I4CIel solid.CIel11*a01A1^2+2*a01A1*solid.CIel12*a01A2+2*a01A1*solid.CIel13*a01A3+solid.CIel22*a01A2^2+2*a01A3*solid.CIel23*a01A2+solid.CIel33*a01A3^2 Fourth invariant, Adventitia I6CIel solid.CIel11*a02A1^2+2*a02A1*solid.CIel12*a02A2+2*a02A1*solid.CIel13*a02A3+solid.CIel22*a02A2^2+2*a02A3*solid.CIel23*a02A2+solid.CIel33*a02A3^2 Sixth invariant, Adventitia W1 cA/2*(solid.I1CIel-3) Isotropic isochoric strain energy density W4 k1A/(2*k2A)*(exp(k2A*(I4CIel-1)^2)-1)*(I4CIel>1) Anisotropic strain energy density, first fiber family W6 k1A/(2*k2A)*(exp(k2A*(I6CIel-1)^2)-1)*(I6CIel>1) Anisotropic strain energy density, second fiber family Wvol kappa/2*(solid.Jel-1)^2 Volumetric strain energy density