Cure monitoring of the liquid composite molding process using fiber optic sensors

Fluorescence has been demonstrated to be an accurate tool for monitoring resin cure. It is measured using an evanescent wave fiber-optic sensor. An economical optical fiber sensor has been developed with a refractive index greater than 1.6, permitting evanescent wave monitoring of epoxy resins. The fluorescence wavelength-shift, which has been correlated with monomer conversion, is monitored during the liquid molding process. Unidirectional glass fabrics with volume fractions from 40% to 60% were injected with epoxy resin at a variety of driving pressures and cured at several temperatures. Several composite parts were fabricated to test the effects of vacuum pressure, injection rate, cure temperature, and fiber fraction on the performance of the sensor. The sensitivity of the evanescent wave fluorescence sensor to the condition of the resin system was also examined. Two sets of resin / hardener samples were subjected to rigorous chemical analysis to determine the extent of their differences.

[1]  G. Martin,et al.  Diffusion and Diffusion-Controlled Kinetics during Epoxy-Amine Cure , 1994 .

[2]  N. Sung,et al.  In‐situ cure monitoring of diamine cured epoxy by fiberoptic fluorimetry using extrinsic reactive fluorophore , 1994 .

[3]  L. Nicolais,et al.  Impedance Spectroscopy of Reactive Polymers Correlations with Chemorheology during Network Formation , 1995 .

[4]  Hyung‐Joon Paik,et al.  Fiberoptic intrinsic fluorescence for in-situ cure monitoring of amine cured epoxy and composites , 1994 .

[5]  King-Fu Lin,et al.  Fluorescence monitoring of polarity change and gelation during epoxy cure , 1994 .

[6]  D. O. Bowen,et al.  Effect of Hydroxyl Compounds on Reactivity of Epoxy Resins , 1970 .

[7]  C. L. Tucker,et al.  Thermal dispersion in resin transfer molding , 1995 .

[8]  Tomas Hirschfeld,et al.  Effect of numerical aperture on signal level in cylindrical waveguide evanescent fluorosensors. , 1987, Applied optics.

[9]  D. Hunston,et al.  Cure Monitoring for Polymer Matrix Composites , 1986 .

[10]  L. Mandel,et al.  Absorption and Emission of Evanescent Photons , 1972 .

[11]  In situ sensor monitoring and intelligent control of the resin transfer molding process , 1994 .

[12]  Peter Craven,et al.  Smoothing noisy data with spline functions , 1978 .

[13]  M. Afromowitz,et al.  Fiber optic polymer cure sensor , 1988 .

[14]  John F. Maguire,et al.  Remote Raman spectroscopy as a sensor technology in composite materials processing , 1995 .

[15]  F. Phelan,et al.  Interpretation of 3‐D permeability measurements for RTM modeling , 1995 .

[16]  S. D. Schwab,et al.  Monitoring the composite curing process with a fluorescence-based fiber-optic sensor† , 1991 .

[17]  R. Loutfy.  High-conversion polymerization of fluorescence probes. 1. Polymerization of methyl methacrylate , 1981 .

[18]  M. F. Hutchinson,et al.  Algorithm 642: A fast procedure for calculating minimum cross-validation cubic smoothing splines , 1986, TOMS.

[19]  G. A. Pogany.  Gamma relaxation in epoxy resins and related polymers , 1970 .

[20]  N. J. Harrick,et al.  Internal reflection spectroscopy , 1968 .

[21]  Joseph L. Rose,et al.  In‐line optical monitoring of polymer injection molding , 1994 .

[22]  Martin Y.M. Chiang,et al.  Assessment of the State-Of-The-Art for Process Monitoring Sensors for Polymer Composites , 1992 .

[23]  Chong Sook Paik Sung,et al.  Characterization of epoxy cure by UV-visible and fluorescence spectroscopy: azo chromophoric labeling approach , 1986 .