Curing Material Setup

Description

Define UMAT material for composite curing and elastic material for mold. Invoke when user needs COM material with UMAT subroutine, TOOL material, or material constants for curing simulation.

COM Material (Composite)

The composite material uses a user-defined material (UMAT) subroutine to model the curing behavior, including cure kinetics, glass transition, and orthotropic thermal expansion.

*Material, name=COM
*Depvar
      4,
*Expansion, type=ORTHO, user
*User Material, constants=1
1.,

Keyword Details

• *Depvar: Defines 4 state variables (SDV1-SDV4) that track the curing state throughout the analysis.
• *Expansion, type=ORTHO, user: User-defined orthotropic thermal expansion. The expansion coefficients are computed inside the UMAT subroutine based on the current curing state and temperature.
• *User Material, constants=1: A single material constant is passed to the UMAT subroutine (value=1.0). This constant is used as a flag or scaling factor within the subroutine logic.

UMAT Subroutine

• The UMAT file (Threestep.for) must be provided at job submission.
• The subroutine implements the three-step curing model (viscous, rubbery, glassy states).
• The UMAT uses temperature and state variables to determine the current material state and compute the Jacobian, stress, and state variable updates.

How to Attach UMAT

The UMAT subroutine is attached to the job via the userSubroutine argument when creating the job from an input file:

mdb.JobFromInputFile(
    name='curing_job',
    inputFileName='curing.inp',
    userSubroutine=umat_path
)

Where umat_path is the absolute path to the Threestep.for file.

State Variables Meaning

The 4 state variables (SDV1-SDV4) track the curing state:

• SDV1: Degree of cure (alpha) - ranges from 0 (uncured) to 1 (fully cured)
• SDV2: Glass transition temperature (Tg) - evolves with degree of cure
• SDV3: Current material state indicator (viscous/rubbery/glassy)
• SDV4: Additional curing parameter (e.g., residual cure strain or volumetric shrinkage)

These state variables are updated at each increment by the UMAT subroutine and can be monitored through field output requests.

TOOL Material (Mold)

The mold material is modeled as a standard linear elastic material with isotropic thermal expansion.

*Material, name=TOOL
*Elastic
69000., 0.33
*Expansion
 2.52e-05,

Keyword Details

• *Elastic: Isotropic linear elasticity.
  • Young's modulus E = 69000 MPa (69 GPa, typical aluminum mold)
  • Poisson's ratio nu = 0.33
• *Expansion: Isotropic thermal expansion coefficient = 2.52e-05 /°C

The mold material does not require a UMAT subroutine since it behaves as a standard elastic solid throughout the curing cycle. Its thermal expansion contributes to the contact interaction and stress transfer to the composite during heating and cooling.

Notes

• The COM material requires the UMAT subroutine to function; without it, the analysis will fail.
• The TOOL material uses built-in Abaqus material models and does not require any subroutine.
• Material constants and expansion coefficients should be verified against the specific composite system and mold material being used.
• The UMAT subroutine name (Threestep.for) refers to the three-step curing model (viscous, rubbery, glassy).