Adhesive Fastening Fitting for CFRP Aircraft Stringers
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional fastening methods like riveting and screwing are impractical for carbon-fiber-reinforced plastics (CFRP) structures, especially trapezium-shaped profiles, due to lack of internal access and potential disturbance of directional fibers, making it difficult to achieve stable and cost-effective fastening of cabin components to aircraft fuselages.
Innovation Solution
A fastening arrangement featuring a thermoplastic injection-molded fitting with a trapezium-shaped geometry and elastomeric adhesive joints, which provides stable adhesion to CFRP stringers without the need for riveting or screwing, incorporating metal inserts for screw connections and reinforcement ribs for added strength and weight reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional riveting or screwing methods are used to fasten cabin components to CFRP stringers, then stable fastening can be achieved, but internal access is required which is not available in trapezium-shaped profiles
Solution Approach 1:
Instead of fastening from the inside of the hollow profile (conventional method), the invention fastens from the outside using an adhesive applied to the external connection surface of the stringer. The fastening fitting is bonded to the exterior, reversing the traditional fastening direction to eliminate the need for internal access.
Solution Approach 2:
The invention replaces mechanical fastening systems (rivets, screws requiring internal access and closing heads) with a chemical bonding system (adhesive). This substitution eliminates the need for mechanical fasteners and internal access, allowing fastening from the outside of hollow CFRP profiles.
2Ease of operation
If conventional blind riveting is used, then fastening without internal access is possible, but the closing head disturbs the directional fibers in CFRP structures
Solution Approach 1:
The invention replaces mechanical blind riveting with adhesive bonding. The adhesive is applied to the external connection surface and bonds the fastening fitting without requiring a closing head that would penetrate and disturb the CFRP fibers, thus preserving fiber integrity while achieving fastening without internal access.
3Strength
If special rivets with snap heads and closing heads are used in CFRP structures, then fiber disturbance is reduced, but application in hollow profiles without internal access becomes impractical or requires great effort
Solution Approach 1:
The invention replaces specialized mechanical rivets (snap heads, closing heads) with an adhesive bonding system. This substitution maintains CFRP fiber integrity while eliminating the complexity of applying mechanical fasteners to hollow profiles, as adhesive can be easily applied to external surfaces without requiring internal access or complex tooling.
4Ease of manufacture
If aluminum stringers and formers are used, then conventional fastening methods are practicable, but the aircraft weight increases
Solution Approach 1:
The invention changes the material parameter of the stringer from aluminum to CFRP (carbon-fiber-reinforced plastic). This material substitution reduces aircraft weight while the accompanying fastening method change (to adhesive bonding) ensures that the lighter CFRP material can be effectively fastened without internal access.
Solution Approach 2:
The invention utilizes CFRP composite material for the stringer to reduce weight. The trapezium-shaped CFRP profile is bonded to the aircraft skin and fastened using adhesive, demonstrating the application of composite materials in aerospace structures with appropriate fastening solutions.
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
Enables stable, cost-effective fastening of cabin components to CFRP stringers, effectively transferring operating and crash loads, allowing for easy retrofitting and accommodating various cabin configurations, while reducing labor and weight.
Implementation Method 1
an elastomeric adhesive joint for stable fastening of the connection portion of the fastening fitting to the associated connection surface of the structural component
Implementation Method 2
a fastening fitting which has a geometry matched to the geometrical shape of the structural component, has a connection portion associated with the connection surface of the structural component and is produced from a thermoplastic injection-molding material
Data Source
AI summary
A fastening arrangement for fastening a component, in particular a cabin component, to a structural component of an aircraft or spacecraft, including a structural component which has a connection surface; a fastening fitting which has a geometry matched to the geometrical shape of the structural component, has a connection portion associated with the connection surface of the structural component and is produced from a thermoplastic injection-moulding material; and an elastomeric adhesive joint for stable fastening of the connection portion of the fastening fitting to the associated connection surface of the structural component. A corresponding fastening fitting and an aircraft or spacecraft comprising a fastening arrangement of this type and/or a fastening fitting of this type are also described.