Composite Consolidation via Hydraulic Fluid Cycling
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Solution Overview
Problem
Current methods for manufacturing composite articles, such as ballistic armor, face challenges including high-pressure requirements for optimal ballistic performance, air entrapment issues, and inefficiencies in production time and tooling costs, particularly with axial pressing and autoclave processes.
Innovation Solution
A programmable system for pressure and thermal cycling using a closed liquid-filled circuit with hydraulic pressurization, circulation, heating, and cooling systems, employing silicone oil and a heat-sealable plastic bag to consolidate composite articles, allowing for increased pressure and uniform processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high axial pressure (350 bar) is applied to consolidate composite articles for optimal ballistic performance, then ballistic performance increases by approximately 10%, but the required press capacity increases to 270 tons per square meter, making the equipment expensive and uncommon
Solution Approach 1:
The patent employs hydraulic pressurization system with fluid-filled circuit to generate and distribute high consolidation pressure uniformly across the composite article. The hydraulic system allows achievement of high pressure (350 bar) with more manageable press capacity by distributing force through fluid medium, resolving the contradiction between high ballistic performance requirement and excessive press capacity demand.
Solution Approach 2:
The invention transitions from uniaxial compression to multi-directional consolidation by applying pressure through fluid saturation from all directions. This dimensional change allows uniform consolidation without requiring extremely high axial force, reducing the press capacity requirement while maintaining optimal ballistic performance.
2Ease of manufacture
If conventional axial pressing is used to consolidate composite articles, then manufacturing is simpler, but air entrapment occurs between layers creating bubbles and delamination areas
Solution Approach 1:
The patent uses hydraulic fluid to saturate the composite stack from all directions, allowing air bubbles to be displaced and evacuated during consolidation. This fluid-based approach maintains manufacturing simplicity while eliminating air entrapment issues that plague conventional axial pressing, achieving uniform consolidation without delamination.
Solution Approach 2:
The invention employs flexible consolidation chambers or bags that conform to the composite article shape and allow uniform pressure distribution. These flexible enclosures enable complete saturation of the material stack while providing escape paths for trapped air, resolving the contradiction between simple manufacturing and uniform consolidation.
3Manufacturing precision
If conventional axial pressing with rigid metallic matched die sets is used, then tooling provides precise geometry control, but production speed is slow with cycle time of approximately 45 minutes per SAPI due to heating and cooling requirements
Solution Approach 1:
The patent utilizes hydraulic pressurization with fluid circulation systems that enable rapid pressure cycling and temperature control. This allows faster consolidation cycles compared to conventional axial pressing, increasing production speed while maintaining geometry control through fluid-filled chambers that conform to the desired article shape.
Solution Approach 2:
The invention changes the consolidation parameters by using fluid pressure and temperature cycling instead of slow axial compression with extended heating/cooling periods. By adjusting pressure, temperature, and fluid circulation rates, the process achieves both geometric precision and faster production cycles.
4Manufacturing precision
If incremental pressure ramping is applied to counter air entrapment during axial pressing, then air bubbles are reduced, but cycle time is extended
Solution Approach 1:
The patent applies hydraulic pressure from the beginning of the cycle, allowing air to be progressively displaced and evacuated as the fluid saturates the material stack. This eliminates the need for incremental pressure ramping, achieving uniform consolidation without extending cycle time.
Solution Approach 2:
The invention performs preliminary air evacuation by allowing fluid to penetrate and displace air before full consolidation pressure is applied. This preliminary action removes air entrapment issues upfront, enabling rapid subsequent consolidation without time-consuming incremental pressure increases.
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 enhances ballistic performance, reduces weight, and significantly decreases production time by enabling higher consolidation pressures and minimizing air entrapment, while also reducing the need for expensive and complex tooling.
Implementation Method 1
a processing fluid pressurisation system having means to increase or decrease pressure within the closed processing fluid filled circuit
Implementation Method 2
an external processing fluid heating system fluidly connected to the closed processing liquid filled circuit
Implementation Method 3
an external processing fluid cooling system fluidly connected to the closed processing liquid filled circuit
Implementation Method 4
a sealable membrane to maintain the composite article in a pressure below atmospheric pressure prior to the application of external processing fluid pressure
Data Source
AI summary
A method and apparatus for manufacturing composite articles such as laminate ballistic protection and structural reinforcements. The method involves placing a composite assembly in a sealable membrane system, e.g. a vacuum bag and placing the vacuum bag in a pressure vessel to apply heat and pressure to the composite assembly, thereby manufacturing a composite article. The apparatus comprises: a pressure vessel; a source of processing liquid to apply isostatic pressure to the vacuum bag; processing liquid heating, cooling, pressurizing and circulating means; and a control system to control the heating, cooling and pressurizing means. The sealable membrane system may preferably comprise: a sealable membrane to separate the composite article from the processing liquid and maintain the composite article below atmospheric pressure; and a membrane to cushion the composite article and resist adhesion of the article to other membranes. The processing liquid is preferably silicone oil.