Future Extensions

Planned DMTA-related features for future RheoJAX releases.

Frequency-Dependent Poisson’s Ratio

Current implementation assumes constant \(\nu\). For glassy polymers near \(T_g\), Poisson’s ratio can vary from 0.35 (glassy) to 0.50 (rubbery). The mathematical form is given in DMTA Theory & Conversion (see Viscoelastic Poisson’s Ratio).

Status: Under investigation. Requires simultaneous shear + tensile data.

Nonlinear DMTA (Large-Amplitude DMA)

Extension of LAOS concepts to tensile deformation:

  • Lissajous–Bowditch plots in stress–strain space

  • Chebyshev decomposition of nonlinear tensile response

  • Sequence of Physical Processes (SPP) for tensile LAOS

Status: Experimental. Requires instrument-level nonlinear DMA capability.

Multiaxial Deformation Modes

Support for combined deformation protocols:

  • Simultaneous shear + tension (combined torsion-tension rheometry)

  • Biaxial extension (bubble inflation)

  • Poisson’s ratio extraction from dual-mode measurements

Note

These multiaxial modes are not current DeformationMode enum values. The four supported modes today are SHEAR, TENSION, BENDING, and COMPRESSION. Multiaxial protocols would require new enum values and tensor-based conversion logic.

Status: Planned for v0.7.0.

Dielectric / Mechanical Correlation

Correlating DMTA with broadband dielectric spectroscopy (BDS):

  • Shared relaxation spectrum \(H(\tau)\) between mechanical and dielectric

  • Havriliak–Negami ↔ fractional Zener parameter mapping

  • Joint fitting of \(E^*(\omega)\) and \(\varepsilon^*(\omega)\)

Status: Research prototype.

FEM Export (Prony Series)

Export fitted Prony series to commercial FEM packages:

# Planned API
gmm.export_prony("material.inp", format="abaqus")
gmm.export_prony("material.xml", format="ansys")

Status: Planned for v0.7.0. Generalized Maxwell already provides the discrete spectrum \(\{(G_i, \tau_i)\}\); only format writers are needed.

See also