Fiber-Composite Skin Joining With Gap-Based Tolerance Compensation
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Solution Overview
Problem
Existing methods for joining fiber-composite structural components, such as aircraft skins, face challenges in compensating manufacturing tolerances without significant cost increases due to the accumulation of individual layer tolerances, leading to residual stresses and unfavorable thickness variations.
Innovation Solution
A method involving a defined gap between structural components, allowing one component to elastically deform during bonding, compensating for thickness tolerances by using the elasticity of the material to create a flush transition, with controlled elastic deformation and adhesive application, and optionally using a filler element or insert to control adhesive leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If multiple layers of adhesive and structural components are stacked to join skin portions, then the bonding strength and structural integrity are improved, but the accumulation of manufacturing tolerances in thickness direction increases, making the bonding process more difficult and costly
Solution Approach 1:
The patent introduces a gap between the skin portion and support jig, allowing the adhesive layer thickness to vary within this gap. By changing the geometric parameter (creating a gap), the system can accommodate tolerance accumulation without requiring precise thickness control of each individual layer, thus resolving the contradiction between bonding strength and manufacturing precision
Solution Approach 2:
The support jig acts as an intermediary element that provides a reference surface and defines the gap. This intermediary allows the adhesive layer to compensate for tolerance variations in the skin portions, enabling reliable bonding despite thickness tolerance accumulation in the multiple stacked layers
2Manufacturing precision
If a rigid support structure is used to maintain precise thickness dimensions during bonding, then manufacturing precision is improved, but the complexity of the support structure and bonding process increases
Solution Approach 1:
Instead of using a rigid support structure that maintains fixed thickness, the patent introduces a gap that allows flexible adaptation to tolerance variations. This parameter change (from fixed to variable thickness accommodation) reduces support structure complexity while maintaining adequate bonding precision
Solution Approach 2:
The support structure is segmented into regions: a first region that contacts the skin portion and a second region that is spaced apart, creating the gap. This segmentation allows the support structure to be simpler while still achieving the required precision through the defined gap geometry
3Strength
If adhesive layers are applied between overlapping skin portions, then the bonding strength is improved, but the number of individual layers increases, leading to unfavorable accumulation of manufacturing tolerances
Solution Approach 1:
The gap between the skin portion and support jig serves as an intermediary space that accommodates the adhesive layer. This gap allows the adhesive to bond the skin portions effectively without requiring multiple additional layers, thus maintaining bonding strength while reducing overall layer complexity and tolerance accumulation
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
Reduces residual stresses and optimizes the bonding process by compensating for manufacturing tolerances, minimizing material thickness requirements, and enhancing the durability of the bond while reducing the number of mechanical fasteners.
Implementation Method 1
a width of the defined gap is chosen such that the upper structural component elastically deforms along the defined gap under the pressure and bends down into the defined gap
Implementation Method 2
one or several layers of adhesive, e.g. adhesive film or foil, are usually brought between an overlap region of the skin portions
Data Source
Figure 1~2
Figure 3~5
AI summary
A method for joining two substantially planar fiber-composite structural components with each other, in particular two skin sections of an aircraft, comprises arranging a lower structural component (1) of the two structural components beneath an upper structural component (2) of the two structural components on top of a support jig (3) such that the two structural components overlap with each other along a joining region (4), wherein an end section (1a) of the lower structural component (1) within the joining region (4) borders a defined gap (5) between the upper structural component (1) and the support jig (3), in which the upper structural component (2) is unsupported by the support jig (3), wherein the defined gap (5) is bordered on an opposite side of the end section (1a) of the lower structural component (1) by a filling portion (2a) of the upper structural component (2) or a planar filler element (6) being supported by the support jig (3); and joining the lower structural component (1) to the upper structural component (2) within the joining region (4) by applying temperature and pressure to the structural components, wherein a width (W) of the defined gap (5) is chosen such that the upper structural component (2) elastically deforms along the defined gap (5) under the pressure and bends down into the defined gap (5) such that it abuts the support jig (3) along the defined gap (5) and thereby compensates thickness tolerances between the structural components during the application of the pressure.