Micromechanics-based simulations were conducted to evaluate the linear and nonlinear properties of natural fiber-reinforced plastic composites with fibers in various waving and kinked forms. Natural fibers, such as woodfibers and fibers from plants, have length-aspect ratio of longitudinal and transverse at or greater than 20. At such high aspect ratio, the natural fiber normally presents in waving, bending, twisting, kinking morphology in the composites. This paper presents a series of micromechanical simulations to predict the elastic and nonlinear elastic behaviors of natural fiber-reinforced plastic composites (NF-PCs) considering the effects of fiber kinking, waving, and arrangements on the stress-strain relationship. A set of three-dimensional unit cells (UC) were developed to mimic various fiber morphologies with the fiber volume fraction of fifty percent, a typical fiber volume fraction for the natural fiber plastic composites. Periodic displacement boundary conditions were implemented on the UC to simulate a unidirectional strain field. The homogenized anisotropic stress-strain relations for NF-PCs were predicted by postulating nonlinear behavior of plastic matrix and perfect and imperfect interface between the NF and the matrix. Stress distributions in the natural fiber were presented as a function of the fiber aspect ratio and the fiber waving and kinking forms. Even though, the high fiber aspect ratio provides relatively high elastic modulus and nonlinear hardening, it also induces high stresses or stress concentration in the fiber that may result in earlier failure of the fiber when the composites undergone a relatively large deformations (> 4%).
Surface grinding of carbon fiber–reinforced plastic composites using rotary ultrasonic machining: Effects of tool variables
