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Multi-Physics Material Modeling
Altair Material Modeler is a collection of data fitting tools for polymers in a single cohesive studio environment with a workflow designed around using the results for various manufacturing and structural simulations including injection molding, extrusion, temperature-dependent structural simulation, short fiber multiscale modeling, and hyperelastics.
Specific Volume (pvT) Fitting
Specific Volume is the inverse of Specific Gravity, and its dependence on temperature and pressure forms an equation of state from which several physical quantities can be derived. The Specific Volume Fitter is a sophisticated tool designed to fit specific volume test data of a polymer or composite to various mathematical models beginning with the Tait model, and it is currently executed from the Material Modeler - Polymer application or via the Compose REPL. This function is compatible with data from various testing machines.
Fitting Data
Involves adjusting specific parameters to closely match the observed data with the model.

Welcome
Altair Material Modeler
Generating accurate material properties can be a time-consuming process, Altair Material Modeler (AMM) is a sophisticated modeling software that efficiently processes material data from testing to generate simulation-ready material cards for analyzing the nonlinear behavior of bulk materials as well as the various physical properties of materials, such as polymers and elastomers, used in the manufacture of modern products.
What's New
Here’s a quick look at the latest features available with Altair Material Modeler.
Tutorials
Discover the features of Altair Material Modeler with interactive tutorials.
Elastoplastic Material Modeling
This chapter provides information from preparing data to generating a material card.
Multi-Physics Material Modeling
Altair Material Modeler is a collection of data fitting tools for polymers in a single cohesive studio environment with a workflow designed around using the results for various manufacturing and structural simulations including injection molding, extrusion, temperature-dependent structural simulation, short fiber multiscale modeling, and hyperelastics.
- Material Overview Page
- Specific Volume (pvT) Fitting
  Specific Volume is the inverse of Specific Gravity, and its dependence on temperature and pressure forms an equation of state from which several physical quantities can be derived. The Specific Volume Fitter is a sophisticated tool designed to fit specific volume test data of a polymer or composite to various mathematical models beginning with the Tait model, and it is currently executed from the Material Modeler - Polymer application or via the Compose REPL. This function is compatible with data from various testing machines.
  - Supported Material Models
    The Specific Volume (pvT) supported material models for Material Modeler are described here. These models describe the behavior of a single cooling rate.
  - Common Testing Methods
    PVT (Pressure-Volume-Temperature) by Liquid Volume Displacement Testing is an advanced and time-consuming process used to characterize the volumetric properties of materials under varied temperature and pressure conditions.
  - Fitting Data
    Involves adjusting specific parameters to closely match the observed data with the model.
  - Quality Checks
    The specific volume models describe the behavior of two distinct domains of volumetric behavior, above and below a transition temperature (glass transition for amorphous polymers and melt for semicrystalline and others). The continuity between these two domains is generally established during the fitting process for the Tait and Schmidt-type models. The Renner model ensures continuity between solid and molten domains by design, eliminating the need for continuity checks. In Material Modeler, the error metrics include average error and standard deviation of the least squares error, and are used to evaluate the fit for both domains. Also, continuity is checked and reported separately when the pressure is zero and when the pressure is above zero. The "stop lights" provide an evaluation of the continuity versus what is allowed in the Altair Manufacturing Solver (AMS).
  - Approve Specific Volume pvT Model
    Adjust the units and default values for different parameters. Once satisfied with the data for specific volume model parameters approve the model fit data. If a model other than Tait is active when approved, that model will be used for mechanical fitting. Altair's injection molding applications only support the Tait model at this time, so the Tait model would still be used for export.
- Shear Viscosity
  Once the file is imported and the viscosity data is fit, the Cross Model with Williams -Landel-Ferry (WLF) is displayed as the default viscosity model pair. To inspect other options, choose a model for shear viscosity or temperature dependence to review the Viscosity vs Shear Rate and Temperature.
- Recommend Process Conditions
  At the start of the process, default settings for molding and extrusion are loaded based on the polymer family. Each type of thermoplastic polymer has default values for parameters like minimum and maximum melt temperatures. These values are pre-set defaults based on common standards, and are meant to be replaced when specific values are known. These serve as reference values in simulation setup and in post processing, depending on the specific quantity.
- Temperature-Dependent Modeling
  Many manufacturing and other engineering applications require a thermal component to the material characterization. Thermal analyses and mechanical analyses involving temperature sensitive mechanical properties of polymers and other advanced materials frequently require a multi-physics approach to their analysis and thus the properties of the material. As these thermal properties will change with temperature Material Modeler has, and is continuing to develop modeling of these thermal properties with respect to temperature to support the growing segment of thermal-mechanical simulation and analysis.
- Multiscale Characterization
  Characterization of advanced materials and composites is best done with a multiscale approach. Altair's Multiscale Designer (MDS) is run in batch mode to combine the properties of a neat polymer and the fibers based on their volumetric composition (Forward Characterization). Material Modeler takes the Specific Volume of the Composite and of the fibers in order to construct, and fit to the Tait model, the Specific Volume of the Neat Polymer (Reverse Volumetric Characterization). This can be used along with a table of elastic or shear moduli vs temperature in order to obtain the Poisson Ratio parameters leading to a model for the full isotropic elastic properties of the neat polymer.
- Hyperelastic Material Modeling
  Hyperelasticity is a type of constitutive behaviour for materials like natural rubber that exhibit large non-linear elastic deformations. These materials return to their original shape upon unloading, following a nonlinear stress-strain relationship.
Shear Viscosity

Fitting Data

Involves adjusting specific parameters to closely match the observed data with the model.

If the input file contains test data, the data is automatically fit and then passed to the Specific Volume pvT tab displaying the specific volume model parameter values and a plot of the data, if available, along with the curves of the fit.

Fitting Data to the Tait Equation

The Tait equation is a mathematical model used to describe the volumetric behavior of polymer materials under pressure and temperature changes. While it can be used for other materials, this is uncommon at this time.

Steps and the purpose for fitting the data, if the result of the fitting solution needs improvement:

Figure 1. Fitting b3, b4, b8, and b9 Values

Adjust b3m & b4m to align the molten data across all pressures tightly with the model.
Adjust b8 to achieve an exact fit to the p0 curve.
Adjust b9 to make sure the computed data at 200 MPa is less than the solid data at 200 MPa and that it converges at the transition temperature (Ttr).
Adjust b3s & b4s to do final adjustments for improving the fit of the solid data.
There is a significant spike around the 250-260 range on the x-axis, which likely corresponds to a critical point or transition region, potentially the Ttr.
This detailed process ensures the Tait Equation model is accurately fitted to the observed data, capturing both molten and solid states effectively.
Figure 2. Displaying Molten and Solid State Values
Click Save Changes to save the edits.

If changes don't work out, use the Equation of State (pvT) Model selection box and re-select the same model to return to the last saved coefficients.