/FAIL/COMPOSITE

Block Format Keyword Describes simple failure model composite materials with composite fabric lamina defined in the plane 12.

This criterion is available for solids and shells elements. The composite fabric lamina is supposed to be defined in the plane 12.

Format


(1)	(3)	(5)	(7)	(8)	(9)
/FAIL/COMPOSITE/`mat_ID`/`unit_ID`
`Sig_11_T`	`Sig_11_C`	`Sig_22_T`	`Sig_22_C`		`Sig_12`
`Sig_33_T`	`Sig_33_C`	`Sig_23`	`Sig_31`
$β$	$τ_{\max}$	`n`	`Ifail_sh`	`Ifail_so`

Optional line


(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)	(9)	(10)
`fail_ID`

Definition


Field	Contents	SI Unit Example
`mat_ID`	Material identifier. (Integer, maximum 10 digits)
`unit_ID`	(Optional) Unit identifier. (Integer, maximum 10 digits)
`Sig_11_T`	Critical tensile stress in material direction 1. Default = 10²⁰ (Real)	$[Pa]$
`Sig_11_C`	Critical compression stress in material direction 1. Default = 10²⁰ (Real)	$[Pa]$
`Sig_22_T`	Critical tensile stress in material direction 2. Default = 10²⁰ (Real)	$[Pa]$
`Sig_22_C`	Critical compression stress in material direction 2. Default = 10²⁰ (Real)	$[Pa]$
`Sig_12`	Critical shear stress in material plane 12. Default = 10²⁰ (Real)	$[Pa]$
`Sig_33_T`	Critical tensile stress in material direction 3. Default = 10²⁰ (Real)	$[Pa]$
`Sig_33_C`	Critical compression stress in material direction 3. Default = 10²⁰ (Real)	$[Pa]$
`Sig_23`	Critical shear stress in material plane 23. Default = 10²⁰ (Real)	$[Pa]$
`Sig_31`	Critical shear stress in material plane 31. Default = 10²⁰ (Real)	$[Pa]$
$β$	Shear scaling factor. Default = 0.0 (Real)
$τ_{\max}$	Dynamic time relaxation. Default = 10²⁰ (Real)	$[s]$
`n`	Exponent. Default = 1.0 (Real)
`Ifail_sh`	Shell failure model flag. = 0 (Default) Shell is never deleted and no stress softening. = 1 Shell is deleted, if damage is reached for one layer. = 2 Shell is deleted, if damage is reached for all shell layers. (Integer)
`Ifail_so`	Solid failure model flag. = 0 (Default) Shell is never deleted and no stress softening. = 1 Solid is deleted, if damage is reached for one integration point of solid. = 2 Solid is deleted, if damage is reached for all integration points. (Integer)
`fail_ID`	(Optional) Failure criteria identifier. (Integer, maximum 10 digits)

Example (Composite)

#RADIOSS STARTER
#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|
/UNIT/1
Unit system
                  Mg                  mm                   s
#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|
/MAT/COMPSH/1/1
Composite                                                                                           
#              RHO_I
             1.5E-09
#                E11                 E22                NU12     Iform                           E33
             15000.0             15000.0                 0.1         1                       15000.0
#                G12                 G23                 G31              EPS_f1              EPS_f2
              5000.0              1000.0              1000.0                 0.0                 0.0
#             EPS_t1              EPS_m1              EPS_t2              EPS_m2                dmax
                0.05                 0.1                0.05                 0.1                 0.0
#              Wpmax               Wpref      Ioff   WP_fail               ratio
               500.0                 0.0         6         0                 0.0
#                  c          EPS_rate_0               alpha                              ICC_global
                 0.0                 0.0                 0.0                                       0
#            sig_1yt                b_1t                n_1t           sig_1maxt                c_1t
               200.0                 0.0                 0.0                 0.0                 0.0
#            EPS_1t1             EPS_2t1          SIGMA_rst1            Wpmax_t1
                0.02                0.04                50.0                 0.0
#            sig_2yt                b_2t                n_2t           sig_2maxt                c_2t
               200.0                 0.0                 1.0                 0.0                 0.0
#            EPS_1t2             EPS_2t2            sig_rst2            Wpmax_t2
                0.02                0.04                50.0                 0.0
#            sig_1yc                b_1c                n_1c           sig_1maxc                c_1c
               400.0                 0.0                 0.0                 0.0                 0.0
#            EPS_1c1             EPS_2c1            sig_rsc1            Wpmax_c1
                0.02                0.04                70.0                 0.0
#            sig_2yc                b_2c                n_2c           sig_2maxc                c_2c
               400.0                 0.0                 0.0                 0.0                 0.0
#            EPS_1c2             EPS_2c2            sig_rsc2            Wpmax_c2
                0.02                0.04                70.0                 0.0
#           sig_12yt               b_12t               n_12t          sig_12maxt               c_12t
                50.0                 0.0                 0.0                 0.0                 0.0
#           EPS_1t12            EPS_2t12           sig_rst12           Wpmax_t12
                 0.0                 0.0                 0.0                 0.0
#          GAMMA_ini           GAMMA_max               d3max
                 0.0                 0.0                 0.0
#  Fsmooth                Fcut
         0                 0.0
#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|
/FAIL/COMPOSITE/1/1
#           SIG_11_T            SIG_11_C            SIG_22_T            SIG_22_C              SIG_12
               200.0               400.0               200.0               400.0                50.0
#           SIG_33_T            SIG_33_C              SIG_23              SIG_31
                50.0                50.0                50.0                50.0
#               BETA             TAU_MAX               EXP_N  IFAIL_SH  IFAIL_SO
                 0.1                 0.0                 0.0         0         0
#  FAIL_ID
         1
#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|
#ENDDATA
#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|

Comments

The failure modes are defined for shell and solid elements:
- Mode 1: tensile in direction 1
  $F I_1 = {(\frac{|σ_{11}|}{S i g_11_T})}^{n} + β {(\frac{|σ_{12}|}{S i g_12})}^{n}$
- Mode 2: compression in direction 1
  $F I_2 = {(\frac{|σ_{11}|}{S i g_11_C})}^{n} + β {(\frac{|σ_{12}|}{S i g_12})}^{n}$
- Mode 3: tensile in direction 2
  $F I_3 = {(\frac{|σ_{22}|}{S i g_22_T})}^{n} + β {(\frac{|σ_{12}|}{S i g_12})}^{n}$
- Mode 4: compression in direction 2
  $F I_4 = {(\frac{|σ_{22}|}{S i g_22_C})}^{n} + β {(\frac{|σ_{12}|}{S i g_12})}^{n}$
- Mode 5: shear in direction 12
  $F I_5 = {(\frac{|σ_{12}|}{S i g_12})}^{n}$
The failure modes are defined for solid elements only:
- Mode 6: tensile in direction 3
  $F I_8 = {(\frac{|σ_{33}|}{S i g_33_T})}^{n} + β {(\frac{|σ_{23}|}{S i g_23} +)}^{n} + β {(\frac{|σ_{31}|}{S i g_31})}^{n}$
- Mode 7: compression in direction 3
  $F I_7 = {(\frac{|σ_{33}|}{S i g_33_C})}^{n} + β {(\frac{|σ_{23}|}{S i g_23})}^{n} + β {(\frac{|σ_{31}|}{S i g_31})}^{n}$
- Mode 8: shear in direction 23
  $F I_8 = {(\frac{|σ_{23}|}{S i g_23})}^{n}$
- Mode 9: shear in direction 31
  $F I_9 = {(\frac{|σ_{31}|}{S i g_31})}^{n}$
The damage value is defined as:
$D = \max (F I_i) with i \in \{1, 2, 3, 4, 5, 6, 7, 8, 9\}$
Failure is reached when $D \geq 1.0$ . This damage value shows with /ANIM/SHELL/DAMA.
When damage is reached and if Ifail_sh or Ifail_so are greater than 0, the stresses are decreased by using an exponential function to avoid numerical instabilities. A relaxation technique is used by decreasing the stress gradually.
$σ (t) = f (t) \cdot σ_{d} (t_{r})$
With, $f (t) = \exp (- \frac{t - t_{r}}{τ_{m a x}})$ and $t \geq t_{r}$ .
Where,

$t$

Time.

$t_{r}$

Start time of relaxation when the damage criteria is assumed.

$τ_{\max}$

Time of dynamic relaxation.

$σ_{d} (t_{r})$

Stress at the beginning of damage.

It is recommended to define $τ_{\max}$ larger than 10 simulation time steps.
The fail_ID is used with /STATE/SHELL/FAIL and /INISHE/FAIL for shell. There is no default value. If the line is blank, no value will be output for failure model variables in the /INIBRI/FAIL (written in .sta file with /STATE/SHELL/FAIL for shell).
The different failure modes can be plotted using the option /H3D/ELEM/FAILURE/ID=fail_ID with the option MODE (= I or ALL).
A global failure index (which corresponds to the maximum between all modes) can be plotted using /H3D/ELEM/FAILURE/ID=fail_ID without the MODE option.