The aim of this research is to model the deformation and fracture behaviour of wafers used
in chocolate confectionery products. Compression and bending tests showed that the
mechanical behaviour of the wafer was characteristic of a brittle foam.
The wafer sheet was examined with a Scanning Electron Microscope (SEM) to determine the
wafer dimensions and to observe the internal microstructure. These images showed that the
core of the wafer sheet was more porous than the dense skins of the wafer. An analytical
model was developed to calculate the modulus of the wafer core and skin sections.
A finite element (FE) model using a simple repetitive geometry of the wafer was
implemented. The ‘crushable foam’ material model was the closest fit to the wafer
deformation under compression and was applied to the core of the wafer. An alternative FE
model was proposed, which used the actual complex architecture of the wafer.
To attain the wafer architecture, X-ray Microtomography (XMT) was used on a sample to
produce a stack of image slices which were reconstructed as a 3D volume. The
microstructure of the 3D volume was characterised and then meshed with tetrahedral
elements for finite element analysis. The cell walls of the model were given a linear elastic
material model and a damage criterion to simulate the fracture of the cell walls.
In-situ SEM and XMT experiments were conducted which allowed the deformation and
fracture of the wafer sheet to be observed simultaneously as the global mechanical response
was recorded.
The FE model of the complex architecture was able to predict the deformation behaviour of
the wafer in compression. In the future, the model can be used to simulate the cutting
process of the wafer, allowing the effect of parameters such as cutting speed and blade
dimensions to be determined efficiently.