Meccanica Magazine n. 4

Progetto Lis4.0
104
ENG
LIS4.0 project: interview with Stefano Beretta, DMEC professor
involved in WP3
1. What is WP3 of the LIS4.0 project about? Which are the
challenges it must face?
The WP3 “Metastructures” is dealing with the study of design tools
/properties / applications of cellular materials based on a regular
micro-structure called unit cell that is periodically repeated in
the space to obtain a meta-material characterized by a regular
combination of tiny structures (beams /surfaces /masses) joined
together. The physical length of the unit cell is shorter than the
wavelength of interest (loads in a structure, heat and sound waves)
to obtain “metamaterials”, that are solids with ‘homogeneized’
properties not existing in nature. They are ‘novel engineered
materials’ with an higher degree of complexity respect to traditional
composite materials.
The challenges are to design with/manufacture and apply new
metamaterials that become ‘multifuctional’ because they can
combine lightweight with other properties. The first example can
be a lattice material with a limited heat conductivity that we have
applied in a space component (Fig. 1a) or other surface/sheet based
cells that allow a very efficient heat exchange between 2 liquids (Fig.
1b). At the level of structures/components a ‘meta-structure’ can
then be designed/obtained with the hybrid combinations of different
material solutions.
The challenge, surely aligned with our mission of mechanical
engineers, is to transfer the conceptual design of the metamaterials/
metastructures to real applications, taking into account the design
constraints at a component level and the real properties of the
new materials (led by the rapidly evolving manufacturing cycles),
especially considering multi-material combinations. The edge of
current developments for industrial applications is the possibility
to eventually qualify the industrial components that have been
designed with such a degree of novel solutions.
2. Which innovative instrument/approaches are required to
address the design and development of products based on metastructures?
The tools needed for design and development of components of
metamaterials and metastructures should enable the engineer
to handle models /structures characterized by an high degree of
complexity. Efficient tools, instead of a massive application of
traditional computational tools, are aimed at reducing the scale of
the model along different lines:
- Ontology-based models able to overcome the impossibility
to obtained detailed FE models of components with different
metamaterials;
- Homogeneized failure criteria that allow us to ‘build’ a library of
cellular materials available for the design of different applications
under static and fatigue loading. Such homogeneized models for
describing the mechanical behaviour (elastic, non-linear monotonic
and cyclic) are based on the real modelling of the as-manufactured
cells, thus allowing to inherently consider the anomalies/deviations
respect to ideal configurations.
- AR/VR tools that could allow the engineer to handle efficiently the
CT scans of complex metamaterials and find/analyze the defects of
manufactured parts for a quick qualification of parts ‘ready to fly’
(Fig. 2).
3. Which were the main prototype developed?
The prototypes that have been developed are:
- A sound-absorption panel that can easily, and has been proven to,
reduce noise transmission by more than 8-10dB (Fig. 3)
- An innovative arm for a McPherson suspension made of an hydrid
polymer/metal structure. In detail the additively manufactured
polymeric part has been optimized considering the real stresses
in the component together with the suitable joining solutions for
ensuring the desired structural response (Fig. 4);
- An hybrid (combination of solid skins and cellular parts) space
component manufactured by additive manufacturing, Fig. 1a: the
cellular parts have been optimized for the structural and thermal
response of the entire component adopting the homogeneized
approaches developed in WP3.