ausblenden:
Schlagwörter:
Fiber composite, lamellar bone, stiffness matrix, configurational forces, fracture toughness
Zusammenfassung:
Twisted plywood architectures can be observed in many biological materials with high
fracture toughness, such as in arthropod cuticles or in lamellar bone. Main purpose of this
paper is to analyze the influence of the progressive rotation of the fiber direction on the spatial
variation of the crack driving force and, thus, on the fracture toughness of plywood-like
structures. The theory of fiber composites is used to describe the stiffness matrix of a twisted
plywood structure in a specimen-fixed coordinate system. The driving force acting on a crack
propagating orthogonally to the fiber-rotation plane is studied by methods of computational
mechanics, coupled with the concept of configurational forces. The analysis unfolds a spatial
variation of the crack driving force with minima that are beneficial for the fracture toughness
of the material. It is shown that the estimation of the crack driving force can be simplified by
replacing the complicated anisotropic twisted plywood structure by an isotropic material with
appropriate periodic variations of Young’s modulus, which can be constructed based either on the local stiffness or local strain energy density variations. As practical example, the concepts are discussed for a specimen with a stiffness anisotropy similar to lamellar bone.
