Hollow Support Element Removal in Composite Moulding
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Solution Overview
Problem
The existing methods for removing support elements from fibre-reinforced composite parts, such as inflatable bladders, either require large openings that weaken the part or use dissolvable materials that lack sufficient strength to support carbon fibre mats and resin during the resin transfer moulding process.
Innovation Solution
A method involving heating a liquid to a temperature equal to or above the softening temperature of the support element material, injecting it into the part to deform the material, and removing the deformed material and liquid through a small opening, which can be done using polyethylene glycol or polypropylene glycol, and optionally mixing with gas to aid in the removal process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the support element is removed in one piece by deflating and pulling it through the opening, then the removal process is simple, but the opening must be sufficiently large which reduces the strength of the part
Solution Approach 1:
The support element is divided into multiple segments that can be removed sequentially through a small opening. The bladder is collapsed into a compact form and removed in stages rather than as a single large piece, allowing passage through a small opening while maintaining part strength.
Solution Approach 2:
The material properties of the support element are changed by heating it to above its melting point, transforming it from a solid state to a molten state. This parameter change allows the support element to be removed through a small opening without requiring a large opening in the part, as the molten material can flow through the small opening and be removed in a controlled manner.
2Ease of operation
If the bladder is made from a polymer such as Polyethylene and pulled out mechanically at ambient temperature, then the removal process is straightforward, but the rigidity of the bladder makes it difficult to remove
Solution Approach 1:
The temperature parameter of the bladder material is changed by heating it to above its melting point. This transforms the bladder from a rigid solid state to a molten state, making it flexible and easy to remove through a small opening. The material loses its rigidity at the elevated temperature, allowing straightforward removal without mechanical difficulty.
3Ease of operation
If the bladder is heated to remove it, then the removal process becomes easier, but the heating weakens the bladder substantially rendering it subject to breakage
Solution Approach 1:
The bladder is heated to above its melting point before the removal process begins. This preliminary heating action transforms the material state to molten, making it easy to remove. The heating is performed in advance while the bladder is still contained within the mould, and the molten material is then removed through a small opening in a controlled manner, preventing breakage.
4Area of stationary object
If a dissolvable material such as PVA is used for the support element, then a smaller opening is required for removal, but the material does not have sufficient strength to support the carbon fibres mats and resin
Solution Approach 1:
The material properties of the support element are changed by selecting a material with a melting point below the RTM process temperature but above ambient temperature. This allows the support element to maintain sufficient strength during the moulding process while being removable through a small opening after heating to above its melting point. The material transitions from a strong solid state during moulding to a molten state for removal.
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 method effectively reduces the weight of the part by removing the support element without compromising the strength of the fibre-reinforced composite, allowing for smaller removal openings and using materials that can support the structural integrity of the part during the process.
Implementation Method 1
heating a liquid to a temperature at least equal to the softening temperature of the material; injecting the heated liquid into an opening in the moulded part to deform the material
Data Source
AI summary
A method for removing a hollow support element (17) from within a moulded part (15) to form a cavity (25) within the moulded part, the hollow support element being disposed within the moulded part and composed of material having a softening temperature, the method comprising: heating a liquid (20) to a temperature at least equal to the softening temperature of the material; injecting the heated liquid into an opening (24) in the moulded part to deform the material; and removing deformed material and liquid from the cavity.