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Inrekor intelligent sandwich technology
UK-based Inrekor has developed a patented lightweight sandwich technology which appears simple - an aluminium skin bonded with an expanded polypropylene (EPP) core. But its simplicity should not disguise the big potential that Inrekor sees in automotive chassis and other structural parts.
Inrekor and JSP, which makes the Arpro EPP in the panels' core, launched the product in September 2010. A prototype of a four-seat vehicle chassis demonstrated that Inrekor can reduce weight from 300kg typical for such a chassis to 160kg.
The launch was timely as the recent explosion of electric vehicle (EV) projects has created demand for lightweight chassis structures. One of the first uses for Inrekor technology will be in the chassis of the Ecomove Qbeak EV (pictured) being developed in Denmark.
But it is not just in the vehicle chassis that Inrekor is finding applications, says Inrekor's technical director, Stewart Morley, who has extensive design engineering experience working for Saab, Volvo and Scania in Sweden. One of the first commercialised applications for Inrekor is in the fuel tank housing of the Aston Martin GT race car.
The company is working on more than 20 development projects; half in automotive and the others in applications in other sectors. Inrekor's adaptability to many applications is intentional.
Morley acknowledges there are competing honeycomb sandwich technologies which combine light-weight and tensile performance in the automotive and aviation sectors, but he says flexibility is integral to Inrekor and was a vital attribute demanded at the concept stage and in its development.
"We started with the structures that were needed and then thought about how we could make them more cost effective," says Freddy Page-Roberts, sales director, and Morley's partner in the Inrekor business.
One way the company achieved cost-effectiveness is in the materials it selected. Thin gauge aluminium and Arpro EPP are mass produced and already widespread in the auto sector.
These are "very familiar materials to the automotive industry", says Morley, which is an advantage for Inrekor's uptake in new applications. Arpro is used in bumper cores and its performance is predictable from previous crash tests, as well as tests on Inrekor impact absorption beams carried out by UK-based Mira on behalf of Inrekor.
Arpro is a closed cell foam and when impacted, energy dissipates in all directions. Other properties of Inrekor are that it is 100% recyclable and provides thermal, sound and vibration insulation.
Cost effectiveness works hand in hand with the adaptability of Inrekor technology. The panels can be made in various gauges and densities. Connecting the panels to each other or other structures can be done with rivets, fasteners, spot welds or adhesive bonds.
Water cutting is used for the Arpro core and laser cutting for the aluminium skin. Using these methods makes panel manufacturing a lot faster than using CNC cutting in honeycomb panel technologies.
In addition, the manufacturing process can build "intelligence" into the panels, says Inrekor. If the application requires, for example, mounting points for cables or air ducts, these can be moulded as part of the Arpro core.
This adaptability promotes design freedom. Customers can think of a design solution, make changes in existing CAD files and rapidly test their design using Inrekor in a gauge and dimension specific to their needs.
"Development projects with our customers are a very interesting experience," says Morley. "We learn as much from our clients as we teach them."
Inrekor's design flexibility allows selective strengthening of part of a structure. Also, impact absorption beams can be fine-tuned for performance variables caused by the different weights of models in a vehicle range.
A major cost advantage of Inrekor is the minimal impact caused by design changes. In small volume production, the use of water and laser cutting makes it straightforward to change Inrekor panels. But as the company has made the technology scalable, it has also thought of cost impacts in high volume production.
Inrekor expects that customers producing panels in large volumes would use stamping and pressing equipment for the aluminium sheet and steam chest moulding for the Arpro.
Automotive plants making structural parts have to invest in expensive tools to stamp and press 3-4mm steel sheet, says Morley. "When you degauge [by using thin aluminium sheet in Inrekor panels], you can create tools at a lower cost and which have a longer life," he says.
Inrekor has two development projects involving volume car production. It cannot reveal details, but one is for seat backs, with an expected production run of 120,000-140,000 parts per annum.
"Inrekor technology is just as cost effective for making hundreds of thousands of parts as it is for making one part," says Morley.
In this respect, Inrekor believes its technology compares favourably with CFRP which is increasingly being used for lightweight automotive structures.
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