In the world of materials science, strength and toughness are often seen as competing properties. Typically, materials that are strong are brittle, while those that are tough tend to be weaker. However, a team of researchers at the University of Pittsburgh Swanson School of Engineering has found a way to combine these two properties in a new class of self-healing materials.

The team, led by assistant professor of mechanical engineering and materials science Abdon Pena-Francesch, developed a new type of composite material that is made up of a strong, brittle matrix and a soft, tough reinforcement. The reinforcement is made up of tiny droplets of a liquid that is encapsulated in a polymer shell. When the material is damaged, the droplets break and release the liquid, which then fills the cracks and heals the damage.

The researchers found that the addition of the soft, tough reinforcement significantly increased the toughness of the material without sacrificing its strength. In fact, the material was even stronger than the original brittle matrix. This is because the droplets of liquid act as a sacrificial phase that absorbs energy and prevents the cracks from propagating.

The researchers believe that this new class of materials could have a wide range of applications, such as in the construction of bridges, buildings, and aircraft.

"These materials could potentially revolutionize the way we design and build structures," Pena-Francesch said. "By combining strength and toughness, we can create materials that are more resistant to damage and that can last longer."

The research was published in the journal Nature Materials.