Numerical simulation of anisotropic polymeric foams

Abstract

This paper shows in detail the modelling of anisotropic polymeric foam under compression and tension loadings, including discussions on isotropic material models and the entire procedure to calibrate the parameters involved. First, specimens of poly(vinyl chloride) (PVC) foam were investigated through experimental analyses in order to understand the mechanical behavior of this anisotropic material. Then, isotropic material models available in the commercial software Abaqus TM were investigated in order to verify their ability to model anisotropic foams and how the parameters involved can influence the results. Due to anisotropy, it is possible to obtain different values for the same parameter in the calibration process. The obtained set of parameters are used to calibrate the model according to the application of the structure. The models investigated showed minor and major limitations to simulate the mechanical behavior of anisotropic PVC foams under compression, tension and multi-axial loadings. Results show that the calibration process and the choice of the material model applied to the polymeric foam can provide good quantitative results and save project time. Results also indicate what kind and order of error one will get if certain choices are made throughout the modelling process. Finally, even though the developed calibration procedure is applied to specific PVC foam, it still outlines a very broad drill to analyze other anisotropic cellular materials.

Failure strength predictions for closed-cell polyvinyl chloride foams

“…The expressions for PVC foam tensile strengths, given in equations (10) and (12), do not take into account of the effect of stretching of foam cell walls (in the rise direction) on the strength of the foam-matrix base polymer. It is well known that stretching a polymeric film would induce preferential orientation of polymeric molecules and could lead to directionally-dependent film properties.…”

“…Hence, in using equation (10) to predict the PVC foam strength in the rise direction (3-direction), the ultimate tensile strength of the PVC foam-matrix base polymer, mu , needs to increase to mu . Similarly, in using equation (12) to predict foam in-plane tensile strength, the ultimate tensile strength of the PVC foam-matrix base polymer, mu , needs to decrease to mu =.…”

“…This is in contrast with the recent research which focuses on employing numerical methods, such as the finite element method, to predict foam strength and stiffness. [12][13][14][15] Complex foam models (for examples, the Kevin cell model and Voronoi foam model) that require detailed information on foam microstructure characteristics are often used to numerically model the anisotropic behavior of PVC foam. [13][14][15] From the observed foam behavior under compression, 8 strength equations are derived for predicting in-plane and out-of-plane compressive failure of closed-cell PVC foams, based on an approximate theory developed in an earlier study of compressive strength of unidirectional composites.…”

Energy absorbing composite structure for frontal pedestrian protection in electric light vehicles

“…The mechanical properties considered for the PVC foam were obtained from the data for 'DIAB Klegecell Ò R 60 Rigid, Closed Cell PVC Foam Core Material' recommended for high-strength, lowweight composite structures in vehicles: The PVC foam's stress-strain curve is defined in Figure 7, which was obtained from uniaxial compression tests by Tita and Caliri. 30 Finally, the foam core was characterized in Ls-Dyna by means of a MAT_LOW_DENSITY_FOAM (057) material model, including the following parameters:…”

Propagation behaviour of guided waves in tapered sandwich structures and debonding identification using time reversal

“…The finite element model of the tapered sandwich plate consisted of shell elements for the skin (S4R, a 4-node quadrilateral shell element with 6 DoF) using an orthotropic elastic model for the material due to the lay-up structure; solid elements being selected for the core (C3D8R, an 8-node linear brick with 3 translational DoF) using an elastic isotropic model [22]. A summary of the material properties assigned in the model is shown in Table 1.…”