Counteracting Pressure Composite Tooling for Shear Web Distortion
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Solution Overview
Problem
Existing methods for producing large, complex-shaped, three-dimensional fiber reinforced composite structures often result in buckling, warping, or distortion of structural features during the autoclave and cure process, particularly for components like shear webs and plates that do not come into primary contact with the tooling.
Innovation Solution
The use of counteracting pressures applied to a structural lay-up of fiber plies, combined with high-modulus stiffeners abutted against structural features, maintains the desired shape of these features during the manufacturing process, minimizing distortion. This involves pressurizable members with sufficient rigidity and a modulus of elasticity greater than the resin, along with strategically positioned stiffeners to counteract pressures and maintain geometric accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If plaster mandrels are used to form complex-shaped composite structures, then the manufacturing process is simple and cost-effective, but the structural strength and geometric precision are insufficient for high-strength components
Solution Approach 1:
The tooling system is segmented into multiple functional components: a rigid mold surface for geometric precision, removable plaster mandrels for complex shape formation, and auxiliary support structures. This segmentation allows each component to fulfill its specific function optimally while working together as an integrated system.
Solution Approach 2:
The invention employs composite tooling structures combining rigid materials (metal or hard composite mold surfaces) with plaster mandrels. This composite approach leverages the strength and precision of rigid materials while utilizing the shape-forming capabilities of plaster, resolving the contradiction between manufacturing ease and structural strength.
2Manufacturing precision
If counteracting pressures are applied during autoclave curing, then geometric precision is maintained, but the process complexity increases
Solution Approach 1:
Counteracting pressures are applied during autoclave curing to compensate for the softening and deformation of plaster mandrels under heat and resin saturation. The counterpressure system acts as a mechanical counterweight that maintains geometric precision by opposing the detrimental effects of thermal and chemical processes.
Solution Approach 2:
The mold surface and support structures are pre-configured with precise geometric features before the curing process begins. This preliminary action ensures that the final composite structure achieves the desired geometric precision without requiring extensive post-processing or complex real-time adjustments during curing.
3Stability of the object's composition
If high-modulus stiffeners are positioned against structural features, then buckling and warping are prevented, but the device complexity increases
Solution Approach 1:
High-modulus stiffeners are pre-positioned against critical structural features such as shear webs and plates before the resin infusion and curing processes. This preliminary positioning ensures that these vulnerable areas are supported during the curing process, preventing buckling and warping without requiring complex active control systems during manufacturing.
Solution Approach 2:
Stiffeners are strategically positioned only at critical locations where buckling and warping are most likely to occur, such as shear webs, plates, and other structural features not in primary contact with the mold surface. This localized approach provides maximum structural stability with minimal additional complexity, rather than uniformly reinforcing the entire structure.
4Ease of manufacture
If plaster mandrels are removed by striking and crumbling, then the hollow composite structure is released, but surface quality and dimensional accuracy deteriorate
Solution Approach 1:
A release layer or barrier coating is applied to the rigid mold surface before placing the plaster mandrel. This preliminary action facilitates easy mandrel removal by preventing adhesion between the plaster and mold surface, allowing the mandrel to be struck and crumbled without damaging the composite structure's surface quality or dimensional accuracy.
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 effectively prevents buckling and warping, ensuring the production of complex-shaped composite structures with precise geometric features, enhancing the structural integrity and reducing the likelihood of unwanted distortions, thereby improving the manufacturing process for aerospace and other high-strength components.
Implementation Method 1
pressurizing an outer surface of the composite assembly with a first pressure; and pressurizing the inner surface of the pressurizable members with a second pressure
Implementation Method 2
the at least one stiffener having a modulus of elasticity that is substantially larger than a modulus of elasticity of the resin
Data Source
AI summary
A complex-shaped, three-dimensional fiber reinforced composite structure may be formed by using counteracting pressures applied to a structural lay-up of wetted fibers. The wetted fibers are arranged on pressurizable members and may be configured to include internal structural features, such as shear webs. A reinforcement stiffener may be located adjacent to at least one of the pressurizable members and the wetted fibers that form the internal structural feature. The reinforcement stiffener includes a modulus of elasticity that is substantially higher than a modulus of elasticity of the resin used to wet the fibers. In one embodiment, the reinforcement stiffener may be received in a pocket of one of the pressurizable members and may include a releasing agent that permits removal of the stiffener after the composite structure has been pressurized and cured.