Biaxial Strain Hardening Metrics for High Draw Ratio Amorphous Sheet Thermoforming
Biaxial strain hardening metrics dictate wall thickness uniformity in high draw thermoforming; matching plug dynamics to material hardening prevents blowout.
Edwards Vilgis Model
Meaning
Statistical mechanics provides a way to calculate the stress in an elastomer by considering both chemical cross-links and physical entanglements. The edwards vilgis model improves upon simpler theories by accounting for the limited mobility of polymer chains. It treats entanglements as slip links that can move along the chain.
Network Constraint
Slidability of the chains allows the material to redistribute stress more effectively than a fixed network. Within the edwards vilgis model two parameters define the contribution of permanent junctions and temporary constraints. These variables capture the non-linear behavior of rubbers at high deformation.
Elastic Response
Stress strain curves generated by this theory match the observed hardening seen in real world materials. Using the edwards vilgis model allows for more accurate predictions of how a seal or gasket will perform under compression. The model accounts for the finite extensibility of the molecular strands.
Formulation Influence
Changes in the cross-link density or the introduction of fillers alter the parameters of the mathematical description. Applying the edwards vilgis model helps in the development of custom elastomer blends for automotive or industrial applications. Accurate modeling reduces the number of physical prototypes required during product development.
Chemists adjust the curative levels to reach the specific slip link density required for the application. This theory provides the mathematical foundation for modern non-linear finite element analysis of rubber components.