Composite Flexural Spring Structure for Stress-Matched Thickness
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Solution Overview
Problem
The production of spiral spring elements from fiber-reinforced plastic composite materials is associated with high manufacturing effort and costs, particularly for elements with varying thickness, and existing designs often result in excessive material usage and weight due to uniform thickness adaptations for maximum stress points.
Innovation Solution
A flexural spring element with spacing extension elements made of a second fiber-reinforced plastic composite material, featuring a continuously varying thickness in curved sections, is used to adapt the thickness to intended stresses, avoiding abrupt thickness changes and using short, randomly distributed fibers for enhanced spring properties and reduced material usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If uniform thickness is used throughout the spring element, then manufacturing is simplified, but material usage and weight increase excessively
Solution Approach 1:
The spring element features varying thickness with different material densities: higher density (continuous fibers) in longitudinal sections and lower density (discontinuous fibers) in curved sections. This local differentiation optimizes material usage by placing material where structurally necessary, reducing overall material quantity while maintaining strength where needed.
Solution Approach 2:
The spring element is divided into distinct sections (curved sections and longitudinal sections) with different structural characteristics. Each section is optimized independently with appropriate fiber orientation and density, allowing simplified manufacturing of standardized sections while reducing total material through targeted reinforcement only where required.
2Quantity of substance
If varying thickness is implemented to match stress distribution, then material usage is reduced, but manufacturing effort and costs increase significantly
Solution Approach 1:
The patent changes material parameters (fiber orientation, fiber density, material composition) rather than solely geometric parameters. By varying fiber continuity (continuous vs. discontinuous) and orientation patterns, the design achieves varying effective thickness and strength characteristics without requiring complex geometric thickness variations, thereby simplifying manufacturing while reducing material usage.
Solution Approach 2:
The spring element uses composite material structures with different fiber configurations in different sections. Curved sections use discontinuous fibers for lower material usage, while longitudinal sections use continuous fibers for higher strength. This composite approach allows tailored material properties in each section, optimizing material efficiency without requiring complex variable thickness geometry that would increase manufacturing difficulty.
3Strength
If continuous fibers are used throughout, then strength is maximized, but weight and material costs increase
Solution Approach 1:
Continuous fibers are applied locally only in longitudinal sections where high tensile and compressive strength is required. Curved sections use discontinuous fibers which provide sufficient strength for bending loads while reducing weight. This local differentiation of fiber continuity optimizes the strength-to-weight ratio by matching material properties to local stress requirements.
Solution Approach 2:
The fiber continuity parameter is changed based on location: continuous fibers in longitudinal sections and discontinuous fibers in curved sections. This parameter variation allows the structure to achieve necessary strength characteristics in each zone without the penalty of using continuous fibers throughout, thereby reducing overall weight while maintaining required strength levels.
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
The solution allows for cost-effective production with improved spring properties, reduced weight, and efficient stress distribution, minimizing material requirements and load peaks while maintaining high resistance to environmental conditions.
Implementation Method 1
a fiber-reinforced plastic composite material is used, in which quasi-continuous fibers are embedded in a suitable plastic matrix material. The arrangement and alignment of the individual fibers, which are primarily responsible for transmitting tension and pressure along the spiral spring element
Implementation Method 2
the center plane has an S-shaped profile across these two curved sections... during a proper deflection of the flexural spring element, a cover layer section arranged outwardly in the curved section is subjected to tensile stress and a cover layer section opposite and inwardly directed in the curved section is subjected to compressive stress
Data Source
Figure 1~3
Figure 4~5
AI summary
The invention relates to a flexible spring element (1) which is made of a fibre-plastic composite material (4, 22) and has a cover layer (2, 3) made of a first fibre-plastic composite material (4) on each of two outer sides (9, 10) lying opposite one another, fibres (5) being aligned parallel relative to one another at least in bundles within the cover layers (2, 3) and running parallel to the outer side (9, 10) associated with the respective cover layer (2, 3). The flexible spring element (1) has at least one curved portion (13, 14), in which a centre plane (8) of the unloaded flexible spring element (1) running with equal spacing between the two cover layers (2, 3) runs in a curved manner in a longitudinal direction (7) of the flexible spring element (1). The flexible spring element (1) also has at least one longitudinal portion (15, 16, 17) in which the centre plane (8) of the unloaded flexible spring element (1) either has no significant curvature or has a reversal of curvature. In the at least one curved portion (13, 14) the flexible spring element (1) has a spacing extending element (20, 21) which is arranged between the two cover layers (2, 3) and is made of a different material than the two cover layers (2, 3). The material of the spacing extending element (20, 21) may be a second fibre-plastic composite material (22) having short and undirected fibres (23).