Stiffness and strength of suture joints in nature

Abstract

Suture joints are remarkable mechanical structures found throughout nature composed of compliant interlocking seams connecting stiffer components. This study investigates the underlying mechanisms and the role of geometry governing the unique mechanical behavior of suture joints. Analytical and numerical composite models are formulated for two suture geometries characterized by a single repeating wavelength (e.g., triangular and rectangular). Stiffness, strength, and local stress distributions are predicted to assess variations in deformation and failure mechanisms. A unique homogeneous stress field is observed throughout both the skeletal and interfacial components of the triangular geometry, thus providing advantages in load transmission, weight, stiffness, strength, energy absorption, and fatigue over the rectangular geometry. The results obtained have relevance to biomimetic design and optimization, suture growth and fusion, and evolutionary phenotype diversity.

Stochastic Interdigitation as a Toughening Mechanism at the Interface between Tendon and Bone

“…Interdigitations are believed to improve load transmission and increase energy absorption of the interfaces between bones in the skull (28). Advanced micromechanical models exist for a range of these interfaces (29,30).…”

Overcoming the brittleness of glass through bio-inspiration and micro-architecture

“…Here, we engraved a weak interface with jigsaw-like features ahead of an incident crack. This intricate line, reminiscent of sutures in some natural materials 46 , consisted of a periodic repetition of tabs with round features to limit stress concentrations (Fig. 4a).…”

The armored carapace of the boxfish

“…In addition, these latter organisms have Sharpey's fibers that bridge the gap directly between the mineralized sutures. Li et al [44][45][46] reported extensively on a mathematical model to determine the stress and failure modes of suture structures in biological systems. According to this model, the strength-optimized angle for triangular sutures made of bone-and collagen-like constituents is 2h = 24°where the failure mode shifts from the compliant interface (for lower angles) to the suture teeth (for higher angles) thus producing the highest fracture strength [45].…”

“…Li et al [44][45][46] reported extensively on a mathematical model to determine the stress and failure modes of suture structures in biological systems. According to this model, the strength-optimized angle for triangular sutures made of bone-and collagen-like constituents is 2h = 24°where the failure mode shifts from the compliant interface (for lower angles) to the suture teeth (for higher angles) thus producing the highest fracture strength [45]. The suture angles of the red-eared slider, stickleback, and white tailed deer are very similar to this effective suture angle and, conversely, the sutures of the boxfish are significantly larger and thus likely to create a weaker interface.…”