|Research on polymers (polymeric materials)
In this laboratory, some research regarding polymers, or plastics, as
well as metals is carried out. Almost all daily necessaries around us are
polymer molding. In addition, polymers are used as strengthening members
(e.g., bumpers of cars) because of their light weight and high strength.
Strengthening members are generally used under the condition of a large
load or a large impact. Designing structures safely with such materials
requires a sufficient grasp of their material properties and resulting
deformation simulations with high accuracy.
Fig. 1 Bumper of a car
We have been conducting research from various angles, aiming at predicting
the deformation behavior of polymers with high accuracy by simulation.
It is known that the polymer blend technique improves the material properties
of polymers. Polymer blends are made by taking some different materials
and mixing them with a polymer, which is used as a base material. For example,
a polymer blend with rubber particles inside it has higher toughness than
normal polymers. However, as the polymer blend becomes deformed, the particles
debond or break to form voids. Considering the circumstances mentioned
above, we have been pursuing the construction of material models from both
angles－experiment and simulation－considering the following:
(i) anisotropy that spherical voids grow into elliptical figures along the tensile direction
(ii) the effect of volume change with void growth.
Fig. 2 Variation in the spherical shape of voids with material deformation
Additionally, there are many other factors to be considered such as
anisotropy due to molecular chain orientation along the tensile direction,
temperature dependence, strain rate dependence, etc. We conduct some experimental
research focusing on these factors using normal polymers.
Fig. 3 Comparison between experiment and simulation of the deformation
(tensile test using a polymer blend)