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The long awaited successor to the Murciélago, the Aventador LP700-4, has recently been unveiled at the 2011 Geneva Auto Show. It is now gaining widespread recognition as an extremely important model, being the first flagship from Automobili Lamborghini SpA to feature a production carbon fibre chassis, made using an Araldite resin system for RTM.
Automobili Lamborghini SpA has been working with carbon fibre composites for 30 years; indeed the Italian auto-maker was responsible for the first carbon fibre component on a production car and the first carbon fibre tub on a road car. Composites were also used to produce all of the body panels and several portions of the Murciélago’s spaceframe structure, when it was in production between 2002 and 2010.
In order to meet increasingly stringent environmental regulations, Lamborghini’s corporate strategy is now directed at increasing the power-to-weight ratios of its cars, reducing the overall weight and thereby reducing vehicle emissions.
To achieve this goal, the company has identified carbon fibre composites as a key technology. It is committed to become a ‘Centre of Excellence’, promoting collaboration and developing best practices to maximise the use of composite materials in production vehicles, as well as driving technological advancement in this area forward.
The company’s current R&D activities are aimed at the development of composite-intensive primary structures that meet weight, cost and production rate requirements, to fulfil the corporate strategy. This involves the evaluation of non-conventional technologies as well as the development of new ones.
While traditional composites used in the luxury sports car industry have typically utilised aerospace-derived prepreg materials for autoclave cure, out-of-autoclave processes are now believed to provide unparalleled efficiencies in terms of cost and production rate, while leaving performance and quality unaffected. Among these processes, Lamborghini is focusing on liquid resin processes (VaRTM and RTM), oven-cure prepregs, preforming technologies (braiding, non-crimp fabrics and thermoforming), and advanced compression molding.
The first project to come out of the company’s new corporate strategy is the Aventador LP700-4’s carbon composite chassis. Designed, developed and manufactured at Lamborghini’s headquarters at Sant’Agata Bolognese, where all the bull signed cars are manufactured, this carbon chassis is also expected to be built into other Lamborghinis in the future.
Lamborghini produced the bulk of the chassis with the support of Huntsman Advanced Materials, who provided an Araldite® resin system especially adapted for Lamborghini’s ‘RTM-Lambo’; a Resin Transfer Molding (RTM) processing technique.
During the patented ‘RTM-Lambo’ process to produce the chassis, pre-formed carbon fibre reinforcements are impregnated with a precise amount of the Araldite® resin. This advanced technique uses lighter molds made of carbon fibre, rather than steel or aluminium and is heavily automated.
The Aventador’s chassis also includes epoxy foam sections, adding the space needed to create shapes without introducing unnecessary layers of carbon fibre. The foam also dampens noise and harmonic vibrations, like heavy insulation would on a metal-chassised car.
To meet all the RTM requirements, the resin must have a very low viscosity, sufficient-pot life and good fibre impregnation capabilities. Furthermore, it must be able to deliver the mechanical properties required to ensure the strength and torsional rigidity of the chassis. In being adapted with a carbon fabric orientation and quality, the Araldite® resin fulfils all these requirements.
The entire passenger cell of the Aventador, including the roof, weighs just 147.5kg. This lightweight is not at the expense of rigidity - indeed it takes 35,000 Nm (25,800lb ft) of torque to twist it by one degree.
By comparison, the Murciélago, with its metal chassis, had a torsional rigidity rated at around 20,000 Nm per degree. In effectively deploying carbon composite materials, the Aventador is more robust and boasts a much higher torque than its predecessor.
“The Araldite® resin system developed by Huntsman has been extremely well adapted for the ‘RTM-Lambo’ technique. It has excellent mechanical and curing properties and a suitable viscosity profile versus time, allowing us to meet rigorous performance and cost requirements,” explained Luciano De Oto, Head of Lamborghini Advanced Composite Research Center (ACRC).
“To fulfil increasing production rates as we move forward with our strategy to deploy more carbon fibre in the future generations of our high performance cars, this RTM process is the answer.”
In combination with the Araldite® resin, the ‘RTM-Lambo’ technique creates a chassis that is lightweight, robust and capable of delivering the power-to-weight ratios outlined in Lamborghini’s corporate strategy. It also offers a cost effective solution for the repeatable production of structural parts with mechanical and thermal performances comparable to autoclaved prepregs.
With the Aventador’s chassis, Lamborghini and Huntsman have created a ground-breaking package. The first production carbon fibre chassis from Lamborghini is also recognised as being steps ahead of any other production carbon chassis available today.
More information: www.huntsman.com/advanced_materials
The RTM process grew out of the need to increase the manufacturing productivity at a lower cost. It also allows to make complex partin one shot. Here are a few examples and update of this...