Composite Tube End-Fitting Overmolding for Thermal Separation Resistance

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Solution Overview

Problem

Thermosetting composite tubes used in industrial and aeronautical sectors face challenges with traction, compression, torsional vibration, and temperature gradients due to material expansion coefficient differences between thermosetting carbon and thermoplastic materials, leading to potential separation and accidents.

Innovation Solution

A method involving machining the thermosetting composite profile member, positioning a plug, thermal conditioning, and injecting a thermoplastic end-fitting to create a strong junction, with optional chemical or laser treatments to enhance the link between materials, allowing the assembly to withstand significant forces and temperature variations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If thermoplastic end-fitting is overmolded on thermosetting composite profile member, then the assembly can withstand significant forces and temperature gradients, but the different expansion coefficients of the two materials induce risks of separation

Engineering Contradiction:

Improvestrength of connectionVSAvoidrisk of separation

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The profile member is pre-machined with specific geometric features (such as recesses, grooves, or asymmetric shapes) in the injection zone before overmolding. This preliminary machining creates a mechanical interlock that prevents separation caused by thermal expansion differences between the thermosetting profile member and thermoplastic end-fitting.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The injection zone of the profile member is given different local geometric properties compared to the rest of the structure. This localized machining creates specific interlocking features that enhance the connection strength at the critical interface while maintaining the overall structural integrity and accounting for thermal expansion differences.

Inventive Principle:

Principle #3Local quality

2Strength

If thermosetting profile member is machined on the outside, then the mechanical linking with end-fitting is improved, but additional internal machining may be required for optimal connection

Engineering Contradiction:

Improvemechanical linking strengthVSAvoidnumber of machining operations

Core Design Contradiction:

StrengthVSDevice complexity

Solution Approach 1:

The invention performs machining on the outside surface of the profile member in the injection zone, which is sufficient to create effective mechanical interlocking features. While internal machining could provide additional benefit, the external machining alone achieves the required connection strength, avoiding the complexity and cost of internal machining operations.

Inventive Principle:

Principle #16Partial or excessive action

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 method results in assemblies that can withstand high traction, compression, and temperature gradients, providing a strong and reliable connection between thermosetting and thermoplastic materials with different expansion coefficients, reducing the risk of separation and enhancing the structural integrity of components like connecting rods.

Implementation Method 1

The machining of the shape of the profile member will allow the mechanical linking of the profile member and the end-fitting

Methodology Applied

Scientific EffectMechanical interlock: Mechanical Fastener

Implementation Method 2

This chemical treatment after the machining of the profile member in the machined part of the profile member can include or can consist of the use of a solvent, an adhesive or a wetting agent

Methodology Applied

Scientific EffectAdhesion: Adhesive

Implementation Method 3

The plug will possibly have a length greater than or equal to the length of the injection zone in order to withstand the injection pressure exerted on the walls of the profile member

Methodology Applied

Scientific EffectPressure distribution: Pressure Gradient

Implementation Method 4

The two materials (thermosetting carbon and thermoplastic plug and end-fitting) have different expansion coefficients and the temperature differences induce risks of separation of the two materials

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Data Source

PatentUS10987836B2Hollow profile member such as a tube made of thermosetting composite materials and corresponding method

Publication Date: 2021.04.27 EPSILON COMPOSITE

AI summary

A method for overmolding a thermoplastic tip onto a hollow profile member made of thermosetting composite and to an assembly including a thermosetting profile member and a thermoplastic tip, wherein it includes machining the shape of the profile member made of thermosetting composite on the injection region; positioning a cap in the profile member; thermally conditioning the profile assembly and the cap; and injecting the tip with thermoplastic composite in order to create the junction of the profile member, the cap and the tip.