PEEK Composite Pipe Crystallinity Control for Fatigue Resistance
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Solution Overview
Problem
Composite pipes used in high-pressure fluid transportation and exposed to external forces often experience premature failure due to internal stress caused by varying crystallinity across their wall thickness, leading to fatigue and cracking.
Innovation Solution
A method of producing composite pipes with reduced internal stress by controlling the crystallinity of the polymeric material, specifically using FTIR to assess and adjust the crystallinity of the outer region to be less than 21%, and applying a reinforcing means with a thermoplastic resin and fibrous material to bond with the pipe, increasing the crystallinity uniformly across the pipe wall.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the inner pipe expands and contracts due to pressure changes, then the pipe can transport fluid effectively, but fatigue and cracking occur leading to premature failure
Solution Approach 1:
The patent bonds the reinforcing tape to the inner pipe using a bonding agent, merging the tape and pipe into a composite structure that moves as one unit. This eliminates relative motion between the tape and pipe during pressure cycles, preventing fatigue at the interface while maintaining the pipe's ability to expand and contract for fluid transportation.
Solution Approach 2:
The patent creates a composite structure by bonding the reinforcing tape (comprising fibrous material embedded in thermoplastic or thermosetting resin) to the inner pipe. This composite construction combines the flexibility needed for pressure-induced expansion with the strength of the reinforcing tape, preventing cracking and premature failure while maintaining operational capability.
2Ease of manufacture
If the reinforcing tape is not bonded to the inner pipe, then manufacturing is simpler, but internal stress causes premature failure
Solution Approach 1:
The patent introduces a bonding agent to merge the reinforcing tape with the inner pipe, creating a unified structure that prevents relative motion and reduces internal stress. This bonding step adds minimal manufacturing complexity while dramatically improving pipe longevity by preventing premature failure due to internal stress.
3Productivity
If the crystallinity varies across the pipe wall thickness, then the pipe can be manufactured efficiently, but internal stress increases leading to failure
Solution Approach 1:
The patent controls the crystallinity of the polymeric material in the reinforcing tape by adjusting manufacturing parameters such as cooling rate and temperature. By optimizing these parameters, the patent achieves uniform crystallinity across the pipe wall thickness, reducing internal stress and preventing failure while maintaining efficient manufacturing processes.
4Ease of operation
If the pipe is subjected to high pressure, then fluid transportation capability is improved, but the inner pipe may crack due to fatigue
Solution Approach 1:
The patent creates a composite structure by bonding the reinforcing tape to the inner pipe. This composite construction provides the additional strength needed to resist cracking under high pressure while maintaining the pipe's ability to expand and contract for effective fluid transportation. The bonding ensures the reinforcing tape and pipe move together, distributing stress evenly.
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
The method reduces internal stress and extends the lifetime of composite pipes by ensuring uniform crystallinity and bonding the reinforcing means with the pipe, thereby enhancing mechanical and thermal resistance and preventing premature failure.
Implementation Method 1
FTIR may be used to assess crystallinity and this may be used to assess the level of crystallinity at a surface and/or across the thickness of a sample
Implementation Method 2
heating it to a temperature above the melting temperature (Tm) of said polymeric material
Implementation Method 3
at least part of the outer region of the pipe P1 melts
Implementation Method 4
crystallinity of the outer region is increased by heating it to a temperature above the melting temperature (Tm) of said polymeric material such that at least part of the outer region of the pipe P1 melts
Implementation Method 5
The reinforcing means may comprise a thermoplastic resin and fibrous material and the reinforcing means is bonded with the pipe with the thermoplastic resin fusing with the polymeric material of the pipe
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
A composite pipe comprises a polyetheretherketone innermost pipe (2) around which a reinforcing overwrap (4) is arranged. A protective sheath (5) surrounds the overwrap (4). Such a composite pipe may be made by selecting a polyetheretherketone pipe having an outer region having a crystallinity of less than 25%; overlaying the selected pipe with overwrap (4); and subjecting the combination to heat, thereby causing the crystallinity of the outer region of the polyetheretherketone pipe to increase. The method reduces the risk of pipe failure.