Adhesive bonding and miscellaneous chemical manufacture – Surface bonding means and/or assembly means therefor – Automatic and/or material-triggered control
Reexamination Certificate
2000-02-18
2002-06-25
Yao, Sam Chuan (Department: 1732)
Adhesive bonding and miscellaneous chemical manufacture
Surface bonding means and/or assembly means therefor
Automatic and/or material-triggered control
C156S441000, C156S180000, C264S137000, C425S110000
Reexamination Certificate
active
06408915
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a method and apparatus for profiling the cure within a pultrusion tool. Monitoring the profile of the degree of cure along the length of a pultrusion tool (die) allows understanding of the cure profile's response to different processing parameters. Once this understanding is complete and simulations are developed to model the cure profile's performance, the profile can be used as a process control input. Then the process can be fully automated to insure optimal processing and quality.
Composite materials can be manufactured in many ways, the most economical of which is pultrusion. Pultrusion is used to manufacture constant cross-section material in a continuous process. It is desired to optimize processing to maintain quality and increase line speed to its maximum. Current state of the art includes extensive heat transfer and resin kinetic modeling (see Sumerak, Joseph E., “Pultrusion Die Design Optimization Opportunities Using Thermal Finite Element Analysis,” The Society of the Plastics Industry, Inc. Feb. 7-9, 1994, session 9-C pp. 1-7). These models are then coupled to process sensors to allow for process control. As Dr. Joseph Sumerak on pultrusion process control has stated: “The most critical controls are found in the control of line speed and die temperatures, both of which have primary impact on the state of cure of the composite pultrusion. Sophisticated control scenarios for closed-loop line speed control and PID temperature control provide precision in response to operator setpoints. Unfortunately, however, the ability to continuously detect the degree of cure of the composite for use as a process control parameter does not yet exist. ” Sumerak, Joseph E., “The Pultrusion Process for Continuous Automated Manufacture of Engineered Composite Profiles,” Composites Engineering Handbook, Edited by P. K. Mallick, 1997, Chapter 11, pp. 549-577.
Several attempts at placing pressure, temperature, and dielectric sensors into the die have been made (see Nolet, S. C., “Development of a Sensor for Continuously Monitoring the Degree of Cure of Composite Materials during Pultrusion,” Report No.: NSF/ISI-89022. Cable, D., “Embedded fiber optic pressure and temperature sensors enable cure monitoring of pultruded composite materials,” Society of Manufacturing Engineers, Conference on Effective Manufacturing Methods of Pultrusion, Manhattan Beach, Calif., May 9-10, 1990, pp. 6. Fanucci, J. P.; Nolet, S. C.; Koppernaes, C.; Chou, Hsin-Nan, “Thin disposable pressure sensors for composite material process monitoring,” Society for the Advancement of Material and Process Engineering, 1990, pp. 1205-1219. Methven, J. M.; Katramados, Y., “In-line quality monitoring of pultruded profiles using dielectric Measurements,” Polymers and Polymer Composites, 5, (1), pp. 15-20). The present invention inexpensively, continuously, and easily profiles the degree of cure in the pultrusion die.
SUMMARY OF THE INVENTION
An important object of the invention is to provide an improved method and apparatus to determine the degree of cure along the length of a pultrusion die. Advantages of the invention include increased accuracy, increased applicability, and reduced costs.
First, the invention offers considerable increases in accuracy by (1) using a sensor methodology that is not as subject to degradation as dielectric sensors; (2) using an electrical circuit configuration that allows direct measurement across the resin material; and (3) using a series of sensors across cross-sections of a die to monitor the cure profile along the length of the die in different thickness regions; and (4) using a series of sensors that allow the cure profile along the length of the pultrusion tool to be monitored.
Second, the invention offers considerably increased applicability by (1) using a sensor configuration that is easily integrated into the tool; (2) monitoring the degree of cure along the length of the tool; (3) using a sensor material that is easy to integrate into the preform; (4) using a sensor material that is common to composite material construction to therefore prevent any degradation of the properties of the composite material; and (5) using either Alternating Current (AC) or Direct Current (DC).
Finally, the invention offers a considerable cost savings advantage by (1) eliminating expensive sensors; (2) eliminating the need for specialized coating of sensors to extend life; and (3) allowing the process to be optimized and then fully automated.
REFERENCES:
patent: 5635845 (1997-06-01), Strong et al.
patent: 6061902 (2000-05-01), Kalamkarov et al.
Shanku et al, “Dielectric and Thermal cure Characterization of resin Used in Pultrusion”, 42ndInternational SamPE Symposium, 42, May 4-8, 1400-1413, 1997 (abstract).
Ballata William O.
Klinger J. Robert
Spagnuolo David
Biffoni U. John
Clohan, Jr. Paul S.
Randolph William
The United States of America as represented by the Secretary of
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