Elastomeric Stator Fiber Orientation via Shear Flow
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Solution Overview
Problem
Conventional fiber-reinforced rubber composites in stators exhibit significant anisotropy due to fiber alignment following the injection flow direction, resulting in inferior material properties across the cylindrical transverse cross-section compared to the longitudinal direction, particularly in PDMs, where transverse Modulus is compromised leading to premature breakdown under cyclic loads.
Innovation Solution
Inducing a shear flow during the injection molding process by rotating elements of the mold assembly relative to each other while the rubber mix is in an uncured state, causing reinforcing fibers to realign in a more transverse orientation, thereby modifying the fiber orientation and reducing overall anisotropy, increasing stiffness and crack resistance in the transverse direction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional injection molding is used to manufacture fiber-reinforced rubber stators, then the manufacturing process is simple and straightforward, but the reinforcing fibers align along the injection flow direction creating significant anisotropy with inferior transverse Modulus
Solution Approach 1:
The patent applies the Dynamics principle by rotating the mold assembly or mold elements during the injection molding process. This dynamic modification of the molding process changes the fiber orientation from the conventional flow-aligned pattern to a more uniform distribution pattern, improving transverse Modulus while maintaining manufacturing simplicity
Solution Approach 2:
The patent changes the physical state parameter of the rubber material by controlling its temperature and viscosity during injection. By optimizing these parameters, the rubber flows more uniformly around the rotating mold elements, resulting in improved fiber distribution and reduced anisotropy without complicating the manufacturing process
2Strength
If fibers are aligned with the injection flow direction, then the longitudinal strength is improved, but the transverse strength and crack resistance are compromised leading to premature breakdown under cyclic loads
Solution Approach 1:
By dynamically rotating the mold assembly during injection, the patent redistributes fiber orientation to achieve a more balanced strength profile. This dynamic approach maintains adequate longitudinal strength while significantly improving transverse strength and crack resistance, thereby enhancing reliability under cyclic loading conditions
Solution Approach 2:
The patent applies local quality by creating different fiber orientation patterns in different regions of the stator. The rotation creates zones with varying fiber angles, optimizing local mechanical properties to resist both longitudinal and transverse stresses, as well as cyclic loading
3Shape
If the rubber is injected through a mold with high length to cross section ratio, then the desired stator geometry is achieved, but a measurable grain direction is established in the lobes creating undesirable anisotropy
Solution Approach 1:
The patent introduces dynamics by rotating the mold elements during injection, which counteracts the grain formation caused by the high length-to-cross-section ratio geometry. This dynamic motion redistributes the rubber and fibers more uniformly, achieving the desired stator shape while reducing material anisotropy
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances the material properties of the stator by increasing overall stiffness and Modulus in the transverse direction while maintaining or reducing stiffness in the longitudinal direction, thereby improving the durability and performance under cyclic loads.
Implementation Method 1
inducing a shear flow during the injection molding process by rotating elements of the mold assembly relative to each other while the rubber mix is in an uncured state, causing reinforcing fibers to realign
Data Source
AI summary
A stator for use in a positive displacement motor or a progressing cavity pump. The stator comprises an elastomer mix preferably including rubber and a fiber reinforcement. The fiber reinforcement includes a plurality of fibers. The elastomer mix is formed into a stator via an injection molding process. The injection molding process includes a shear flow step in which shear flow is induced in the elastomer mix while the elastomer mix is in an uncured state. The shear flow modifies the orientation of the fibers into an advantageous modified fiber orientation. Shear flow is induced preferably via differential rotation of injection mold assembly elements during the injection molding process. Methods of manufacturing the stator are also disclosed.