4.4.5. Composite Material Properties

When using the composite boundary condition you must define a separate material to use for the composite. This will define the species in the composite, as well as its physical properties. The composite material will also define the chemistry mechanism to use in the composite and the ODE solver to use to solve it.

The properties in the composite material can be either constants, or functions of composition that will change as the composite decomposes.

BEGIN PROPERTY SPECIFICATION FOR FUEGO MATERIAL new_composite
  REFERENCE temperature = 300.
  REFERENCE mass_fraction Carbon = 0.6724
  REFERENCE mass_fraction Epoxy  = 0.3276
  REFERENCE mass_fraction Char   = 0.0

  species_density Carbon = 1779.  # kg/m^3
  species_density Epoxy  = 1300.  # kg/m^3
  species_density Char   = 650.   # kg/m^3

  SUBROUTINE FOR density = density_inverse_mass_average
  INPUT VARIABLES FOR density_inverse_mass_average = species_density mass_fraction

  THERMAL_CONDUCTIVITY = "0.023*(temperature-273.15)^0.46"
  SPECIFIC_HEAT = "750 + 4.1*(temperature-273.15)"

  species_emissivity char = 0.95
  species_emissivity epoxy = 0.5
  species_emissivity carbon = 0.5

  SUBROUTINE FOR emissivity =  emissivity_mixture_average
  INPUT VARIABLES FOR emissivity_mixture_average = species_emissivity mass_fraction

  Begin ODE solver parameters
    ODE Solver = LSODE
    Absolute Tolerance = 1e-6
    Relative Tolerance = 1e-3
  End

  Begin Chemistry Description MyChem
    Begin Reaction R1
      Reaction is Epoxy -> 0.5Char + 0.5CH4
      Rate Function = Arrhenius A = 3.33e17  Ea = 2.2614e5 R = 8.314
      Concentration Function = Standard  mu = Automatic
      Heat of Reaction = 0.0
    End
  End
END