Multilayer Offshore Pipe Structure Balancing Strength and Flexibility
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Solution Overview
Problem
Existing composite pipes for offshore oil and gas extraction face challenges with mechanical strength and thermal resistance due to the glass transition temperature (Tg) of the matrix being lower than the operating temperature, leading to rubbery behavior and reduced fatigue resistance, while high Tg materials result in rigid sealing sheaths that limit flexibility and pose processing difficulties.
Innovation Solution
A multilayer structure comprising a semi-crystalline thermoplastic polymer sealing layer with a low melting point and a high Tg composite reinforcement polymer, allowing for good adhesion and maintaining mechanical strength and flexibility, with the sealing layer processed at moderate temperatures and the composite reinforcement remaining in its glassy state for high rigidity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a polymer matrix with high glass transition temperature (Tg) is used for composite reinforcement, then mechanical strength and rigidity are improved, but the sealing sheath becomes rigid and flexibility is reduced
Solution Approach 1:
The pipe is divided into two distinct layers with different material properties: a sealing sheath layer made of low-Tg polymer for flexibility and a composite reinforcement layer made of high-Tg polymer for mechanical strength. This segmentation allows each layer to independently fulfill its specific function without compromising the other.
Solution Approach 2:
Different regions of the pipe structure are assigned different material qualities: the inner sealing sheath uses a polymer with low glass transition temperature to provide flexibility and fatigue resistance, while the outer composite reinforcement uses a polymer with high glass transition temperature to provide rigidity and mechanical strength. Each layer's material properties are optimized for its specific functional requirements.
2Strength
If a polymer matrix with high glass transition temperature (Tg) is used for composite reinforcement, then mechanical strength is improved, but processing temperature increases
Solution Approach 1:
The processing temperature challenge is resolved by segmenting the structure into two layers with different thermal requirements. The sealing sheath layer can be processed at moderate temperatures suitable for low-Tg polymers, while the composite reinforcement layer uses high-Tg polymer that requires higher processing temperatures, but only for the reinforcement layer itself.
Solution Approach 2:
The sealing sheath is extruded first at moderate temperatures, and then the composite reinforcement layer is applied subsequently. This preliminary action allows the sealing sheath to be processed without exposing it to the high temperatures required for the composite reinforcement, thus protecting the sealing sheath's material properties while still achieving the high mechanical strength of the overall structure.
3Reliability
If the same polymer is used for both sealing sheath and composite matrix, then adhesion is improved, but the composite matrix becomes rubbery at operating temperature
Solution Approach 1:
Different material qualities are assigned to different layers: the sealing sheath uses a polymer with low glass transition temperature to remain flexible at operating temperatures, while the composite reinforcement uses a polymer with high glass transition temperature to maintain rigidity and mechanical strength. The adhesion between these dissimilar polymers is achieved through surface treatment or chemical coupling agents.
Solution Approach 2:
The invention uses a composite structure combining two different polymers with complementary properties. The sealing sheath polymer provides flexibility and fatigue resistance, while the composite matrix polymer provides rigidity and mechanical strength. The combination creates a composite material system where the weaknesses of one polymer are compensated by the strengths of the other.
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 solution provides enhanced mechanical strength, flexibility, and chemical resistance, ensuring durable adhesion and improved fatigue resistance without increasing extrusion temperatures, addressing the limitations of previous materials.
Implementation Method 1
said sealing layers consisting of a composition predominantly comprising at least one semi-crystalline thermoplastic polymer P1i (i=1 to n, n being the number of sealing layers), the Tm of which, as measured according to ISO 11357-3: 2013, is less than 280° C.
Implementation Method 2
said at least one composite reinforcing layers consisting of a fibrous material in the form of continuous fibers impregnated with a composition predominantly comprising at least one thermoplastic polymer P2j, (j=1 to m, m being the number of reinforcing layers), in particular semi-crystalline, said thermoplastic polymer P2j having a Tg, as measured according to ISO 11357-3: 2013, greater than the maximum temperature of use of said structure (Tu), with Tg≥Tu+20° C.
Implementation Method 3
said innermost composite reinforcing layer being welded to said outermost adjacent sealing layer
Data Source
AI summary
A multilayer structure for transporting or storing gas or for exploiting oil or gas deposits under the sea, including, from the inside to the outside, at least one sealing layer and at least one composite reinforcing layer, the innermost composite reinforcing layer being welded to the outermost adjacent sealing layer, the sealing layers of a composition including at least one semi-crystalline thermoplastic polymer, the Tm of which is less than 280° C., wherein at least one of the composite reinforcing layers of a fibrous material in the form of continuous fibers impregnated with a composition including at least one thermoplastic polymer, the thermoplastic polymer having a Tg greater than the maximum temperature of use of the structure (Tu), with Tg≥Tu+20° C., Tu being greater than 50° C., and a multilayer structure selected from a reservoir, a pipe or a tube for transporting or storing hydrogen being excluded.