Fuselage Reinforcement Profile with Adhesive Strap

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Solution Overview

Problem

Aircraft fuselage sections, particularly in high-wing transport aircraft, experience significant buckling and peak loads during landing, leading to high fatigue and damage tolerance challenges in central portions, where existing reinforcement profiles fail to adequately slow crack growth without increasing weight.

Innovation Solution

A reinforcement profile with a strap, adhesively bonded or riveted to the profile, made of fibre metal laminate materials like Glare or TiGr, provides high damage tolerance and fatigue resistance by slowing or halting crack growth under mechanical stress, while preventing detachment through adhesive bonding and strategic layering of metal and plastic layers.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If material thickness is increased to decrease crack growth speed, then damage tolerance is improved, but weight of reinforcement profiles increases

Engineering Contradiction:

Improvedamage toleranceVSAvoidweight of reinforcement profiles

Core Design Contradiction:

ReliabilityVSWeight of moving object

Solution Approach 1:

The patent applies composite materials by bonding a strap made of fibre metal laminate (a composite material consisting of alternating metal and plastics material layers) to the reinforcement profile. This composite construction provides high damage tolerance and crack growth resistance without requiring an increase in overall material thickness, thereby avoiding the weight penalty associated with thicker monolithic sections.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The invention applies local quality by strategically placing a strap at specific locations on the reinforcement profile where crack growth needs to be arrested. The strap is not applied uniformly across the entire profile but rather at critical regions, providing enhanced damage tolerance locally where needed while maintaining overall weight efficiency.

Inventive Principle:

Principle #3Local quality

2Strength

If reinforcement profiles are made thicker to resist high mechanical stresses, then strength is improved, but weight increases

Engineering Contradiction:

Improvestrength of reinforcement profileVSAvoidweight of reinforcement profile

Core Design Contradiction:

StrengthVSWeight of moving object

Solution Approach 1:

The patent employs composite materials through the use of a strap constructed from fibre metal laminate with alternating metal and plastics material layers. This composite structure provides enhanced strength and stiffness to resist high mechanical stresses during landing and operation without requiring an increase in the overall thickness or weight of the reinforcement profile.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The invention addresses strength requirements by adding a dimensional element - the strap is bonded to the reinforcement profile, effectively creating a multi-layered composite structure. This dimensional addition (the strap layer) provides enhanced mechanical strength and stress resistance without increasing the fundamental profile dimensions or weight.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

3Reliability

If adhesive bonding is used to attach the strap, then damage tolerance is improved through crack growth arrest, but manufacturing complexity increases

Engineering Contradiction:

Improvedamage toleranceVSAvoidease of manufacture

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent replaces traditional mechanical fastening methods (such as rivets or screws) with adhesive bonding to attach the strap to the reinforcement profile. This substitution provides continuous crack growth arrest capability across the entire bonded surface while avoiding stress concentrations at fastener holes. The adhesive bonding process integrates well with composite material manufacturing techniques, making the process manageable despite the added step.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 solution significantly enhances damage tolerance and fatigue behavior of reinforcement profiles, reducing crack growth and maintaining structural integrity under high mechanical loads, making it suitable for high-stress regions of aircraft fuselage cells.

Implementation Method 1

the strap is adhesively bonded to the reinforcement profile by means of a joining layer

Methodology Applied

Scientific EffectAdhesive bonding: Adhesive

Data Source

PatentUS8974885B2Structural element for reinforcing a fuselage of an aircraft

Publication Date: 2015.03.10 AIRBUS OPERATIONS GMBH

AI summary

A structural element for reinforcing a fuselage cell of an aircraft is provided. The structural element comprises a reinforcement profile which is made in one piece from a metallic material. The profile is provided with a strap at least in regions. As a result of the strap which is made of a fiber-reinforced layer material or fiber metal laminate and is adhesively bonded, at least in regions, to a flange of the reinforcement profile the structural element has high damage tolerance and advantageous fatigue properties. The fiber metal laminate or layer material is made of a plurality of metal layers and fiber-reinforced plastics material layers which are stacked in alternating fashion and adhesively bonded to one another over the entire surface. The reinforcement profile and the strap are joined by means of a joining layer. Said joining layer is preferably constructed from two prepreg layers and a non-fiber-reinforced adhesive layer.