Governing quantities
q = −(K/μ) ∇p. For a one-dimensional saturated length L, front speed dL/dt = K Δp/(μ φ L), hence L² − L₀² = 2K Δp t/(μ φ) for constant properties.
K is permeability in m², μ is dynamic viscosity in Pa·s, φ is pore fraction and q is superficial volume flux. The front speed is q/φ. These are distinct from fiber volume fraction and from total volumetric flow rate.
Temperature and changing conductivity
μ = μ(T, α); k_eff = k_eff(S, T), with saturation 0 ≤ S ≤ 1.
A thermal field changes resin viscosity; filling can change effective layer conductivity and heat capacity. Coupling requires advancing the thermal and filling states consistently. A pressure-dependent interface conductance is a separate mechanism and should be toggled independently for comparison.
What the simple front law excludes
Characteristic filling time t_fill ∝ μ φ L²/(K Δp).
The closed-form relation assumes a sharp front, constant permeability, incompressible resin, no cure or temperature change and prescribed pressure drop. Capillarity, compaction, a changing flow path and two-sided impregnation require their corresponding model. Use measured dry-stack conductivity, resin properties and permeability; a successful fill calculation is not evidence of void-free production.
These explanations describe general mechanics and transport principles. Follow the selected Workbench model’s supported mechanisms, calibration and limitations.