求助：急急急！！！关于复合材料层合板参数的问题

4.这是一组复合材料层合板参数（AS4、3502Gr/Ep）：
E1=143.9E9
E2=11.86E9
E3=11.86E9
G12=6.688E9
G13=6.688E9
G23=3.8E9
v12=0.326
v13=0.54
v23=0.54
材料参数应该没有问题，它应该不是正交各向异性的，因为不符合1.0 - V12**2*E1/E2- v23**2*E2/E3 - v13**2*E1/E3 -2.0*v12*v23*v13*E1/E3
我用的是shell99单元，材料设置如上，ansys好像默认为是正交各向异性的，出现了如下错误：
*** ERROR *** CP = 77.781 TIME= 19:32:55
The stress-strain matrix of material 1 is not positive definite, which
is required for real materials. Being positive definite means that
1.0 - NUXY**2*EX/EY - NUYZ**2*EY/EZ - NUXZ**2*EX/EZ -
2.0*NUXY*NUYZ*NUXZ*EX/EZ must be positive, but is equal to
-6.42592419. Consider reducing the Poisson's ratios.

EX = 1.439E+11 EY = 1.186E+10 EZ = 1.186E+10
NUXY = 0.326 NUYZ = 0.54 NUXZ = 0.54
GXY = 6.688E+09 GYZ = 3.8E+09 GXZ = 6.688E+09.
那位大侠指点一下是为什么呀？
我该怎么设定材料参数？？？、、
急急！！