Stuffer boxes are commonly used to texture the synthetic fibers in the textile industry. Crimping of fibers improves their insulation performance and comfort properties. The stuffer box works on the basis of compressing fibers in its box. In this study, the buckling behavior of fibers in stuffer box was investigated. In order to model the primary crimp, a single fiber was modeled using Euler-Bernoulli’s beam theory and the governing equation was derived by making use of some simplifying assumptions. The governing equation which is a nonlinear differential equation was solved using the approximated Galerkin method. In addition, the problem was simulated using ABAQUS finite element code and its results were compared with those obtained from the other solution method. The results showed that all methods predict the same buckling critical load. Two dimensional parameters x and y which represent half the wave length and wave amplitude respectively, were measured. Profile picture with an accuracy of 0.1 micrometer manufactured by Motic Company was used to measure the dimensions. This measurement was repeated three times for a crimped fiber and all its waves were measured. Then, the average of measurements were calculated to be compared with the simulation results. Crimp form predicted by the Galerkin method was compared with the experimentally measured dimensions. Simulation results of Galerkin method showed that the free-free beam model correlates with experiment better than the fixed-fixed beam model. In the Galerkin solution method, the material was assumed to be elastic. However, in practice, due to the high temperature chamber and low flow stress of the material, the fibers deform permanently. So, an elastoplastic material model was used in the simulations in order to improve the results. Finally, the fiber zig-zag form after passing through the pair of rollers of stuffer box was simulated using ABAQUS commercial finite element package with the purpose of predicting the secondary crimps of the fibers. The simulation results were compared with the mean wavelength of fiber. The comparison showed that the simulation results were in agreement with the experiment. After validating the results, the effect of various process parameters was studied on the crimp form. The weight of fiber, radius and speed of rollers on the wavelengths were investigated. Also, the friction between the fiber and the chamber geometry were considered. The effect of roller speed on the results was negligible and by decreasing the radius of the rollers, the wavelength was increased. An increase in the friction between the chamber geometry and fiber was shown the wavelength of the fiber to reduce. The results also showed that the back pressure had a significant effect on the results. Finally, the results showed that the elastoplastic model had a significant effect on the simulation results. Keywords: Stuffer box, Crimp, Galerkin finite element method, Elastic beam, Post-buckling.
