Numerical Modeling of the Dynamic Properties of Flax/PP Nonwoven Composites

This paper aims to estimate the dynamic properties of nonwoven flax fiber-reinforced polypropylene (PP) composites using a numerical finite element model. The proposed 2.5D numerical model comprises an in-plane generation of a nonwoven fiber reinforcement network and a three-dimensional generation of the porous PP matrix. The embedded element technique, available in ABAQUS Software, is used to introduce the fiber network in the matrix space and to solve the difficulty of meshing. Many parameters are considered for the plane fiber network generation, such as the undulation, length, and orientation of the reinforcement fibers in the plane direction. Indeed, based on microscopic observations, the flax fiber nonwovens are modeled by sinusoidal functions with a specified average length and orientation. For the three-dimensional matrix network, the porosities are modeled by randomly dispersed cylinders of voids in a homogenous PP matrix. The first five natural frequencies of the flax/PP nonwoven composite are estimated using the developed model. A parametric study concerning the orientation of the flax fibers according to the composite thickness is also conducted, and many configurations of possible orientations in this direction are investigated. By comparing the natural frequencies of the different configurations with the experimental results, we show that the configuration of parallel flax fiber layers according to the thickness most agrees with the experimental results. Moreover, a parametric study of the natural frequencies is conducted on the flax/PP nonwoven composite with different fiber weight ratios and porosity contents. The obtained results are found to agree well with the experimental results. Finally, the loss factor of the flax fiber used in the studied composite is predicted using the strain energy method.