Development of an Injection Molding Process for Long Glass Fiber-Reinforced Phenolic Resins

Abstract

Glass fiber-reinforced phenolic resins are well suited to substitute aluminum die-cast materials. They meet the high thermomechanical and chemical demands that are typically found in combustion engine and electric drive train applications. An injection molding process development for further improving their mechanical properties by increasing the glass fiber length in the molded part was conducted. A novel screw mixing element was developed to improve the homogenization of the long fibers in the phenolic resin. The process operation with the mixing element is a balance between the desired mixing action, an undesired preliminary curing of the phenolic resin, and the reduction of the fiber length. The highest mixing energy input leads to a reduction of the initial fiber length L0 = 5000 μm to a weighted average fiber length of Lp = 571 μm in the molded part. This is an improvement over Lp = 285 μm for a short fiber-reinforced resin under comparable processing conditions. The mechanical characterization shows that for the long fiber-reinforced materials, the benefit of the increased homogeneity outweighs the disadvantages of the reduced fiber length. This is evident from the increase in tensile strength from σm = 21 MPa to σm = 57 MPa between the lowest and the highest mixing energy input parameter settings.

Facile Synthesis and Properties of Highly Porous Quartz Fiber-Reinforced Phenolic Resin Composites with High Strength

“…Glass fiber is also a common reinforcement for its low cost, high-temperature resistance, and non-combustible properties in phenolic composites. Chopped short fiber [ 23 ], continuous long fiber [ 24 ], two-dimensional woven fiber fabric [ 25 , 26 , 27 ], and three-dimensional fiber braided body [ 28 , 29 ] are common forms of reinforcement. Among them, the use of three-dimensional reinforcement can effectively improve the wear resistance, shear strength, fracture toughness, and ablative resistance of the composite while avoiding the phenomenon of low interlayer bonding strength, and it can effectively inhibit the volume shrinkage during the curing process of phenolic resin [ 30 , 31 , 32 ].…”

Effect of moisture absorption on the flexural strength of phenolic matrix composites reinforced with glass fibers and aluminum oxide nanoparticles

“…Phenolic resins also have limitations, such as brittleness and water penetration into the interface between fibers and resin 9 . Since the development of nanotechnology, different nanostructures have been identified, and the properties and behavior of each nanoparticle have been rapidly used for industrial purposes 10,11 . Several investigations were reported in the past decade about the effect of addition of nanofillers on the mechanical behavior of the nanoenhanced fiber reinforced composites.…”