School of Materials Engineering, Purdue University, West Lafayette, IN 47907, USA.
School of Manufacturing Systems and Networks, Arizona State University, 7001 E Williams Field Rd, Mesa, AZ 85212, USA.
Acta Biomater. 2023 May;162:304-311. doi: 10.1016/j.actbio.2023.03.024. Epub 2023 Mar 23.
The fibers of the deep-sea sponge Euplectella aspergillum exhibit exceptional mechanical properties due to their unique layered structure at a micrometer length scale. In the present study, we utilize a correlative approach comprising of in situ tensile testing inside a scanning electron microscope (SEM) and post-failure fractography to precisely understand mechanisms through which layered architecture of fibers fracture and improves damage tolerance in tensile loading condition. The real-time observation of fibers in the present study confirms for the first time that the failure starts from the surface of fibers and proceeds to the center through successive layers. The concentric layers surrounding the central core sacrifice themselves and protect the central core through various toughening mechanisms like crack deflection, crack arrest, interface debonding, and fiber pullout. STATEMENT OF SIGNIFICANCE: Biological materials often exhibit multiscale hierarchical structures that can be incorporated into the design of next generation of engineering materials. The fibers of deep-sea sponge E. aspergillum possess core-shell like layered architecture. Our in situ study reveals astounding strategies by which this architecture delays the fracture of the fiber. The core-shell architecture of these fibers behaves like fiber-reinforced ceramic matrix composite, where the outer shells act as a matrix and the central core acts as a fiber. The outer shells take the environmental brunt and scarify themselves to protect the central core. The precise understanding of damage evolution presented here will help to design architected materials for load-bearing applications.
深海海绵 Euplectella aspergillum 的纤维由于其在微米长度尺度上的独特分层结构，表现出非凡的机械性能。在本研究中，我们采用了一种包含原位拉伸测试的关联方法，在扫描电子显微镜（SEM）内部进行，并进行失效后的断口形貌分析，以精确理解纤维分层结构断裂的机制，并提高拉伸加载条件下的损伤容限。本研究中对纤维的实时观察首次证实，失效是从纤维表面开始，并通过连续的层逐渐向中心扩展。围绕中心核心的同心层通过各种增韧机制，如裂纹偏转、裂纹止裂、界面脱粘和纤维拔出，牺牲自己并保护中心核心。 意义陈述：生物材料通常具有多尺度的层次结构，可以将其纳入下一代工程材料的设计中。深海海绵 E. aspergillum 的纤维具有核壳状的分层结构。我们的原位研究揭示了这种结构延迟纤维断裂的惊人策略。这些纤维的核壳结构类似于纤维增强陶瓷基复合材料，其中外壳作为基体，中心核心作为纤维。外壳承受环境冲击并牺牲自己以保护中心核心。这里呈现的对损伤演化的精确理解将有助于为承载应用设计结构材料。
