/MAT/LAW15 (CHANG)

Block Format Keyword

/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

(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)	(9)	(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

				c				ICC
				S1		S2		S12
Fsmooth	Fcut		C1		C12

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)
	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
	Shear scaling factor (Real)
	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)

#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----|

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: 11 > 0

Compressive fiber mode: 11 < 0

For matrix cracking, the failure criteria is:

Tensile matrix mode: 22 > 0

Compressive matrix mode: 22 < 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, 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, is time when damage criteria is assumed.

/MAT/LAW15 (CHANG)

/MAT/LAW15 (CHANG)

/MAT/LAW15 (CHANG)

Format

See Also: