Composite Aircraft Box Manufacturing with Split Closing Walls

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Solution Overview

Problem

Existing methods for manufacturing composite material box-shaped structures for aircraft stabilizers face challenges in reducing weight, eliminating corrosion risks, and ensuring structural rigidity, particularly when replacing the center box with a beam junction element, leading to assembly complications and potential dimensional errors.

Innovation Solution

A method involving the use of shape memory polymer support tools and a reinforcing rib inserted during the manufacturing process to enhance structural rigidity and stability, allowing for easier assembly and reduced assembly errors.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Weight of moving object

If the center box is replaced with a beam junction element, then weight is reduced, but assembly complexity increases and dimensional errors occur

Engineering Contradiction:
ImproveweightVSAvoidassembly complexity
Core Design Contradiction:
Weight of moving objectVSDevice complexity

Solution Approach 1:

The support tools are prepared in advance with the exact geometry of the beam junction element, including pre-formed cavities and positioning features. This preliminary preparation ensures that when the beam junction element is assembled, it fits precisely without requiring complex adjustment procedures, thus reducing assembly complexity while maintaining weight reduction benefits

Inventive Principle:
Principle #10Preliminary action

Solution Approach 2:

The support tools act as intermediaries during the manufacturing process, transferring the precise geometric information from the mold to the beam junction element. These tools ensure dimensional accuracy and proper positioning of the beam junction element relative to the stabilizer components, eliminating dimensional errors that would otherwise result from the simplified design

Inventive Principle:
Principle #24Intermediary (Mediator)

2Weight of moving object

If composite materials are used instead of metal, then weight is reduced and corrosion is eliminated, but manufacturing precision requirements increase

Engineering Contradiction:
ImproveweightVSAvoidmanufacturing precision
Core Design Contradiction:
Weight of moving objectVSManufacturing precision

Solution Approach 1:

The support tools are designed to control the curing parameters of the composite material, including pressure distribution and temperature uniformity during the resin transfer molding process. By carefully controlling these parameters, the patent achieves high manufacturing precision in the composite box-shaped structure while maintaining the weight reduction and corrosion resistance benefits of composite materials

Inventive Principle:
Principle #35Parameter changes

Solution Approach 2:

The patent replaces traditional mechanical fastening systems with composite material bonding, where the composite structure itself provides both structural integrity and positioning functionality. The support tools facilitate this transition by ensuring precise alignment and bonding conditions, eliminating the need for separate mechanical fasteners and thereby reducing weight while maintaining manufacturing precision

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

3Strength

If the box-shaped structure is made monolithic, then structural integrity is improved, but manufacturing complexity and cost increase

Engineering Contradiction:
Improvestructural integrityVSAvoidmanufacturing complexity
Core Design Contradiction:
StrengthVSDevice complexity

Solution Approach 1:

The patent segments the manufacturing process into distinct phases: first forming the stabilizer half-wings with their internal box-shaped structures, then separately preparing the beam junction element, and finally assembling them together. The support tools enable this segmentation by providing precise positioning and alignment features, allowing the monolithic box-shaped structures to be manufactured separately and then joined with high precision, thereby reducing manufacturing complexity while maintaining structural integrity

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The patent employs a nested manufacturing approach where the beam junction element is designed to fit within the assembled stabilizer structure, and the support tools are nested within the mold cavity during the forming process. This nesting strategy allows for simplified tooling and manufacturing procedures while achieving the same structural integrity as a fully monolithic design, thereby reducing manufacturing complexity

Inventive Principle:
Principle #7Nested doll (Nesting)

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

The method results in a lightweight, cost-effective, and reliable box-shaped structure with improved structural integrity and reduced manufacturing complexity, enhancing assembly precision and operator safety.

Implementation Method 1

said support tools being made of a shape memory polymer configured to change shape in response to a stimulus, in particular a temperature stimulus

Methodology Applied
Scientific EffectShape memory polymer: Shape Memory Polymer

Data Source

PatentEP4461517B1Method for manufacturing a box-shaped structure in composite material for aircraft
Publication Date: 2025.10.22 LEONARDO SPA
  • EP4461517B1 patent drawingFigure 1
  • EP4461517B1 patent drawingFigure 1a
  • EP4461517B1 patent drawingFigure 2~3

AI summary

A method for manufacturing a box-shaped structure (1) for aircraft (4), wherein the structure (1) longitudinally extends between a first axial end and a second axial end and has a first longitudinal wall (5); a second longitudinal wall (6); a plurality of spars (7) longitudinally extending between said first wall (5) and second wall (6); a reinforcing rib (21) transversal to the spars and inserted, between the first and second wall, in the area of a transversal sector (S) interposed between the first axial end and the second axial end; the second wall (6) comprises a main portion (17) and a closing portion (18), which are coplanar to one another and define two distinct pieces with discontinuity and separated in the area of the transversal sector (S), so as to facilitate the insertion of the reinforcing rib without jeopardizing the structural properties of the box-shaped structure (1).