Efficient Characterization and Modelling of the Nonlinear Behaviour of LFT for Crash Simulations

Abstract

Modeling the nonlinear material behaviour of long fiber reinforced thermoplastics (LFT) presents a challenging task since local inhomogeneities and nonlinear effects must be taken into account also on the microscale. We present a computational method with which we can predict the nonlinear material response of a composite material using only standard DMA measurements on the pure polymer matrix material. The material models considered include plasticity, damage, viscoelasticity, and viscoplasticity as described in [1]. These models can be combined similar to the model from [2] and extended to the composite by assigning linear elastic properties to the fibers. The mechanical response of the composite is computed using an FFT-based technique [3]. The geometry of the composite, in particular the fiber orientation, can be characterized using injection molding simulations or micro CT scans. We create virtual models of the composite using the algorithm of [4]. We show that with this method, the material behaviour of the composite can be predicted while the experimental complexity needed for the material characterization is low.

Adaptive material evaluation by stabilized octree and sandwich coarsening in FFT‐based computational micromechanics

“…The viscous effects are described by the drag stress $$$ {\sigma}_d $$$, the rate‐sensitivity $$$ m $$$ exponent and the reference strain rate $$$ {\dot{\varepsilon}}_0 $$$. The stress tensor and the driving forces compute as We consider a linear‐exponential hardening function For the studied example, the nonlinear parameters of the PP matrix are taken from Grimm‐Strele et al 38 and are reproduced in Table 2.…”

“…This time we are interested in the viscoplastic response of the composite, relying upon the viscoplastic model described in Section 4.1 which supplements the isotropic and linearly elastic E‐glass fibers. Please notice that the parameters of the material model were fitted to the experimental data of a commercially used polypropylene matrix, see Grimm‐Strele et al 38 for details. In fact, the material model serves as a true challenge for the considered composite/voxel methods and coarsening strategies.…”

“…For the studied example, the nonlinear parameters of the PP matrix are taken from Grimm-Strele et al 38 and are reproduced in Table 2.…”

“…Material parameters for the viscoplastic material model of PP 38. Viscoelastic material parameters42 for polypropylene (PP): Relaxed Young's modulus E r = 320MPa, Poisson's ratio 𝜈 = 0.44 as well as normalized relaxation coefficients 𝛾 j and relaxation times 𝜏 j for each Maxwell element.…”

Microstructural characterisation of 3D printed and injection‐moulded glass fibre‐reinforced polypropylene by image analysis, simulation and experimental methods

“…The same parameters were used for both composite materials even though they were identified on the injection‐moulded material only. [ 36 ] We apply a tensile load of 1 % in direction. A visualisation of both the segmented fibre geometry and the calculated von Mises strain distribution is shown in Figure 14 for samples 3DP‐1 and IM‐1.…”