Two-Piece Fitting for Variable Thickness Structural Members
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for securing structural members in aircraft, such as two-piece attachment angles and one-piece Pi fittings, face issues with structural loading, installation complexity, and adhesive disturbance, leading to potential de-bonding and fracture under high pull-off and impact loads, especially with thickness variations.
Innovation Solution
A two-piece fitting with variable distance between sections, allowing for secure attachment of structural members with a T-shaped first piece and a second piece having perpendicular sections, enabling secure adhesion without disturbing existing adhesive and accommodating thickness variations, and reinforced with stitching or Z-pins for enhanced strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a one-piece Pi fitting is used to secure structural members, then structural strength under pull-off loads is improved, but installation complexity increases and adhesive disturbance occurs due to fixed distance between sections
Solution Approach 1:
The Pi fitting is divided into two separate pieces: a first piece with a first section and second section, and a second piece with a third section, fourth section, and fifth section. This segmentation allows the pieces to be installed independently and adjusted to accommodate thickness variations, eliminating the installation difficulties of the one-piece design while maintaining structural strength.
Solution Approach 2:
The distance between the sections of the Pi fitting is made variable through the two-piece design, allowing adjustment during installation. The first and second pieces can be positioned at different distances from each other to accommodate variations in structural member thickness, providing dynamic adaptability that the fixed one-piece design lacks.
2Ease of manufacture
If a one-piece Pi fitting with fixed distance between sections is used, then manufacturing simplicity is improved, but adaptability to thickness variations deteriorates
Solution Approach 1:
By segmenting the Pi fitting into two independently manufacturable pieces, each piece can be produced with standard tolerances and then assembled with adjustable spacing. This maintains manufacturing simplicity while enabling adaptability to different thickness variations through the variable distance between the first and second pieces.
Solution Approach 2:
The design allows the distance parameter between the first and second pieces to be varied during installation to accommodate different thickness variations. This parameter change capability is built into the two-piece design, allowing the same fitting design to adapt to multiple thickness scenarios without requiring custom manufacturing for each case.
3Ease of operation
If two-piece attachment angles with radiused corners are used, then ease of installation is improved, but structural strength under impact loads deteriorates due to fracture zones in resin
Solution Approach 1:
The two-piece Pi fitting design segments the attachment structure into separate pieces that can be installed independently, maintaining ease of installation. The sections are configured to distribute impact loads more effectively, reducing the concentration of stresses that create fracture zones in the resin, thereby improving impact resistance while preserving installation ease.
Solution Approach 2:
The Pi fitting configuration extends the attachment in multiple dimensions with sections perpendicular to each other, creating a more distributed load path. This dimensional arrangement helps distribute impact loads across multiple bonding interfaces rather than concentrating them at single radiused corners, reducing fracture zone formation while maintaining installation simplicity.
Data Source
AI summary
Apparatus and methods for securing a first structural member and a second structural member to one another. In one embodiment a two-piece fitting is provided. The fitting includes a variable gap between attachment surfaces, enabling the fitting to accommodate structural members of variable thickness. The fitting also includes overlapping sections that provide increased resistance to pull-off loads and impact loads. The configuration of the fitting advantageously simplifies the assembly process and preserves the integrity of the adhesive to form a strong joint.