Molded-in Insert Groove Design for Composite Retention

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Solution Overview

Problem

Existing molded-in inserts for fiber reinforced thermoplastic composite structures face challenges in achieving high strength retention due to the non-ductile nature of these materials, leading to improper fits, increased manufacturing costs, and incomplete consolidation, especially with compression molded carbon fiber reinforced thermoplastic composite parts.

Innovation Solution

A molded-in insert with a cylindrical body and at least one circumferential groove having a substantially concave configuration, a groove radius of 0.025 inch or greater, and a groove radius greater than or equal to the groove depth, which allows reinforcing fibers to fully fill the groove during the molding process, forming a high strength mechanical locking mechanism.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If known molded-in inserts with sharp grooves and small radii are used, then retention mechanism is provided, but fiber reinforced thermoplastic composite material cannot fully fill the grooves leading to incomplete consolidation and void areas

Engineering Contradiction:

Improveinsert retention strengthVSAvoidgroove filling completeness

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The patent applies curvature by replacing sharp grooves with rounded grooves that have a radius of curvature of at least 0.025 inches. This curvature allows the viscous fiber reinforced thermoplastic composite material to flow into and fully fill the groove during molding, eliminating void areas while maintaining the mechanical locking retention mechanism.

Inventive Principle:

Principle #14Spheroidality (Curvature)

2Ease of manufacture

If press-fit inserts are used in fiber reinforced thermoplastic composite material, then insert installation is simplified, but the non-ductile nature of the material leads to over-stressing or poor retention

Engineering Contradiction:

Improveinsert installation simplicityVSAvoidinsert retention strength

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent applies preliminary action by forming the rounded grooves on the insert before insertion into the composite material. During the molding process, the material is consolidated around the insert in advance, creating a positive mechanical lock before the part is ejected. This eliminates the need for post-molding operations while ensuring reliable retention.

Inventive Principle:

Principle #10Preliminary action

3Ease of manufacture

If known molded-in inserts are used, then manufacturing cost is reduced compared to post-molding methods, but void areas and incomplete consolidation increase

Engineering Contradiction:

Improvemanufacturing costVSAvoidconsolidation quality

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The rounded groove geometry with radius of at least 0.025 inches enables complete material consolidation during the molding process itself, eliminating void areas. This maintains the cost advantage of molded-in inserts while achieving the consolidation quality previously only attainable through more expensive post-molding methods.

Inventive Principle:

Principle #14Spheroidality (Curvature)

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 ensures high strength retention and complete consolidation of the molded-in insert within the fiber reinforced thermoplastic composite structure, minimizing void areas and fiber severance, thus enhancing the structural integrity and reducing manufacturing costs.

Implementation Method 1

allowing the fiber reinforced thermoplastic composite material to flow into and fill the at least one circumferential groove

Methodology Applied

Scientific EffectViscous flow:

Implementation Method 2

heating and compressing the fiber reinforced thermoplastic composite material to consolidate the material around the molded-in insert

Methodology Applied

Scientific EffectCompression: Compression

Data Source

PatentUS10118351B2Method of retaining a molded-in insert in a fiber reinforced thermoplastic composite material

Publication Date: 2018.11.06 THE BOEING CO

AI summary

A method of retaining a molded-in insert in a fiber reinforced thermoplastic composite material and forming a high strength mechanical locking mechanism is provided. The method includes fixing a molded-in insert in a mold cavity. The insert has a cylindrical body and at least one circumferential groove formed in the cylindrical body, and has a substantially concave configuration, and the groove has a groove radius of 0.025 inch or greater, and greater than or equal to a groove depth. The method includes introducing a fiber reinforced thermoplastic composite material into the mold cavity and around the molded-in insert, enclosing the mold cavity, heating and compressing the material in the mold cavity to consolidate the material around the molded-in insert and to form a consolidated fiber reinforced thermoplastic composite structure with the molded-in insert, cooling the structure, and removing the structure with the molded-in insert from the mold cavity.