Table of Contents

Materials and Structure




In crack formation and propagation in polymeric materials the macromolecules can form "bridges" linking the two sides of the crack. Additional work has to be done to break the backbone of these molecules or pull them out of the opposite crack surface. This work increases the effective surface energy and increases the polymers toughness. The photograph shows the crack tip region in polypropylene oxide, the strands linking the sides of the crack in the "craze" zone can be seen. The lower diagram illustrates the process of micro-void coalescence and fracture of the fibrillar micro-bridges in this craze zone as crack propagation progresses.

From: Callister,
"Materials Science and Engineering," Wiley (1997)