Crack Deflection and Toughening in Network Materials With Preferential Fiber Alignment

Abstract

Abstract. Many soft biological and engineering materials, including tendon, cartilage, the dermis, and nonwovens, owe their mechanical properties to a load-bearing network of fibers. Fracture is a critical event in such applications, and various toughening mechanisms operate in these materials. In this work, we show that preferential fiber alignment works as a toughening mechanism in network materials. To this end, we consider network models with various degrees of alignment and pre-existing cracks oriented parallel and orthogonal to the alignment direction and quantify the stiffness and toughness anisotropies introduced by fiber alignment. Further, we show that cracks oriented orthogonal to the alignment direction deflect once the toughness anisotropy is larger than a threshold. This leads to zig–zag crack growth and an overall increase in energy dissipation. The proposed mechanism is supported by clinical observations of tendon rupture reported in the literature.