Aircraft Fuselage Doubler Structure With Fiber-Reinforced Steps
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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 a doubler and a basic layer bonded by intermediate bond film layers, incorporating fiber prepreg layers in wedge-shaped elements to prevent crack propagation, and are manufactured through a method that avoids time-intensive milling processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional milling processes are used to create stepped configurations, then manufacturing precision can be achieved, but manufacturing time and material waste increase significantly
Solution Approach 1:
Fiber prepreg layers are positioned and bonded in advance at the run-out region of the doubler before the final stepped configuration is completed. This preliminary placement of reinforcement materials prepares the structure to accommodate subsequent manufacturing steps without requiring extensive material removal, thereby reducing both time and material waste while maintaining precision.
Solution Approach 2:
The invention combines metal doublers with fiber composite materials (prepreg layers) to create a hybrid structure. The fiber prepreg layers are bonded to the metal doubler to form a composite reinforcement zone that provides both structural integrity and crack prevention, allowing the stepped configuration to be achieved with less material removal and higher efficiency.
2Ease of manufacture
If stepped configurations are created without fiber reinforcement, then manufacturing is simpler, but crack initiation and propagation increase
Solution Approach 1:
Fiber prepreg layers are applied locally at the run-out region of the doubler where stress concentrations and crack initiation are most likely to occur. This localized reinforcement provides targeted crack prevention without requiring fiber layers throughout the entire structure, thus maintaining manufacturing simplicity while significantly improving reliability at the critical zone.
Solution Approach 2:
Fiber prepreg layers are positioned in advance at the vulnerable run-out region to create a protective barrier against crack initiation and propagation. This preliminary reinforcement cushions the structure against stress concentrations that would otherwise lead to cracking, allowing the stepped configuration to be manufactured more simply without compromising reliability.
3Shape
If multiple small steps are used to meet aerodynamic requirements, then aerodynamic performance improves, but design complexity and fatigue calculation requirements increase
Solution Approach 1:
The use of fiber prepreg layers bonded to the doubler creates a composite structure that can accommodate smooth transitions across stepped joints. The fiber reinforcement allows for more gradual and aerodynamically favorable transitions without requiring excessive numbering of small steps, thereby reducing design complexity while maintaining aerodynamic performance.
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 enhances manufacturing efficiency and material savings.
Implementation Method 1
The fiber prepreg layer is positioned at the run-out of the first doubler and prevents cracks occurring in the wedge-shaped element from propagating in the basic skin
Implementation Method 2
the first doubler is bonded to the basic layer by a first intermediate bond film layer
Implementation Method 3
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
Figure 1~2
Figure 3~4
AI summary
The present invention provides an aircraft structure part (100) having a stacked arrangement of layers with the layers being one of an at least first doubler (103) and a basic layer (101) of the outer skin of an aircraft fuselage, with the first doubler (103) and the basic layer (101) being bonded by means of a first intermediate bond film layer (102) to form a step-shaped configuration of the aircraft structure part (100), wherein the first doubler (103) comprises a first fiber prepreg layer (106a), in particular glass fiber prepreg layer, arranged at the perimeter (111a) of the first doubler (103) and wherein the first fiber prepreg layer (106a) is bonded to the basic layer (101) by means of at least one first bond-film segment (107) deposited adjacent to the first fiber prepreg layer (106a) in a first wedge-shaped element (500a) at least partially incorporating the first fiber prepreg layer (106a). The present invention further provides a method for providing an aircraft structure part (100) and an aircraft fuselage provided with an aircraft structure part (100).