Thermoplastic Composite Riveting for High Pull-Out Strength

Solution Overview

Problem

Existing methods for assembling thermoplastic composite parts in aeronautical engineering face challenges in achieving high pull-out and shear strength, particularly due to resin-to-metal contact and limitations in adapting to thermoplastic materials, which are prone to stiffness at ambient temperature.

Innovation Solution

The use of thermoplastic resin-based composite material ties, made from fibers like aramid, carbon, or glass, embedded in overlapping regions of parts, and a method involving transversely holed heating panels to create cylindrical bores for inserting these ties, ensuring high mechanical strength through compatible materials and geometrical reinforcement.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If metal stakes or pins are used for riveting thermoplastic composite parts, then assembly strength is improved, but resin-to-metal contact occurs which reduces pull-out strength

Engineering Contradiction:

Improveassembly strengthVSAvoidpull-out strength

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The patent introduces a thermoplastic resin-based intermediate material between the metal stake and the composite parts. This intermediate resin layer prevents direct contact between the metal stake and the composite resin, eliminating the harmful resin-to-metal contact while maintaining strong mechanical bonding. The intermediate layer acts as a mediator that transfers loads effectively without creating weak interfaces.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent uses a composite rivet structure consisting of a metal stake embedded in thermoplastic resin. This composite rivet combines the high strength of metal with the chemical compatibility and bonding capabilities of thermoplastic resin, creating a fastening element that is optimized for thermoplastic composite parts while avoiding resin-to-metal contact issues.

Inventive Principle:

Principle #40Composite materials

2Adaptability or versatility

If stitching techniques are used for assembling composite materials, then assembly flexibility is improved, but application to thermoplastic materials is difficult due to stiffness at ambient temperature

Engineering Contradiction:

Improveassembly flexibilityVSAvoidease of application to thermoplastic materials

Core Design Contradiction:

Adaptability or versatilityVSEase of manufacture

Solution Approach 1:

The patent employs thermal energy to change the physical state of the thermoplastic material during assembly. By heating the thermoplastic composite parts to above their glass transition or melting temperature, the material becomes more ductile and easier to work with, allowing stitching and forming operations that would be difficult or impossible at ambient temperature. After cooling, the material regains its strength and stiffness.

Inventive Principle:

Principle #35Parameter changes

3Ease of manufacture

If thermoplastic parts are heated above melting point for pinning, then assembly is enabled, but resin-to-metal contact is encouraged which reduces pull-out strength

Engineering Contradiction:

Improveassembly enablementVSAvoidpull-out strength

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent introduces a thermoplastic resin-based intermediate material between the metal stake and the composite parts. This intermediate resin layer prevents direct contact between the metal stake and the composite resin, eliminating the harmful resin-to-metal contact while maintaining strong mechanical bonding. The intermediate layer acts as a mediator that transfers loads effectively without creating weak interfaces.

Inventive Principle:

Principle #24Intermediary (Mediator)

4Strength

If conventional metal riveting is used for thermoplastic composite parts, then assembly strength is improved, but adaptation to thermoplastic materials is poor

Engineering Contradiction:

Improveassembly strengthVSAvoidadaptability to thermoplastic materials

Core Design Contradiction:

StrengthVSAdaptability or versatility

Solution Approach 1:

The patent uses a composite rivet structure consisting of a metal stake embedded in thermoplastic resin. This composite rivet combines the high strength of metal with the chemical compatibility and bonding capabilities of thermoplastic resin, creating a fastening element that is optimized for thermoplastic composite parts while avoiding resin-to-metal contact issues.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent employs thermal energy to change the physical state of the thermoplastic material during assembly. By heating the thermoplastic composite parts to above their glass transition or melting temperature, the material becomes more ductile and easier to work with, allowing stitching and forming operations that would be difficult or impossible at ambient temperature. After cooling, the material regains its strength and stiffness.

Inventive Principle:

Principle #35Parameter changes

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

This approach provides a fault-free join with high pull-out and shear strength, suitable for high-stress applications like aeronautical engineering, by using thermoplastic resin-based composite material ties that are compatible with the parts' materials and reinforced with fibers, ensuring strong mechanical bonding.

Implementation Method 1

using the heating panels to heat the regions of the parts, from their opposite faces, to a temperature at which a holing spike will penetrate

Methodology Applied

Scientific EffectHeating: Heating

Implementation Method 2

inserting at least one holing spike through a first heating panel, with successive holing of the first and of the second part so as to create at least one cylindrical bore

Methodology Applied

Scientific EffectMechanical penetration: Mechanical Force

Implementation Method 3

an assembly tie made of thermoplastic material is inserted into each cylindrical bore... These ties being embedded in said regions... ensuring high mechanical strength through compatible materials and geometrical reinforcement

Methodology Applied

Scientific EffectMechanical bonding: Mechanical Force

Data Source

PatentUS11878474B2Assembly of parts made from thermoplastic material and method for assembling such parts by means of thermoplastic riveting

Publication Date: 2024.01.23 LATECOERE

AI summary

This invention relates to an assembly of regions (10a, 10b) of composite parts (2a, 2b) with thermoplastic matrix, including a plurality of riveting points along regions (10a, 10) of the parts that overlap through the superposition of two faces (12a, 12b) of these regions (10a, 10b) which are positioned facing one another, each region (10a, 10b) having another, opposite, face (11a, 11b) which remains visible with the part (2a, 2b). The riveting is performed using assembly ties (6) made of thermoplastic resin-based composite material compatible with the material of the parts (2a, 2b). These ties (6), which are made up at least in part of a stitch of backstitch produced using a filament of a material selected from a fiber coated with aramid resin, a carbon fiber and a glass fiber, are embedded in said regions (10a, 10b) and passing right through the same with an orientation comprised between 30° and 90° with respect to their faces (11a, 11b; 12a, 12b).