Available parameterizations of second order fiber orientation tensors:
####################
Group: planar
alpha1
Matrix([
[3*alpha1/4 + 1/2, 0, 0],
[ 0, 1/2 - 3*alpha1/4, 0],
[ 0, 0, 0]])
la1
Matrix([
[la1, 0, 0],
[ 0, 1 - la1, 0],
[ 0, 0, 0]])
####################
Group: transv_isotropic
alpha1
Matrix([
[alpha1 + 1/3, 0, 0],
[ 0, 1/3 - alpha1/2, 0],
[ 0, 0, 1/3 - alpha1/2]])
alpha2
Matrix([
[1/3 - alpha2/2, 0, 0],
[ 0, alpha2 + 1/3, 0],
[ 0, 0, 1/3 - alpha2/2]])
alpha3
Matrix([
[1/3 - alpha3/2, 0, 0],
[ 0, 1/3 - alpha3/2, 0],
[ 0, 0, alpha3 + 1/3]])
la1
Matrix([
[la1, 0, 0],
[ 0, 1/2 - la1/2, 0],
[ 0, 0, 1/2 - la1/2]])
####################
Group: orthotropic
la1_la2
Matrix([
[la1, 0, 0],
[ 0, la2, 0],
[ 0, 0, -la1 - la2 + 1]])
la1_la2_la3
Matrix([
[la1, 0, 0],
[ 0, la2, 0],
[ 0, 0, la3]])
alpha1_alpha3
Matrix([
[alpha1 - alpha3/2 + 1/3, 0, 0],
[ 0, -alpha1/2 - alpha3/2 + 1/3, 0],
[ 0, 0, -alpha1/2 + alpha3 + 1/3]])
alpha1_alpha2_alpha3
Matrix([
[alpha1 - alpha2/2 - alpha3/2 + 1/3, 0, 0],
[ 0, -alpha1/2 + alpha2 - alpha3/2 + 1/3, 0],
[ 0, 0, -alpha1/2 - alpha2/2 + alpha3 + 1/3]])