Abstract
Materials are prone to crack under stress — this can either cause materials failure or, when deliberately induced, offer a useful manufacturing step. In both situations, knowing how to control and predict how materials crack will help in their design and synthesis. Yet exerting control is difficult — for example, we have all seen pottery cracked along random directions. Yong Zhao and co-workers have now prepared core–shell fibres that undergo helical cracking at specific positions. A tough glass fibre was dip-coated with a brittle metal oxide film featuring regular spindle knots. On calcination, the thermal expansion undergone by the tough core does not match that of the brittle shell, creating longitudinal and circumferential stresses. The stress lines in turn cause the knots to crack into helical coils, whose shapes depend on the initial formation process. These findings represent a step forward along the way of controllable fracture.
Highlights
Cracks are often regarded as an undesirable phenomenon, because they may induce material failure, breakdown of devices and collapse of buildings
Controllable 3D helical cracks on heterogeneous spindle knots induced with biaxial thermal stresses are reported, which are of great significance for fracture mechanisms and material fracture techniques
(2) Formation of helical crack: A glass microfiber was ultrasonically cleaned for 5 min in purified water, acetone and ethanol
Summary
Cracks are often regarded as an undesirable phenomenon, because they may induce material failure, breakdown of devices and collapse of buildings. Various methods from continuous[1,2] to atomistic mechanics[3,4] have been developed to investigate the failure of materials spanning a wide range of temporal and spatial scales.5–7A crack is initiated when the stresses exceed the material strength and will tend to propagate along whichever path allows the most energy to be released. Cracks in normal 3D modes are of significance in theoretical studies, and for practical applications. Experimental and theoretical investigations for controlling cracks in normal 3D modes have been rare. Controllable 3D helical cracks on heterogeneous spindle knots (the knots with spindle shape) induced with biaxial thermal stresses are reported, which are of great significance for fracture mechanisms and material fracture techniques
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
