Braided Composite Hole Formation Without Fibre Severance
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Solution Overview
Problem
Existing methods for forming holes in composite structures, such as carbon fibre materials, often weaken the structure by severing fibres, which reduces their strength and ability to transfer forces like torque, especially in high-specification applications like aerospace.
Innovation Solution
A method involving a mandrel with conical parts and a braiding machine is arranged to prevent fibre tows from intersecting with the vertex of the conical parts during the braiding process, allowing for the formation of holes without fibre severance by adjusting variables like the height and angle of the conical parts, and the relative positions of the mandrel and braiding machine.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If holes are formed by drilling or machining after the composite structure is fully formed and cured, then holes can be created for joints and connections, but the strength of the structure is significantly reduced due to fibre severance
Solution Approach 1:
The conical parts are incorporated into the mandrel before the braiding process begins. During braiding, the fibre tows are routed around these conical parts, which automatically create hole formations as the fibres are laid. This preliminary arrangement of the mandrel geometry ensures that holes are formed during the composite manufacturing process itself, rather than requiring subsequent machining that would sever fibres and weaken the structure.
Solution Approach 2:
The conical parts on the mandrel serve as intermediary elements that facilitate hole formation without requiring direct fibre severance. The fibres are guided around these conical intermediaries during braiding, allowing hole creation while maintaining continuous fibre paths. The conical parts act as temporary form-giving elements that enable the desired hole geometry without compromising structural integrity.
2Strength
If the braiding machine runs slowly with manual adjustment to avoid fibres intersecting the vertex of the cone, then fibre integrity is maintained, but manufacturing time and labour increase significantly
Solution Approach 1:
The critical parameter change involves positioning the vertex of the conical part at a specific location relative to the braiding machine's fibre path. By carefully selecting the vertex position, the fibres are naturally routed around the cone without intersecting it, eliminating the need for slow manual adjustments. This parameter optimization allows the braiding machine to operate at normal speeds while maintaining fibre integrity.
Solution Approach 2:
The mandrel with conical parts is designed to automatically guide the fibres around the vertex during the braiding process. The geometry of the conical parts self-regulates the fibre path, eliminating the need for manual intervention or slow-speed operation. The system serves itself by using the mandrel geometry to prevent fibre intersection without requiring external control or adjustment during manufacturing.
3Strength
If manual adjustment is used to move fibre tows away from the vertex of the cone during braiding, then fibre breakage is avoided, but health and safety hazards arise when personnel must remain outside the operational area
Solution Approach 1:
The mandrel with conical parts is designed to automatically guide the fibres around the vertex during the braiding process. The geometry of the conical parts self-regulates the fibre path, eliminating the need for manual intervention or slow-speed operation. The system serves itself by using the mandrel geometry to prevent fibre intersection without requiring external control or adjustment during manufacturing.
Data Source
Figure 1a~1b
Figure 1c~1d
Figure 2
AI summary
A method of manufacturing a composite structure (2) comprising providing a mandrel (4) comprising a base part (6) and at least one conical part (8a-d). The base part (6) comprises an elongate shaft. The base part (6) of the mandrel (4) comprises a cylindrical surface around a longitudinal axis of the base part (6). The at least one conical part (8a-d) extends from the cylindrical surface of the base part (6). The mandrel (4) and a braiding machine (24) are moved relative to one another such that fibre tows (30) are braided over at least the base part (6) of the mandrel (4). The mandrel (4) and the braiding machine (24) are arranged such that during the braiding process, none of the fibre tows (30) intersect with a vertex (10) of the at least one conical part (8a-d) of the mandrel (4).