Gas Turbine Fan Casing Fire Resistant Composite Rib
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Solution Overview
Problem
Fan casings with carbon fibre/BMI resin composite reinforcing ribs fail to meet fire resistance standards due to sustained flame from excessive resin thickness, and attempts to address this with metal reinforcements increase weight, cost, and part count.
Innovation Solution
Replacing thickened portions of the projection with a composite shell containing a fire-resistant core, such as a metallic or ceramic matrix composite, that maintains structural integrity and allows for rapid resin burn-off, eliminating the need for metal reinforcements and interface fasteners.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the thickness of the composite reinforcing rib is increased to provide structural rigidity, then the structural strength is improved, but the fire resistance deteriorates due to excessive resin pool that cannot be burned off
Solution Approach 1:
The reinforcing rib is segmented into a composite shell portion and a fire-resistant core portion, separating the structural function from the fire-resistant function. The composite shell provides strength while the core prevents sustained burning, resolving the contradiction between structural strength and fire resistance.
Solution Approach 2:
The reinforcing rib uses a composite structure combining composite material (carbon fibre/BMI resin) for strength and fire-resistant material (metallic, ceramic, or CMC) for fire resistance. This composite approach allows both structural strength and fire resistance to be achieved simultaneously.
2Reliability
If metal portions are bolted to the composite reinforcing rib to replace thicker composite portions, then the fire resistance is improved, but the weight, cost, and part count increase
Solution Approach 1:
The fire-resistant core is integrated within the composite shell to form a unified reinforcing rib structure, eliminating the need for separate metal portions bolted to the composite rib. This merging reduces part count, assembly complexity, and overall weight while maintaining fire resistance.
Solution Approach 2:
The use of a composite structure with fire-resistant core material integrated within the composite shell provides fire resistance without requiring additional metal reinforcements, thereby reducing weight compared to bolted metal portion solutions.
3Reliability
If metal plates are bolted through the composite reinforcing rib to reduce thickness, then the fire resistance is improved, but the composite rib is shielded from flame causing sustained resin ignition
Solution Approach 1:
The fire-resistant core material is extracted from the composite shell structure, allowing the composite shell to remain thin and flame-exposed while the core provides fire resistance. This prevents the shielding effect that occurs with metal plates bolted through the composite, as the core is positioned to allow flame contact with the composite shell.
4Strength
If thickened portions are provided for mounting pads to support accessories, then the mounting strength is improved, but the fire resistance deteriorates due to excessive resin reservoir
Solution Approach 1:
The mounting pad is segmented into a composite shell portion and a fire-resistant core portion, similar to the reinforcing rib. This segmentation allows the pad to have sufficient thickness for mounting strength while the fire-resistant core prevents excessive resin accumulation that would cause sustained burning.
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
The solution enhances fire resistance while maintaining structural strength and reducing weight and cost by ensuring the composite material burns off quickly, meeting industry standards without excessive resin residue.
Implementation Method 1
The core is selected such that it maintains its structural integrity at high temperatures, does not thermally decompose to generate flammable fluids
Implementation Method 2
the pool of flammable resin is reduced thus avoiding continued burn of the projection after removal of the heat source during tests
Implementation Method 3
has a similar coefficient of thermal expansion to the shell portion over normal operating temperatures (to avoid excessive interface stresses)
Data Source
Figure 1
Figure 2~2b
Figure 3
AI summary
The present invention relates to a fire resistant fan casing for a gas turbine engine. The casing has a projection such as a reinforcing rib or a mounting pad. The projection comprises at least one shell portion formed of a fibre/plastic composite material encasing a core of fire resistant material such as a metallic material or a ceramic matrix composite material.