Composite Core Extraction via Segmented Bladder and Granular Fill

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Solution Overview

Problem

The production of composite parts with complex shapes often faces challenges in removing cores from the mold without damaging the part, especially for hollow or enveloping shapes, due to dimensional instability and the need for expensive, complex multi-part cores or materials that can withstand extreme conditions during the manufacturing process.

Innovation Solution

A flexible bladder filled with a solid granular material and an intergranular fluid is used to ensure core rigidity and controlled volume modification, balancing pressures and maintaining dimensional accuracy during the curing process, allowing for the extraction of the core without damaging the part.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If a rigid core is used to maintain dimensional stability during composite part manufacturing, then manufacturing precision is improved, but the core cannot be extracted from the finished part

Engineering Contradiction:

Improvedimensional stabilityVSAvoidcore extraction

Core Design Contradiction:

Manufacturing precisionVSEase of operation

Solution Approach 1:

The core is divided into two functional segments: an outer rigid shell providing dimensional stability and an inner deformable bladder enabling extraction. The rigid shell maintains geometric tolerances during manufacturing while the deformable bladder can be collapsed and removed through a extraction opening, resolving the contradiction between rigidity and extractability.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The deformable bladder is nested within the rigid shell, with the bladder serving as an inner element that can be independently manipulated. The bladder is positioned inside the rigid shell structure, allowing it to be collapsed and extracted through an opening while the rigid shell remains as the final core structure in the part.

Inventive Principle:

Principle #7Nested doll (Nesting)

2Ease of operation

If a deformable core material is used to enable extraction, then ease of operation is improved, but manufacturing precision deteriorates due to dimensional instability

Engineering Contradiction:

Improvecore extractionVSAvoiddimensional stability

Core Design Contradiction:

Ease of operationVSManufacturing precision

Solution Approach 1:

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The inner bladder is made of a deformable material that can be collapsed and extracted, providing the necessary flexibility for removal. This deformable bladder is enclosed within the rigid shell, allowing the core to be extracted by deforming the bladder through an opening while the rigid shell maintains dimensional accuracy.

Inventive Principle:

Principle #30Flexible shells and thin films

3Reliability

If expensive specialized materials are used for the core to withstand extreme manufacturing conditions, then reliability is improved, but device complexity and cost increase

Engineering Contradiction:

Improvecore strength under extreme conditionsVSAvoidcore design complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The core uses a composite structure combining a rigid shell material (such as metal or rigid plastic) with an inner deformable bladder material. This composite approach allows the rigid shell to withstand extreme manufacturing conditions while the deformable bladder provides extraction capability, avoiding the need for expensive specialized materials that would need to simultaneously provide both extreme condition resistance and deformability.

Inventive Principle:

Principle #40Composite materials

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 method ensures the production of composite parts with precise geometric tolerances and structural integrity by controlling pressure and thermal expansion, reducing scrap rates and maintaining material health, while allowing for the extraction of the core without damaging the part.

Implementation Method 1

pressure is exerted on the interior surface of the bladder by the solid granular material and/or fluid so that the volume of the core is changed in a controlled manner

Methodology Applied

Scientific EffectPressure: Pressure Increase

Implementation Method 2

coefficient of thermal expansion close to the thermal expansion of the composite material of the part

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Data Source

PatentEP1996390B1Method for producing structures of complex shapes of composite materials

Publication Date: 2010.08.04 EURON AERONAUTIC DEFENCE & SPACE

Figure 1~3
Figure 4~6

AI summary

The invention concerns a method for producing a composite material part having a so-called non-strippable shape which consists in producing mold components, or cores, which are to be extracted from the part after the composite material has been cured. The method consists in a first step in producing a core from an elastomeric bladder (21) the desired shape of which is obtained by filling the bladder with a granular solid material (31) and in depressurizing the bladder and in a second step, after setting the core and the composite material (12) in modifying in controlled manner the volume of the core for example by selecting the solid granular material based on its thermal expansion properties or by acting on the pressure in the bladder.