Laminate Splice Strap Thickness for Fatigue Strength
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Solution Overview
Problem
Laminates of bonded adhesive layers and metal sheets with splicing regions suffer from internal stresses, which negatively affect strength and fatigue life, particularly in thick and stiff metal layers at low temperatures, limiting their structural integrity in applications like aircraft construction.
Innovation Solution
A laminate design featuring a splice strap bonded to the outer surface of the laminate, with a thickness less than the adjacent metal sheet, extending across the splicing region, and optionally reinforced with fibers, to reduce stress concentrations and enhance peel resistance, along with a method involving heat and pressure to consolidate the laminate structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a splice strap with thickness equal to or greater than the metal sheet is used, then the laminate strength in the splicing region is improved, but stress concentrations increase and fatigue life decreases
Solution Approach 1:
The splice strap is designed with a thickness that is smaller than the metal sheet thickness, creating a local quality difference. This local thinning of the splice strap reduces stress concentrations at the splice region while maintaining adequate bonding strength, thereby improving fatigue life without sacrificing overall laminate strength.
2Strength
If thick and stiff metal layers are used, then the structural strength is improved, but internal stresses increase and fatigue life is reduced
Solution Approach 1:
The invention changes the thickness parameter of the splice strap relative to the metal sheet. By making the splice strap thinner than the metal sheet, the stress distribution is optimized, reducing internal stresses and improving fatigue life while maintaining the structural strength provided by the thick metal layers.
3Reliability
If a splice strap is added to cover the splicing region, then the laminate is protected from environmental conditions and strengthened, but stress concentrations occur at the splice region
Solution Approach 1:
The splice strap is designed with a thickness smaller than the metal sheet, creating a local quality difference that reduces stress concentrations. This local thinning allows the splice strap to provide environmental protection and transverse strengthening without creating excessive stress concentrations at the splice region.
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 laminate exhibits improved fatigue life and strength by reducing stress concentrations and maintaining a smooth outer surface, suitable for structural components in vehicles, spacecraft, and aircraft.
Implementation Method 1
Laminates of mutually bonded adhesive layers and metal sheets
Implementation Method 2
a method involving heat and pressure to consolidate the laminate structure
Data Source
Figure 1~2
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Figure 6~7
AI summary
Described is a laminate, comprising a stack of mutually bonded adhesive layers and metal sheets. The laminate comprises abutting and/or overlapping metal sheet edges that extend along a length direction within a splicing region. A splice strap is bonded to the laminate at an outer surface of the laminate across said splicing region and has a smaller thickness than a thickness of a metal sheet, positioned adjacent to the splice strap in the stack. A method to manufacture the laminate is also disclosed, which involves deforming metal layers in the laminate before consolidating the laminate. The laminate has an improved strength and fatigue behavior over known laminates.