Interfacial shear strength in abalone nacre.
The shear strength of the interface between tiles of aragonite in the nacre of red abalone Haliotis rufescens was investigated through mechanical tensile and shear tests. Dog-bone shaped samples were used to determine the tensile strength of nacre when loaded parallel to the plane of growth; the mean strength was 65 MPa. Shear tests were conducted on a special fixture with a shear gap of 200 microm, approximately 100 microm narrower than the spacing between mesolayers. The shear strength is found to be 36.9+/-15.8 MPa with an average maximum shear strain of 0.3. Assuming the majority of failure occurs through tile pull-out and not through tile fracture, the tensile strength can be converted into a shear strength of 50.9 MPa. Three mechanisms of failure at the tile interfaces are discussed: fracture of mineral bridges, toughening due to friction created through nanoasperities, and toughening due to organic glue. An additional mechanism is fracture through individual tiles.
Lin
Albert Yu-Min
AY
Materials Science and Engineering Program, University of California, San Diego, La Jolla, CA 92093-0411, USA. a5lin@ucsd.edu
Meyers
Marc André
MA
D000818:Animals; D001696:Biomechanical Phenomena; D049851:Gastropoda / Q000033:anatomy & histology*; D008855:Microscopy, Electron, Scanning; D033081:Shear Strength; D013718:Tensile Strength; D016474:Weight-Bearing