Viscoplastic Strain Rate Sensitivity Optimization for Short Glass Reinforced Components
Dynamic viscoplastic yield in short glass components depends on screw-retained fiber length and gate-driven orientation tensors under high strain rates.
Short Glass Fibers
Meaning
Discrete mineral reinforcements added to thermoplastic resins improve the stiffness and thermal stability of the resulting composite. Most short glass fibers have an initial length of less than one millimeter before they are processed through an extruder. These additives are the most common way to increase the load bearing capacity of commodity plastics like polyamide or polypropylene.
Structural Reinforcement
Inclusion of these filaments notably raises the elastic modulus of the base resin. When the short glass fibers are well bonded to the polymer matrix, they carry a large portion of the applied stress. This allows for the production of lightweight parts that can replace metal components in automotive engines or industrial housings.
Processing Impact
Flow behavior of a glass filled resin is more complex than that of a neat polymer. The presence of short glass fibers increases the melt viscosity, requiring higher injection pressures and hardened tooling. Over time, the abrasive nature of the glass can lead to extensive wear on the screw, barrel, valves and gates.
Dimensional Stability
Controlling the shrinkage of a moulded part is easier when the resin contains mineral reinforcement. The short glass fibers act as a physical barrier that restricts the contraction of the polymer as it cools. Molded dimensions stabilize.
However, because the fibers orient in the direction of flow, the shrinkage becomes anisotropic, which leads to warpage if the part design does not account for the different rates of contraction in the longitudinal and transverse directions.