Unitized Composite Stiffeners via Co-Infusion

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Solution Overview

Problem

Existing methods for reinforcing composite structures, such as those in the aerospace industry, require costly capital equipment and labor-intensive processes, and often result in increased weight and complexity due to discrete stiffeners, which can limit production efficiency and flexibility.

Innovation Solution

The integration of modular stiffeners into composite structural members through a vacuum-assisted resin infusion process, allowing for the co-infusion of fiber reinforcements and preforms to form a unitized structure with simplified tooling, reducing the need for expensive equipment and enabling flexible stiffener designs and layouts.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If individual stiffeners are attached using secondary assembly processes (discrete fasteners, bonding, co-bonding, co-curing), then the structure gains additional strength and rigidity, but the assembly time, labor requirements, and capital equipment costs increase

Engineering Contradiction:

Improvestructural strengthVSAvoidassembly time

Core Design Contradiction:

StrengthVSLoss of time

Solution Approach 1:

The patent merges the stiffener and structural member into a single unitized structure by integrating stiffeners directly into the mold during the primary manufacturing process. This eliminates secondary assembly operations (fastening, bonding, co-curing) and reduces assembly time while maintaining structural strength through integral construction.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The stiffeners are pre-positioned within the mold before the resin infusion process begins. This preliminary placement allows the stiffeners to be integrated into the structural member during the initial manufacturing cycle, avoiding subsequent assembly steps and reducing overall production time.

Inventive Principle:

Principle #10Preliminary action

2Strength

If individual stiffeners are attached using secondary assembly processes, then the structure gains additional strength and rigidity, but the need for expensive capital equipment such as autoclaves increases

Engineering Contradiction:

Improvestructural strengthVSAvoidmanufacturing cost

Core Design Contradiction:

StrengthVSEase of manufacture

Solution Approach 1:

The patent combines the stiffener attachment function with the primary structural member manufacturing process. By integrating stiffeners into the mold and using resin infusion to bond them during initial production, the need for separate expensive equipment like autoclaves is eliminated, reducing manufacturing costs while achieving the required structural strength.

Inventive Principle:

Principle #5Merging (Combining)

3Productivity

If modular stiffeners are integrated during the manufacturing process through co-infusion, then production efficiency and flexibility improve, but the manufacturing process complexity increases

Engineering Contradiction:

Improveproduction efficiencyVSAvoidprocess complexity

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The patent uses modular stiffener components that can be independently designed, positioned, and integrated into the mold. This segmentation allows for flexible configuration of stiffeners while maintaining a relatively simple manufacturing process, as each module can be separately prepared and then assembled into the final structure during resin infusion.

Inventive Principle:

Principle #1Segmentation

4Ease of operation

If discrete fasteners are used to attach stiffeners, then the assembly process is simplified, but the weight and part count of the structure increase

Engineering Contradiction:

Improveassembly simplicityVSAvoidstructure weight

Core Design Contradiction:

Ease of operationVSWeight of moving object

Solution Approach 1:

The patent eliminates discrete fasteners by merging the stiffener and structural member into a single integral component. The stiffeners become an inherent part of the structural member through the resin infusion process, removing the need for separate fastening elements and reducing overall structure weight while maintaining assembly simplicity.

Inventive Principle:

Principle #5Merging (Combining)

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 enables the cost-effective production of stiffened composite structures with enhanced strength and stiffness, reduced weight, and improved inspection accessibility, while minimizing the use of expensive capital equipment and allowing for more complex stiffener configurations, thereby enhancing production efficiency and performance.

Implementation Method 1

a vacuum is drawn in the bag. The reinforcement and the preform are co-infused with a thermoset resin

Methodology Applied

Scientific EffectVacuum pressure: Vacuum

Data Source

PatentEP2585287B1Composite structures having integrated stiffeners and method of making the same

Publication Date: 2014.10.01 THE BOEING CO

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AI summary

A composite structure is made by placing a stiffener preform and a composite structure reinforcement on a tool. The preform and the reinforcement are vacuum bagged processed and co-infused with a thermoset resin to form a stiffened, unitized structure.