Microtomography on polypropylene foam under dynamic loading: 3D analysis of bead morphology evolution

Abstract

is an open access repository that collects the work of Arts et Métiers ParisTech researchers and makes it freely available over the web where possible. AbstractA dynamic crash loading experiment is performed on polypropylene foam which is used in composite sandwich structures for safety applications. Several interrupted shocks are conducted, in between which, microtomographic acquisitions are made showing the change of the sample during its compression. These data can help construct and validate predictive models, although, because this material is multi-scale (constitutive beads at the mesoscopic scale are made of microscopic closed cells), image processing is required to extract useful quantitative measurements. Such processing is described here, so as to determine a representative volume for each bead of the sample, to associate values such as bead density to each bead and to each stage of the compression. This can help build a predictive model at the mesoscopic scale.

Impact on multi-layered polypropylene foams

“…50 kg m À3 , with this kind of organized system of heterogeneities. In this case, the approximation of this range performed for another EPP material by Viot et al [7] and mentioned previously (Section 2.1) would be a mean to reduce the difference. Further investigations related to this topic will be part of future research work.…”

“…However this study could not be used to determine bead densities with accuracy because a significant error on local porosity is generated by measurements. For our study, the EPP material is different from the one used by Viot et al [7] and the density range used in the FE simulation is therefore chosen arbitrarily and discussed afterward.…”

“…2b). Viot et al [7] have shown that this density range can reach 200 kg m À3 but the manufacturers try to reduce this variation in density in the microstructure to obtain more homogeneous material. Moreover, it is difficult to estimate precisely the density range in industrial foams.…”

“…Another experimental work by Viot et al [7] based on the X-Ray micro-tomography technique studied the microstructure of the EPP material. Authors analyzed micro-tomography images and observed a strong heterogeneity at the bead scale.…”

“…The expanded polypropylene (EPP) material of this study is constituted of large mesoscopic beads and microscopic cells [7]. This kind of material shows a multi-scale structure where the millimetric beads (about 2e5 mm) are themselves constituted of microscopic closed cells (Fig.…”