Metal Matrix Structural Fuse for Fatigue-Resistant Shear Loads
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Solution Overview
Problem
Structural fuses, such as fuse pins in aircraft, experience fatigue cracks due to cyclic loading, leading to premature failure and the need for increased size and weight to mitigate this, resulting in excessive weight addition to the aircraft.
Innovation Solution
A structural fuse with a metal matrix composite comprising longitudinal reinforcing elements, such as ceramic fibers, arranged in specific orientations within a metal matrix, which improves fatigue properties and allows for tailored shearing characteristics without increasing weight, using materials like aluminum, titanium, or steel, and incorporating hollow metal ceramic spheres for enhanced load absorption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the size of the fuse pin is increased to reduce fatigue failures, then the fatigue resistance is improved, but the weight of the aircraft increases considerably
Solution Approach 1:
The fuse pin is constructed as a metal matrix composite material comprising a metal matrix (such as aluminium, titanium, or steel) and a reinforcement phase (such as ceramic fibres like aluminium oxide or silicon carbide, or carbon fibres). This composite structure provides superior fatigue resistance compared to solid metal, allowing the fuse pin to maintain its function with reduced size and weight while resisting fatigue cracks from cyclic loading.
2Reliability
If the fuse pin is made stronger to prevent premature failure, then the reliability is improved, but the weight of the pin and attached components increases
Solution Approach 1:
The metal matrix composite provides high strength-to-weight ratio, enabling the fuse pin to be stronger without proportionally increasing weight. The ceramic or carbon fibre reinforcement embedded in the metal matrix creates a material that is both stronger and lighter than solid metal alternatives.
Solution Approach 2:
The reinforcement phase is distributed throughout the metal matrix to provide localized strength where needed. The composite structure allows for tailored material properties in different regions of the fuse pin, optimizing strength where fatigue resistance is critical while minimizing weight in less critical areas.
3Ease of manufacture
If conventional metal fuse pins are used, then the manufacturing is simple, but the fatigue properties are poor leading to short operational life
Solution Approach 1:
The metal matrix composite can be manufactured using established metallurgical processes such as casting, powder metallurgy, or infiltration. The metal matrix provides a familiar manufacturing base while the reinforcement phase is introduced during processing, combining the ease of metal fabrication with the superior fatigue properties of composite materials.
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 extends the operational life of structural fuses while maintaining or reducing weight, allowing for precise engineering of the shearing load range and preventing damage to aircraft components during impacts, with potential fuel savings and reduced emissions.
Implementation Method 1
The provision of such a so-called metal matrix composite results in a fuse having improved fatigue properties and hence a longer operating life
Implementation Method 2
at least a portion of the metal matrix may comprise a plurality of hollow metal ceramic spheres. This results in a foam-like material that can absorb higher loads than a solid metal fuse
Implementation Method 3
at least some of the reinforcing elements are arranged substantially parallel to the longitudinal axis, so that the fuse is stronger along its longitudinal axis but not heavier than a conventional fuse
Implementation Method 4
The shearing of the fuse pin may dissipate energy and prevent other components from being damaged due to the hard landing and/or impact
Data Source
AI summary
A structural fuse is disclosed and configured to shear upon an application of a predetermined load and includes a plurality of elongate reinforcing elements in a metal matrix. The provision of a so-called metal matrix composite results in a fuse that is lighter in weight than a conventional metal pin and has improved fatigue properties and hence a longer operating life. The load (or range of loads) at which the fuse is arranged to shear can be engineered by careful arrangement of the orientation of the reinforcing elements, and by selecting the proportion of reinforcing elements in the matrix. Thus, a fuse having a narrower load range than hitherto achievable can be produced.