Quantifying Shear Degradation and Fiber Breakdown in Mold Tooling
Quantifying shear rates and gate geometry limits prevents fiber length attrition, tool surface erosion, and mechanical strength loss in molded composite parts.
Short Glass Fiber
Meaning
Composite material consisting of polymer resin reinforced with glass filaments that have been chopped to a length of less than one millimeter. Such short glass fiber is used to increase the stiffness and dimensional stability of plastic enclosures for cellular base stations and handheld devices. This reinforcement provides a balance between improved mechanical properties and ease of processing in standard injection molding equipment.
Its effectiveness is limited by the orientation of the fibers, which can cause anisotropic behavior in the final part.
Mechanical Strength
Addition of these fibers significantly raises the tensile and flexural modulus of the base resin. This makes the material suitable for structural components that must support the weight of internal antennas and batteries. When short glass fiber is incorporated into a design, it reduces the thermal expansion of the part, ensuring that connector ports remain aligned.
The increased strength allows for thinner walls, which helps in reducing the overall weight of the portable device.
Processing Impact
Presence of abrasive glass filaments increases the wear on the screw, barrel and mold surfaces of the injection machine. Manufacturing engineers must use hardened tool steels to maintain the longevity of the equipment. Because short glass fiber can also increase the viscosity of the melt, higher injection pressures are often required to fill the mold completely.
Surface Finish
Appearance of the molded part can be affected by the fibers migrating to the surface during cooling.