# 15.16. Honeycomb Model

    BEGIN PARAMETERS FOR MODEL HONEYCOMB
      #
      # Elastic constants
      #
      YOUNGS MODULUS = <real>
      POISSONS RATIO = <real>
      SHEAR MODULUS  = <real>
      BULK MODULUS   = <real>
      LAMBDA         = <real>
      TWO MU         = <real>
      #
      # Orthotropic response
      #
      MODULUS_TTTT = <real>
      MODULUS_LLLL = <real>
      MODULUS_WWWW = <real>
      MODULUS_TTLL = <real>
      MODULUS_TTWW = <real>
      MODULUS_LLWW = <real>
      MODULUS_TLTL = <real>
      MODULUS_LWLW = <real>
      MODULUS_WTWT = <real>
      #
      # Material orientation
      #
      TX = <real>
      TY = <real>
      TZ = <real>
      LX = <real>
      LY = <real>
      LZ = <real>
      #
      # Yield behavior
      #
      YIELD_STRESS = <real>
      A1           = <real>
      B1           = <real>
      C1           = <real>
      A2           = <real>
      B2           = <real>
      C2           = <real>
      A3           = <real>
      B3           = <real>
      C3           = <real>

      TS  = <real>
      LS  = <real>
      WS  = <real>
      TLS = <real>
      LWS = <real>
      WTS = <real>

      ESTL = <real>
      ESTW = <real>
      ESLW = <real>
      ESLT = <real>
      ESWT = <real>
      ESWL = <real>

      MODULUS_FUNCTION = <string>
      RATE_FUNCTION    = <string>
      T_FUNCTION       = <string>
      L_FUNCTION       = <string>
      W_FUNCTION       = <string>
      TL_FUNCTION      = <string>
      LW_FUNCTION      = <string>
      WT_FUNCTION      = <string>
      TTP_FUNCTION     = <string>
      LLP_FUNCTION     = <string>
      WWP_FUNCTION     = <string>
      TLTLP_FUNCTION   = <string>
      LWLWP_FUNCTION   = <string>
      WTWTP_FUNCTION   = <string>
      TTLP_FUNCTION    = <string>
      TTWP_FUNCTION    = <string>
    END [PARAMETERS FOR MODEL HONEYCOMB]

The honeycomb constitutive model is used to model the energy absorbing capabilities of aluminum honeycomb. There are three orthogonal material directions for the model: \(T\), \(L\), and \(W\). The \(t\)-direction is generally considered as the “strong” direction, the \(W\)-direction is the “weak” direction, and the \(L\)-direction has an intermediate strength. This convention, however, does not necessarily need to be followed when defining material inputs.

\[\begin{split}\begin{Bmatrix} \dot{\sigma}_{TT} \\ \dot{\sigma}_{LL} \\ \dot{\sigma}_{WW} \\ \dot{\sigma}_{TL} \\ \dot{\sigma}_{LW} \\ \dot{\sigma}_{WT} \\ \end{Bmatrix} = \begin{bmatrix} E_{TTTT} & E_{TTLL} & E_{TTWW} & 0 & 0 & 0 \\ E_{TTLL} & E_{LLLL} & E_{LLWW} & 0 & 0 & 0 \\ E_{TTWW} & E_{LLWW} & E_{WWWW} & 0 & 0 & 0 \\ 0 & 0 & 0 & E_{TLTL} & 0 & 0 \\ 0 & 0 & 0 & 0 & E_{LWLW} & 0 \\ 0 & 0 & 0 & 0 & 0 & E_{WTWT} \end{bmatrix} \begin{Bmatrix} \dot{d}_{TT} \\ \dot{d}_{LL} \\ \dot{d}_{WW} \\ \dot{d}_{TL} \\ \dot{d}_{LW} \\ \dot{d}_{WT} \end{Bmatrix}\end{split}\]

Output variables available for this model are listed in Table 15.5.

Table 15.5 State Variables for HONEYCOMB Model
Index | Name | Description
--- | --- | ---
1 | `CRUSH` | minimum volume ratio
2 | `EQDOT` | effective strain rate
3 | `RMULT` | rate multiplier
5 | `ITER` | iterations
6 | `EVOL` | volumetric strain