At full stretch Exploring the boundaries of an under-used resource - expanded metal - there are potential design improvement opportunities for automotive and aerospace applications, especially in terms of strength to weight ratio. Exploring the boundaries of an under-used resource - expanded metal - there are potential design improvement opportunities for automotive and aerospace applications, especially in terms of strength to weight ratio.

The slitting and stretching process to produce expanded metal mesh was pioneered by The Expanded Metal Company in 1889. The initial focus and supply of the various gauges during the 19th and early 20th centuries were mainly for agricultural machinery and shows.

The company evolved with emerging markets to supply a number of industries such as construction, shipbuilding, filtration, aerospace and automotive.Now currently working with the hi-tech industries and design-focused consultants, and exploring the boundaries of this versatile material, its producers argue that it is an underused resource with virtually limitless physical parameters.

The company has undertaken an exacting research programme into the product's physical properties, which has included commissioning an exhaustive series of tests at Teesside University. The research found that when a metal is cold worked the yield strength is increased as a result of the process of slitting and stretching.

Earlier work carried out by Teesside University had determined that expanded metal is stronger in the direction of the diamond pattern's long axis than its short axis. The purpose of the latest programme was to carry out bending/tensile tests on 87 different types and grades of expanded metal.

Samples from 0.5 to 1.5mm thick were tested on Lloyds M1000K and LR6000R machines using 30 and 100kN load cells, using samples measuring 100 by 60mm.Accepted formulae were employed for analysing the data obtained and excluding rogue results, with the spread of figures clearly showing that the expanded metal's performance exceeds expectations based on the mass of metal present.

To date, expanded sheet steel has been successfully used in a variety of applications, which demonstrably draw on the material's physical attributes without pushing the boundaries of its potential.One of the most challenging of these applications has been in the development of new, protective cladding to encapsulate the nuclear industry's 48Y containment cylinders, used to transport uranium hexafluoride (UFe) by road and rail.

Representing an international consortium, British Nuclear Fuels Ltd approached VT to produce a cover that would reduce heat transfer to the cylinders in the event of a sustained fire.A mere 6.5mm thickness of composite, comprising polyester resin and chopped strand, reinforced with metal mesh (expanded metal) and silica fabric could meet the requirement for a 50% reduction in heat transfer over a 30 minute exposure to a temperature of 800 degrees C.

As well as consistently withstanding such extreme conditions in the laboratory, the composites were also found to be able to cope with the repeated mechanical handling, while the expanded metal's low density helped keep the weight for the largest section down to a maximum of 40kg.Some 850 sets of Composite Thermal Protectors have now undergone thousands of cycles of reuse without suffering any undue wear or other ill effects.

Weight saving is becoming more important, driven by legislation and energy prices. Accordingly, the company is engaged in researching the structural or load carrying potential of the product, which could be of real benefit to the aerospace as well the automotive industry.

The general rule of thumb in car design is that if weight can be reduced by 10%, this will be rewarded with a 5.5% improvement in fuel economy. Aviation companies are even keener to cut payloads.

In many instances where volume car manufacturers are concerned, beneath the body shell itself, sheet steel is used mainly to provide something to screw a fixing into.It does not need to be a solid piece of metal across its whole area.

While it is routine for sizeable cut outs to be incorporated to save weight, there is also a class of expanded metal referred to as selvedge, where the machine produces an area of blank metal.The Expanded Metal Company is set to bring new equipment online, which can fabricate product with multiple alternate areas of blank and expanded steel.

This raises the viability of customers specifying product runs with sections of solid metal only where they want to achieve a fixing, while the weight across the rest of the panel is reduced by two thirds.The equipment can also provide clients with a wide choice of bespoke sheet products.

This means not only offering made to measure sheet sizes to optimise production yield, but also gauges running from the finest gauze up to 50mm thick metal.Different shapes and patterns of openings (square, circular, diamond and so on) are also possible while the manufacturer has even processed mesh from precious metals such as platinum and gold for special orders.