Difference between revisions of "Transversely Isotropic Material"

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This anisotropic [[Material Models|material]] is a [[Material Models#Linear Elastic Small Strain Materials|small strain, linear elastic material]]. The stress (σ) and strain (ε) are related by:
== Constitutive Law ==


This anisotropic [[Material Models|MPM material]] (or [[FEA Material Models|FEA material]]) is a [[Material Models#Linear Elastic Small Strain Materials|small strain, linear elastic material]]. The stress (σ) and strain (ε) are related by:
     
<math>\vec\varepsilon = \mathbf{S}\vec\sigma + \vec\alpha\Delta T + \vec\beta c</math>
<math>\vec\varepsilon = \mathbf{S}\vec\sigma + \vec\alpha\Delta T + \vec\beta c</math>


&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
<math>\vec\sigma = \mathbf{C}\vec\varepsilon + \vec M\Delta T + \vec M_\beta c</math>
<math>\vec\sigma = \mathbf{C}\vec\varepsilon + \vec M\Delta T + \vec M_\beta c</math>


where <b>S</b> and <b>C</b> is the compliance and stiffness tensors, <math>\vec\alpha</math> and <math>\vec\beta</math> are the thermal and moisture expansion tensors, and <math>\vec M</math> and <math>\vec M_\beta</math> are the stress-temperature and stress-concentraion tensors. &Delta;T is difference between current temperature and the stress free temperature and c is the weight fracture solvent concentration. These equations use contracted notation where stress and strain tensors contract to vectors:
where <b>S</b> and <b>C</b> are the compliance and stiffness tensors, <math>\vec\alpha</math> and <math>\vec\beta</math> are the thermal and solvent expansion tensors, and <math>\vec M</math> and <math>\vec M_\beta</math> are the stress-temperature and stress-concentraion tensors. &Delta;T is difference between current temperature and the stress free temperature and c is the weight fracture solvent concentration. These equations use contracted notation where stress and strain tensors contract to vectors:


&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
<math>\vec\varepsilon = (\varepsilon_{xx},\varepsilon_{yy},\varepsilon_{zz},\varepsilon_{yz},\varepsilon_{xz},\varepsilon_{xy})</math>
<math>\vec\varepsilon = (\varepsilon_{xx},\varepsilon_{yy},\varepsilon_{zz},\varepsilon_{yz},\varepsilon_{xz},\varepsilon_{xy})</math>


&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
<math>\vec\sigma = (\sigma_{xx},\sigma_{yy},\sigma_{zz},\sigma_{yz},\sigma_{xz},\sigma_{xy})</math>
<math>\vec\sigma = (\sigma_{xx},\sigma_{yy},\sigma_{zz},\sigma_{yz},\sigma_{xz},\sigma_{xy})</math>


and the order of the shear terms is by the standard convention. The stiffness and compliance tensors contract to 6X6 matrices while all thermal and moisture expansion tensors contract to a vector.
and the order of the shear terms is by the standard convention. The stiffness and compliance tensors contract to 6X6 matrices while all thermal and moisture expansion tensors contract to a vector. When used as an [[FEA Material Models|FEA material]], the solvent expansion and solvent concentration terms are not used.


In a transversely isotropic [[Material Models|material]], one plane is isotropic while the direction normal to that plane defines a unique axis with different properties. Properties in the isotropic plane are subscripted &quot;T&quot; for transverse plane properties and properties along the unique axis are subscripted &quot;A&quot; for axial properties. You can pick from two types of transversely isotropic [[Material Models|materials]], which differ only by orientation on the unique axes. The only reason two are needed is support all options in 2D calculations.
In a transversely isotropic [[Material Models|MPM material]] (or [[FEA Material Models|FEA material]]), one plane is isotropic while the direction normal to that plane defines a unique axis with different properties. Properties in the isotropic plane are subscripted "T" for transverse plane properties and properties along the unique axis are subscripted "A" for axial properties.


== Transverse 1 ==
== Transverse Material Properties ==


In this transversely isotropic [[Material Models|material]], the isotropic plane in the x-y plane, which is the plane for 2D analyses. The axial direction is along the z axis, which is in the thickness direction for 2D analyses. The stiffness and compliance tensors are:
When created, the transversely isotropic [[Material Models|MPM material]] (or [[FEA Material Models|FEA material]]), the isotropic plane is the x-y plane, which is the plane for 2D or axisymmetric analyses. The axial direction is along the z axis, which is in the thickness direction for 2D analyses or the hoop direction for axisymmetric analyses. The stiffness and compliance tensors are:


&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
<math>
<math>
   \mathbf{C}^{-1} = \mathbf{S} =  
   \mathbf{C}^{-1} = \mathbf{S} =  
Line 34: Line 41:
</math>
</math>


where E and G are tensile and shear moduli, &nu; are Poisson's ratios, and A and T refer to axial and transverse properties. The thermal and moisture expansion tensors are
where E and G are tensile and shear moduli, &nu; are Poisson's ratios, and A and T refer to axial and transverse properties. This tensor can be explicitly inverted to:
 
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
<math>
  \mathbf{S}^{-1} = \mathbf{C} = = \left(\begin{array}{cccccc}
        K_T+G_T & K_T-G_T & 2K_T\nu_A 
                    & 0 & 0 & 0 \\
      K_T-G_T & K_T+G_T & 2K_T\nu_A
                    & 0 & 0 & 0 \\
      2K_T\nu_A & 2K_T\nu_A & E_A + 4K_T\nu_A^2
                    & 0 & 0 & 0 \\
                0 & 0 & 0 & G_A & 0 & 0 \\
                0 & 0 & 0 & 0 & G_A & 0 \\
                0 & 0 & 0 & 0 & 0 & G_T
        \end{array}\right)
</math>
 
where <math>G_T</math> is transverse shear modulus and <math>K_T</math> is the transverse, plane-strain bulk modulus. These new properties are related to properties in '''S''' by:
 
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
<math>G_T = {E_T\over 2(1+\nu_T)}
\qquad {\rm and} \qquad
\frac{1}{K_T} = {2(1-\nu_T)\over E_T} - {4\nu_A^2\over E_A}
</math>
 
The thermal and solvent expansion tensors are


&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
<math>\vec\alpha = (\alpha_T, \alpha_T,\alpha_A,0,0,0)</math>
<math>\vec\alpha = (\alpha_T, \alpha_T,\alpha_A,0,0,0)</math>


&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
<math>\vec\beta = (\beta_T, \beta_T,\beta_A,0,0,0)</math>
<math>\vec\beta = (\beta_T, \beta_T,\beta_A,0,0,0)</math>


where again, A and T refer to axial and transverse properties. The stress-temperature and stress-concentration tensors are found from
where again, A and T refer to axial and transverse properties. The stress-temperature and stress-concentration tensors are found from


&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
<math>\vec M = -\mathbf{C}\vec\alpha \quad{\rm and}\quad \vec M_\beta = -\mathbf{C}\vec\beta</math>
<math>\vec M = -\mathbf{C}\vec\alpha \quad{\rm and}\quad \vec M_\beta = -\mathbf{C}\vec\beta</math>


All these properties are set as explained [[#Material Properties|below]].
All these properties are set as explained [[#Material Properties|below]]. The solvent expansion terms are for MPM only.
 
This transversely isotropic material is a special case of an [[Orthotropic Material|orthotropic material]] where <math>E_{x}=E_{y}=E_T</math>, <math>E_{z}=E_A</math>, <math>\nu_{xy}=\nu_{yx}=\nu_T</math>, <math>\nu_{xz}=E_T\nu_A/E_A</math>, <math>\nu_{zx}=\nu_A</math>, <math>\nu_{yz}=E_T\nu_A/E_A</math>, <math>\nu_{zy}=\nu_A</math>, <math>G_{xy}=G_T=E_T/(2(1+\nu_T))</math>, <math>G_{xz}=G_{yz}=G_A</math>, <math>\alpha_{x}=\alpha_{y}=\alpha_T</math>, <math>\alpha_{z}=\alpha_A</math>, <math>\beta_{x}=\beta_{y}=\beta_T</math>, and <math>\beta_{z}=\beta_A</math>.
 
=== Rotated Material Axes ===


== Transverse 2 ==
As defined, transversely isotropic materials have their axial direction along the ''z'' axis. You can change to any other orientation when defining material points (in MPM) or elements (in FEA) by selecting rotations angles for MPM particles or FEA elements.


In this transversely isotropic [[Material Models|material]], the isotropic plane in the x-z plane. The axial direction is along the y axis, which is in the plane for for 2D analyses. The stiffness and compliance tensors are:
In 2D, however, the only rotation angle that is allowed is about the ''z'' axis, which means the axial direction will always be along the ''z'' axis. To allow simulations with axial direction in the plane of a 2D analysis, set the material <tt>swapz</tt> property greater than zero. When that property is used, the initial material will have its axial direction along the ''y'' axis and the ''x-z'' plane will be isotropic. You can rotate as needed about the ''z'' axis to orient the axial direction anywhere in the ''x-y'' plane. For axisymmetric calculations, the <tt>swapz</tt> property changes axial direction from &theta; direction to the ''Z'' direction and the ''r-&theta;'' plane becomse the isotropic plane. You can reoriented the axial direction as needed in the ''R-Z'' plane.


<math>
Note that for 2D analyses, the axial direction has to be either in the x-y plane (<tt>swapz=0</tt>) or normal to the x-y plane (<tt>swapz=1</tt> with optional rotations). Any other orientation would induce out-of-plane shear that is not allowed in 2D calculations. To handle such material orientations, you need to use 3D calculations (MPM only).
  \mathbf{C}^{-1} = \mathbf{S} =
 
  \left(\begin{array}{cccccc}
The <tt>swapz</tt> property is not allowed in 3D MPM simulations; use material point rotation angles instead to get any desired material orientation.
          {1\over E_T} & -{\nu_A\over E_A} & -{\nu_T\over E_T}
 
                          & 0 & 0 & 0 \\
== Material Properties ==
          -{\nu_A\over E_A} & {1\over E_A} & -{\nu_A\over E_A}
                          & 0 & 0 & 0 \\
          -{\nu_T\over E_T} & -{\nu_A\over E_A} & {1\over E_T}
                          & 0 & 0 & 0 \\
                    0 & 0 & 0 & {1\over G_T} & 0 & 0 \\
                    0 & 0 & 0 & 0 & {1\over G_A} & 0 \\
                    0 & 0 & 0 & 0 & 0 & {1\over G_A}
            \end{array}\right)
</math>


where E and G are tensile and shear moduli, &nu; are Poisson's ratios, and A and T refer to axial and transverse properties. The thermal and moisture expansion tensors are
The properties are


<math>\vec\alpha = (\alpha_T, \alpha_A,\alpha_T,0,0,0)</math>
{| class="wikitable"
|-
! Property !! Description !! Units !! Default
|-
| EA || Axial tensile modulus || [[ConsistentUnits Command#Legacy and Consistent Units|pressure units]] || none
|-
| ET || Transverse tensile modulus || [[ConsistentUnits Command#Legacy and Consistent Units|pressure units]] || none
|-
| GA || Axial shear modulus || [[ConsistentUnits Command#Legacy and Consistent Units|pressure units]] || none
|-
| GT || Transverse shear modulus || [[ConsistentUnits Command#Legacy and Consistent Units|pressure units]] || none
|-
| nuA || Axial Poisson's ratio || none || 0.33
|-
| nuT || Transverse Poisson's ratio || none || none
|-
| alphaA || Axial thermal expansion coefficient || ppm/K || 40
|-
| alphaT || Transverse thermal expansion coefficient || ppm/K || 40
|-
| swapz || Set to &gt;0 to move axial direction from ''z'' axis to the ''y'' axis (or from &theta; axis to ''Z'' axis in axisymmetric calculations). This property is only needed for 2D simulations that want axial direction in the analysis plane (it is not allowed in 3D MPM simulations). || none || 0
|}


<math>\vec\beta = (\beta_T, \beta_A,\beta_T,0,0,0)</math>
In a transversely isotropic material, the three transverse properties (ET, GT, and nuT)  are not independent (see above). As a consequence, you can only specify two of these three properties. The Poisson ratios cannot assume any values. They must obey the following relations:


where again, A and T refer to axial and transverse properties. The stress-temperature and stress-concentration tensors are found from
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
<math>-1<\nu_T<1 \qquad {\rm and} \qquad
  |\nu_A| < \sqrt{{E_A(1-\nu_T)\over 2E_T}}</math>


<math>\vec M = -\mathbf{C}\vec\alpha \quad{\rm and}\quad \vec M_\beta = -\mathbf{C}\vec\beta</math>
The following properties are only allowed in MPM calculations:


All these properties are set as explained [[#Material Properties|below]].
{| class="wikitable"
|-
! Property !! Description !! Units !! Default
|-
| betaA || Axial solvent expansion coefficient || 1/(wt fraction) || 0
|-
| betaT || Transverse solvent expansion coefficient || 1/(wt fraction) || 0
|-
| DA || Axial solvent diffusion constant || [[ConsistentUnits Command#Legacy and Consistent Units|diffusion units]] || 0
|-
| DT || Transverse solvent diffusion constant || [[ConsistentUnits Command#Legacy and Consistent Units|diffusion units]] || 0
|-
| kCondA || Axial thermal conductivity || [[ConsistentUnits Command#Legacy and Consistent Units|conductivity units]] || 0
|-
| kCondT || Transverse thermal conductivity || [[ConsistentUnits Command#Legacy and Consistent Units|conductivity units]] || 0
|-
| ([[Common Material Properties|other]]) || Properties common to all materials || varies || varies
|}


== Material Properties ==
=== Deprecated Material Properties ===


Can rotate to any other orientation
Prior to the <tt>swapz</tt> material property, there were two types on transversely isotropic material named "Transverse 1" and "Transverse 2". Although these can still be used as the material type, they are deprecated. The prior "Transverse 1" is identical to this material with <tt>swapz=0</tt>. The prior "Transverse 2" material is identical to this material with <tt>swapz=1</tt>.


== History Variables ==
== History Variables ==


None
None
== Examples ==
These commands model carbon fibers as a transversely isotropic material with axial direction in the y direction
Material "carbon","Carbon Fiber","Transverse 2"
  EA 220000
  ET 20000
  GA 18000
  nuT 0.3
  nuA .2
  alphaA -.4
  alphaT 18
  rho 1.76
Done

Latest revision as of 16:33, 2 February 2023

Constitutive Law

This anisotropic MPM material (or FEA material) is a small strain, linear elastic material. The stress (σ) and strain (ε) are related by:

      [math]\displaystyle{ \vec\varepsilon = \mathbf{S}\vec\sigma + \vec\alpha\Delta T + \vec\beta c }[/math]

      [math]\displaystyle{ \vec\sigma = \mathbf{C}\vec\varepsilon + \vec M\Delta T + \vec M_\beta c }[/math]

where S and C are the compliance and stiffness tensors, [math]\displaystyle{ \vec\alpha }[/math] and [math]\displaystyle{ \vec\beta }[/math] are the thermal and solvent expansion tensors, and [math]\displaystyle{ \vec M }[/math] and [math]\displaystyle{ \vec M_\beta }[/math] are the stress-temperature and stress-concentraion tensors. ΔT is difference between current temperature and the stress free temperature and c is the weight fracture solvent concentration. These equations use contracted notation where stress and strain tensors contract to vectors:

      [math]\displaystyle{ \vec\varepsilon = (\varepsilon_{xx},\varepsilon_{yy},\varepsilon_{zz},\varepsilon_{yz},\varepsilon_{xz},\varepsilon_{xy}) }[/math]

      [math]\displaystyle{ \vec\sigma = (\sigma_{xx},\sigma_{yy},\sigma_{zz},\sigma_{yz},\sigma_{xz},\sigma_{xy}) }[/math]

and the order of the shear terms is by the standard convention. The stiffness and compliance tensors contract to 6X6 matrices while all thermal and moisture expansion tensors contract to a vector. When used as an FEA material, the solvent expansion and solvent concentration terms are not used.

In a transversely isotropic MPM material (or FEA material), one plane is isotropic while the direction normal to that plane defines a unique axis with different properties. Properties in the isotropic plane are subscripted "T" for transverse plane properties and properties along the unique axis are subscripted "A" for axial properties.

Transverse Material Properties

When created, the transversely isotropic MPM material (or FEA material), the isotropic plane is the x-y plane, which is the plane for 2D or axisymmetric analyses. The axial direction is along the z axis, which is in the thickness direction for 2D analyses or the hoop direction for axisymmetric analyses. The stiffness and compliance tensors are:

      [math]\displaystyle{ \mathbf{C}^{-1} = \mathbf{S} = \left(\begin{array}{cccccc} {1\over E_T} & -{\nu_T\over E_T}& -{\nu_A\over E_A} & 0 & 0 & 0 \\ -{\nu_T\over E_T} & {1\over E_T} & -{\nu_A\over E_A} & 0 & 0 & 0 \\ -{\nu_A\over E_A} & -{\nu_A\over E_A} & {1\over E_A} & 0 & 0 & 0 \\ 0 & 0 & 0 & {1\over G_A} & 0 & 0 \\ 0 & 0 & 0 & 0 & {1\over G_A} & 0 \\ 0 & 0 & 0 & 0 & 0 & {1\over G_T} \end{array}\right) }[/math]

where E and G are tensile and shear moduli, ν are Poisson's ratios, and A and T refer to axial and transverse properties. This tensor can be explicitly inverted to:

      [math]\displaystyle{ \mathbf{S}^{-1} = \mathbf{C} = = \left(\begin{array}{cccccc} K_T+G_T & K_T-G_T & 2K_T\nu_A & 0 & 0 & 0 \\ K_T-G_T & K_T+G_T & 2K_T\nu_A & 0 & 0 & 0 \\ 2K_T\nu_A & 2K_T\nu_A & E_A + 4K_T\nu_A^2 & 0 & 0 & 0 \\ 0 & 0 & 0 & G_A & 0 & 0 \\ 0 & 0 & 0 & 0 & G_A & 0 \\ 0 & 0 & 0 & 0 & 0 & G_T \end{array}\right) }[/math]

where [math]\displaystyle{ G_T }[/math] is transverse shear modulus and [math]\displaystyle{ K_T }[/math] is the transverse, plane-strain bulk modulus. These new properties are related to properties in S by:

      [math]\displaystyle{ G_T = {E_T\over 2(1+\nu_T)} \qquad {\rm and} \qquad \frac{1}{K_T} = {2(1-\nu_T)\over E_T} - {4\nu_A^2\over E_A} }[/math]

The thermal and solvent expansion tensors are

      [math]\displaystyle{ \vec\alpha = (\alpha_T, \alpha_T,\alpha_A,0,0,0) }[/math]

      [math]\displaystyle{ \vec\beta = (\beta_T, \beta_T,\beta_A,0,0,0) }[/math]

where again, A and T refer to axial and transverse properties. The stress-temperature and stress-concentration tensors are found from

      [math]\displaystyle{ \vec M = -\mathbf{C}\vec\alpha \quad{\rm and}\quad \vec M_\beta = -\mathbf{C}\vec\beta }[/math]

All these properties are set as explained below. The solvent expansion terms are for MPM only.

This transversely isotropic material is a special case of an orthotropic material where [math]\displaystyle{ E_{x}=E_{y}=E_T }[/math], [math]\displaystyle{ E_{z}=E_A }[/math], [math]\displaystyle{ \nu_{xy}=\nu_{yx}=\nu_T }[/math], [math]\displaystyle{ \nu_{xz}=E_T\nu_A/E_A }[/math], [math]\displaystyle{ \nu_{zx}=\nu_A }[/math], [math]\displaystyle{ \nu_{yz}=E_T\nu_A/E_A }[/math], [math]\displaystyle{ \nu_{zy}=\nu_A }[/math], [math]\displaystyle{ G_{xy}=G_T=E_T/(2(1+\nu_T)) }[/math], [math]\displaystyle{ G_{xz}=G_{yz}=G_A }[/math], [math]\displaystyle{ \alpha_{x}=\alpha_{y}=\alpha_T }[/math], [math]\displaystyle{ \alpha_{z}=\alpha_A }[/math], [math]\displaystyle{ \beta_{x}=\beta_{y}=\beta_T }[/math], and [math]\displaystyle{ \beta_{z}=\beta_A }[/math].

Rotated Material Axes

As defined, transversely isotropic materials have their axial direction along the z axis. You can change to any other orientation when defining material points (in MPM) or elements (in FEA) by selecting rotations angles for MPM particles or FEA elements.

In 2D, however, the only rotation angle that is allowed is about the z axis, which means the axial direction will always be along the z axis. To allow simulations with axial direction in the plane of a 2D analysis, set the material swapz property greater than zero. When that property is used, the initial material will have its axial direction along the y axis and the x-z plane will be isotropic. You can rotate as needed about the z axis to orient the axial direction anywhere in the x-y plane. For axisymmetric calculations, the swapz property changes axial direction from θ direction to the Z direction and the r-θ plane becomse the isotropic plane. You can reoriented the axial direction as needed in the R-Z plane.

Note that for 2D analyses, the axial direction has to be either in the x-y plane (swapz=0) or normal to the x-y plane (swapz=1 with optional rotations). Any other orientation would induce out-of-plane shear that is not allowed in 2D calculations. To handle such material orientations, you need to use 3D calculations (MPM only).

The swapz property is not allowed in 3D MPM simulations; use material point rotation angles instead to get any desired material orientation.

Material Properties

The properties are

Property Description Units Default
EA Axial tensile modulus pressure units none
ET Transverse tensile modulus pressure units none
GA Axial shear modulus pressure units none
GT Transverse shear modulus pressure units none
nuA Axial Poisson's ratio none 0.33
nuT Transverse Poisson's ratio none none
alphaA Axial thermal expansion coefficient ppm/K 40
alphaT Transverse thermal expansion coefficient ppm/K 40
swapz Set to >0 to move axial direction from z axis to the y axis (or from θ axis to Z axis in axisymmetric calculations). This property is only needed for 2D simulations that want axial direction in the analysis plane (it is not allowed in 3D MPM simulations). none 0

In a transversely isotropic material, the three transverse properties (ET, GT, and nuT) are not independent (see above). As a consequence, you can only specify two of these three properties. The Poisson ratios cannot assume any values. They must obey the following relations:

      [math]\displaystyle{ -1\lt \nu_T\lt 1 \qquad {\rm and} \qquad |\nu_A| \lt \sqrt{{E_A(1-\nu_T)\over 2E_T}} }[/math]

The following properties are only allowed in MPM calculations:

Property Description Units Default
betaA Axial solvent expansion coefficient 1/(wt fraction) 0
betaT Transverse solvent expansion coefficient 1/(wt fraction) 0
DA Axial solvent diffusion constant diffusion units 0
DT Transverse solvent diffusion constant diffusion units 0
kCondA Axial thermal conductivity conductivity units 0
kCondT Transverse thermal conductivity conductivity units 0
(other) Properties common to all materials varies varies

Deprecated Material Properties

Prior to the swapz material property, there were two types on transversely isotropic material named "Transverse 1" and "Transverse 2". Although these can still be used as the material type, they are deprecated. The prior "Transverse 1" is identical to this material with swapz=0. The prior "Transverse 2" material is identical to this material with swapz=1.

History Variables

None

Examples

These commands model carbon fibers as a transversely isotropic material with axial direction in the y direction

Material "carbon","Carbon Fiber","Transverse 2"
  EA 220000
  ET 20000
  GA 18000
  nuT 0.3
  nuA .2
  alphaA -.4
  alphaT 18
  rho 1.76
Done