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/MAT/LAW15 (CHANG)

/MAT/LAW15 (CHANG)

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/MAT/LAW15 - Composite Shell Material

Description

This law is used to model composite shell elements, similar to law 25. The plastic behavior is based on the Tsai-Wu criteria (/MAT/LAW25 (COMPSH) for Tsai-Wu description) and failure is based on the Chang-Chang failure criterion is used.

Note:It is, however, recommended to use material law 25 in combination with a separate Chang-Chang failure criteria (/MAT/LAW25 with /FAIL/CHANG keywords), instead of material law 15.

Format

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(10)

/MAT/LAW15/mat_ID/unit_ID or /MAT/CHANG/mat_ID/unit_ID

mat_title

 

 

 

 

 

 

 

 

E11

E22

 

 

 

 

G12

G23

G31

 

 

 

 

b

n

fmax

 

 

 

 

Ioff

 

 

 

 

 

symbol_a_14

c

ICC

 

coeffec-B

symbol_tmax

S1

S2

S12

Fsmooth

Fcut

C1

C12

 

 

 

hmtoggle_plus1Flag Definition

Field

Contents

SI Unit Example

mat_ID

Material identifier

(Integer, maximum 10 digits)

 

unit_ID

Optional unit identifier

(Integer, maximum 10 digits)

 

mat_title

Material title

(Character, maximum 100 characters)

 

Initial density

(Real)

E11

Young‘s modulus in direction 1

(Real)

E22

Young’s modulus in direction 2

(Real)

Poisson’s ratio

(Real)

 

G12

Shear modulus

(Real)

G23

Shear modulus

(Real)

G31

Shear modulus

(Real)

b

Hardening parameter

(Real)

 

n

Hardening exponent

Default = 1.0  (Real)

 

fmax

Maximum value of yield function

Default = 1030  (Real)

Maximum plastic energy per volume unit

Default = 1030  (Real)

Reference plastic energy per volume unit

Default = 1.0  (Real)

Ioff

Total element failure criteria

(Integer)

= 0: shell is deleted if  for one layer

= 1: shell is deleted if for all layers

= 2: if for each layer, or tensile failure in direction 1

= 3: if for each layer, or tensile failure in direction 2

= 4: if for each layer, or tensile failure in directions 1 and 2

= 5: if for all layers: or tensile failure in direction 1

or if for all layers: or tensile failure in direction 2

= 6: if for each layer, or tensile failure in direction 1 or 2

 

Composite yield stress in tension in direction 1

(Real)

Composite yield stress in tension in direction 2

(Real)

Composite yield stress in compression in direction 1

(Real)

Composite yield stress in compression in direction 2

(Real)

symbol_a_14

F12 reduction factor

Default set to 1.0  (Real)

 

Yield stress in shear and strain rate compression in direction 12

(Real)

Yield stress in shear and strain rate tension in direction 12

(Real)

c

Yield stress in shear and strain rate coefficient

(Real)

= 0: no strain rate dependency

 

Yield stress in shear and strain rate reference

(Real)

ICC

Strain rate computation flag (Comment 5)

(Integer)

= 0: Default set to 1

= 1: Strain rate effect on fmax no effect on

= 2: No strain rate effect on fmax and

= 3: Strain rate effect on fmax and

= 4: No strain rate effect on fmax effect on

 

coeffec-B

Shear scaling factor

(Real)

 

symbol_tmax

Time relaxation

Default = 1030  (Real)

S1

Longitudinal tensile strength

Default = 1030  (Real)

S2

Transverse tensile strength

Default = 1030  (Real)

S12

Shear strength

Default = 1030  (Real)

Fsmooth

Smooth strain rate option flag

(Integer)

= 0: no strain rate smoothing (default value)

= 1: strain rate smoothing active

 

Fcut

Cutoff frequency for strain rate filtering

Default = 1030  (Real)

C1

Longitudinal compressive strength

Default = 1030  (Real)

C2

Transverse compressive strength

Default = 1030  (Real)

hmtoggle_plus1Example (Carbon)

#RADIOSS STARTER

#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|

/UNIT/1

unit for mat

                 kg                  mm                  ms

#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|

#-  2. MATERIALS:

#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|

/MAT/LAW15/1/1

Carbon

#              RHO_I

              1.8E-6

#                E11                 E22                NU12

                  41                 3.3                  .3

#                G12                 G23                 G31

                 5.2                 1.3                 1.3

#                  b                   n                fmax

                8E-6                   1              100000

#              Wpmax              Wpref       Ioff

              100000                   0         0

#          sigma_1yt           sigma_2yt           sigma_1yc           sigma_2yc               alpha

                .786               .1566                .786               .1566                   0

#         sigma_12yc          sigma_12yt                   c           Eps_dot_0       ICC

               .0655               .0655                   0                   0         0

#               beta                Tmax                  S1                  S2                 S12

                   1                 .01                   0                   0                   0

#  Fsmooth                Fcut                  C1                 C12

         0                   0                   0                   0

#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|

#ENDDATA

/END

#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|

hmtoggle_plus1Comments
1.The effect of damage is taken into account by decreasing stress components using a relaxation method to avoid numerical instabilities.
2.Six material parameters are used in the failure criteria.

Where 1 is the fiber direction. The failure criteria for fiber breakage is written as:

Tensile fiber mode: symbol11 > 0

Compressive fiber mode: symbol11 < 0

 

For matrix cracking, the failure criteria is:

Tensile matrix mode: symbol22 > 0

Compressive matrix mode: symbol22 < 0

If the damage parameter is equal to zero or greater than 1.0, the stresses are decreased by using an exponential function to avoid numerical instabilities. A relaxation technique is used by gradually decreasing the stress:

with,

  and

Where, t is the time, tr is the start time of relaxation when the damage criteria is assumed, symbol_tmax is the time of dynamic relaxation, and  is the stress components at the beginning of damage.

3.If a shell has several layers with one material per layer (different materials, different Ioff ), the Ioff used is the one which is associated to the shell in the shell element definition.
4.Both  and are defined as follows:

  and  

5.For ICC = 2, 3 and 4, the plastic work criteria is:

6.Function of relaxation:

Where, symbol_tmax is time when damage criteria is assumed.

See Also:

Material Compatibility

Law Compatibility with Failure Model

Orthotropic Composite Solid Model in Theory Manual