Composite Honeycomb Layup Tie-Down for Stable Autoclave Cure

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Solution Overview

Problem

Existing methods for preventing core movement and crush during autoclave cure in composite honeycomb core sandwich structures using unidirectional tape are inadequate, as they rely on woven fabric material that does not extend beyond the structure's edges, leading to rework or scrap.

Innovation Solution

The use of an automated fiber placement process to lay up unidirectional tows over a rough textured surface, forming under-core and over-core composite plies that tie down the honeycomb core, ensuring stability during autoclave cure.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If woven fabric material is used for tie down method, then core movement is prevented, but the method does not work for unidirectional tape

Engineering Contradiction:

Improvematerial compatibilityVSAvoidcore stability

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The invention changes the material parameter from woven fabric to unidirectional tape, requiring a modification in the tie-down mechanism. The unidirectional tows are configured to extend beyond the structure edges and contact the grit strip, adapting the tie-down method to work with the new material type while maintaining core stability.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The composite structure is segmented into multiple unidirectional plies with specific orientations. At least one ply is oriented perpendicular to the main axis, creating a multi-layered tie-down system that effectively restrains core movement in multiple directions, compensating for the lack of bidirectional reinforcement in unidirectional material.

Inventive Principle:

Principle #1Segmentation

2Manufacturing precision

If unidirectional tows are used instead of woven fabric, then manufacturing precision is improved, but existing tie down methods fail

Engineering Contradiction:

Improveply placement accuracyVSAvoidtie down implementation

Core Design Contradiction:

Manufacturing precisionVSEase of manufacture

Solution Approach 1:

The invention introduces a dynamic configuration where unidirectional tows can be oriented at different angles in different plies. The automated fiber placement process allows for precise control of tow orientation, enabling the structure to adapt its reinforcement pattern to counteract lateral pressures from various directions during autoclave curing.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The solution adds a dimensional aspect to the tie-down method by extending plies beyond the typical manufacturing excess of the structure to contact the grit strip. This extension into the lateral dimension provides the necessary restraint for unidirectional tows, which lack the inherent bidirectional reinforcement of woven fabrics.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

3Manufacturing precision

If pressure is applied during autoclave cure, then structure is consolidated, but core movement and crush occur

Engineering Contradiction:

Improvestructure consolidationVSAvoidcore position stability

Core Design Contradiction:

Manufacturing precisionVSStability of the object's composition

Solution Approach 1:

The unidirectional tows are pre-configured to contact the grit strip before autoclave curing begins. This preliminary tie-down arrangement establishes restraint against lateral movement before the consolidating pressure is applied, preventing core migration and crush that would otherwise occur during the curing process.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The extended plies creating friction contact with the grit strip provide a preliminary counter-force to the lateral pressures that will be applied during autoclave curing. This anti-action prevents the harmful effects of pressure-induced core movement and crush, allowing safe consolidation of the structure.

Inventive Principle:

Principle #9Preliminary anti-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

Prevents core movement and crush during autoclave cure, enabling the production of complex composite honeycomb core sandwich structures without rework or scrap.

Implementation Method 1

laying up unidirectional tows to form a stack of composite plies tied down to a rough textured surface

Methodology Applied

Scientific EffectFriction: Friction

Data Source

PatentUS12552110B2Methods for fabrication of layups for composite honeycomb core sandwich structures and said composite honeycomb core sandwich structures

Publication Date: 2026.02.17 THE BOEING CO

AI summary

A method for fabrication of a layup for a composite honeycomb core sandwich structure includes laying up a first plurality of unidirectional tows over a tool for layup of the composite honeycomb core sandwich structure using an automated fiber placement process to form a stack of under-core composite plies that are tied down to a rough textured surface bonded to the tool; placing a honeycomb core on the stack of under-core composite plies within the rough textured surface; and laying up a second plurality of unidirectional tows over the honeycomb core using the automated fiber placement process to form a stack of over-core composite plies that tie down the honeycomb core to the rough textured surface. The method may also include placing an under-core film adhesive on the stack of under-core composite plies and placing an over-core film adhesive on the honeycomb core.