MAT8

Shell Element Orthotropic Material Property Definition

Description: Defines the material property for an orthotropic material for isoparametric shell elements.

Format:

Example:

Field	Definition	Type	Default
MID	Material identification number. Referenced on a PSHELL or PCOMP entry only.	Integer > 0	Required
E1	Modulus of elasticity in longitudinal direction, also defined as the fiber direction or 1-direction.	Real ≠ 0.0	Required
E2	Modulus of elasticity in lateral direction, also defined as the matrix direction or 2-direction.	Real ≠ 0.0	Required
NU12	Poisson's ratio ( for uniaxial loading in 1-direction). Note that for uniaxial loading in 2-direction is related to , E 1, and E 2 by the relation .	Real	Required
G12	In-plane shear modulus.	Real ≥ 0.0 or blank	0.0
G1Z	Transverse shear modulus for shear in 1-Z plane.	Real > 0.0 or blank	See Remark 2.
G2Z	Transverse shear modulus for shear in 2-Z plane.	Real > 0.0 or blank	See Remark 2.
RHO	Mass density.	Real or blank	0.0
Ai	Thermal expansion coefficient in i-direction.	Real or blank	0.0
TREF	Reference temperature for the calculation of thermal loads.	Real or blank	0.0
Xt, Xc	Allowable stresses or strains in tension and compression, respectively, in the longitudinal direction. Required if composite element failure index is desired.	Real ≥ 0.0 or blank	Default value for Xc is Xt
Yt, Yc	Allowable stresses or strains in tension and compression, respectively, in the lateral direction. Required if composite element failure index is desired.	Real ≥ 0.0 or blank	Default value for Yc is Yt
S	Allowable stress or strain for in-plane shear.	Real ≥ 0.0 or blank	0.0
GE	Structural element damping coefficient. See Remarks 7, 8, and 10.	Real or blank	0.0
F12	Interaction term in the tensor polynomial theory of Tsai-Wu. Required if composite element failure index by Tsai-Wu theory is desired and if value of F12 is different from 0.0. See Remark 11.	Real	0.0
STRN	For the maximum strain theory only (see STRN in PCOMP entry). Indicates whether Xt, Xc, Yt, Yc, and S are stress or strain allowables.	Real = 1.0 for strain allowable	Blank for stress allowable
CS	Honeycomb sandwich core cell size. Required if material defines the core of a honeycomb sandwich and dimpling stability index is desired (LAM = HCS on the PCOMP entry).	Real ≥ 0.0 or blank	0.0
EC	Honeycomb sandwich core Young's modulus used for stability index analysis.	Real ≥ 0.0 or blank	See Remark 12
GC	Honeycomb sandwich core shear modulus used for stability index analysis.	Real ≥ 0.0 or blank	See Remark 12
ALPHA0	Fracture angle for uniaxial transverse compression in degrees. Used in the NASA LaRC02 failure theory only (see LARC02 in PCOMP entry). See Remark 13.	0.0 < Real < 90.0	53.0
SB	Allowable inter-laminar shear stress of the composite laminate bonding material (allowable interlaminar shear stress). See Remark 14.	Real ≥ 0.0 or blank	See Remark 14
EF1	Modulus of elasticity of fiber. Used in the Puck PCP failure theory only (see PUCK in PCOMP entry). See Remark 15.	Real > 0.0 or blank	E1/0.6
NUF12	Poisson's ratio of fiber. Used in the Puck PCP failure theory only (see PUCK in PCOMP entry).	Real ≥ 0.0 or blank	0.3
MSMF	Mean stress magnification factor. Used in the Puck PCP failure theory only (see PUCK in PCOMP entry). See Remark 15.	Real ≥ 0.0 or blank	1.1
PNPT	Failure envelop slope parameter for transverse tension. Used in the Puck PCP failure theory only (see PUCK in PCOMP entry). See Remark 16.	Real ≥ 0.0 or blank	0.35
PNPC	Failure envelop slope parameter for transverse compression. Used in the Puck PCP failure theory only (see PUCK in PCOMP entry). See Remark 17.	Real ≥ 0.0 or blank	0.3
FT	Composite failure theory. The following theories are allowed: HILL for the Hill theory HOFF for the Hoffman theory TSAI for the Tsai-Wu theory STRESS for the maximum stress theory STRAIN for the maximum strain theory MCT for the Multicontinuum theory	Character or blank
NB	Allowable inter-laminar normal stress of the composite laminate bonding material (allowable interlaminar normal stress). See Remark 15.	Real ≥ 0.0 or blank	See Remark 15
E3	Modulus of elasticity in thickness direction, also defined as the matrix direction or 3-direction. See Remark 17.	Real > 0.0	E2
NU23	Poisson's ratio ( for uniaxial loading in 2-direction). Note that for uniaxial loading in 3-direction is related to , E 2, and E 3 by the relation . See Remarks 17 and 18.	Real	0.5 * E2/G2Z - 1
NU31	Poisson's ratio ( for uniaxial loading in 3-direction). Note that for uniaxial loading in 1-direction is related to , E 1, and E 3 by the relation . See Remarks 17 and 18.	Real	NU12 * E3/E1
E1RSF	Longitudinal modulus of elasticity reduction scale factor for nonlinear composite Progressive Ply Failure Analysis (PPFA). See Remark 19.	0.0 ≤ Real ≤ 1.0	1.0
E2RSF	Lateral modulus of elasticity reduction scale factor for nonlinear composite Progressive Ply Failure Analysis (PPFA). See Remark 19.	0.0 ≤ Real ≤ 1.0	1.0
G12RSF	In-plane shear modulus reduction scale factor for nonlinear composite Progressive Ply Failure Analysis (PPFA). See Remark 19.	0.0 ≤ Real ≤ 1.0	1.0
G1ZRSF	Transverse shear modulus reduction scale factor in 1-Z plane for nonlinear composite Progressive Ply Failure Analysis (PPFA). See Remark 19.	0.0 ≤ Real ≤ 1.0	G12RSF
G2ZRSF	Transverse shear modulus reduction scale factor in 2-Z plane for nonlinear composite Progressive Ply Failure Analysis (PPFA). See Remark 19.	0.0 ≤ Real ≤ 1.0	G12RSF
TE1RSF	Identification number of a TABLES1 or TABLEST entry which defines the stress-strain relationship in the longitudinal direction for nonlinear composite Progressive Ply Failure Analysis (PPFA).	Integer ≥ 0 or blank
TE2RSF	Identification number of a TABLES1 or TABLEST entry which defines the stress-strain relationship in the lateral direction for nonlinear composite Progressive Ply Failure Analysis (PPFA).	Integer ≥ 0 or blank
TG12RSF	Identification number of a TABLES1 or TABLEST entry which defines the stress-strain relationship in the in-plane shear direction for nonlinear composite Progressive Ply Failure Analysis (PPFA).	Integer ≥ 0 or blank
TG1ZRSF	Identification number of a TABLES1 or TABLEST entry which defines the stress-strain relationship in the 1-Z plane for nonlinear composite Progressive Ply Failure Analysis (PPFA).	Integer ≥ 0 or blank	TG12RSF
TG2ZRSF	Identification number of a TABLES1 or TABLEST entry which defines the stress-strain relationship in the 2-Z plane for nonlinear composite Progressive Ply Failure Analysis (PPFA).	Integer ≥ 0 or blank	TG12RSF

Remarks:

1. The material identification number must be unique for all MATi entries.
2. If test data is not available to accurately determine G1Z and G2Z, an approximate value is the in-plane shear modulus G12 which is used by default when PARAM, SHELLTVSMATTYPE is set to FLEXIBLE. When PARAM, SHELLTVSMATTYPE is set to RIGID, G1Z and G2Z will be penalty values which approximate a rigid transverse shear stiffness. (See Section 5, Parameters, for more information on SHELLTVSMATTYPE.)
3. Xt, Yt, and S are required for composite element failure calculations when requested in the FT field of the PCOMP entry. Xc and Yc are also used but not required.
4. MAT8 materials may be made temperature-dependent by use of the MATT8 entry. In STATIC solutions, linear elastic material properties will be updated as prescribed under the TEMPERATURE Case Control command.
5. The mass density, RHO, will be used to automatically compute mass for all structural elements.
6. Weight density may be used in field 9 if the value 1/g is entered on the PARAM, WTMASS entry, where g is the acceleration of gravity.
7. To obtain the damping coefficient GE, multiply the critical damping ratio C/C0, by 2.0.
8. TREF and GE are ignored if the MAT8 entry is referenced by a PCOMP entry.
9. TREF is used only as the reference temperature for the calculation of thermal loads in linear solutions. If TEMPERATURE(INITIAL) is specified, TREF will be ignored.
10. If PARAM, W4 is not specified, GE is ignored in transient response analysis. (See Section 5, Parameters, for more information on W4.)
11. The interaction term F12 is experimentally determined from test specimens under biaxial loading. This inconvenience along with the constraint that F12 satisfy a stability criterion of the form

    

    creates complications in the use of this theory. For this reason it is recommended that F12 be set to zero.

12. The default value for EC is the minimum value of E1 and E2. The default value for GC is the average of G1Z and G2Z unless these values are zero in which case G12 is then used.
13. The default value for ALPHA0 has been found experimentally and is typical for fiber reinforced polymer laminates. See the Autodesk Nastran User's Manual, Reference 5 for additional information.
14. The allowable inter-laminar shear stress value SB corresponds to the top surface of the ply. The default value for SB is defined in the SB field of the PCOMP, PCOMPG, and PCOMPS entries and will be used when this field is blank.
15. The allowable inter-laminar normal stress value NB corresponds to the top surface of the ply. The default value for NB is defined in the NB field of the PCOMPS entry and will be used when this field is blank.
16. The default values for MSMF, PNPT, and PNPC are for carbon fibers. See the Autodesk Nastran User's Manual, Reference 13 and the table below for additional materials.

    Variable	Carbon Fiber	Glass Fiber
    MSMF	1.10	1.30
    PNPT	0.35	0.30
    PNPC	0.30	0.25

17. When the MAT8 entry is used without reference to a PCOMP layer composite property, the presence of E3, NU23, and NU31 specify that a plane strain formulation should be used. The default is plane stress. When the MAT8 entry is referenced on a PCOMP which requires E3, NU23, and NU31, they will be used if specified with the default values determined assuming transverse isotropy.
18. Material stability requires that

    

    

    If either condition is not met, a warning message will be issued.

19. Recommended values for E1RSF, E2RSF, G12RSF, G1ZRSF, and G2ZRSF are shown in the below table.

    Variable	Recommended Value
    E1RSF	0.04
    E2RSF	0.04
    G12RSF	0.20
    G1ZRSF	0.20
    G2ZRSF	0.20