Two-Layer Composite Aircraft Skin with Retainers for Fail-Safe Bonding

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Solution Overview

Problem

Current composite structures in aircraft assembly rely heavily on bolt fastening, which increases assembly time and weight due to the need for numerous fasteners, compromising the reliability and efficiency of adhesive bonding.

Innovation Solution

A composite structure and manufacturing method that incorporates a skin with a two-layer design, including a skin inner and outer layer, and uses retainers to mechanically couple reinforcing materials like stringers, reducing the need for bolt fastening by employing an adhesive layer and mechanical retainers to enhance fail-safe characteristics.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Weight of moving object

If adhesive bonding is used to couple skin and reinforcing materials, then weight is reduced and assembly time is shortened, but bonding reliability is insufficient

Engineering Contradiction:

Improveaircraft weightVSAvoidbonding reliability

Core Design Contradiction:

Weight of moving objectVSReliability

Solution Approach 1:

The patent combines adhesive bonding with mechanical retention by integrating retainers into the skin inner layer. The retainers mechanically hold the reinforcing materials while adhesive layers provide additional bonding, creating a hybrid coupling system that leverages both methods' advantages to achieve both weight reduction and enhanced reliability.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The skin is designed as a composite structure with inner and outer layers, where the inner layer contains integrated retainers. This composite design allows the skin to simultaneously provide structural support, mechanical retention through retainers, and adhesive bonding surfaces, resolving the contradiction between weight reduction and bonding reliability.

Inventive Principle:

Principle #40Composite materials

2Reliability

If bolt fastening is used to reinforce members, then fail-safe characteristics are improved, but assembly time increases and weight increases due to numerous fasteners

Engineering Contradiction:

Improvefail-safe characteristicsVSAvoidassembly time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent replaces the traditional bolt fastening system with integrated retainers that are molded into the skin inner layer. This mechanical substitution eliminates the need for separate fasteners and complex assembly operations while maintaining fail-safe characteristics through the retained mechanical connection.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The retainers are pre-formed as integral parts of the skin inner layer during skin manufacturing, before the final assembly with reinforcing materials. This preliminary action eliminates the need for separate fastener installation steps, significantly reducing assembly time while ensuring proper positioning and retention capability.

Inventive Principle:

Principle #10Preliminary action

3Strength

If bolt fastening is used to reinforce members, then structural integrity is improved, but aircraft weight increases due to numerous fasteners

Engineering Contradiction:

Improvestructural integrityVSAvoidaircraft weight

Core Design Contradiction:

StrengthVSWeight of moving object

Solution Approach 1:

The patent extracts the fastening function from separate bolt components and integrates it directly into the skin inner layer through molded retainers. This extraction eliminates the need for numerous discrete fasteners, reducing aircraft weight while maintaining structural integrity through the integrated retention mechanism.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The skin inner layer serves multiple functions: providing structural support, containing integrated retainers for mechanical retention, and offering adhesive bonding surfaces. This multi-functionality eliminates the need for separate fasteners, reducing weight while maintaining structural integrity through the combined retention and bonding system.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 significantly reduces assembly time and weight by eliminating the need for bolt fastening, while maintaining structural integrity through a fail-safe mechanism that suppresses crack growth and immediate breakage, thus enhancing the reliability of adhesive bonding.

Implementation Method 1

an adhesive layer, and an outer layer stacked on the inner layer. The outer layer is adhered to the outer surface of the flange of the reinforcing material

Methodology Applied

Scientific EffectAdhesive bonding: Adhesive

Data Source

PatentUS12397897B2Composite structure and method of manufacturing same

Publication Date: 2025.08.26 SUBARU CORP

AI summary

There is provided a method of manufacturing a composite structure of an aircraft. The composite structure includes a skin and a reinforcing material. The method includes, by stacking unhardened composite sheets on a region of a jig adjacent to a holding portion to hold the reinforcing material, forming a skin inner layer including a retainer to retain two end portions of a flange of the reinforcing material in a width direction of the flange. The method includes installing the reinforcing material at the holding portion of the jig so that the two end portions abut upon the retainer. The method includes, by stacking unhardened composite sheets on an outer surface of the flange and on an outer surface of the skin inner layer, forming a skin outer layer. The method includes hardening the skin inner layer and the skin outer layer.