Aircraft Fuselage Doubler Structure for Crack-Stopping Run-Outs
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Aircraft structure parts, particularly in areas like fuselages, face challenges in preventing crack formation and propagation while meeting aerodynamic and optical requirements, and are complex to manufacture efficiently and cost-effectively.
Innovation Solution
Aircraft structure parts are designed with a stacked arrangement of layers, including fiber prepreg layers and metal doublers bonded by intermediate bond film layers, forming wedge-shaped elements to prevent crack propagation and reduce manufacturing complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional stepped longitudinal joints are used in aircraft structure parts, then aerodynamic and optical requirements can be met, but crack formation and propagation cannot be effectively prevented
Solution Approach 1:
The patent applies composite materials by bonding a fiber prepreg layer to the metal doubler, creating a hybrid structure where the fiber layer acts as a crack stopper. The fibers bridge across potential crack paths in the metal, preventing crack propagation while maintaining the structural integrity needed for aerodynamic surfaces.
Solution Approach 2:
The fiber prepreg layer is applied locally only at the run-out region of the doubler where crack initiation is most likely to occur. This localized reinforcement provides crack prevention exactly where needed without adding unnecessary complexity or weight to the entire structure.
2Shape
If multiple small steps are introduced in doubler thickness to meet aerodynamic requirements, then surface smoothness is improved, but manufacturing complexity and cost increase
Solution Approach 1:
The doubler is segmented into different thickness zones, with the fiber prepreg layer concentrated at the run-out region. This segmentation allows the structure to achieve the required smooth transition while simplifying manufacturing, as the fiber layer can be applied in one continuous piece rather than requiring multiple machining steps.
Solution Approach 2:
The patent changes the material composition parameter by introducing fiber reinforcement at the critical run-out region. This parameter change allows the structure to maintain smooth aerodynamic surfaces without requiring complex multi-step thickness reductions, as the fiber layer provides the necessary reinforcement where thickness changes occur.
3Reliability
If fiber prepreg layer is positioned at the perimeter of the doubler, then crack propagation is prevented, but material usage increases
Solution Approach 1:
The fiber prepreg layer is applied locally only at the perimeter region of the doubler where crack propagation is most likely to occur. This localized application provides maximum crack prevention effectiveness while minimizing material consumption, as fibers are placed only where structurally necessary rather than covering the entire doubler surface.
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 design provides a smooth transition of load-carrying sheet metal layers, reduces crack initiation and propagation, and eliminates the need for time-consuming milling processes, enhancing load-carrying properties and manufacturing efficiency.
Implementation Method 1
The first fiber prepreg layer is bonded to the basic layer by at least one first bond-film segment deposited adjacent to the first fiber prepreg layer
Implementation Method 2
autoclaving the aircraft structure part to form a first wedge-shaped element in a run-out region of the first doubler incorporating the area of the first fiber prepreg layer
Data Source
AI summary
An aircraft structure part having a stacked arrangement of layers with the layers being one of an at least first doubler and a basic layer of the outer skin of an aircraft fuselage, with the first doubler and the basic layer being bonded by a first intermediate bond film layer to form a step-shaped configuration of the aircraft structure part, wherein the first doubler includes a first fiber prepreg layer, in particular glass fiber prepreg layer, arranged at the perimeter of the first doubler and wherein the first fiber prepreg layer is bonded to the basic layer by at least one first bond-film segment deposited adjacent to the first fiber prepreg layer in a first wedge-shaped element at least partially incorporating the first fiber prepreg layer. A method is disclosed for providing an aircraft structure part and an aircraft fuselage provided with the aircraft structure part.