On the Growth-of-Waviness in Fiber-Reinforced Polymer Composites: Viscoelastic Bifurcation and Imperfection Sensitivity

Abstract

The time-dependent, local microbuckling of fibers in polymer composites is modeled in the context of viscoelasticity. The instability or “growth-of-waviness”-type analysis is carried out for bifurcation (initially straight fibers), as well as for imperfection sensitivity (initially wavy fibers). The concept of dominant wavelength, previously defined for viscoelastic bifurcation by Biot, is generalized for viscoelastic imperfection sensitivity. A parametric study is presented to encompass a wide range of physically useful values to study the effects of matrix properties, fiber-matrix interfacial conditions, and time-dependent loads on dominant wavelengths. A marked difference is observed between the viscoelastic bifurcation and imperfection sensitivity dominant wavelength results. The bifurcation dominant wavelength is seen to depend negligibly on matrix properties, yet highly on the applied load and the interfacial conditions. On the other hand, the imperfection sensitive dominant wavelength is strongly dependent on matrix properties, while negligibly on load and interface conditions.