Modelling the mechanical response of cellular PVC foams using detailed nite element analysis
Typ
Examensarbete för masterexamen
Program
Applied mechanics (MPAME), MSc
Publicerad
2019
Författare
Berg, Rikard
Billberg, Adam
Modellbyggare
Tidskriftstitel
ISSN
Volymtitel
Utgivare
Sammanfattning
The use of composites with a foam core is becoming more and more common as industries strive to
make lighter structures. However, the mechanical response of cellular foams is hard to model properly
due to its complicated microstructure and deformation mechanisms. Previous work in the eld of
modelling cellular foams have focused on capturing the yield surface using both advanced material
models and by modelling the microstructure of the foam. The current study aims at capturing the
macroscale stress-strain response during uniaxial tension, compression, and shear loads by performing
analyses on a geometry representing the foam microstructure. Two foams are investigated in the
current study; Divinycell H60 and H100, manufactured by Diab.
The Kelvin tetrakaidecahedron was used to represent the foam microstructure of a single cell. The
e ciency of the simulations were greatly enhanced by the use of a Representative Volume Element
(RVE) with Periodic Boundary Conditions (PBC) to emulate an in nitely large foam under constant
average strain using a single foam cell. This allowed for calibration of key parameters through an
iterative process, with the aim to capture the mechanical response for one of the investigated foams,
Divinycell H100. Experimental results from the remaining foam, Divinycell H60, was then used to
validate the derived parameters without a separate optimisation procedure.
The study found that an RVE can be used to accurately model the initial mechanical response of
foam in both the elastic and plastic region. By optimising material and geometric parameters for the
H100 foam, the elastic region was captured well for both tension and shear in two principal directions.
Furthermore, the compressive behaviour in the elastic region and the initial phase of buckling was
captured in two principal directions. By using the same material parameters and re-scaling the
geometric parameters, good correlations to the experimental data was achieved also for H60. Due
to the progressive crushing at large compressive strains, cellular foams do not behave periodically in
the direction of the load. This makes it impossible to capture the full true deformation mechanisms
using full PBC's, since they imply that the material behaves periodically in all directions.
Beskrivning
Ämne/nyckelord
PVC Foam , Representative Volume Element , Periodic Boundary Conditions , Finite Element Analysis, , Divinycell , Microstructure