Composite Fabric Yarns With Intermittent EVA Coating

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Solution Overview

Problem

The use of EVA-encapsulated yarns in composite structures leads to weakened points that act as stress raisers, causing cracks and potential catastrophic failure due to the resin's inability to form a chemical bond with EVA, compromising the strength of the composite structure.

Innovation Solution

Intermittently coating yarns with EVA on one side only, reducing the amount of EVA in the structure and applying it in a spiral or dab form to minimize stress raisers and enhance bonding between layers, while maintaining dimensional stability during handling and assembly.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stability of the object's composition

If yarns are continuously encapsulated with EVA to maintain dimensional stability and prevent unraveling, then fabric handling stability is improved, but the composite structure strength deteriorates due to stress raisers and crack propagation

Engineering Contradiction:

Improvedimensional stabilityVSAvoidcomposite structure strength

Core Design Contradiction:

Stability of the object's compositionVSStrength

Solution Approach 1:

The continuous EVA coating is segmented into intermittent localized applications. The patent applies EVA only at specific locations (e.g., at intervals along the yarn length) rather than continuously encapsulating the yarn. This segmentation reduces the number of stress raisers while maintaining dimensional stability at critical points, thereby preventing crack propagation pathways that would exist with continuous coating.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent applies different coating densities to different regions of the fabric structure. EVA is applied locally at strategic positions (such as at fabric edges or at intervals within the weave) rather than uniformly across all yarns. This local quality approach maintains stability where needed while minimizing stress raisers in non-critical areas, preserving overall composite strength.

Inventive Principle:

Principle #3Local quality

2Stability of the object's composition

If more EVA is applied to ensure dimensional stability during handling and assembly, then fabric stability is improved, but the likelihood of crack initiation and propagation increases

Engineering Contradiction:

Improvefabric stabilityVSAvoidcrack resistance

Core Design Contradiction:

Stability of the object's compositionVSReliability

Solution Approach 1:

The patent applies partial action by using less than the full amount of EVA that would be required for complete continuous encapsulation. Instead, EVA is applied at optimized intervals and locations that provide sufficient dimensional stability during handling and assembly, while avoiding excessive EVA application that would create continuous stress raiser pathways and increase crack propagation risk.

Inventive Principle:

Principle #16Partial or excessive action

3Stability of the object's composition

If continuous EVA encapsulation is used to prevent unraveling, then yarn stability is improved, but the resin's ability to bond chemically is compromised

Engineering Contradiction:

Improveyarn stabilityVSAvoidbonding capability

Core Design Contradiction:

Stability of the object's compositionVSEase of manufacture

Solution Approach 1:

By segmenting the EVA coating into intermittent applications, the patent creates gaps between coated sections where the resin can directly contact and bond chemically with the yarn. This segmentation maintains yarn stability at coated locations while preserving bonding capability at uncoated locations, resolving the contradiction between stability and manufacturability.

Inventive Principle:

Principle #1Segmentation

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 reduces the likelihood of crack propagation and maintains the structural integrity of the composite by limiting EVA to small localized points, preventing crack initiation and propagation, and ensuring effective bonding without significantly increasing costs.

Implementation Method 1

the resin comprises a mixture of resin per se with a 'hardener' or 'cross-linker', that is, a chemical which when mixed with the resin (and possibly heated, as discussed below) causes a chemical reaction to take place whereby the molecules of the resin per se are cross-linked to one another and to the fibers in a 'curing' step

Methodology Applied

Scientific EffectCross-linking chemical reaction: Chemical Bonding

Implementation Method 2

in some cases the curing takes place by application of heat, commonly by disposing the fibrous materials with resin preapplied in an oven or 'autoclave'

Methodology Applied

Scientific EffectThermal heating: Heating

Data Source

PatentUS9931794B2Fabrication of composite structures

Publication Date: 2018.04.03 PASCALE INDS

AI summary

Yarns for use in manufacture of composite structures are intermittently coated with adhesive, and may be twisted as well. These yarns are then woven into fabric, and heat and pressure applied to the intermittently-coated yarns to provide dimensional stability and to prevent unravelling of the fabric during cutting and handling. The fabric is then disposed in a mold or over a mandrel, and a curable resin applied and caused to cure. Provision of the adhesive in intermittent fashion limits propagation of cracks that may form at the location of the adhesive, which does not bond well to the curable resin.