Mentioning parts of racing cars in your own thesis? That’s exactly what Micaela Boscia did, currently student of automotive engineering post-graduate course, she graduated in automotive engineering at Politecnico di Torino in March. For her thesis, she decided to talk about bioinspired materials and their application in the automotive industry. In this article, that will be published in two episodes, we’ll focus on three parts of a car: the tyres, the suspension system and the disc brake.
Introduction to bioinspired materials
In nature many examples of architectures and structures exist that present outstanding mechanical properties. Scientists and companies have tried to replicate these structures to obtain lighter materials with better performance such as strength and toughness.
That’s how Micaela started her thesis, explaining what bioinspired materials are and why there are so many studies behind them. Briefly, bioinspired materials are synthetic materials that mimic the natural properties and structures of materials that are present in nature.
Pneumatic and non-pneumatictyres: Michelin "Visual Concept" and Goodyear "reCharge"
The first part of a car that we’ll talk about with Micaela is the tyres. To overcome problems like punctures or brusts, non-pneumatic tyres have been developed: these are tyres that are supported by elastic structures. Micaela explains that currently two types of tyres are produced: Tweel tyres and honeycomb ones, which are both examples of bioinspired applications.
Their structure is mainly constituted of three parts: the rigid hub, the tread and the support structures. Based on their structure, tyres can be classified into “spoke tyres” and “multi-hole”. The perfect example of a spoke type is the “Tweel” Michelin type, composed by a rigid hub, rubber tread and polyurethane spokes whose main aim is to support weights, absorb shocks and reduce load on the suspensions.
Honeycomb tires and Michelin "Visual Concept"
Honeycomb tires are an example of the second type of tires, “multi-hole”. They’re amongst the most used bioinspired structures, thanks to their high compression and their shear properties; this type of tires also allows to save weight and material.
A prototype of a honeycomb tyre has been designed and analysed by the VIT university, in India. The tyre is composed of a rigid hub made of aluminium alloy, polyurethane deformable spokes, reinforced shear band and rubber tread. The design of the tyre was mainly focused on the spokes since they influence the stiffness and resilience of the non-pneumatic tyre.
The second example Micaela gave us, the one regarding “multi-hole” tyres, is the “Visual Concept” presented by Michelin in 2017. The French company is known in the world of motorsport for being official supplier of the WEC’s premier class, the Hypercar. The new project is focused on creating an airless wheel inspired by important properties of alveolar coral structure. The tread is produced by 3D printing with biodegradable materials that can be adjusted for any type of road condition.
Goodyear's "reCharge" and "Eagle 360 Urban"
The American tyres are known in motorsport because they’re used in several championships, including WEC, especially in the LMGT3 class starting from 2024. Goodyear have introduced two types of tyres that Micaela has presented. In 2020 they designed the “reCharge concept”, that falls in the convex type. The compound is made from biodegradable material reinforced by a lightweight and strong biological material, such as spider silk.
The ‘reCharge’ is a self-regenerative and adaptable tyre concept, in fact tyres have a rechargeable capsule in the core with a customized liquid that allows the regeneration of the tread and the adjustment of the tyre to weather and road conditions.
Talking about “solid type” tires, in 2017 Goodyear introduced “Eagle 360 Urban”, a tyre bioinspired by human skin. This is very different from the other tires due to its spheric shape, made by super-elastic polymer that allows it to expand and contract mimicking human skin properties. Self-healing bioinspired materials are used to repair punctures during travelling while the tyre is rotated to give different contact patches.
Tires bioinspired by shark's skin
To introduce this new type of tyre we offer an example that we often see during the race weekends: the phenomenon of aquaplaning. When the track is wet due to rain, we find ourselves in front of a situation where drivers have low visibility due to aquaplaning: with high speed, cars tend to raise loads of water and who’s behind has many disadvantages.
Aquaplaning is the condition in which the tyre can’t expel enough water and loses contact with the ground and consequently loses steering and braking capability.
For this reason, Shandong and Jiangsu Universities, in China, have designed a nonsmoothed tyre bioinspired by a shark-skin riblet structure. Shark skin is in fact one of the most drag-reduction surfaces thanks to its composition made by a matrix containing collagen fibers with embedded mineralized dermal denticles.
Bioinspired materials are therefore proving to be crucial for progress and innovation. In this first part, we have analyzed the tyres produced with bioinspired materials, stay tuned for the second part of the article, where we’ll talk about the suspension system and the disc brake.
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