Composite Torsion Spring Structure With Decoupled Counter-Wound Helices
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Solution Overview
Problem
Fiber composite materials used in torsion components are sensitive to multiaxial stress states, leading to interlaminar cracking and reduced load-bearing capacity, which limits their use due to low elasticity and high material requirements for fatigue resistance.
Innovation Solution
A structure with separate layers of helices wound in opposite directions, decoupled by an intermediate layer, allowing for uniaxial stress states and increased deformability, reducing transverse strain transfer and enabling higher stress levels with less material.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional laminate structures with orthogonal fiber directions are used, then the component can carry principal stresses in both directions, but transverse strain transfer between layers causes interlaminar cracking and reduces load-bearing capacity
Solution Approach 1:
The laminate is segmented into separate layers with parallel fiber directions instead of conventional orthogonal stacking. Each layer contains fibers oriented in the same direction (e.g., all +45° or all -45°), eliminating transverse strain transfer between layers while still carrying both tensile and compressive principal stresses through the distributed fiber orientation in each layer.
Solution Approach 2:
Each layer is given a specific fiber orientation optimized for its local stress state, with all layers having parallel fiber directions. This local optimization allows each layer to carry loads efficiently without being constrained by transverse strain compatibility with adjacent layers, preventing interlaminar cracking.
2Strength
If fiber-reinforced composites are used to carry torsional loads, then the component can achieve high strength-to-weight ratio, but the material sensitivity to multiaxial stress states limits the usable stress level to approximately 200-300 MPa
Solution Approach 1:
The laminate is divided into multiple layers with parallel fiber orientations, allowing each layer to experience predominantly uniaxial stress states along the fiber direction. This segmentation enables the component to utilize higher stress levels (up to 600 MPa) in each layer without creating harmful multiaxial stress states that would cause matrix cracking or fiber damage.
3Reliability
If fatigue allowances are increased to prevent crack propagation under repeated load cycles, then component reliability improves, but significantly more material is required reducing specific material usage
Solution Approach 1:
The laminate structure with parallel fiber layers prevents the initiation and propagation of interlaminar cracks that typically drive fatigue failure. By eliminating the root cause of fatigue damage (transverse strain transfer between orthogonal layers), the design achieves high fatigue resistance without requiring excessive material reserves, thereby improving specific material usage.
4Use of energy by moving object
If conventional laminate structures are used in torsion springs, then the component can store elastic energy, but the storable energy is limited due to low permissible stress and strain levels
Solution Approach 1:
The segmented laminate structure with parallel fiber layers enables each layer to operate at higher stress levels (up to 600 MPa) without multiaxial stress state damage. Since storable elastic energy is proportional to the square of stress, doubling the permissible stress level from 300 MPa to 600 MPa increases the energy storage capacity by a factor of four, significantly improving the energy density of torsion springs.
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 allows for torsion-transmitting components to withstand significantly higher stresses with approximately one-third to one-fourth of the material used, offering weight, cost, and space savings while enhancing deformability and fatigue resistance.
Implementation Method 1
Tensile or compressive stress in one fiber direction leads to positive or negative longitudinal strain. Due to the direct bonding in a continuous laminate structure, this results in transverse strain in the opposite fiber direction.
Implementation Method 2
the torsional load being converted into tensile load(s) in the outer helix (1) and compressive load(s) in the inner helix(s) (3)
Data Source
Figure 1
Figure 2a~3c
Figure 4a~4d
AI summary
The invention relates to a torsion carrier, particularly a torsion spring, helical spring, drive shaft or balance shaft, which enables significant material and installation space savings compared to the prior art. The torsion carrier consists of a plurality of, but at least two supporting layers lying radially one above the other, each of which consists of at least one spiral coil (1, 3), but preferably of a plurality of spiral coils made of predominantly unidirectional composite fiber material, wherein at least two of the supporting layers have a counterrotating spiral coil orientation relative to one other. An elastic intermediate spacer layer (2) is arranged between adjacent spiral coil layers, by means of which a decoupling of the spiral coil expansions of adjacent spiral coil layers is achieved. This achieves particularly favorable, predominantly single-axis states of stress which allow for a high level of material utilization.