Mechanisms of toughening of a natural rigid composite

A study of the structure and toughness of the spicules of the sponge Euplectella aspergillum (Ea) under tension and bending was performed, and the results were compared with those of a silica glass. Very different fracture morphologies were observed in the spicules that failed in bending and in tension, and toughness of the spicules in bending and the toughness in tension exceeded that of the glass fibers by a factor of 6–7. These results have been explained by the controlling role of thin organic layers in the failure processes. A significant feature of this study was the great effect that a minor organic constituent (2–3 vol.%) had on the toughness of the spicule glass/organic composite fibers.