This invention relates to techniques for inspecting materials. More specifically, this invention is in relation to techniques for inspecting composite joints and repairs.
Composite materials are increasingly being used in various industrial segments. The aerospace sector is the area that uses this type of material the most. However, the oil, gas and energy industries are following this trend, mainly as a function of the high resistance/weight relationship, immunity to corrosion, and the possibility of “cold” application of these materials. In the oil and gas industry, the possibility of cold application of joints and repairs is quite attractive, as it eliminates the need to isolate the environment and ensure it is free of the risks of combustion and explosion.
Two types of uses for composite materials are being established in the oil, gas, and energy industries: repairs using composite materials, and structural elements produced entirely out of composite materials. The first involves applying a layer of composite material over a metal structural element, either to serve as a barrier against corrosion, or as structural reinforcement. The second type involves mainly pipes and pressure vessels made completely of composite materials.
In the oil, gas, and energy industries, the history of failures with composite materials is predominantly related to defects in assembly or problems during application of coatings in the field. This is typical of repairs and protective coatings of composites and joints between pipes made of composite materials.
In both cases, the application conditions are usually unfavorable, resulting in a higher probability that defects will occur, such as: adhesion failures (on metal-composite interface and composite-composite interfaces); delamination (adhesion failures between the layers of the composite); inclusions (presence of bubbles and foreign objects between the composite layers), and non-uniform distribution of fibers in the composite. There may also be defects in the structure arising from the component manufacturing process.
Defects in protective coatings and repairs may compromise the efficacy of the protection or structural reinforcement. If not detected and corrected, defects in joints and connections of composite pipe structures may progress and lead to operational failures, producing the risk of product leakage.
Repairing metal pipes using composite materials has grown in the field; however the lack of effective field inspection techniques greatly restricts their use. Therefore, as these materials are currently used, it is necessary to inspect the coatings applied and repairs made in the field, as well as connections and joints in structures made of composite materials.
Shearography and thermography equipment are capable of performing non-destructive inspection of composite materials. However, detecting internal defects using shearography or thermography requires the generation of a thermal gradient (excitation) inside the composite. In addition to thermal excitation, shearography may also be used with vibrational excitation to detect defects.
The current state of the art contains some repair-monitoring techniques in which sensors are inserted inside the repair so it can be monitored continuously.
Document ES2368541B1, for example, reveals a procedure for repairing metal aeronautical structures using composite material. This method comprises inserting optical fiber between the structure of the airplane and the repair that uses composite material, allowing practical inspection of the integrity of the repair.
Document CN101561400B also reveals a method for repairing structural damage to an airplane using composite material, inserting optical fiber into the repair to monitor the integrity of the repair through fiber Bragg grating (FBG). Using this technique, the repair can be monitored in real time.
However, continuous (online) monitoring techniques are very expensive, as they require a system dedicated entirely to monitoring.
In the current state of the art, therefore, there is a need for a low-cost technique that will allow repairs or joints made of composite material to be inspected using thermal and/or vibrational excitation.
As will be further detailed below, this invention seeks to resolve the problem in the state of the art described above in a practical and efficient manner.
The main objective of this invention is to provide a low-cost, very effective system to inspect a repair or joint made of composite material applied to a structure.
In order to attain the objective described above, this invention provides a system for inspecting a repair or joint made of composite material applied to a structure, comprising at least one exciter or element that is excitable to a thermal and/or vibrational stimulus, or at least one exciter or excitable element being integrated in the repair or joint.
The detailed description presented below references the attached figures and their respective reference numbers.
First, please note that the following description will begin with the preferred realization of the invention. As will be evident to anyone skilled in the matter, however, the invention is not limited to this particular realization.
The system for inspecting a repair or joint made of composite material applied to a structure, according to this invention, comprises at least one exciter or element that is excitable to a thermal and/or vibrational stimulus, in which the at least one exciter or excitable element is integrated in the repair or joint.
Depending on the height of the repair, it may be necessary to use two or more layers of carbon fiber 2 to ensure excitation along the entire thickness of the composite repair 1. In the first realization, illustrated in
The system of this invention may also comprise at least one thermal connector 4 adapted to connect each one of the carbon fiber layers to a voltage source 5. Thus, the carbon fiber layers are thermally excited through at least one thermal connector 4.
Preferably, a first electric cable 6 connects the thermal connector 4 to the voltage source 5. Additionally, and also preferably, a second electric cable 7 connects the voltage source 5 to the electricity network (not shown).
The second realization of the system of this invention may also comprise at least one vibrational connector 11 adapted to connect and send the external signal to each of the actuators. Thus, each of the piezoelectric actuators 10 is connected to the adjacent actuators. Furthermore, the vibrational connector 11 receives the signal from an amplified signal generator 12 for harmonic vibration of varied frequency. The signal that is sent to the vibrational connector 11 is distributed to the piezoelectric actuators 10.
Optionally, as shown in
Analogous to the first realization, preferably, a first electric cable 6 connects the vibrational connector 11 to the amplified signal generator 12. Additionally, and also preferably, a second electric cable 7 connects the amplified signal generator 12 to the electricity network (not shown).
In the third realization, as well as in the first, at least one carbon fiber layer 2 is provided inside the joint so that it can receive an exterior thermal stimulus. Preferably, at least one layer of carbon fiber 2 is provided in the adhesive layer 21 (shown in the upper part of
Similar to the first realization, preferably, a first electric cable 6 connects the carbon fiber layers 2 (optionally through a thermal connector) to the voltage source 5. Additionally, and also preferably, a second electric cable 7 connects the voltage source 5 to the electricity network (not shown).
During thermal excitation (heating), the joint is observed using a non-destructive inspection system 18, as shown in
Preferably, the composite material used in the repair of this invention comprises a matrix material and a reinforcement material. More preferably, the matrix material is a plastic material or a resin, while the reinforcement material may be, for example, glass fiber.
Thus, this invention provides a system for inspecting a repair or joint of composite material applied to a structure (piping, for example), that is low cost and that considerably improves the efficacy of thermography or shearography inspection methods.
Countless variations to the scope of protection of this application are allowed. Thus, the fact is reinforced that this invention is not limited to the specific configurations/realizations described above.
Number | Date | Country | Kind |
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BR 102018012268-1 | Jun 2018 | BR | national |
Filing Document | Filing Date | Country | Kind |
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PCT/BR2019/050222 | 6/13/2019 | WO | 00 |