Composite Flexible Pipe Armour With Woven Tape Against Cracking
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Solution Overview
Problem
Conventional metallic tensile armours for flexible pipes used in offshore oil exploitation face weight issues at great depths, where the increased section of steel armours adds more weight than axial strength, and composite armours have lower compressive strength, leading to transverse cracking and degradation under high external pressures.
Innovation Solution
A composite armour design featuring a unidirectional composite profile with a woven reinforcement tape, where the warp threads are parallel and weft threads are perpendicular to the longitudinal direction, providing enhanced transverse strength and preventing incipient cracks while maintaining longitudinal strength, using carbon fibres embedded in a polymer resin with a high fibre volume ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If metallic tensile armours are used to provide longitudinal strength, then the axial strength is improved, but the weight increases significantly at great depths
Solution Approach 1:
The patent replaces conventional metallic tensile armours with composite armours made of carbon fibres embedded in a polymer resin matrix. This composite material provides the necessary longitudinal tensile strength while significantly reducing the weight compared to steel armours, making the flexible pipe suitable for deepwater applications where weight is a critical factor.
2Weight of moving object
If composite armours are used to reduce weight, then the weight is reduced, but the transverse strength decreases leading to cracking under external pressure
Solution Approach 1:
The patent applies a woven reinforcement tape specifically to the transverse direction (perpendicular to the longitudinal axis) of the composite armour. This tape, made of fibres impregnated with polymer material, provides localized transverse reinforcement where it is most needed to prevent cracking under external hydrostatic pressure, while maintaining the low-weight advantage of the composite structure.
Solution Approach 2:
The patent creates a hybrid composite structure combining unidirectional carbon fibre reinforcement for longitudinal strength with woven fibre tape reinforcement for transverse strength. This multi-directional composite approach ensures comprehensive mechanical performance in both longitudinal and transverse directions while maintaining overall light weight.
3Strength
If the section of steel armours is increased to provide axial strength at great depths, then the axial strength is improved, but the weight increases more than the strength
Solution Approach 1:
The patent changes the material parameters from dense steel to lightweight composite materials with high specific strength (strength-to-weight ratio). By using carbon fibres in a polymer matrix, the armour achieves the required axial strength at great depths without the excessive weight penalty that would result from increasing the section of steel armours.
Data Source
AI summary
A composite armour for a flexible pipe includes a composite profile and a reinforcement tape. The composite profile includes longitudinally oriented reinforcement fibres embedded in a polymer matrix. The reinforcement tape includes a woven tape comprising fibres impregnated with a polymer material, in such a way that the weft thread of the reinforcement tape is orthogonal to the longitudinal direction of the profile, and the warp thread is parallel to the longitudinal direction of the profile.