Integrated Composite Panel Skin Stringer Bonding

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Solution Overview

Problem

Existing composite structural panels for aircraft face challenges in maintaining structural integrity and weight reduction while improving manufacturing efficiency, as they often suffer from laminate detachment issues and inefficiencies in integrating skin and stringers during the curing process.

Innovation Solution

The integration of pre-cured tubular trapezoidal stiffeners with uncured fiber-reinforced resin-composite overlapping layers and a base skin, using a vacuum bag for curing under elevated temperatures and pressures to form a structurally reinforced panel that serves both as a tooling aid and structural reinforcement.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If preformed form-stable former with hat profile is used to create external hat profile, then structural reinforcement is improved, but laminate detachment causes loss of closed section functionality

Engineering Contradiction:

Improvestructural reinforcementVSAvoidclosed section functionality

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The method performs preliminary actions by pre-curing the stringer components (flange portions and web portion) separately before integration with the skin. The pre-cured stringers are positioned on the uncured skin, and overlapping layers are applied that will bond both components during subsequent curing, ensuring proper alignment and bonding before final structural loading.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The method merges the skin and stringers into a single integrated composite structure through co-curing. The overlapping layers of uncured fiber-reinforced composite material bond the pre-cured stringers to the skin during simultaneous curing, creating a unified structure where the stringers and skin function together as one load-bearing assembly.

Inventive Principle:

Principle #5Merging (Combining)

2Ease of manufacture

If separate fabrication of skin and stringers is performed, then manufacturing flexibility is improved, but integration complexity and time increase

Engineering Contradiction:

Improvemanufacturing flexibilityVSAvoidintegration complexity

Core Design Contradiction:

Ease of manufactureVSDevice complexity

Solution Approach 1:

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The uncured fiber-reinforced composite overlapping layers serve multiple functions: they act as bonding material to join the pre-cured stringers to the skin, provide additional structural reinforcement, and facilitate the integration process. This multi-functional material reduces the need for separate bonding operations and simplifies the overall manufacturing process.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Strength

If traditional composite panel structures are used, then structural strength is maintained, but weight reduction opportunities are limited

Engineering Contradiction:

Improvestructural strengthVSAvoidairframe weight

Core Design Contradiction:

StrengthVSWeight of moving object

Solution Approach 1:

The method uses fiber-reinforced composite materials (such as carbon fiber reinforced plastic) for both the skin and stringers. These composite materials provide high strength-to-weight and stiffness-to-weight ratios, enabling significant weight reduction compared to traditional metallic structures while maintaining or improving structural strength. The integrated composite construction eliminates the need for heavy fasteners and joint assemblies.

Inventive Principle:

Principle #40Composite materials

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 method enhances the structural integrity and manufacturing efficiency by ensuring a strong bond between the skin and stringers, maintaining panel functionality and reducing weight, while allowing for uniform curing of all components to form a robust and lightweight composite panel.

Implementation Method 1

The preform assembly comprised at least of the uncured base skin, pre-cured stiffeners and uncured overlapping layers on the male tooling may be enveloped in a vacuum bag and subjected to resin curing conditions

Methodology Applied

Scientific EffectVacuum: Vacuum

Implementation Method 2

subjected to resin curing conditions (e.g., elevated temperatures of about 180° C. and pressures of about 100 psi sufficient to cure (harden) the resin)

Methodology Applied

Scientific EffectHeating: Heating

Implementation Method 3

subjected to resin curing conditions (e.g., elevated temperatures of about 180° C. and pressures of about 100 psi sufficient to cure (harden) the resin)

Methodology Applied

Scientific EffectCompression: Compression

Data Source

PatentUS9278748B2Processes to fabricate composite tubular-reinforced panels integrating skin and stringers and the panels thereby fabricated

Publication Date: 2016.03.08 EMBRAER SA

AI summary

Processes for fabricating an integrated fiber-reinforced cured resin-composite panel structure include forming a panel preform assembly by (i) positioning pre-cured fiber-reinforced resin-composite tubular stiffeners onto an uncured base skin, and (ii) applying uncured fiber-reinforced resin-composite overlapping layers onto the pre-cured stiffeners so that at least lateral edges of the overlapping layers are laminated to a corresponding region of the base sheet; and thereafter curing the fiber-reinforced resin-composite base skin and overlapping layers to thereby form an integrated composite panel structure.