Vented Form for Composite Laminate Curing
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Solution Overview
Problem
The existing methods for fabricating composite aerostructure articles, such as co-curing with honeycomb cores, result in strength loss due to dimpling and require additional plies that increase weight and cost, while traditional mandrels can cause distortion and require secondary bonding processes.
Innovation Solution
A fabrication process using a vented form that eliminates the need for rigid or inflatable mandrels by allowing pressure equalization within the form, which is made of lightweight materials like paper, and becomes a permanent part of the composite laminate product, facilitating single-stage curing and reducing manufacturing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If co-curing with honeycomb core is used, then manufacturing steps are reduced, but strength is lost due to dimpling of composite plies
Solution Approach 1:
A compressible foam core is introduced as an intermediary element between the inner and outer composite skins. The foam core serves as a mediator that distributes autoclave pressure uniformly, preventing the dimpling effect that occurs with traditional honeycomb cores during co-curing processes.
Solution Approach 2:
The patent changes the physical properties of the core material from rigid honeycomb structure to compressible foam structure. This parameter change allows the core to deform under pressure, absorbing stress and preventing ply dimpling while maintaining structural integrity during curing.
2Strength
If additional plies are added to compensate for strength loss, then strength is improved, but weight and cost increase
Solution Approach 1:
The foam core replicates the load-bearing function of traditional honeycomb cores but with superior pressure distribution characteristics. This allows the structure to maintain or improve strength without adding weight, as the foam's compressibility provides inherent stress management.
3Stability of the object's composition
If traditional rigid mandrels are used, then structural support is provided, but distortion occurs and secondary bonding processes are required
Solution Approach 1:
The mandrel transitions from a rigid, static structure to a compliant, dynamic structure that can deform under autoclave pressure. This dynamic response allows the mandrel to accommodate pressure changes without causing distortion, eliminating the need for secondary bonding processes.
Solution Approach 2:
The mandrel material properties are changed from rigid to compliant, allowing it to flex and adapt to pressure changes during curing. This parameter change in material stiffness prevents distortion while maintaining structural support throughout the manufacturing process.
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 prevents collapse of the composite laminate under autoclave pressure, reduces weight and cost, and allows for the formation of complex shapes incompatible with traditional mandrels, while maintaining structural integrity and reducing labor costs.
Implementation Method 1
a vacuum applied within the bag, to bond the sections
Implementation Method 2
The bagged form and laminate assembly are then autoclaved to cure the bonded laminate sections
Data Source
AI summary
A fabrication process using an integrated form includes assembling at least two independent sections of composite laminate about a form, such that at least a portion of the sections overlap. A bonding agent is applied between the sections, at the overlap, and the form and laminate assembly are vacuum-bagged. The bag is sealed around a vent in the form, and about the laminate assembly. A vacuum is applied within the bag, to bond the sections, and the bagged assembly is autoclaved, to cure the bonded laminate sections. The vent allows equalization of autoclave pressures within and outside of the form, to prevent crushing or deformation of the form during cure. The form becomes an integral and permanent part of the final composite product.