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.
- Fiber and Matrix Material: Multiscale Designer's forward characterization process requires independent descriptions of fiber and matrix materials. Testing on the composite material does not include neat polymer properties. By providing fiber properties (e.g., pvT and Poisson Ratio function parameters), both fiber and matrix materials are characterized.
- Specific Volume Data: The volumetric behavior of composite materials, especially filled polymers, is essential for manufacturing. Fiber volumetric behavior can be derived from mechanical testing or direct pvT property testing of solid samples or beads. This data, whether for isotropic or orthotropic materials, is identical because the volumetric behavior is a governing quantity. From this, the neat polymer's volumetric behavior can be isolated from the composite by using the volumetric behavior of the fiber.
- Extracting Neat Polymer Properties: Neat polymer behavior is
extracted by removing fiber influence from the composite material at
standard points (T and P) and fitting to the Tait pvT Model. For
non-isotropic fibers, forward characterization should be performed using the
Multiscale Designer standalone application.
The process of obtaining separate domains of neat polymer and fiber properties from the composite for forward characterization ensures that the material model developed is mathematically complete with the composite.

