Diagram of New, Metal Core (IMAGE) North Carolina State University Caption NC State University researchers created fibers consisting of a gallium metal core surrounded by an elastic polymer sheath. When placed under stress, the fiber has the strength of the metal core. But when the metal breaks, the fiber doesn't fail - the polymer sheath absorbs the strain between the breaks in the metal and transfers the stress back to the metal core. Credit Michael Dickey, NC State University Usage Restrictions Credit must be given. License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.