Phase Change Bladder for Composite Cavity Formation
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Solution Overview
Problem
Existing methods for manufacturing complex hollow composite structures face challenges in providing internal support during curing, as multi-piece hard tools and mandrels are difficult to remove, and bladders require ports for pressurization, limiting the types of parts that can be made and failing to establish support for fully enclosed volumes.
Innovation Solution
A method involving a bladder with a phase change material that expands during curing to apply pressure, allowing the formation of internal cavities and enabling the bladder to remain within the composite structure, thus providing internal support without the need for removal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If multi-piece hard tools and mandrels are used to provide internal support during curing, then structural support is provided, but the tooling is difficult to remove and complete removal can be an issue
Solution Approach 1:
The patent utilizes phase change material that transitions from solid to liquid state during the curing process. This phase transition allows the material to change from a rigid support structure to a removable liquid state, solving the contradiction between providing structural support during curing and enabling easy removal afterward. The material melts and can be drained or pumped out of the composite structure.
Solution Approach 2:
The invention changes the physical state parameters of the support material from solid to liquid through temperature control. By heating the composite structure during curing, the support material undergoes parameter change (melting point transition), transforming from a rigid form-providing state to a fluid removable state, thus resolving the removal difficulty.
2Stress or pressure
If bladders are used to provide internal support, then pressurization capability is provided, but ports are required which limits the types of parts that can be made and fails to establish support for fully enclosed volumes
Solution Approach 1:
The patent employs phase change material that can be introduced in solid or liquid form and then transitions to provide pressurization during curing. This eliminates the need for pre-installed ports or openings, as the material can be introduced through minimal access points and then transforms to fill and pressurize the entire enclosed volume, enabling fabrication of fully enclosed composite structures.
Solution Approach 2:
The invention extracts the port requirement from the system by using phase change material that can be introduced through minimal or no ports. The material is introduced in a compact form (solid or viscous liquid) and then transforms to fill the entire volume, eliminating the need for permanent port openings and enabling fully enclosed structures.
3Shape
If phase change material is used to expand and apply pressure during curing, then internal cavities can be formed and the bladder can remain within the composite structure, but the system complexity increases
Solution Approach 1:
The phase change material serves multiple functions automatically: it provides structural support during curing, applies pressurization through its own phase transition, and forms the desired internal cavity shape without requiring external control systems. The material self-regulates its expansion and pressurization based on temperature conditions, eliminating the need for complex external pressurization systems.
Solution Approach 2:
The phase change material performs multiple functions simultaneously: structural support, pressurization, cavity formation, and potential post-cure removal. This multi-functionality reduces overall system complexity by replacing what would otherwise require separate systems for each function with a single versatile material.
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
Enables the fabrication of complex hollow composite structures with internal geometries, reducing weight and maintaining structural integrity while allowing the bladder to remain inside, addressing the limitations of existing support methods.
Implementation Method 1
the phase change material contained within the bladder to change to a second phase to expand from the first volume to a second volume
Implementation Method 2
change to a second phase to expand from the first volume to a second volume and apply a pressure
Data Source
AI summary
A method of fabricating a composite structure includes laying at least one composite ply about a bladder, the bladder comprising a phase change material in a first phase having a first volume, positioning an outer mold about the bladder and the at least one composite ply, and curing the at least one composite ply to form the composite structure. Curing causes the phase change material contained within the bladder to change to a second phase to expand from the first volume to a second volume and apply a pressure to an interior surface of the composite ply and press an outer surface of the composite ply against the outer mold to form an interior cavity. The bladder is not removable from the formed interior cavity.