Transversely Isotropic Failure Surface
Introduction
This damage initiation law predicts failure in transversely isotropic materials. Because it deals with a specific material type, this law is only appropriate for TransIsoSoftening 1 and 2 materials.
Failure Surface
This failure surface has five failure properties. First, are two tensile strengths [math]\displaystyle{ \sigma_A }[/math] and [math]\displaystyle{ \sigma_T }[/math]. The first tensile strength is for tensile loading in the axial direction. The second is for tensile failure in the isotropic plane, which occurs in the maximum normal stress direction in that plane.
Second, are three shear strengths [math]\displaystyle{ \tau_A }[/math], [math]\displaystyle{ \tau_T }[/math], and [math]\displaystyle{ \tau_{RS} }[/math]. The first two shear strength are for failure at maximum shear stress in planes parallel to the axial direction. When failure occurs in such a plane, the resulting crack will either be parallel to the axial direction (if [math]\displaystyle{ \tau_A \lt \tau_T }[/math]) or through the axial direction (if [math]\displaystyle{ \tau_T\lt \tau_A }[/math]) . The last shear strength is for failure in the isotropic plane, which occurs in the maximum shear stress direction in that plane.
Damage Law Properties
The following table lists the input properties for this initiation law
| Property | Description | Units | Default |
|---|---|---|---|
| sigmacA | Critical stress for failure in the axial direction (output as sigcA) | pressure units | infinite |
| sigmac | Critical transverse tensile strength for tensile failure in the isotropic plane (output as sigcT) | pressure units | infinite |
| taucA | Critical shear stress for failure due to axial shear stress with failure parallel to the axial direction | pressure units | infinite |
| taucT | Critical shear stress for failure due to axial shear stress with failure through the axial direction | pressure units | infinite |
| tauc | Critical transverse shear stress for shear failure n the isotropic plane (output as taucRS) | pressure units | infinite |
Notice this law has two axial shear strengths (taucA and taucT). Axial shear failure will always occur at the minimum of these two values. Two properties are provided to facilitate comparison to material characterization. For example, in wood, taucA is called "shear parallel strength", tauT is called "shear perpendicular strength", and tauc is called "rolling shear strength". For wood, tauT is must large than taucA, which failure is by shear cracks parallel to the wood fibers.