Composite Product Core Structure for RTM Layer Thickness Control
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Solution Overview
Problem
The existing resin transfer moulding (RTM) method for producing composite products often results in hollow composite products that lack sufficient stiffness and strength, requiring additional steps like filling with structural foam cores, and has limited control over layer thickness.
Innovation Solution
A method involving an additive manufacturing process to create a core structure with a fluid-impermeable shell enclosing an internal chamber, allowing for precise control of fluid pressure and layer thickness, which is integrated into the mould with reinforcement fibers to form a composite product under controlled moulding pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a bladder is placed inside the mould and pressurized to withstand high moulding pressure, then the hollow composite product can be formed, but the resulting composite product lacks sufficient stiffness and strength
Solution Approach 1:
The core structure is pre-formed with an internal chamber before the moulding process, allowing pressure to be applied in advance to position reinforcement fibers away from the center. This preliminary positioning ensures structural integrity without requiring additional filling steps later.
Solution Approach 2:
The core structure with internal chamber is nested within the mould, and reinforcement fibers are arranged around it. This nested arrangement allows the core structure to serve as both a positioning element and a structural support, eliminating the need for separate filling operations.
2Manufacturing precision
If a bladder is used to position reinforcement fibers away from the center, then hollow composite product is formed, but control on layer thickness is limited
Solution Approach 1:
The core structure features a non-uniform outer surface with varying distances from the center, creating different layer thicknesses in different regions. This local variation in geometry allows precise control over layer thickness distribution without complex mould adjustments.
Solution Approach 2:
Instead of controlling layer thickness through mould pressure or bladder positioning in one dimension, the invention uses the third dimension (radial distance from center) to define layer thickness. The outer surface of the core structure is designed with specific radial distances to achieve desired layer thicknesses.
Data Source
AI summary
A method is provided for preparing a composite product, the method comprising: forming a core structure having a plurality of layers, each layer being build by an additive manufacturing process; wherein the core structure has a shell substantially enclosing an internal chamber of the core structure, wherein the shell is fluid-impermeable, and wherein the outer surface of the shell has a predefined shape; introducing a fluid into the chamber of the core structure; arranging the core structure and reinforcement fibers in a mould, wherein the mould is arranged to accommodate the core structure including the reinforcement fibers, and wherein the reinforcement fibers and the outer surface of the shell are arranged in contact with each other; providing the reinforcement fibers and a resin on the outer surface of the shell of the core structure; and solidifying the resin to form the composite product inside the mould at a moulding pressure Pm, while controlling the fluid pressure PF of the fluid in the core structure.