Thermoplastic Composite Joining by Melt Injection Through Orifices

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Solution Overview

Problem

Existing methods for permanently joining thermoplastic composite parts in aircraft construction, such as ultrasonic and resistance welding, fail to achieve the desired quality and are not suitable for carbon fiber reinforced thermoplastics, limiting productivity and strength.

Innovation Solution

A method involving the injection of melted thermoplastic material through an orifice in one part to join it with another part, allowing the surfaces to melt and solidify, forming a permanent bond.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If ultrasonic welding or resistance welding is used to join thermoplastic composite parts, then the joining speed is fast, but the joining quality is insufficient and the technology is not suitable for carbon fiber reinforced thermoplastics

Engineering Contradiction:

Improvejoining speedVSAvoidjoining quality

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The invention changes the physical state parameter of the thermoplastic material by heating it above its melting point and then allowing it to solidify. This phase change enables high-quality joining of carbon fiber reinforced thermoplastics while maintaining fast processing speed, resolving the contradiction between joining speed and joining quality

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention utilizes the phase transition of thermoplastic material from solid to melted state and back to solid state. By injecting melted thermoplastic material into the joint area and allowing it to solidify, the process achieves both fast joining speed and high joining quality suitable for carbon fiber reinforced thermoplastics

Inventive Principle:

Principle #36Phase transitions

2Reliability

If mechanical fasteners like rivets are used to join composite parts, then the joining reliability is high, but the productivity is reduced due to the time-consuming process

Engineering Contradiction:

Improvejoining reliabilityVSAvoidproductivity

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The invention replaces the mechanical fastening system (rivets, screws) with a thermal joining system that uses melted thermoplastic material to create bonds. This substitution eliminates the need for multiple mechanical fasteners and complex installation processes, significantly improving productivity while maintaining joining reliability through the solidified thermoplastic material

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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

Enables fast and high-quality joining of thermoplastic composite parts, enhancing productivity and enabling the welding of long parts like stringers with multiple injection spots.

Implementation Method 1

Injecting melted thermoplastic material through the orifice to contact the first and the second composite part in a contact area, whereby surfaces of the first and the second composite part in that contact area melt together

Methodology Applied

Scientific EffectConduction (thermal): Conduction (thermal)

Implementation Method 2

Injecting melted thermoplastic material through the orifice... surfaces of the first and the second composite part in that contact area melt together... Solidifying the thermoplastic material in the orifice and in the contact area to permanently join the first composite part to the second composite part

Methodology Applied

Scientific EffectMelting: Melting

Implementation Method 3

Methodology Applied

Scientific EffectPhase Change: Phase Change

Data Source

PatentUS12502842B2Method of permanently joining composite parts made from thermoplastic material, arrangement of composite parts, and aircraft

Publication Date: 2025.12.23 AIRBUS OPERATIONS GMBH

AI summary

A method of permanently joining composite parts made from thermoplastic material includes providing a first composite part and a second composite part, both made from thermoplastic material, wherein an orifice is provided in at least one of the composite parts, positioning both composite parts such that a portion of the composite part which includes the orifice is adjacent to a portion of the other composite part, injecting melted thermoplastic material through the orifice to contact the first and the second composite part in a contact area, whereby surfaces of the first and the second composite part in that contact area melt together; and solidifying the thermoplastic material in the orifice and in the contact area to permanently join the first composite part to the second composite part.