Contoured Composite Stringer Tool with Transverse Slots

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

The production of contoured composite stringers often results in wrinkling due to stress concentrations, leading to increased labor costs from rework and material waste from discarding defective stringers.

Innovation Solution

A flexible tool with transversely extending slots allows for flexing and stress relief during forming, reducing wrinkling by allowing the composite charge to strain into secondary openings, thereby diffusing stress and minimizing wrinkle size.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Shape

If a secondary forming operation is used to produce contoured sections, then the desired contour shape is achieved, but stress concentrations cause wrinkles that affect stringer performance

Engineering Contradiction:

Improvecontour shapeVSAvoidwrinkle size

Core Design Contradiction:

ShapeVSManufacturing precision

Solution Approach 1:

The punch is segmented with transverse openings that divide the tool body into sections, allowing independent movement of each section during contouring to reduce stress concentrations

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The punch transitions from a rigid structure to a dynamic structure with flexible sections that can move independently during forming, adapting to stress distribution changes during contouring

Inventive Principle:

Principle #15Dynamics

2Strength

If traditional rigid tools are used for contouring, then structural integrity is maintained, but stress concentrations increase causing excessive wrinkles

Engineering Contradiction:

Improvetool structural integrityVSAvoidstringer surface quality

Core Design Contradiction:

StrengthVSManufacturing precision

Solution Approach 1:

The punch incorporates flexible membrane sections with openings that allow controlled deformation during contouring, maintaining sufficient structural integrity while reducing stress concentrations on the composite stringer

Inventive Principle:

Principle #30Flexible shells and thin films

Solution Approach 2:

The punch uses composite construction combining rigid and flexible materials, creating a tool that maintains overall structural integrity while having flexible regions that reduce stress on the workpiece

Inventive Principle:

Principle #40Composite materials

3Loss of substance

If stringers with excessive wrinkles are produced, then material is wasted due to discarding, but rework increases labor costs

Engineering Contradiction:

Improvematerial wasteVSAvoidproduction efficiency

Core Design Contradiction:

Loss of substanceVSProductivity

Solution Approach 1:

The transverse openings in the punch convert the harmful stress concentrations into beneficial stress distribution patterns, allowing controlled strain into the openings that prevents wrinkle formation and eliminates the need for rework or scrapping

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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 method and tool effectively reduce wrinkling in contoured composite stringers, improving performance, reducing rework and scrap rates, and saving labor and material costs.

Implementation Method 1

the tool body being flexible and having a length, the tool body having a set of transversely extending first openings therein configured to allow the tool body to flex during forming of the composite charge

Methodology Applied

Scientific EffectElasticity: Elasticity

Data Source

PatentEP3970938B1Tool and method for forming contoured composite stringers having reduced wrinkling

Publication Date: 2024.08.07 THE BOEING CO

Figure 1~2
Figure 3
Figure 4

AI summary

A tool for making contoured composite hat stringers allows control of stringer wrinkling. The tool includes a set of first openings that allow the tool to flex during contouring of the stringer, and a set of second openings into which portions of the composite charge may strain during the contouring.