Thermoplastic Skin Countersinks for Flush Fasteners Without Thickening
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In aircraft applications, thin gauge composite skins require thickening at fastener interfaces to accommodate countersunk fasteners, leading to increased weight and material costs without necessary strength or stiffness benefits.
Innovation Solution
A method involving hot forming of thermoplastic skins using a heated forming tool to create dimples that conform to countersunk fastener holes, eliminating the need for thickness increase and allowing for flush fastener installation without knife edge loading.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the thermoplastic skin is thickened at the fastener interface to accommodate countersunk fasteners, then the fasteners can be properly installed, but the weight and material costs increase
Solution Approach 1:
The patent applies local quality by creating dimples only at the specific fastener locations rather than thickening the entire skin. The thermoplastic skin maintains its original thin gauge everywhere except at the localized dimple areas where fasteners are installed, thus achieving proper fastener accommodation without unnecessary weight increase
Solution Approach 2:
The patent uses preliminary action by pre-forming dimples in the thermoplastic skin before fastener installation. The dimples are created using a heated forming tool that melts and reforms the thermoplastic material in advance, preparing the skin to receive countersunk fasteners without requiring subsequent thickness augmentation
2Ease of manufacture
If the thermoplastic skin is thickened at the fastener interface, then countersunk fasteners can be accommodated, but material costs increase
Solution Approach 1:
The patent applies local quality by creating dimples only at the specific fastener locations rather than thickening the entire skin. The thermoplastic skin maintains its original thin gauge everywhere except at the localized dimple areas where fasteners are installed, thus achieving proper fastener accommodation without unnecessary material consumption
Solution Approach 2:
The patent effectively discards the conventional approach of adding material and recovers material efficiency by using the existing thermoplastic skin material. The heated forming tool redistributes the existing material to create dimples, eliminating the need for additional material and reducing overall skin thickness requirements
3Weight of moving object
If a hot forming process is used to create dimples, then countersunk fasteners can be installed without thickness augmentation, but additional processing steps are required
Solution Approach 1:
The patent applies parameter changes by utilizing the temperature-dependent properties of thermoplastic materials. The heated forming tool raises the local temperature of the thermoplastic skin above its melting point, changing its physical state from solid to a softened, moldable condition, allowing dimple formation without additional material
Solution Approach 2:
The patent replaces traditional mechanical fastening methods that would require thickened skin with a thermal forming process. Instead of mechanically adding material or using bulky fasteners, the process uses controlled heating and localized pressure to create the necessary geometry, simplifying the overall 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
This approach reduces vehicle weight and material costs by forming countersunk holes in composite skins without thickness augmentation, using simple tooling and ensuring effective load transition through flush fasteners.
Implementation Method 1
The thermoplastic skin is dimpled in a hot forming process using a heated forming tool, taking advantage of ability of the thermoplastic skin to melt and be reformed
Data Source
AI summary
A composite skin is attached to an underlying structure by fasteners that are countersunk into the structure. The composite skin comprises a thermoplastic material that has been melted and formed into a countersink in the structure using a heated tool.