Degradable polymers are under intense development for applications in healthcare and sustainability. Recent research has shown that these materials are susceptible to a phenomenon in which cracks grow under a small applied load due to chemical reactions at the crack tip. A team at the Harvard MRSEC led by Suo and Vlassak has exploited mechanics to design a degradable composite that resists this phenomenon. In the composite, a crack in the matrix is blunted and stresses are distributed over a long fiber segment. As a result, cracks are pinned at the interface between the matrix and embedded fibers and do not grow. The idea is demonstrated using a composite made entirely of polydimethylsiloxane (PMDS) with different crosslink densities. Experiments show that cracks propagate much more slowly in the PDMS composite than in homogeneous PDMS. It is anticipated that this concept will contribute to the development of degradable materials with enhanced reliability.
Jiao, Q., M. Shi, T. Yin, Z. Suo, and J.J. Vlassak, "Composites retard hydrolytic crack growth," Extreme Mechanics Letters 48, 101433 (2021)
Zhigang Suo (Mechanical Engineering), and
Joost J. Vlassak (Material Science & MechE)
2020-2021 Harvard MRSEC (DMR-2011754)