Expanded sheet materials are designed with patterns of diamond-shaped openings and are produced by slitting and stretching the sheet materials. They are used as screens in separators and walkways, and as sunscreens and decorative coverings. Products are also used in filtration, ventilation, drainage, reinforcement, and building and construction applications. Batteries and fuel cells also use expanded sheet materials.
Types of Expanded Sheet Materials
There are two types of expanded sheet materials: metal and plastic.
- Metal expanded sheet materials are made in a slit-and-stitch process where a precision die slits and stretches the sheet material in a single operation. Suppliers use many different dies to offer a variety of configurations. When selecting a pattern, uniformity and electrical conductivity are important considerations. Generally, metal sheet materials with solid foil structures are more durable and provide less contact resistance than woven wire cloth strands.
- Plastic expanded sheet materials include expanded PVC sheet, a lightweight material that combines the chemical resistance of polyvinyl chloride (PVC) with a closed cell expanded core. Some plastic expanded sheet materials feature a high-quality surface that is suitable for printing, painting, or spraying. Others meet regulatory requirements from the U.S. Department of Agriculture (USDA) for food processing.
Why Tooling is Important
With expanded metals, the tooling that is used determines the shape, size, and number of openings. This precision die also determines the long way of the diamond (LWD) size, which is generally measured in either millimeters (mm) or inches. A specification called the short way of the diamond (SWD) is selectable and machine-adjustable. After the slit-and-stitch process is complete, metal expanded sheet materials passed through a set of rollers to produce the desired thickness. The final product is designed to meet particular dimensional requirements.
Sheet Material Specifications and Testing Procedures
Product specifications for expanded metals include mesh per inch (MPI), opening per square inch, coverage area, open areas, weight per area, and total surface area. Testing procedures include tensile testing, bend testing, pull testing, and salt solution plating tests. Features include high rigidity and small pore sizes. Expanded sheet materials that are made from rigid steel and used as drainage barriers or for material storage where high ventilation is required must meet all application requirements.