Monitoring technology

Abstract

A process for infrared spectroscopic monitoring of insitu compositional changes in a polymeric material comprises the steps of providing an elongated infrared radiation transmitting fiber that has a transmission portion and a sensor portion, embedding the sensor portion in the polymeric material to be monitored, subjecting the polymeric material to a processing sequence, applying a beam of infrared radiation to the fiber for transmission through the transmitting portion to the sensor portion for modification as a function of properties of the polymeric material, monitoring the modified infrared radiation spectra as the polymeric material is being subjected to the processing sequence to obtain kinetic data on changes in the polymeric material during the processing sequence, and adjusting the processing sequence as a function of the kinetic data provided by the modified infrared radiation spectra information.

What is claimed is: 
     
       1. An infrared spectroscopy system for monitoring the processing of a polymeric material comprising a source of infrared radiation for generating a beam of infrared radiation,   infrared spectrum analyzing means,   an infrared radiation transmission fiber that has a transmission portion and a sensor portion adapted to be embedded in the polymeric material to be monitored, and   means for coupling said transmission fiber to said source to transmit a beam of infrared radiation through said fiber to said sensor portion and for coupling said fiber to said infrared spectrum analyzing means for analyzing the resulting spectra as said polymeric material is processed to provide kinetic information on the processing of said polymeric material.   
     
     
       2. The system of claim 1 wherein said source is of the Michelson interferometer type. 
     
     
       3. The system of claim 1 wherein said spectrum analyzing means is of the Fourier transform type. 
     
     
       4. The system of claim 1 wherein the material of said fiber is selected from the class consisting of chalcogenide glass such as arsenic sulfide or arsenic germanium selenide, heavy metal fluoride glass, such as a mixture of zirconium, barium, lanthanum and aluminum fluorides, and polycrystalline or single crystal materials such as thallium bromoiodide or cesium iodide. 
     
     
       5. The system of claim 1 wherein said sensor .[.fiber.]. .Iadd.portion .Iaddend.has a diameter of at least about one hundred micrometers and a refractive index greater than 1.7. 
     
     
       6. The system of claim 1 wherein said .[.sensor-transmitter.]. .Iadd.transmission .Iaddend.fiber has a length of at least about two meters with a clad transmission portion and an unclad sensor portion, both of which are adapted to be embedded in the polymer material to be monitored. 
     
     
       7. The system of claim 6 wherein said fiber has a diameter of at least about one hundred micrometers, a refractive index greater than 1.7 and an overall transmission loss of less than 5 dB per meter over an 1800-750 wavenumber bandwidth and said sensor portion of said fiber has a length that is less than about five percent of the overall length of said fiber. 
     
     
       8. The system of claim 7 wherein the material of said fiber is selected from the class consisting of chalcogenide glass such as arsenic sulfide or arsenic germanium selenide, heavy metal fluoride glass, such as a mixture of zirconium, barium, lanthanum and aluminum fluorides, and polycrystalline or single crystal materials such as thallium bromoiodide or cesium iodide. 
     
     
       9. The system of claim 1 wherein said .[.sensor-transmitter.]. .Iadd.transmission .Iaddend.fiber has an overall transmission loss of less than 5 dB per meter over an 1800-750 wavenumber bandwidth. 
     
     
       10. A process for infrared spectroscopic monitoring of insitu compositional changes in a polymeric material comprising the steps of providing an elongated infrared radiation transmitting fiber that has a transmission portion and a sensor portion,   embedding said sensor portion in the polymeric material to be monitored,   subjecting said polymeric material to a processing sequence,   applying a beam of infrared radiation to said fiber for transmission through said transmitting portion to said sensor portion for modification as a function of properties of the polymeric material, and   monitoring the modified infrared radiation spectra as said polymeric material is being subjected to said processing sequence to obtain kinetic data on changes in the polymeric material during the processing sequence.   
     
     
       11. The process of claim 10 and further including the step of adjusting the processing sequence as a function of the kinetic data provided by said modified infrared radiation spectra information. 
     
     
       12. The process of claim 10 wherein a polymer-fiber matrix is being monitored, said polymer-fiber matrix including alternating layers of fibers and polymer resins, and the sensor portions of a plurality of said infrared radiation transmitting fibers are embedded in spaced relation in said polymer resin layers. 
     
     
       13. The process of claim 12 wherein said polymeric material being monitored is selected from the class consisting of epoxies and polyimides. 
     
     
       14. The process of claim 13 wherein the material of said infrared radiation transmitting fibers is selected from the class consisting of chalcogenide glass such as arsenic sulfide or arsenic germanium selenide, heavy metal fluoride glass, such a mixture of zirconium, barium, lanthanum and aluminum fluorides, and polycrystalline or single crystal materials such as thallium bromoiodide or cesium iodide. 
     
     
       15. A elongated infrared radiation transmitting process monitoring fiber for use in the process of claim 10, said fiber having a transmission portion and a sensor portion, said fiber having a length of at least about one meter and said sensor portion having a length that is less than about five percent of the overall length of said fiber. 
     
     
       16. The fiber of claim 15 wherein said fiber has an overall transmission loss of less than 5 dB per meter over an 1800-750 wavenumber bandwidth, a diameter of at least about one hundred micrometers, a refractive index greater than 1.7, said sensor portion is unclad, and said transmission portion is clad. 
     
     
       17. The fiber of claim 16 wherein the material of said fiber is selected from the class consisting of chalcogenide glass such as arsenic sulfide or arsenic germanium selenide, heavy metal fluoride glass, such a mixture of zirconium, barium, lanthanum and aluminum fluorides, and polycrystalline or single crystal materials such as thallium bromoiodide or cesium iodide. 
     
     
       18. A system for insitu infrared spectroscopic monitoring of a polymer-fiber matrix to provide kinetic information during the curing of the polymeric constituent of said polymeric fiber matrix, said polymer-fiber matrix including alternating layers of fibers and polymer resins, comprising a plurality of infrared radiation transmitting fibers, each said .Iadd.transmitting .Iaddend.fiber having a transmission portion and a sensor portion, the sensor portions of said .Iadd.transmitting .Iaddend.fibers being adapted to be embedded in spaced relation in said layers of polymer resin,   a source of infrared radiation for generating a beam of infrared radiation,   means for coupling said transmitting fibers to said source to transmit infrared radiation through said fibers to said sensor portions,   infrared spectrum analyzing means, and   means for coupling said .Iadd.transmitting .Iaddend.fibers to said infrared spectrum analyzing means for analyzing the resulting infrared spectra as said polymer resin constituents are being cured to provide kinetic information on the curing of said polymer resins.   
     
     
       19. The system of claim 18 wherein each said infrared radiation transmitting fiber has a diameter of at least about one hundred micrometers and a length of at least about one meter, each said transmission portion is clad and each said sensor portion is unclad, each said sensor portion has a length that is less than about five percent of the overall length of its .Iadd.transmitting .Iaddend.fiber. 
     
     
       20. The system of claim 19 wherein the material of said infrared radiation transmitting fibers is selected from the class consisting of chalcogenide glass such as arsenic sulfide or arsenic germanium selenide, heavy metal fluoride glass, such a mixture of zirconium, barium, lanthanum and aluminum fluorides, and polycrystalline or single crystal materials such as thallium bromoiodide or cesium iodide; said polymer-fiber matrix includes fiber of material such as graphite or boron and polymers of materials such as epoxies or polyimides; each said infrared radiation transmitting fiber has a refractory index greater than 1.7 and an overall transmission loss of less than 5 dB per meter over an 1800-750 wavenumber bandwidth; and further including autoclave type containment structure for receiving said polymer-fiber matrix during cure, said containment structure including gland structure through said transmission portions of said .Iadd.transmitting .Iaddend.fibers are connected to said infrared radiation source and said infrared spectrum analyzer means. .Iadd. 
     
     
       21.  A system for detecting chemical characteristics within a material comprising: an optical fiber embedded in a material, the fiber having an unclad sensor section;   source means connected to direct optical radiation into the fiber;   encoding means to modulate the optical radiation; and   spectrum analyzer means connected to the fiber to detect at least a part of the spectrum of the modulated optical radiation and, thereby, to detect chemical characteristics of the material in which the sensor section is embedded. .Iaddend. .Iadd.22. A system according to claim 21 wherein the unclad sensor section comprises a section between the ends of the fiber, and said source means is connected to one end of the fiber and said spectrum analyzer means is connected to the other end of the fiber. .Iaddend. .Iadd.23. A system according to claim 21 wherein the unclad sensor section is at the end of the fiber, and said source means and said spectrum analyzer means are connected to the same end of the fiber.   
     
     
        .Iaddend. .Iadd.24.  A system according to claim 21 wherein said optical fiber extends outside said spectrum analyzer means. .Iaddend. .Iadd.25. A system according to claim 23 wherein the tip of the unclad sensor section of the fiber is generally planar. .Iaddend. .Iadd.26. A system according to claim 21 wherein said spectrum analyzer means comprises a Fourier transform analyzer. .Iaddend. .Iadd.27. A system according to claim 21 wherein said encoding means comprises an interferometer. .Iaddend. .Iadd.28. A system according to claim 21 wherein said unclad sensor section is formed from chalcogenide glass. .Iaddend. .Iadd.29. A system according to claim 21 wherein said chalcogenide glass is arsenic germanium selenide glass. .Iaddend. .Iadd.30. A system according to claim 21 wherein said sensor section is formed from metal fluoride glass. .Iaddend. .Iadd.31. A system for providing in-situ detection of the chemical state within a fiber-reinforced composite material, comprising: an optical fiber embedded in the fiber-reinforced composite material, the fiber having an unclad sensor section and the remainder of the fiber being clad;   a light source connected to direct infrared radiation into the fiber;   a detector connected to detect infrared radiation emerging from an end of the fiber; and   a spectrum analyzer connected to the detector for measuring at least a part of the spectrum of infrared radiation absorbed by the composite material   
     
     
        adjacent the sensor section. .Iaddend. .Iadd.32.  A system according to claim 31 wherein the unclad sensor section comprises a section intermediate the ends of the fiber, and the light source is connected to one end of the fiber and the spectrum analyzer is connected to the other end of the fiber. .Iaddend. .Iadd.33. A system according to claim 31 wherein the unclad sensor section is at the end of the fiber. .Iaddend. .Iadd.34. A system according to claim 33 wherein the light source and the spectrum analyzer are in optical communication with the same end of the 
     
     
        fiber. .Iaddend. .Iadd.35.  A system according to claim 31 wherein the spectrum analyzer comprises a Fourier transform analyzer. .Iaddend. .Iadd.36. A system according to claim 31 wherein said light source includes an interferometer. .Iaddend. .Iadd.37. A process for detecting chemical characteristics within a material, comprising the steps of: forming an optical fiber having an unclad sensor section;   embedding the sensor section of the optical fiber in a material to be analyzed;   directing light into the fiber; and   operating a spectrum analyzer connected to the fiber to analyze at least a part of the spectrum of said light absorbed by the material adjacent the sensor section. .Iaddend. .Iadd.38. A process according to claim 37 wherein the material is a thermosettable matrix resin. .Iaddend. .Iadd.39. A process according to claim 38 wherein the analyzer is operated while   
     
     
        curing the resin. .Iaddend. .Iadd.40.  A process according to claim 39 wherein the analyzer measures the degree of cross-linking of the resin. .Iaddend. .Iadd.41. A process according to claim 37 wherein a plurality of the optical fibers, each having a sensor section, are embedded in the materials at selected locations. .Iaddend. .Iadd.42. A process according to claim 37 wherein the material to be analyzed is located external of the analyzer. .Iaddend. .Iadd.43. A process according to claim 42 wherein the analyzer is a Fourier transform infrared analyzer. .Iaddend. .Iadd.44. A process according to claim 43 wherein the analyzer radiation is in the mid-radiation spectrum. .Iaddend. .Iadd.45. A process according to claim 44 wherein the wavelengths of analyzed radiation ranges from about five to about fifteen microns. .Iaddend. .Iadd.46. A process according to claim 45 wherein the spectrum analysis is accomplished by measuring multiple 
     
     
        internal reflections. .Iaddend. .Iadd.47.  A process according to claim 37 wherein the unclad sensor section is connected between the ends of the fiber and light is directed into one end of the fiber and the spectrum analyzer is connected to the other end of the fiber. .Iaddend. .Iadd.48. A process according to claim 37 wherein the unclad sensor section is at the end of the fiber. .Iaddend. .Iadd.49. A process according to claim 37 wherein the core of the optical fiber is formed from chalcogenide glass. .Iaddend. .Iadd.50. A process according to claim 37 wherein the core of the optical fiber is formed from metal fluoride glass. .Iaddend. .Iadd.51. A process for providing in-situ detection of chemical conditions within a fiber reinforced composite material during curing, comprising: embedding an optical fiber in the fiber-reinforced composite material with at least one end of the fiber extending from the material, the fiber having an unclad sensor section and the remainder of the fiber being clad;   connecting a source of infrared radiation to the fiber; and   connecting a Fourier transform spectrum analyzer to the fiber for detecting the spectrum of infrared radiation absorbed by the composite material   
     
     
        adjacent the unclad sensor section. .Iaddend. .Iadd.52.  A process according to claim 51 wherein the unclad sensor section is at the end of the fiber. .Iaddend. .Iadd.53. A process according to claim 51 wherein the unclad sensor section is between the ends of the fiber. .Iaddend. .Iadd.54. A sensor for use with a spectrum analyzer for detecting the chemical state of materials external to the spectrometer comprising: an optical fiber having an unclad sensor section for insertion into a material whose chemical state is to be measured and an end adapted for connection to a spectrum analyzer. .Iaddend. .Iadd.55. A sensor according to claim 54 wherein the material comprising the sensor section is compatible with Fourier transform infrared spectrum analyzer. .Iaddend.   
     
     
        .Iadd.56.  A system for detecting chemical characteristics of a material comprising a source of radiation for generating a beam of radiation,   analyzing means,   an optical radiation transmission fiber that has a transmission portion and a sensor portion adapted to be disposed in said material to be monitored, and   means for coupling said transmission fiber to said source to transmit a beam of radiation through said fiber to said sensor portion and for coupling said fiber to said analyzing means for detecting chemical   
     
     
        characteristics of said material. .Iaddend. .Iadd.57.  The system of claim 56 wherein the material of said transmission portion of said optical radiation transmission fiber is different from the material of said sensor 
     
     
        portion. .Iaddend. .Iadd.58.  A system for providing insitu detection of the chemical state of a fiber-reinforced composite material comprising an optical fiber, said fiber having a transmission portion and a sensor portion, the sensor portion of said fiber being adapted to be disposed in said fiber-reinforced composite material,   a source of radiation for generating a beam of radiation,   means for coupling said optical fiber to said source to transmit radiation through said fiber to said sensor portion,   spectrum analyzing means, and   means for coupling said fiber to said spectrum analyzing means for measuring at least a part of the radiation absorbed by the composite material adjacent said sensor portion. .Iaddend.