Applied Auxetics: Utilising Parametric Customisation to Translate Auxetic Structure Theory into Additively Manufactured Multi-Material Performative
Geometries
Authors:   , Mark Brittany 
Published: March 2021

Auxetic Structures are a class of meta-materials uniquely characterised by their Negative Poisson’s Ratio, thus when a lateral force is applied the structure expands longitudinally, becoming thicker and stronger, perpendicular to the strain. This counterintuitive behaviour has many enhanced behavioural properties, such as increased energy absorption, indentation resistance and fracture toughness, they also have the ability to bend in a synclastic manner, making them the ideal candidate to fit to curvature. Subsequently, this research looks to harness these exceptional mechanical properties, focusing specifically on the Auxetic response to impact forces for sports protection scenarios.

<p>Previously manufacturing Auxetic Structures has been a challenge, as often they are constructed of single materials which compromises the auxetic performance. Recent advances in AM technology through the Stratasys J750 Printer makes multi-material fabrication of Auxetic Structures with varying density micro structures a possibility. The multi-material printer enables outputs to be performative, with reactive physical properties. Auxetic behaviours are a result of the structures internal topology, the geometrical arrangements form the micro architecture of the structure thus dictating their dynamic responses to Impact. This study explores digital manipulation through CAD and Generative Programming of Auxetic geometries for AM.
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<p>Parametric software, Rhino and plugin Grasshopper allow for customisation of a structure’s internal topology as well as morphing of the architectures to fit an assigned curvature. This digital customisation is key to the iterative development of Auxetic Structures for situational specific 4Dimensional printing; a 3Dimensional print which translates with time. 4D printing Auxetics enables the opportunity for geometries to be uniquely reactive to a force, designed for pre-determined impact scenarios.
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<p>Auxetic Structures have been clearly linked to enhanced behavioural properties in response to impact. Through systematic investigations into Auxetic theory and studies of injury data for sporting instances, as well as the analysis of existing protection solutions, design development of enhanced, impact protection application can take place. Through parametric, generative design, anatomical specific curvature can have customised, geometry assigned to the form, proposing protection componentry which demonstrates the Auxetic effect, programmed for a targeted impact context.
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<p>This study will produce multi-materiality in 4D Auxetic demonstrators, both constructed and controlled through parametric software and exploited for their structure specific behaviours, designed to complement the body through anatomical curvature in impact scenarios. The final speculative designs will use multi-material 4D printing to effectively takes Auxetic Structure theory and translate the mathematical models into physical objects, through parametric design to dynamically perform in an Auxetic manner.</p>