ACM Shaft Thermal Expansion Control via Electrodeposited Metal Coating

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Solution Overview

Problem

Shafts for air cycle machines (ACMs) made from exotic materials are often expensive and heavy, and those additively manufactured from plastic with strengthening coatings can fail due to differing coefficients of thermal expansion.

Innovation Solution

A method of forming a shaft for an ACM using additively manufactured thermoplastic polymers with different coefficients of thermal expansion (CTEs), combined with a metallic coating applied via electrolysis deposition, to control thermal expansion and contraction.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If a shaft is made from exotic materials, then strength and thermal resistance are improved, but weight and cost increase

Engineering Contradiction:

Improveshaft strengthVSAvoidshaft weight

Core Design Contradiction:

StrengthVSWeight of moving object

Solution Approach 1:

The shaft is constructed as a composite structure with a plastic core providing lightweight structural support and a metal coating layer providing surface strength and thermal resistance. This composite approach combines the advantages of both materials while avoiding their individual disadvantages of weight and cost.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

Instead of making the entire shaft from heavy exotic materials, the metal coating is applied only to the surface where strength and thermal resistance are most needed, while the interior remains lightweight plastic. This local application of material properties optimizes the strength-to-weight ratio.

Inventive Principle:

Principle #3Local quality

2Strength

If a plastic shaft is coated with strengthening metal material, then strength is improved, but the coating separates or fails due to different coefficients of thermal expansion

Engineering Contradiction:

Improveshaft strengthVSAvoidcoating adhesion

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The patent modifies the thermal expansion characteristics of the plastic substrate by selecting specific plastic materials and designing the core geometry to compensate for the differential thermal expansion between the plastic core and metal coating. This parameter adjustment prevents coating separation during thermal cycling.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The plastic core acts as an intermediary layer that mediates between the thermal expansion of the metal coating and the overall shaft structure. Its lower thermal expansion coefficient and flexible nature help accommodate thermal stresses without causing coating failure.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Weight of moving object

If a shaft is made from plastic, then cost and weight are reduced, but thermal expansion control and abrasion resistance deteriorate

Engineering Contradiction:

Improveshaft weightVSAvoidthermal expansion

Core Design Contradiction:

Weight of moving objectVSObject-affected harmful factors

Solution Approach 1:

The composite structure combines plastic's low weight advantage with metal's thermal expansion control and abrasion resistance. The metal coating layer provides the protective functions that pure plastic lacks, while the plastic core maintains the weight advantage.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The metal coating is applied locally to the shaft surface where abrasion resistance and thermal stability are required, while the bulk of the shaft remains lightweight plastic. This localized material application provides protection only where needed.

Inventive Principle:

Principle #3Local quality

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 provides a cost-effective, lightweight, and abrasion-resistant shaft that optimizes thermal deflections, reduces induced stress and weight, and enhances performance by controlling thermal expansion.

Implementation Method 1

forming an upper support section on the shaft by depositing on the lower support section, along each of the discrete sections, via electrolysis deposition, a metallic coating, to thereby control thermal expansion and contraction of the shaft along the discrete sections

Methodology Applied

Scientific EffectElectrolysis deposition: Electrodeposition

Implementation Method 2

the first thermoplastic polymer surface having a first coefficient of thermal expansion (CTE), and the second thermoplastic polymer surface having a second CTE

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Data Source

PatentUS20250033272A1Metal plated additively manufactured plastic ACM shafts with internal thermally adaptive structure

Publication Date: 2025.01.30 HAMILTON SUNDSTRAND CORP

AI summary

Forming an ACM shaft by: forming a base of (i) a thrust shaft having a first section connecting with an ACM tie rod when installed; a second section connecting with an ACM motor rotor when installed; a third section forming a shaft joint that connects adjacent portions of the thrust shaft; or (ii) a compressor rotor shaft having a fourth section connecting with an ACM tie rod support when installed; and fifth section connecting with the ACM motor rotor when installed; forming the base includes: printing polymer surfaces having differing CTSs from polymers disposed against each other; forming a lower support section on the base by printing along the discrete sections a mixture of a third thermoplastic polymer and a catalyst formed with metal; and forming an upper support section on the shaft by depositing on the lower support section, along the discrete sections, via electrolysis deposition, a metallic coating.