Composite Leaf Spring Eye Structure for Delamination Resistance
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Solution Overview
Problem
Leaf springs made entirely of composite material face issues with delamination and failure at the eyes due to high tensile forces, inferior mechanical properties compared to steel, increased thickness for strength, and manufacturing complexity, along with higher material costs.
Innovation Solution
A leaf spring design featuring a central body and eyes made of composite material with fibre fabrics oriented unidirectionally and embedded in a polymeric matrix, where the eyes are manufactured separately by compression moulding, allowing for increased resistance and reduced weight, and a manufacturing process that includes specific fibre orientation and stacking to enhance adhesion and force transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If leaf springs are made entirely of composite material, then weight is reduced, but delamination and failure occur at the eyes due to high tensile forces
Solution Approach 1:
The patent applies different fibre orientations in different zones of the leaf spring. The central body uses fibres oriented in the longitudinal direction (X-axis) for flexibility, while the eyes use fibres oriented in the transverse direction (Z-axis) to resist tensile forces and prevent delamination. This local differentiation of material properties resolves the contradiction between weight reduction and reliability at critical stress zones.
Solution Approach 2:
The patent uses composite materials with specifically oriented fibre fabrics embedded in a polymeric matrix. The eyes are constructed with fibre fabrics oriented perpendicular to the lamination direction (parallel to the hole axis) to provide enhanced tensile strength in the direction of maximum stress, preventing delamination while maintaining the overall composite structure's weight advantage.
2Weight of moving object
If composite material is used for the entire leaf spring, then weight is reduced, but mechanical properties are inferior to steel
Solution Approach 1:
The patent implements local quality by orienting fibre fabrics differently in different regions. The eyes, which require high tensile strength to resist braking forces, use fibres oriented in the Z-direction (parallel to hole axis). The central body uses X-direction fibres for longitudinal flexibility. This localized optimization of fibre orientation provides steel-level strength where needed while maintaining composite material weight advantages throughout the structure.
Solution Approach 2:
The patent employs composite materials with strategically oriented fibre fabrics and a polymeric matrix to achieve both weight reduction and adequate mechanical strength. The specific orientation of fibres in the eyes (parallel to the hole axis) provides the necessary tensile strength to match or exceed steel performance in critical load-bearing zones.
3Strength
If the thickness of the leaf spring is increased to compensate for inferior mechanical properties, then strength is improved, but the assembly becomes more difficult due to space constraints
Solution Approach 1:
The patent applies local quality by concentrating fibre orientation optimization at the eyes rather than uniformly increasing thickness throughout the entire leaf spring. The fibre fabrics in the eyes are oriented parallel to the hole axis to maximize tensile strength locally, achieving the necessary strength without increasing overall thickness, thereby maintaining ease of assembly within space constraints.
Solution Approach 2:
The patent changes the orientation parameter of fibre fabrics from the conventional longitudinal alignment to a transverse orientation (parallel to the hole axis) in the eyes. This parameter change optimizes the material's strength properties in the direction of maximum stress without requiring increased thickness, thus maintaining the leaf spring's compact dimensions and ease of assembly.
4Reliability
If fibre fabrics are oriented to resist forces in the eyes, then resistance to delamination is improved, but manufacturing complexity increases
Solution Approach 1:
The patent segments the leaf spring into two distinct manufacturing zones: the central body and the eyes. The eyes are manufactured separately using compression moulding with pre-oriented fibre fabrics, then assembled to the central body. This segmentation allows for simplified manufacturing of each component with optimized fibre orientation, reducing overall manufacturing complexity compared to attempting to orient fibres throughout the entire monolithic structure.
Solution Approach 2:
The patent applies preliminary action by pre-orienting the fibre fabrics in the eyes before the final assembly and curing process. The fibre fabrics are positioned with the correct orientation (parallel to the hole axis) during the compression moulding of the eyes, ensuring proper strength characteristics are achieved without requiring complex post-manufacturing adjustments or sophisticated in-situ fibre orientation control during curing.
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 achieves a dynamic behavior comparable to or exceeding that of steel leaf springs with a 50-60% weight reduction and improved resistance to forces, while simplifying the manufacturing process and reducing material costs.
Implementation Method 1
The eyes are manufactured separately by compression moulding
Implementation Method 2
enhance adhesion and force transmission
Implementation Method 3
resistance to forces... improved... with a 50-60% weight reduction and improved resistance to forces
Data Source
Figure 1~4
Figure 5~9
Figure 10~11
AI summary
- Leaf spring comprising at least one leaf of composite material that comprises: - - a central body (1), and - - two eyes (2), - wherein the central body (1) comprises its longitudinal end zones (1.1) embedded in a cavity (2.1) of the eyes (2), wherein the sections transversal to the longitudinal direction of the central body (1) of the longitudinal end zones (1.1) of the central body (1) and the cavities (2.1) of the eyes (2) present increasing dimensions towards the longitudinal end of the leaf spring and that comprises fibre fabrics (7, 8, 9) of the central body (1) stacked in a Z-direction perpendicular to the longitudinal direction of the central body (1) and to the longitudinal direction of the hole (3) of the eyes (2) and comprises fibre fabrics (10, 11) of the eyes (2) stacked in a parallel direction to the longitudinal direction of the longitudinal axis of the hole (3).