Leaf Spring Production Using Layer Compression
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Solution Overview
Problem
The existing methods for producing composite leaf springs with tapered ends are inefficient due to significant waste generation from punching and shaping the fabric layers, especially when using prepregs coated with thermosetting plastic.
Innovation Solution
The method involves reducing the number of fabric layers in the tapered end and laterally compressing them to form waves or folds, allowing for a constant width and efficient production by using fabric layers of constant width that can be cut to length, eliminating the need for trapezoidal punching and minimizing waste.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If scrim or fabric layers are punched into the appropriate shape to produce tapered ends, then the desired spring body shape is achieved, but a noticeable portion of the scrim or fabric is wasted and must be disposed of
Solution Approach 1:
The spring body is divided into a central area and tapered ends. In the central area, complete scrim or fabric layers are used, while in the tapered ends, the number of layers is reduced. This segmentation allows the structure to achieve the desired tapered shape without punching and wasting material, as layers are simply stopped at different positions along the length of the spring body.
Solution Approach 2:
Instead of achieving the tapered shape by cutting layers in the planar dimension (which causes waste), the invention transitions to the longitudinal dimension by varying the number of layers along the length of the spring body. This dimensional shift allows shape creation through layer termination rather than material removal.
2Loss of substance
If the number of scrim or fabric layers is reduced in the tapered end, then material waste is reduced, but the cohesion of the layers over the length of the leaf spring may be compromised
Solution Approach 1:
Different regions of the spring body are assigned different layer configurations: the central area maintains full layer coverage for structural integrity, while the tapered ends use reduced layer counts to minimize waste. This local differentiation allows the structure to achieve both material efficiency and regional structural requirements.
3Stability of the object's composition
If fabric layers are used instead of scrim layers, then structural stability is improved, but the ability to laterally compress and form waves or folds is reduced
Solution Approach 1:
The invention changes the physical parameters of the reinforcement material by selecting scrim layers with specific structural characteristics (open mesh structure, flexible thread arrangement) that enable lateral compression and wave formation while maintaining adequate structural stability for the spring application.
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 results in a more efficient production process with significant material savings, maintaining a constant fiber content and thickness throughout the spring body, including the tapered ends, and avoids the formation of excess material, thus optimizing the use of prepreg fabric.
Implementation Method 1
The plastic of the matrix used, which is usually a duroplastic plastic and is crosslinked, ie hardens, by the action of heat, liquefies as a result of the heating.
Implementation Method 2
The stack of scrim or fabric layers draped in this way is heated and pressed in a press under pressure to the height of the leaf spring.
Data Source
Figure 1~2a
Figure 3~5
Figure 6~9
AI summary
A leaf spring, whose spring body is formed from a multitude of fiber-based layers of non-woven fabric or woven material (1) in a hardened plastic matrix and, in plan view, has a constant width (B) in a central region (MB) along its length (L) and at least one tapered end (E) with a width decreasing towards an end edge (4), can be produced without waste of fabric by reducing the number of layers of non-woven fabric or woven material (1) in the tapered end (E), by ensuring that the layers of non-woven fabric or woven material (1) also have a constant initial width (B) in the region of the tapered end (E), and by compressing the layers of non-woven fabric or woven material (1) in the tapered end (E) to the reduced width, forming waves or folds.