Effective stiffness two step Hashin Shtrikman
Effective_stiffness(upper=array([[ 1.79306622e+01, 6.79183199e+00, 6.44049100e+00, -7.92491438e-03, -1.22458610e-01, 2.79693636e-01],
[ 6.79183199e+00, 1.66571351e+01, 6.50198561e+00, -1.44257800e-02, -9.10987462e-03, 2.56586798e-01],
[ 6.44049100e+00, 6.50198561e+00, 1.43808190e+01, -2.85337268e-03, -4.82239343e-02, -3.03802346e-02],
[-7.92491438e-03, -1.44257800e-02, -2.85337268e-03, 8.56565464e+00, 1.06716825e-01, -7.33643806e-02],
[-1.22458610e-01, -9.10987462e-03, -4.82239343e-02, 1.06716825e-01, 8.95472773e+00, -1.95087657e-02],
[ 2.79693636e-01, 2.56586798e-01, -3.03802346e-02, -7.33643806e-02, -1.95087657e-02, 1.09913269e+01]]), lower=array([[ 1.31958542e+01, 6.53652351e+00, 5.06275498e+00, -2.56586400e-02, -2.11023481e-01, 4.35412759e-01],
[ 6.53652351e+00, 1.13419501e+01, 5.07695238e+00, -2.30964777e-02, -5.61794756e-02, 3.73083046e-01],
[ 5.06275498e+00, 5.07695238e+00, 8.76711885e+00, 8.96494982e-03, -8.82286689e-03, -1.95238689e-02],
[-2.56586400e-02, -2.30964777e-02, 8.96494982e-03, 3.73696055e+00, 1.40581209e-02, -9.26497992e-02],
[-2.11023481e-01, -5.61794756e-02, -8.82286689e-03, 1.40581209e-02, 3.84729163e+00, -3.93273718e-02],
[ 4.35412759e-01, 3.73083046e-01, -1.95238689e-02, -9.26497992e-02, -3.93273718e-02, 7.12215158e+00]]))