Two hypercar designers that choose metal over composites

The 3D printed spaceframe wrapped in material The 3D printed spaceframe wrapped in material
While many automotive manufacturers are looking at composites and aluminium to lightweight, two supercar designers are turning to nature to find fresh innovation in metals. Engineering Materials finds out more.

A couple of supermodel-supercars have come to the fore since the last issue of Engineering Materials. However, while so many manufacturers look at aluminium or composites to fulfil their lightweighting requirements, these cars have opted to put metal innovation at their heart.

The first comes from Mexico by Antonio Ferrarioli, a man who has designed components for Lamborghini. The car known as Infierno is stunning, no doubt, but it comes as a result of material engineers developing porous metal. Components on the Infierno have been made using an exotic steel based metal foam. The material is made through a process that implies a transformation from liquid to a solid state, a technique that’s been established for different metals such as copper, silver, and aluminium.

The Infierno uses a porous metal The material can be manipulated during production according to the application, and possess properties that are reportedly able to stretch 100 times or more and still return to its original state.

The ‘super elastic’ material reflects a geometric expression often seen in nature. One of the objectives of this development was to make metal alloys with a porous capacity similar to bones, sea corals and some rocks. Here, the metal foam can absorb a strong impact and still go back to its original state, important in such an expensive car. Furthermore, most of the components made of the metal foam are low weight.

The porous metal material“The goal is to make designs different to those already known by the international audience,” says Dr Said Robles, an investigator from the Universidad Autónoma del Estado de Morelos, part of the scientific team working on a project to develop and apply the material.

The Mexican enterprise that makes the car and the metal foam, which is already patented, is LTM HOT SPOT. It is currently planning on designing and creating more cars, hinting at those being developed in the electric vehicle space as opposed to hypercars. However, it shows metallic foam can be adjusted to a variety of cars depending on the desired application.

Dr Robles adds that the metal foam can also be applied in the medical area by combining it with hydroxyapatite ceramic, which can be used as an implant. Here, the metal foam becomes biocompatible and can be designed for hips, for example, due to its low density. In addition, because of its relative low cost, it is thought that it could even replace titanium and other heavier and corrosive metals currently favoured for innerbody application. “The material can be part of a new generation of implants,” says Dr Robles.

Bionic beauty
The next example of a metallic hypercar development comes from German based EDAG, with its Light Cocoon concept car. The car is controversial in many ways. It plans to use a spaceframe – a combination of 3D printed connecting elements (nodes) and steel profiles – that will then be covered in an ‘outer skin’ made of a weatherproof textile material. The result is a dramatically lightened structure.

The 3D printed nodes make up the spaceframe

The car is intended to raise eyebrows and challenge opinions about how vehicles are currently designed and manufactured. The thinking is that the nodes can be quickly reconfigured on the production line to make manufacture flexible and multifunctional. The basic idea then is to have a node/profile design that can be optimally customised to reflect what the particular model requires. The result would be a spaceframe structure with optimised load paths for speed, handling, ride... whatever.

Steel bars can also be easily cut to the required shape and length. It means the steel profiles are as easily adapted to meet changing load levels, for examples.

The aim is to produce individual components that can be joined together to produce optimised structures. It’s all a bit Meccano, but the philosophy is intriguing.

The components would likely be welded together with a fillet weld on a lap joint. Laser welding would likely be used as it is able to carry out the intricate welded seams that would be needed, but it also has a relatively low thermal input so to not effect the inner metallic structure.
The profiles would be automatically aligned and fixed in place by the node, with a high-brightness laser used under the careful instruction of robot-guided optics. In other words, the techniques used to produce profiles and nodes can easily be automated in assembly... more easily than composites, perhaps?

This concept offers great potential when it comes to the possibilities additively manufactured processes might one day achieve. As structures can be easily adapted, each iteration can be quickly produced to optimum weight and function, without the legacy of a body-in-white to design around.

The nodes are being developed with the help of Concept Laser, using its LaserCUSING process. The method typically produces parts that have been topologically optimised, giving them an organic bone-like appearance.

This allows the production of components with complex geometrical shapes that would be almost impossible to build using conventional machinery. The use of Concept Laser’s machine completely does away specialist tools, and requires minimal post production.

In order to be able to guarantee a fault-free pert, support structures are used in planes with an angle of less than 45° in relation to the build platform. As well as providing support, these absorb internal stresses and prevent components from warping.

Whether these two cars, or even their controversial philosophies of how to utilise new materials and processes ever get to market is another question. The intrigue is there though. Nature and metal could work, couldn’t it?

Justin Cunningham

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