ISOGRID Stiffener Integration Using Pad-Ups and Mouse Holes

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Solution Overview

Problem

The existing ISOGRID structures face challenges in integrating stiffeners on the face of the panel, which restricts space for pipes and complicates assembly, leading to manufacturing constraints and undesirable bending moments due to the placement of stiffeners on the back of the panel.

Innovation Solution

The integration of modified ISOGRID panels with pad-ups along the edges of triangular pockets and added stiffeners that pass through mouse holes, allowing the stiffeners to be attached on the face instead of the back, maintaining structural integrity and load distribution while providing space for pipes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If stiffeners are attached to the back of the ISOGRID panel, then structural strength is improved, but space for pipes and assembly complexity deteriorate

Engineering Contradiction:

Improvestructural strengthVSAvoidspace for pipes

Core Design Contradiction:

StrengthVSEase of operation

Solution Approach 1:

The stiffeners are inverted from the conventional back-attachment position to the front face position of the ISOGRID panel. This inversion allows pipes to be routed through mouse holes in the stiffeners, eliminating the space constraint while maintaining structural integrity through proper load transfer mechanisms.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

Mouse holes are introduced as intermediary elements within the stiffeners, serving as conduits for pipes to pass through. This mediator approach allows both the stiffener's structural function and the pipe routing requirement to coexist without conflict.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Strength

If stiffeners are attached to the back of the ISOGRID panel, then structural strength is improved, but manufacturing complexity deteriorates

Engineering Contradiction:

Improvestructural strengthVSAvoidmanufacturing complexity

Core Design Contradiction:

StrengthVSEase of manufacture

Solution Approach 1:

By inverting the stiffener position to the front face, the manufacturing process is simplified. Standard attachment methods can be used without requiring specialized tooling to accommodate stiffeners on the back, and alignment with aircraft frames becomes more straightforward.

Inventive Principle:

Principle #13The other way round (Inversion)

3Strength

If stiffeners are attached to the back of the ISOGRID panel, then structural strength is improved, but alignment accuracy deteriorates

Engineering Contradiction:

Improvestructural strengthVSAvoidalignment accuracy

Core Design Contradiction:

StrengthVSManufacturing precision

Solution Approach 1:

Inverting the stiffener position to the front face eliminates the alignment problem caused by longitudinal location differences. The stiffeners can now be directly aligned with aircraft frames above and below the panel, ensuring precise positioning and eliminating undesirable bending moments.

Inventive Principle:

Principle #13The other way round (Inversion)

Data Source

PatentEP4282748A1Stiffener integration in an isogrid structure

Publication Date: 2023.11.29 AIRBUS CANADA LLP

Figure 1A~1B
Figure 2A
Figure 2B

AI summary

There is provided a system for stiffener integration in an ISOGRID structure. The modified ISOGRID structure comprises an ISOGRID panel (14); and at least one added stiffener (10) attached to the ISOGRID panel (14). The added stiffener (10) can be attached by welding, gluing or bolting the stiffener to the ISOGRID panel (14). The modified ISOGRID panel (14) has a pad-up in place of one of the ribs of the triangular pockets, wherein the added stiffener (10) is affixed to the pad-up.