The Structural Origins of Wood Cell Wall Toughness. Issue 16 (1st March 2020)

• Record Type: Journal Article
• Authors: Maaß, Mona‐Christin; Saleh, Salimeh; Militz, Holger; Volkert, Cynthia A.
• Is Part Of: Advanced materials. Volume 32:Issue 16(2020)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2020-03-01
• Subjects: fracture -- microfibril angle -- wood -- wood cell wall toughness; Materials -- Periodicals; Chemical vapor deposition -- Periodicals; 620.11
• DOI: 10.1002/adma.201907693
• Languages: English
• ISSNs: 0935-9648

Abstract

Abstract: The remarkable mechanical stability of wood is primarily attributed to the hierarchical fibrous arrangement of the polymeric components. While the mechanisms by which fibrous cell structure and cellulose microfibril arrangements lend stiffness and strength to wood have been intensively studied, the structural origins of the relatively high splitting fracture toughness remain unclear. This study relates cellulose microfibril arrangements to splitting fracture toughness in pine wood cell walls using in situ electron microscopy and reveals a previously unknown toughening mechanism: the specific arrangement of cellulose microfibrils in the cell wall deflects cracks from the S2 layer to the S1/S2 interface, and, once there, causes the crack to be repetitively arrested and shunted along the interface in a zig‐zag path. It is suggested that this natural adaptation of wood to achieve tough interfaces and then deflect and trap cracks at them can be generalized to provide design guidelines to improve toughness of high‐performance and renewable engineering materials. Abstract : In situ scanning electron microscopy fracture tests reveal a previously unknown strategy for wood to improve its splitting fracture toughness: deflecting and trapping cracks along a tough interface. The structural origin of the toughness is the specific arrangement of the cellulose microfibrils at the S1/S2 cell wall interface, which can be mimicked to improve the toughness of engineering fiber‐reinforced composites.