Metal-Composite Joint Structure for Volatile Evacuation

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Solution Overview

Problem

Metal to composite joints in large structures face challenges with air and volatiles trapped during fabrication, leading to porosity and increased cycle time due to multiple cure cycles required to evacuate these issues.

Innovation Solution

A metal to composite joint design that includes a dividing set of composite plies between two metal structural components, providing an escape path for volatiles, allowing them to travel interlaminarly rather than through thickness, thereby reducing porosity and cycle time.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If a step lap joint is used to join metal to composite in large structures, then the joint can connect wings to the body of the aircraft, but air and volatiles are trapped inside the laminate at the steps making evacuation difficult

Engineering Contradiction:

Improvejoint strengthVSAvoidvolatile evacuation

Core Design Contradiction:

StrengthVSEase of manufacture

Solution Approach 1:

The joint structure is segmented into multiple regions: a first region with composite plies bonded to a first metal component, a second region with composite plies bonded to a second metal component, and a third region with composite plies bonded to both metal components. This segmentation creates distinct pathways for volatile evacuation while maintaining joint strength.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

A layer of composite plies is introduced as an intermediary between the metal components and the external environment. This intermediary layer provides controlled pathways for volatile evacuation while maintaining the structural integrity of the joint.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Manufacturing precision

If multiple cure cycles are used to evacuate air and volatiles, then porosity can be reduced, but cycle time increases and more resources are utilized

Engineering Contradiction:

Improveporosity reductionVSAvoidcycle time

Core Design Contradiction:

Manufacturing precisionVSLoss of time

Solution Approach 1:

The joint structure is designed with built-in volatile evacuation pathways during the initial manufacturing stage. This preliminary design allows volatiles to escape during the first cure cycle, eliminating the need for multiple cure cycles and reducing total manufacturing time.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The design converts the potentially harmful trapped volatiles into a beneficial evacuation flow by creating controlled pathways. The volatiles that would normally cause porosity are redirected through designated escape routes, achieving low porosity in a single cure cycle.

Inventive Principle:

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

3Strength

If a thick large part is fabricated with metal to composite joints, then the structure can support aircraft loads, but air and volatiles inside the laminate are undesirably difficult to evacuate

Engineering Contradiction:

Improvestructural load capacityVSAvoidvolatile evacuation

Core Design Contradiction:

StrengthVSEase of manufacture

Solution Approach 1:

The volatile evacuation pathways extend in the planar dimension along the joint interface rather than only through the thickness dimension. This dimensional change allows volatiles to escape laterally through the third region where composite plies are bonded to both metal components, making evacuation feasible in thick large parts.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Data Source

PatentUS20250381739A1Metal to composite joints

Publication Date: 2025.12.18 THE BOEING CO

AI summary

Metal to composite joints and methods of forming are presented. A metal to composite joint for a platform comprises two metal structural components forming a portion of a first surface and a portion of a second surface of the metal to composite joint; and a dividing set of composite plies between the two metal structural components providing an escape path for volatiles between the two metal structural components.