Enhanced Chemical Bonding at the Fiber-Matrix Interphase in Microwave Processed Composites
- PDF / 276,965 Bytes
- 6 Pages / 420.48 x 639 pts Page_size
- 18 Downloads / 178 Views
ENHANCED CHEMICAL BONDING AT THE FIBER-MATRIX INTERPHASE IN MICROWAVE PROCESSED COMPOSITES
L.
T. DRZAL, Composite Engineering,
K. J. HOOK, AND R. K. AGRAWAL Materials and Structures Center, Department of Chemical Michigan State University, East Lansing, Michigan 48824-1326
ABSTRACT The effect of microwave processing on the chemical interactions occurring between the carbon fiber surface and the epoxy matrix constituents was investigated using X-ray Photoelectron Spectroscopy (XPS). Monofunctional model compounds of the matrix constituents were exposed to the carbon fibers at temperatures similar to those encountered during composite processing. The microwave treatment resulted in a substantial increase in the amount of chemical interaction between the fiber surface and the epoxy resin but little difference for the amine component of the matrix when compared to thermal processing. An epoxy resin/amine hardener adduct compound used to determine the hydroxyl group interaction with the carbon fiber surface indicated a low level of chemical interaction of the hydroxyl with the carbon fiber surface under the conditions used in this study.
INTRODUCTION Electromagnetic processing involving the use of microwave frequency energy offers a new approach to composite processing in which energy is coupled directly into the material without reliance on conduction and convection. An earlier published result [1] reported that in carbon reinforced epoxy composites, significant changes in fiber to matrix adhesion were measured when microwave processing was used in place of thermal processing. Under identical conditions, no change in adhesion to aramid or glass fibers was detected with the epoxy. The conductive nature of the carbon fiber has been shown to result in a preferential absorption of electromagnetic energy causing the fibers to attain a higher temperature than the surrounding epoxy matrix. This study was undertaken to determine if the increased temperature of the fiber resulted in a change in the chemical bonding between fiber and matrix which was a reason for the increase in adhesion. Since it is not possible to determine the chemical bonding between a carbon fiber and epoxy matrix in the solid state with current analytical techniques, a model monofunctional system consisting of a single carbon fiber embedded in a large tensile dogbone shaped cavity was selected as the experimental configuration. It provided conditions identical to those used in the earlier microwave processing studies. In this manner, the samples could be processed with either thermal or microwave energy under identical conditions without polymerization taking place. Specific chemical interactions between the functional groups on the model compounds and the carbon fiber surface could take place in the same manner as in the solid state. The unreacted species could then be removed with low temperature solvent extraction and the carbon fiber surface could be analyzed with X-ray Photoelectron Spectroscopy to quantitate chemical interaction between the amin
Data Loading...
