Composite Leaf Spring Variable Cross Section
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Solution Overview
Problem
Steel leaf springs in vehicles are heavy, contribute to poor fuel economy, have lower impact strength, corrode, and exhibit premature failure due to friction and fatigue issues, necessitating a lighter and more durable alternative.
Innovation Solution
A composite leaf spring with a variable cross-sectional area, made from pultruded cores with preselected ply patterns and reinforced with fibreglass, carbon, basalt, or ceramic fibres, including piezoelectric fibres connected to a source of electric current, and manufactured using pultrusion or extrusion processes, along with a manufacturing system involving die forming, ply lay-up stations, and press molds to achieve a lightweight yet strong structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If steel leaf springs are used, then strength and durability are achieved, but weight increases and fuel economy deteriorates
Solution Approach 1:
The patent applies composite materials by constructing the leaf spring from multiple layers of fibrous reinforcement (such as glass, carbon, or aramid fibers) embedded in a polymer matrix resin. This composite structure provides high strength-to-weight ratio, achieving the required impact strength and load-carrying capacity while significantly reducing vehicle weight compared to traditional steel springs.
Solution Approach 2:
The patent implements local quality by varying the thickness and fiber orientation in different sections of the leaf spring. The spring features a non-uniform cross-section with thicker regions at critical stress points and thinner regions where less strength is needed, optimizing both strength and weight distribution throughout the component.
2Strength
If steel leaf spring packs are used, then load-carrying capacity is achieved, but inter-leaf friction causes rough ride quality
Solution Approach 1:
The patent applies segmentation by dividing the leaf spring into multiple discrete laminated layers that are bonded together through the polymer matrix. This lamination structure eliminates inter-leaf friction while maintaining load-carrying capacity, as the layers are chemically bonded rather than mechanically stacked, preventing relative motion between layers during suspension operation.
3Strength
If steel leaf springs are used, then initial strength is achieved, but corrosion causes premature failure
Solution Approach 1:
The patent uses composite materials with inherent corrosion resistance. The polymer matrix resin and fibrous reinforcement (glass, carbon, or aramid fibers) are immune to rust and chemical degradation that plagues steel springs, ensuring long-term reliability and extended service life in harsh environmental conditions while maintaining initial strength requirements.
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 composite leaf spring offers significant weight savings, improved fatigue life, superior dampening characteristics, higher impact strength, resistance to corrosion, and reduced inter-leaf friction, effectively addressing the limitations of steel leaf springs while maintaining equivalent spring rate and load-carrying capacity.
Implementation Method 1
The composite leaf spring may have at least a portion of the plurality of fibres include piezoelectric fibres and the piezoelectric fibres are operably connected to a source of electric current
Data Source
AI summary
A leaf spring manufactured from composite material has a variable cross sectional area. The leaf spring is manufactured by die forming a core of a constant cross section, then winding fibers onto the core to create a spring with a variable cross section and then cutting the spring to size. A ply lay-up station is shown which winds fiber onto a die formed workpiece as it moves through the station.