A major UK automotive molder will be replacing the steel with a low-pressure thermoformable composite in the bonnet/hood of a high-powered sports vehicle.

As the result of a joint development, GE Advanced Materials' Azdel Superlite composite will be used by BI Composites, a major UK automotive molder, to replace the steel in the bonnet/hood of a high-powered sports vehicle to be launched by a leading international carmaker in early 2004. The bonnet development was driven by the need to provide a cost-effective material solution that could be applied to low-volume production, niche segment vehicles. Key application criteria included recyclability, impact strength, low weight combined with high stiffness, the ability to bond with steel, extremely low coefficient of thermal expansion (CTE), and the ability to obtain a Class A finish with strong paint adhesion.

BI Composites tested a range of high-temperature engineering thermoplastics before selecting Azdel Superlite composite as the material that offered the optimum balance of properties and met the cost-reduction target.

While initial series production using Azdel Superlite composite indicated a premium over that for a steel bonnet skin, the tooling cost for a steel skin solution could only be justified by amortization over high-volume production.

In contrast, tooling for Azdel Superlite composite is a substantially lower investment because of the material's low-pressure formability.

With a EUR 70,000 (approx.

$88,000 USD) tool, meeting a production level of 15,000 units per year, and the process being developed to achieve 150,000 units from a single tool, unit cost represents a 50 percent savings over low-volume steel production and a 75 percent savings over comparable thermoset composites.

This illustrates the competitiveness of Azdel Superlite composite and the low-pressure forming process for vehicle production volumes of between 500 to 50,000 units, whereas steel shows savings after 100,000 units.

'This development also achieved a very considerable weight savings,' says Mike Birrell, business development director for BI Composites.

'With an optimized skin thickness of two millimeters, Azdel Superlite composite gave greater stiffness than the steel it replaced at 50 percent lower weight.

As part of our benchmarking process we also produced a bonnet skin in a carbon fiber/epoxy composite, however, it weighed as much as steel in this application.' The performance of Azdel Superlite composite bonnets was independently measured.

In high-speed, offset front-impact tests, the bonnets exhibited less damage than that sustained by similar steel panels tested under the same procedure.

Moreover, the bonnets' adhesive bonding remained intact throughout impact testing.

As well as delivering high impact strength, the continuous unidirectional glass fiber reinforcement of Azdel Superlite composite, and its thermal stability, enable a Class A paint finish.

The material's surface is flame treated and prepared with a standard polypropylene primer before painting with a finishing coat.

'With Azdel Superlite composite, we are offering the outstanding combination of light weight, high impact strength, and thermal stability properties,' says Gordon King, commercial director of Azdel, Europe.

'We expect Azdel Superlite composite to benefit OEMs in the automotive industry for specific applications - from interior to bonnet - where, previously, composites would not have been considered.' GE Advanced Materials' Azdel Superlite composite is a low-pressure, thermoformable composite developed specifically for automotive applications.

composite is based on short, chopped-fiber reinforcement, with a glass content of 42 to 55 percent and a weight of 600 to 2,000 grams per square meter.

The material can be compression molded in less than one minute at very low pressures of 0.5 to 5 bars.

This ratio of fibers to polymers, as well as the base weight of the web, can be customized for different interior and exterior automotive applications.

Characterized by light weight, a high stiffness-to-weight ratio, good dimensional stability, and high impact resistance over a wide temperature range, Azdel Superlite composite allows engineers to design high-performance components that can replace steel, meet aesthetic demands, and contribute to vehicle weight reduction.

Azdel Superlite composite's good polypropylene/fiber bond enables it to be recycled into other engineering applications at the end of its first-life use.

BI Composites, a leading producer of molded components for executive and luxury cars, is a business of the UK-based BI Group Plc, an international group of specialist engineering companies.

The company has annual worldwide sales of approximately ?

200 million (approx.

$364 million USD) and employs more than 2,000 people in 14 countries.

Azdel Superlite composite is produced and distributed by Azdel, a joint venture of GE Advanced Materials and PPG.

The Azdel business was established in 1972 by PPG Industries, and a 50/50 joint venture was set up with GE in 1986.