Department of Civil and Environmental Engineering, University of Vermont, Burlington, 05405, USA.
Department of Civil Engineering, Taif University, Taif, 21974, Saudi Arabia.
Sci Rep. 2017 Oct 13;7(1):13123. doi: 10.1038/s41598-017-13492-z.
Nacre, a composite made from biogenic aragonite and proteins, exhibits excellent strength and toughness. Here, we show that nacreous sections can exhibit complete brittle fracture along the tablet interfaces at the proportional limit under pure shear stresses of torsion. We quantitatively separate the initial tablet sliding primarily resisted by nanoscale aragonite pillars from the following sliding resisted by various microscale toughening mechanisms. We postulate that the ductility of nacre can be limited by eliminating tablet interactions during crack propagations. Our findings should help pursuing further insights of layered materials by using torsion.
珍珠母是一种由生物成因的文石和蛋白质组成的复合材料，具有优异的强度和韧性。在这里，我们表明，在纯扭转剪切应力下，珍珠母层可以在比例极限处沿着片层界面完全发生脆性断裂。我们定量分离了最初主要由纳米尺度文石柱抵抗的片层滑动，以及随后由各种微尺度增韧机制抵抗的滑动。我们假设，通过在裂纹扩展过程中消除片层相互作用，可以限制珍珠母的延展性。我们的发现应该有助于通过扭转来进一步研究层状材料。
