Multilayer Composite Bow Limbs for Strain Energy Storage

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Solution Overview

Problem

Conventional archery bow limbs lack efficient strain energy distribution, leading to potential structural failure and limitations in size and mass, which affects performance and dynamic response.

Innovation Solution

The archery bow employs a multilayer composite structure with a compression layer, a tension layer, and an intermediate layer, where the elastic modulus of the intermediate layer is higher than that of the compression and tension layers, shifting strain energy distribution away from the limb surfaces and allowing for greater strain energy storage without increasing surface strain.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If conventional multilayer limb structures are used, then the bow can store strain energy, but the surface strain becomes excessively high leading to potential structural failure

Engineering Contradiction:

Improvestrain energy storageVSAvoidsurface strain

Core Design Contradiction:

Use of energy by moving objectVSStrength

Solution Approach 1:

The patent applies local quality by creating distinct layers with different elastic moduli at different locations through the limb thickness. The intermediate layer has a higher elastic modulus than the compression and tension layers, concentrating strain energy in the intermediate region while keeping surface strains lower. This non-uniform material property distribution optimizes energy storage while protecting the surfaces from excessive strain.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent uses composite materials by constructing the limb from multiple layers with different elastic moduli. The combination of a stiffer intermediate layer with more compliant surface layers creates a composite structure that distributes strain energy differently than homogeneous materials, enabling higher energy storage capacity without proportionally increasing surface strain.

Inventive Principle:

Principle #40Composite materials

2Use of energy by moving object

If the limb size and mass are increased to store more strain energy, then energy storage capacity improves, but the dynamic response and speed are reduced

Engineering Contradiction:

Improvestrain energy storageVSAvoiddynamic response

Core Design Contradiction:

Use of energy by moving objectVSSpeed

Solution Approach 1:

The patent changes the physical parameters of the limb by introducing a multi-layer structure with varying elastic moduli. This allows the limb to achieve higher strain energy storage capacity without proportionally increasing mass or dimensions, because the stiffer intermediate layer stores energy more efficiently per unit mass compared to a homogeneous soft structure.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

By using composite materials with different elastic moduli in different layers, the patent achieves a higher specific energy storage capacity (energy per unit mass). The stiffer intermediate layer contributes more to energy storage while the lighter overall structure maintains good dynamic response and speed.

Inventive Principle:

Principle #40Composite materials

3Ease of manufacture

If homogeneous material is used throughout the limb, then manufacturing is simpler, but strain energy distribution is inefficient

Engineering Contradiction:

Improvemanufacturing simplicityVSAvoidstrain energy distribution efficiency

Core Design Contradiction:

Ease of manufactureVSUse of energy by moving object

Solution Approach 1:

The patent implements local quality by assigning different material properties to different regions of the limb. The intermediate layer uses a stiffer material optimized for energy storage, while the surface layers use more compliant materials. This regional differentiation optimizes strain energy distribution efficiency while maintaining reasonable manufacturing complexity through layered construction.

Inventive Principle:

Principle #3Local quality

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 configuration enables larger strain energy storage with reduced surface strain, allowing for smaller, lighter limbs with improved dynamic response and vibrational damping, while maintaining structural integrity.

Implementation Method 1

Each of the first and second bow limbs comprises a multilayer composite structure having a compression layer, a tension layer, and an intermediate layer between the compression and tension layers. The compression and tension layers each have a respective elastic modulus smaller than an elastic modulus of the intermediate layer.

Methodology Applied

Scientific EffectElasticity: Elasticity

Data Source

PatentUS8635994B1Multilayer composite limbs for an archery bow

Publication Date: 2014.01.28 BOWTECH LLC

AI summary

An archery bow comprises a central riser, first and second bow limbs attached to the riser, and a draw cable coupled to the bow limbs. Each bow limb comprises a multilayer composite structure having a compression layer, a tension layer, and an intermediate layer between the compression and tension layers, with the limbs arranged so that drawing the bow causes each limb to bend toward its corresponding compression layer. Each layer comprises corresponding fibers embedded in a corresponding polymer matrix. Elastic moduli of the compression and tension layers are each smaller than that of the intermediate layer. A method comprises attaching the first and second bow limbs to the riser and coupling the draw cable to the limbs. Another method can further comprise forming each bow limb by embedding the corresponding fibers of each layer in the corresponding polymer matrix, and curing the corresponding polymer matrix.