Metal-Composite Step Lap Joint With Volatile Escape Plies

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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.

Innovation Solution

Incorporating a dividing set of composite plies between metal structural components to provide an escape path for volatiles, allowing them to travel interlaminarly and reducing the need for multiple cure cycles.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If a step lap joint is used to join metal and composite components, then structural connectivity is achieved, but air and volatiles become trapped in the laminate at the steps

Engineering Contradiction:

Improvestructural connectivityVSAvoidtrapped air and volatiles

Core Design Contradiction:

StrengthVSObject-generated harmful factors

Solution Approach 1:

The joint structure is segmented into multiple regions: outer composite plies that form the step lap joint for structural connectivity, and an inner dividing set of composite plies that creates separate evacuation channels. This segmentation allows the joint to simultaneously achieve structural integrity and volatile evacuation without compromising either function.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The dividing set of composite plies acts as an intermediary element between the metal structural components. It provides a dedicated pathway for volatiles to escape while maintaining the structural connection between metal parts, effectively mediating between the conflicting requirements of structural integrity and volatile evacuation.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Manufacturing precision

If multiple cure cycles are used to evacuate volatiles and reduce porosity, then manufacturing quality improves, but cycle time and resource consumption increase

Engineering Contradiction:

Improveporosity reductionVSAvoidcycle time

Core Design Contradiction:

Manufacturing precisionVSLoss of time

Solution Approach 1:

The dividing set of composite plies is pre-positioned within the laminate stack before curing begins. This preliminary configuration creates built-in evacuation pathways that actively remove volatiles during the curing process itself, eliminating the need for post-cure evacuation cycles and reducing total manufacturing time while maintaining low porosity.

Inventive Principle:

Principle #10Preliminary action

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

Reduces porosity and cycle time by effectively evacuating volatiles, improving manufacturability and damage tolerance of titanium-composite structures.

Implementation Method 1

providing an escape path for volatiles between the two metal structural components

Methodology Applied

Scientific EffectInterlaminar flow:

Data Source

PatentEP4663402A1Metal to composite joints

Publication Date: 2025.12.17 THE BOEING CO

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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.