John Cove explains the complexities of modern composites and the software required for effective test and measurement applications
According to modern archaeology, one of the earliest examples of a composite material was the carefully soaked layers of linen and plaster used for the Egyptian practice of mummification.
Composites have come a long way since ancient Egypt, and advancements in polymer composites are changing the way these materials are used in industry. The rising popularity of polymer composites is no surprise. These materials have a high strength to weight ratio and are relatively easy and inexpensive to manufacture.
Unfortunately, in applications like construction and rail, composites have a poor reputation compared to their steel predecessors. By their nature, composites are comprised of many variations; different fibres, resins, stack materials and fillers. As a result, composites are subject to vigorous test and measurement processes.
Naturally, product designers and original equipment manufacturers (OEMs) want to ensure their polymer composite can withstand the force that will be placed on it. They also need to know if the material will stretch or elongate and pinpoint its exact breaking point. The major objective of any test and measurement process is to build a coherent set of materials data, but in the case of composite materials, one size rarely fits all.
The diversity of composites raises difficulties when establishing a coherent data set. The data is likely to be completely unique to each sector, product, application and area. The most common tests for tensile strength (MPa or PSI) are tensile chord modulus of elasticity (MPA or PSI), tensile strain (%), Poisson’s ratio and transition strain (%). However, when testing composite materials, the application should not pre-suppose any prior knowledge of which measurements are required.
Take Starrett’s L3 software as an example, rather than providing pre-set data, the user must create a unique test method for the specific material. Using this technique, a product designer or OEM can analyse the stress, strain, load, distance and time for each material, with measurements displayed on graphs and data tables with statistics and tolerances. In the case of Starrett’s L3 software, tests can use tension, compression, flexural, cyclic, sheer and frictional forces.
The unfamiliarity of composite materials requires mechanical testing throughout the entire design and production process. Consequently, automation is becoming increasingly attractive to those manufacturers eager to reap the rewards of composite materials, without wasting time on endless manual testing and measurement.
In a utopia, automated software packages should be capable of creating an interface that links hardware and software to improve processes from the lab, right up to the plant floor. For force measurement software applications, programming experience should be optional, not essential, which is exactly as it with Starrett's easy to use software.
Much like the wider automation industry, where most devices, from an inverter to a suite of robots, use simple languages and interfaces, automation in the software package should be comprehensible for any engineer, with as little as half a day of software training.
One of the major roadblocks of composite materials is that mass manufacturing data is not always available. As some composites are not yet fully scalable materials, testing and measurement will play a major role in the research that creates data.
In today’s competitive manufacturing environment, product designers and OEMs cannot afford to ignore the clear benefits of using composite materials. The sophistication of composites has come a long way since the ancient Egyptian era and naturally, the testing and measurement requirements have evolved too.
John Cove is marketing manager of test and measurement specialist, Starrett.