Flaw sensitivity of cellulose paper

Cellulose is earth-abundant and has exceptional intrinsic mechanical properties. Cellulose-based materials, however, exhibit a large variation in their mechanical properties (e.g., strength, toughness), which calls for the understanding of the sensitivity of these materials to flaws, an area that remains largely unexplored. In this paper, we report a systematic study of the flaw sensitivity of cellulose paper by measuring the fractocohesive lengths of cellulose paper made of cellulose fibers with various diameters (from nanometers to microns) and lengths (from sub-microns to millimeters). Unlike the strength of cellulose paper which depends strongly on the diameter of the constituent cellulose fibers, the flaw sensitivity of cellulose paper is closely related to the aspect ratio (length/diameter) of the cellulose fibers. The larger the aspect ratio of the cellulose fibers, the larger the fractocohesive length, and thus the more flaw tolerant the cellulose paper is. Findings in this paper shed light on designing cellulose-based materials with desirable mechanical performance that is pivotal for the widespread use of this sustainable material.