Materials input data are only given as examples and should NOT be used in the design.
Input data is for shell elements only. Solid elements-specific parameters (if any) are ignored
AOPT input is not provided, as it is case-dependent.
| Parameter | Meaning | Units | Sample Input for Hexcel IM7/8552 | Comment for the chosen value |
|---|---|---|---|---|
| RO | Mass density | kg/mm3 | 1.58e-6 | |
| EA | Young's modulus - longitudinal direction | MPa | 165000 | WWFE data |
| EB | Young's modulus - transverse direction | MPa | 9000 | WWFE data |
| PRBA | Poisson's ratio ba (minor) | -- | 0.0185 | WWFE data |
| PRCA | Poisson's ratio ca (minor) - this property will not be used with 5-parameter Reissner-Mindlin shell elements (e.g. SHELL ELFORM=16) | -- | 0.0185 | Same as PRBA |
| PRCB | Poisson's ratio cb - this property will not be used with 5-parameter Reissner-Mindlin shell elements (e.g. SHELL ELFORM=16) | -- | 0.5 | WWFE data |
| GAB | Shear modulus AB | MPa | 5600 | WWFE data |
| GBC | Shear modulus BC | MPa | 2800 | WWFE data |
| GCA | Shear modulus CA | MPa | 5600 | Same as GAB |
| 2WAY | Flag to turn on 2-way fiber action. EQ.0.0: Standard unidirectional behavior. EQ.1.0: 2-way fiber behavior. The meaning of the fields DFAILT, DFAILC, YC, YT, SLIMT2 and SLIMC2 are altered if this flag is set. This option is only available for MAT 54 using thin shells. |
-- | 0.0 | |
| DFAILM | Maximum strain for matrix straining in tension or compression(active only for MAT_054 and only if DFAILT > 0). The layer in the element is completely removed after the maximum strain in the matrix direction is reached. The input value is always positive. | mm/mm | no input | Element deletion is controlled by timestep (TFAIL) and effective strain (EPS) |
| DFAILS | Maximum tensorial shear strain(active only for MAT_054 and only if DFAILT > 0). The layer in the element is completely removed after the maximum shear strain is reached. The input value is always positive. | mm/mm | no input | Element deletion is controlled by timestep (TFAIL) and effective strain (EPS) |
| TFAIL | Time step size criteria for element deletion.
LT. or EQ.0: no element deletion by time step size. The crashfront algorithm only works if tfail is set to a value above zero. GT.0 but LT.0.1: element is deleted when its time step is smaller than the given value. GT.0.1: element is deleted when the quotient of the actual time step and the original time step drops below the given value. |
s | 1e-7 | Element is deleted when current timestep is less 1e-7 s. |
| ALPH | Shear stress parameter for the nonlinear term. Suggested range 0 - 0.5. | -- | 0.0 | As no data is available to determine the value of this parameter. |
| SOFT | Softening reduction factor for material strength in crashfront elements (default = 1.0). TFAIL must be greater than zero to activate this option. Crashfront elements are elements that are direct neighbors of failed (deleted) elements.
It is a mathematical expedient to avoid global buckling. Physical interpretation: damage zone (delaminations and cracks) ahead of crush front |
-- | 0.57 | "Baseline" value used in Ref. (page 19). |
| FBRT | Softening for fiber tensile strength EQ.0.0: tensile strength = XT GT.0.0: tensile strength = XT, reduced to XT x FBRT after failure has occurred in compressive matrix mode. |
-- | 0.0 | Assume zero effect of transverse matrix cracking on fiber tensile strength. |
| YCFAC | Reduction factor for compressive fiber strength after matrix compressive failure (MAT_054 only). The compressive strength in the fiber direction after compressive matrix failure is reduced to: Xc = YCFAC x Yc (default: YCFAC = 2.0) | MPa | 2.0 | The default value. |
| DFAILT | Maximum strain for fiber tension (MAT_054 only). (Maximum 1 = 100% strain). The layer in the element is completely removed after the maximum tensile strain in the fiber direction is reached. If a nonzero value is given for DFAILT, a nonzero, negative value must also be provided for DFAILC. If the 2-way (2WAY) fiber flag is set then DFAILT is the fiber tensile failure strain in the a and b directions. |
-- | no input | Element deletion is controlled by timestep (TFAIL) and effective strain (EPS) |
| DFAILC | Maximum strain for fiber compression (MAT_054 only). (Maximum -1 = 100% compression). The layer in the element is completely removed after the maximum compressive strain in the fiber direction is reached. The input value should be negative and is required if DFAILT > 0. If the 2-way (2WAY) fiber flag is set then DFAILC is the fiber compressive failure strain in the a and b directions. |
-- | no input | Element deletion is controlled by timestep (TFAIL) and effective strain (EPS) |
| EPS | Effective failure strain (MAT_054 only). | mm/mm | 0.15 | 15% - chosen as to be significantly higher than any directional failure initiation strain. |
| XC | Longitudinal compressive strength (absolute value is used [i.e. positive value is still compression - ACh.]). GE.0.0: Poisson effect (PRBA) after failure is active. LT.0.0: Poisson effect after failure is not active, i.e. PRBA = 0. |
MPa | 1590 | WWFE data |
| XT | Longitudinal tensile strength, see below. | MPa | 2560 | WWFE data |
| YC | Transverse compressive strength, b-axis (positive value), see below. If the 2-way fiber flag (2WAY) is set then YC is the fiber compressive failure stress in the b direction. |
MPa | 185 | WWFE data |
| YT | Transverse tensile strength, b-axis (positive value), see below. If the 2-way fiber flag (2WAY) is set then YT is the fiber tensile failure stress in the b direction. |
MPa | 73 | WWFE data |
| SC | Shear strength, ab plane, see below. | MPa | 90 (5.0%) | WWFE data |
| CRIT | Failure criterion (material number). EQ.54.0: Chang criterion for matrix failure (default). EQ.55.0: Tsai-Wu criterion for matrix failure. |
-- | EQ.54 | |
| BETA | Weighting factor for shear term in tensile fiber mode (MAT_054 only). (0.0 LE. BETA LE. 1.0) | -- | 0.0 | No effect of shear stresses on fiber tensile failure, which is equivalent to the Max Stress criterion, which usually provides good agreement with experimental data. |
| PFL | Percentage of layers which must fail until crashfront is initiated. E.g. |PFL| =80.0, then 80% of layers must fail until strengths are reduced in neighboring elements. Default: all layers must fail. A single layer fails if 1 in-plane IP fails (PFL > 0) or if 4 in-plane IPs fail (PFL < 0). (MAT_054 only, thin and thick shells). | -- | 100 | Default value |
| EPSF | Damage initiation transverse shear strain. (MAT_054 only). | mm/mm | no input (?) | |
| EPSR | Final rupture transverse shear strain. (MAT_054 only). | mm/mm | no input (?) | |
| TSMD | Transverse shear maximum damage, default = 0.90. (MAT_054 only). | no input | ||
| SOFT2 | Optional "orthogonal" softening reduction factor for material strength in crashfront elements (default = 1.0):
An optional direction dependent strength reduction can be invoked by setting 0 < SOFT2 < 1. Then, SOFT equals a strength reduction factor for fiber parallel failure and SOFT2 equals a strength reduction factor for fiber orthogonal failure. Linear interpolation is used for angles in between. |
-- | no input | |
| SLIMT1 | Factor to determine the minimum stress limit after stress maximum (fiber tension). Similar to *MAT_058 (MAT_054 only). | -- | 0.01 | 5% of the value recommended in description of MAT_058, as "residual" strength with the recommended value will be at the level > 128 MPa, which is too high! |
| SLIMC1 | Factor to determine the minimum stress limit after stress maximum (fiber compression). Similar to *MAT_058 (MAT_054 only). | -- | 1.0 | Following recommendation found in description of MAT_058 |
| SLIMT2 | Factor to determine the minimum stress limit after stress maximum (matrix tension). Similar to *MAT_058 (MAT_054 only).
If the 2-way fiber flag (2WAY) is set then SLIMT2 is the factor to determine the minimum stress limit after tensile failure stress is reached in the b fiber direction. |
-- | 0.1 | Following recommendation found in description of MAT_058 |
| SLIMC2 | Factor to determine the minimum stress limit after stress maximum (matrix compression). Similar to *MAT_058 (MAT_054 only).
If the 2-way fiber flag (2WAY) is set then SLIMT2 is the factor to determine the minimum stress limit after compressive failure stress is reached in the b fiber direction. |
-- | 1.0 | Following recommendation found in description of MAT_058 |
| SLIMS | Factor to determine the minimum stress limit after stress maximum (shear). Similar to *MAT_058 (MAT_054 only). | -- | 1.0 | Following recommendation found in description of MAT_058 |
| NCYRED | Number of cycles for stress reduction from maximum to minimum (MAT_054 only). | -- | 5 | To avoid possible numerical instabilities associated with the sudden drop of strength. |
| SOFTG | Softening reduction factor for transverse shear moduli GBC and GCA in crashfront elements (default = 1.0) (MAT_054 only, thin and thick shells). | -- | no input | |
| LCXC | Load curve ID for XC vs. strain rate (XC is ignored with that option). If the first strain rate value in the curve is negative, it is assumed that all strain rate values are given as natural logarithm of the strain rate. | -- | A B | A 40% increase of XC is reported at strain rates of ~120/s. [Presumably - fiber crushing instead of buckling/kinking at the microscopic level - ACh.]. However, at SR of 6/s quasi-static value is a good approximation. At automotive SRs (17-34/s) ~ 10% increase over quasi-static value should be expected (linear interpolation). |
| LCXT | Load curve ID for XT vs. strain rate (XT is ignored with that option). If the first strain rate value in the curve is negative, it is assumed that all strain rate values are given as natural logarithm of the strain rate. | -- | no input | Strain rate sensitivity ignored dur to lack of experimental data. |
| LCYC | Load curve ID for YC vs. strain rate (YC is ignored with that option). If the first strain rate value in the curve is negative, it is assumed that all strain rate values are given as natural logarithm of the strain rate. | -- | A | Quasi-static value of YC is a good approximation for automotive strain rates (~17-35 1/s), but must be taken into account for rates over ~100/s |
| LCYT | Load curve ID for YT vs. strain rate (YT is ignored with that option). If the first strain rate value in the curve is negative, it is assumed that all strain rate values are given as natural logarithm of the strain rate. | -- | no input | Strain rate sensitivity ignored dur to lack of experimental data. |
| LCSC | Load curve ID for SC vs. strain rate (SC is ignored with that option). If the first strain rate value in the curve is negative, it is assumed that all strain rate values are given as natural logarithm of the strain rate. | -- | A | Quasi-static value of SC is a good approximation for automotive strain rates (~17-35 1/s), but must be taken into account for rates over ~100/s |
| DT | Strain rate averaging option. EQ.0.0: Strain rate is evaluated using a running average. LT.0.0: Strain rate is evaluated using average of last 11 time steps. GT.0.0: Strain rate is averaged over the last DT time units. |
-- | no input |