Fracture toughness of a composite reinforced with bone-shaped short fibers

Low fracture toughness has been one of the major drawbacks of short-fiber composites, which is caused mostly by the fiber–matrix interface. A strong interface is required for effective load transfer from the matrix to the fiber. However, a strong interface makes it difficult to relieve the fiber stress concentration in front of an approaching crack, thus resulting in low fracture toughness. On the other hand, a weak interface will lead to an easy fiber pull-out, making the short fibers ineffective in bridging and arresting a propagating crack. We have recently found that bone-shaped-short (BSS) fibers can effectively bridge cracks and increase fracture toughness by transferring load through the enlarged fiber ends while having a weak interface. In this paper, we present our results from both experiments and computational modeling to show the advantages of BSS fibers in improving the fracture toughness.