Tank Pipe Curing Temperature Control for Residual Stress
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Solution Overview
Problem
During the manufacturing process of tanks with fiber reinforced resin reinforcement layers, heating after helical winding causes the resin in the pipe to soften again, leading to a decrease in strength and potential breakage due to residual stress exceeding the pipe's strength.
Innovation Solution
The manufacturing method involves forming a tank with a reinforcement layer comprising a first layer made from a pipe fitted to the liner, and a second layer covering the pipe. The pipe is formed by winding a first fiber reinforced resin around a mandrel and thermally curing it under specific conditions, ensuring the second layer is cured at a temperature where the shear strength of the first resin remains higher than the residual stress in the pipe.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If heating is performed after helical winding to form the second layer, then the second fiber reinforced resin can be thermally cured, but the resin in the pipe softens again due to heat causing the pipe strength to decrease and potential breakage
Solution Approach 1:
The patent applies parameter changes by carefully controlling the heating temperature during thermal curing of the second fiber reinforced resin. The heating temperature is set to a range that enables curing of the second resin while maintaining the pipe strength above the residual stress level, thus preventing pipe breakage. This resolves the contradiction by optimizing the temperature parameter to simultaneously achieve curing and strength maintenance.
2Ease of manufacture
If the pipe is formed by winding fiber reinforced resin around a mandrel and thermally curing it, then the pipe structure is created, but residual stress is generated in the pipe that may exceed the pipe strength during subsequent heating
Solution Approach 1:
The patent applies preliminary action by pre-forming the pipe with controlled residual stress through the winding and thermal curing process around a mandrel. The pipe is manufactured in advance with optimized curing conditions that minimize residual stress generation, preparing it for subsequent heating operations without breakage. This resolves the contradiction by performing the pipe formation with predetermined stress control.
Solution Approach 2:
The patent controls the thermal curing parameters during pipe formation to optimize the residual stress level. By adjusting the curing temperature and time parameters, the residual stress in the pipe is kept at an acceptable level that prevents breakage during subsequent heating of the second layer, thus resolving the stress-related contradiction.
3Reliability
If the shear strength of the first resin is kept higher than the residual stress in the pipe during second layer formation, then pipe breakage is suppressed, but the heating temperature must be limited
Solution Approach 1:
The patent resolves this contradiction by optimizing the heating temperature parameter within a specific range that simultaneously ensures pipe integrity and enables efficient manufacturing. The temperature is controlled to maintain shear strength above residual stress while being high enough for effective curing of the second resin, thus achieving both reliability and productivity.
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 suppresses breakage of the pipe during the formation of the second layer by maintaining the shear strength of the first resin above the residual stress, thereby enhancing the structural integrity of the tank.
Implementation Method 1
thermally curing the first fiber reinforced resin wound around the mandrel under a first heating condition
Implementation Method 2
thermally curing the second fiber reinforced resin wound around the liner under a second heating condition
Implementation Method 3
the pipe and the mandrel have the same coefficient of linear expansion, the pipe and the mandrel thermally expand at the same rate when the pipe is formed
Data Source
AI summary
A manufacturing method for a tank including a liner and a reinforcement layer having a first layer made up of a pipe fitted to an outer surface of the liner and a second layer covering the pipe includes forming the pipe by winding first fiber reinforced resin containing a first fiber and a first resin around a mandrel and thermally curing the first fiber reinforced resin under a first condition, forming the first layer by fitting the pipe to the liner, and forming the second layer by winding a second fiber reinforced resin containing a second fiber and a second resin around the liner to cover the first layer and thermally curing the second fiber reinforced resin under a second condition. The second condition defines an upper limit temperature at which a shear strength of the first resin is kept higher than a residual stress in the pipe.