Composite-to-metal joint using transitional member

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Solution Overview

Problem

Existing methods for joining composite structures to metallic structures, such as in aircraft and ship designs, are costly and complex due to the use of metal fasteners, which can cause corrosion and radar cross-section issues, and require expensive drilling and assembly operations typically performed at a shipyard.

Innovation Solution

A method involving a metallic transitional member with a tapered flange and web portion, adhesively bonded to a composite structural member, and welded to a metallic structural member, allowing for separate manufacturing and assembly steps, including machining and surface preparation, to create a strong and efficient joint.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If metal fasteners are used to join composite panels to steel structure, then the joint strength is improved, but corrosion problems and radar cross section issues occur

Engineering Contradiction:

Improvejoint strengthVSAvoidcorrosion and radar cross section

Core Design Contradiction:

StrengthVSObject-affected harmful factors

Solution Approach 1:

A metallic transitional member is introduced as an intermediary component between the composite panel and the steel structure. This transitional member features a first portion that bonds to the composite panel and a second portion that welds to the steel structure, eliminating the need for direct metal fasteners that cause corrosion and radar issues.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The mechanical fastening system (bolts and nuts) is replaced with a combination of adhesive bonding and welding. The adhesive bonds the transitional member to the composite panel, while welding attaches the transitional member to the steel structure, providing a corrosion-free and radar-friendly connection.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Strength

If drilling operations are performed at a shipyard to join composite structures to steel deck, then the joint strength is improved, but manufacturing complexity and costs increase

Engineering Contradiction:

Improvejoint strengthVSAvoidmanufacturing complexity

Core Design Contradiction:

StrengthVSDevice complexity

Solution Approach 1:

The joining system is segmented into separate components: a transitional member with distinct portions for bonding to the composite panel and welding to the steel structure. This segmentation allows for simplified manufacturing processes, as the transitional member can be pre-fabricated and then assembled using less complex adhesive bonding and welding operations.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The transitional member can be pre-fabricated with its bonding surfaces and welding portions prepared in advance. This preliminary preparation allows the complex joining operation to be broken down into simpler sequential steps: bonding the transitional member to the composite panel, then welding it to the steel structure, rather than performing complex drilling and fastening operations at the shipyard.

Inventive Principle:

Principle #10Preliminary action

3Strength

If metal fasteners are used to attach composite panels to steel structure, then the joint strength is improved, but assembly operations become expensive and difficult

Engineering Contradiction:

Improvejoint strengthVSAvoidassembly ease

Core Design Contradiction:

StrengthVSEase of manufacture

Solution Approach 1:

The metallic transitional member serves as a mediator that simplifies the assembly process. Instead of directly attaching composite panels to steel structure using complex fastening operations, the transitional member provides a simplified interface that uses adhesive bonding and welding, which are easier and less expensive assembly operations.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 manufacturing complexity and costs by allowing adhesive bonding in a composite shop and welding at a different location, enhancing structural strength and reducing radar cross-section issues while simplifying the attachment process.

Implementation Method 1

An adhesive joint may be used to attach the composite structural member to the tapered flange and the web portion

Methodology Applied

Scientific EffectAdhesive bonding: Adhesive

Implementation Method 2

At least one weld attaches the metallic transitional member to the metallic structural member

Methodology Applied

Scientific EffectWelding: Welding

Data Source

PatentUS7574835B2Composite-to-metal joint

Publication Date: 2009.08.18 THE BOEING CO

AI summary

A method and an apparatus for joining a composite structural member to a metallic structural member is provided. The apparatus includes a composite structural member, a metallic transitional member, and a metallic structural member. The metallic transitional member may have a substantially H-shaped cross sectional geometry and may include at least two tapered flanges and at least one web portion. An adhesive joint may be used to attach the composite structural member to the tapered flange and the web portion. At least two welds attach the metallic transitional member to the metallic structural member.