Sea shells inspire composite material

Using a combination of chalk and polystyrene, scientists have produced a tough composite material which could be used as building materials or in bone replacements.

Scientists from the Universities of Manchester and Leeds took inspiration from sea shells – calcium carbonate or chalk to create a tough, strong polymer.

“The mechanical properties of shells can rival those of man-made ceramics” said Dr Stephen Eichhorn from the school of materials at the University of Manchester, “We have replicated nature’s addition of proteins using polystyrene, to create a strong shell-like structure with similar properties to those seen in nature.”

Researchers reinforced the calcium carbonate with polystyrene particles, which makes the material more ductile. The polystyrene also acts as a toughening agent, preventing the growth of cracks. When the reinforced material did crack, the polymer lengthened within the crack – a well-known mechanism for absorbing energy and enhancing the toughness.

“Shells are strong and resistant to fracturing,” Eichhorn said, “This is because the calcium carbonate is combined with proteins which bind the crystals together, like bricks in a wall, to make the material stronger and sometimes tougher.”

Researchers say their method allows the properties of the new material to be tweaked by selecting particles of different shapes, size and composition.

“Further research and testing is still needed but our new research potentially offers a straightforward method of engineering new and tough chalk-based composite materials with a wide range of applications,” Eichhorn said.

The research was funded by grants from the Engineering and Physical Sciences Research Council (EPSRC), and conducted in collaboration with Professor Fiona Meldrum from the University of Leeds.