Exploiting the temperature-memory effect in 3D printed auxetic structures

from experimental design to analytic simulation.

The combined employ of the additive manufacturing approach with shape memory polymers (SMPs) is one of the possible strategies towards 4D-printing, in particular when aiming at the realization of highly effective shape shifting objects. SMPs are in fact active systems, capable of being temporarily fixed in a deformed configuration and to revert to the pristine shape upon application of a thermal stimulus. In addition, this response may be finely tuned by a proper combination of the thermo-mechanical history and of the material macromolecular architecture.

In this work a 4D-printed auxetic structure is prepared through stereolithography starting from a commercial photo-polymer, and its shape memory response is studied, with particular reference to a peculiar characteristic of the polymer. In fact, thanks to its broad glass transition region, the polymer displays the so-called Temperature-Memory Effect (TME), i.e. the ability of the material to remind not only the pristine shape but also the deformation temperature, thus allowing to tailor the thermal trigger of the shape memory effect through the deformation temperature.

The overall shape memory behaviour of an auxetic grid as studied under the application of single- and multiple-training histories, with the aim to verify the possibility to exploit TME to control the transformation temperature and to distribute the recovery process in sequential steps, well distinguished along the temperature and time scales. In addition, a thermo-viscoelastic approach is employed towards modelling the structure evolution with time and temperature starting from viscoelastic parameters measured in dynamic-mechanical analysis.

A presentation by Stefano Pandini, Associate professor – Material Science and Technology at University of Brescia – Department of Mechanical and Industrial Engineering on 3D printed auxetic structures.

Interview

Question 1: What drives you?
Desire to obtain more knowledge, to improve networking, connection and collaboration towards application of the 4D printing promising expectations and to overcome actual challenges. In addition, fascination by smart, shapeshifting, stimuli-responsive materials.

Question 2: Why should the delegate attend your presentation?
My presentation will offer a simple strategy to obtain advanced capabilities from commercial and easy printable systems, it would provide some hints on an experimental protocol to better describe and exploit the effect the material in both practical and simulation (“in silico”) approaches.

Question 3: What emerging technologies/trends do you see as having the greatest potential in the short and long run?
Provided an improved understanding on their potentials and limits, additive manufacturing with material capable of shape memory capabilities (in particular in the case of reversible two-way shape memory polymers) is in my opinion a cutting edge strategy. Further combining it with a conscious simulation approach, will offer the designer very powerful tools to create structures with novel and improved capabilities

Question 4: What kind of impact do you expect them to have?
It will be a slow revolution, but this approach will offer the possibility to create new tools for an advanced, smart mechanics.

Question 5: What are the barriers that might stand in the way?
There are various challenges with both 3D and 4D printing, related to the repeatability of the effect (each structure is in a certain sense unique) and with a proper matching of expectations fulfilment and strategies adopted to such an aim; further technologies, printable materials and softwares are still under development.

About Stefano Pandini
Stefano Pandini is Associate Professor at the University of Brescia. He received his PhD in Materials Engineering at the University of Trento with a thesis entitled “Time-temperature correlation on deformation, yielding and fracture phenomena in thermoplastic polymers for engineering applications”. His field of research regards various aspects of the mechanical and functional behaviour of polymers and composites, among which particular interest is reserved towards the investigation of the shape memory response of polymer-based systems.

About University of Brescia
The University of Brescia is a young university with strong roots in one of the richest and most innovative areas in Europe.
It contributes to the sustainable development of a territory in search of a balance between industrial development, environmental sustainability and quality of life.
The University is a “free learning community” which expresses its social responsibility by committing itself to promoting a peaceful and open society through the inclusion and integration of the many diversities within it.

Stefano Pandini is speaker at the 2022 edition of the 4D Printing & Meta Materials Conference on 3D printed auxetic structures.

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