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Composites Reinforced With 3D Architectures

Composites Reinforced With 3D Architectures

Materials scientists at the ETH-Zurich (Swiss Federal Institute of Technology-Zurich) have developed a technique for creating an entirely new family of composites based on mimicking the way an abalone shell's structure aligns strong, stiff elements within a softer matrix.

The ETH-Zurich research team appears to have solved an essential problem of creating composites by discovering how to build materials that use reinforcing elements within 3D architectures, in a manner similar to those used by biological systems. Examples of such 3D reinforcing strategies are found in abalone shells, as well as in teeth, bone, and plant stems.

Previously, in order to combine different material properties from different classes of materials -- such as simultaneously light and flexible, as well as stiff and strong -- composite manufacturers have had to create materials that are flat. To achieve combinations of different properties, the strong and stiff ceramic or polymer fibers must be correctly oriented and placed within a softer, lighter polymer material, such as an epoxy glue. If the fibers are not correctly oriented, they don't strengthen the softer material.

Since manufacturers have not been able to control the fibers' orientation, composites have been formed by stiff fibers woven into a thin fabric that is permeated with a softer, lighter polymer resin, and stacked in layers. The resulting material is stiff and strong in the plane of the fabric, but not in other directions, making them susceptible to delamination between layers. By contrast, the strong elements in an abalone shell's structure are strong in all three directions because they are oriented to all three directions.

Although the materials commonly used in industrial composites are non-magnetic, the ETH-Zurich team discovered a technique that causes a magnetic response by attaching an extremely small amount of magnetic nanoparticles on the surface of the stiff elements. This works as long as those elements are of a certain size in the micrometer range, which is within the same range of sizes that is of interest to composite manufacturers.

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