Interlocking Tab Slot Joint for Composite Panel Bending

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Solution Overview

Problem

Existing methods for fabricating joints in advanced materials like composite honeycomb panels and aerospace components result in physically weaker and more costly items due to the use of adhesives and fasteners, which also increase weight.

Innovation Solution

A method involving a groove with interlocking tabs and slots in a panel with a core sandwiched between two skins, allowing the panel to be bent without adhesives, reducing weight and cost by stabilizing the joint through intermeshing tabs and slots, and optionally using a small amount of adhesive for added strength.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If adhesives or fasteners are used to construct cut joints, then the joint strength is improved, but the weight and cost of the item increase

Engineering Contradiction:
Improvejoint strengthVSAvoiditem weight
Core Design Contradiction:
StrengthVSWeight of moving object

Solution Approach 1:

The joint is segmented into interlocking components with tabs and slots that fit together mechanically, eliminating the need for adhesives or fasteners. The groove is divided into multiple tabs on one side and corresponding slots on the other side, creating a distributed interlocking system that provides strength without additional materials.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The patent replaces the chemical bonding system (adhesives) with a purely mechanical interlocking system. The tabs and slots engage through geometric compatibility, using mechanical interference and friction to provide joint strength, thereby eliminating the weight and cost associated with adhesive materials and application processes.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

2Strength

If adhesives are used to fill the groove in routed joints, then the joint strength is improved, but the weight and cost of the item increase

Engineering Contradiction:
Improvejoint strengthVSAvoidadhesive quantity
Core Design Contradiction:
StrengthVSQuantity of substance

Solution Approach 1:

The adhesive substance is completely extracted from the joint construction process. Instead of filling the groove with adhesive, the patent uses a purely mechanical interlocking system where tabs fit into slots, eliminating the need for any adhesive material and its associated weight and cost.

Inventive Principle:
Principle #2Taking out (Extraction)

Solution Approach 2:

The joint structure is self-sufficient and does not require external substances like adhesives to function. The tabs and slots are designed to interlock through their own geometric properties, with the mechanical engagement providing sufficient strength without any additional bonding materials.

Inventive Principle:
Principle #25Self-service

3Strength

If folded joints are used in rigid composite panels, then the joint strength is improved, but the manufacturing complexity increases

Engineering Contradiction:
Improvejoint strengthVSAvoidmanufacturing ease
Core Design Contradiction:
StrengthVSEase of manufacture

Solution Approach 1:

The groove with tabs and slots is pre-formed in the panel using routing or machining operations before assembly. This preliminary action creates the interlocking features that will later engage during folding, making the manufacturing process more systematic and easier to control compared to attempting to fold rigid panels without pre-prepared features.

Inventive Principle:
Principle #10Preliminary action

Solution Approach 2:

The groove with tabs and slots acts as an intermediary feature that facilitates the joining of rigid panel sections. Rather than directly folding the rigid materials against each other, the pre-formed groove provides a mediating structure that guides and enables the folding process, reducing manufacturing complexity.

Inventive Principle:
Principle #24Intermediary (Mediator)

Data Source

PatentEP2040980B1Method of fabricating an internal finger joint
Publication Date: 2011.10.26 THE BOEING CO
  • EP2040980B1 patent drawingFigure 1
  • EP2040980B1 patent drawingFigure 2
  • EP2040980B1 patent drawingFigure 3

AI summary

To fabricate a joint in a panel (10), a groove (18) is generated and the panel is bent along the groove. The panel includes a first skin (12), second skin (14), and core (16). The core is sandwiched between the first skin and the second skin. The groove passes through the first skin and at least a portion of the core. The groove includes a set of tabs (20) and a corresponding set of slots (22). The set of tabs intermesh with the set of slots in response to bending the panel along the groove.