribution which corresponds to equation (26) is The Compressive Resoonse with Randomly Spaced Fibers The probability density AV() given in equation (27) was incorporated into the formulation expressed in equations (11) and (13) and employed to predict the compressive response of Gr/PEEK (APC-2) composite with Vf = 0.6 at a temperature of T = 21 C. Based upon the data of Guynn et al [10], the nonlinear shear behavior of the PEEK resin was fitted by a Ramberg-Osgood expression …”