  While stress visualization within 3-dimensional particles would greatly
advance our understanding of the behaviors of complex particles, traditional
photoelastic methods suffer from a lack of available technology for producing
suitable complex particles. Recently, 3D-printing has created new possibilities
for enhancing the scope of stress analysis within physically representative
granules. Here, we investigate and evaluate opportunities offered by
3D-printing a single particle with a complex external shape with photoelastic
properties. We report the results of X-ray computed tomography and 3D-printing,
combined with traditional photoelastic analysis, to visualize strain for
particles ranging from simple 2D discs to complex 3D printed coffee beans,
including with internal voids. We find that the relative orientation of the
print layers and the loading force affects the optical response of the discs,
but without a significant difference in their mechanical properties.
Furthermore, we present semi-quantitative measurements of stresses within
3D-printed complex particles. The paper outlines the potential limitations and
areas of future interest for stress visualization of 3-dimensional particles.
