In this paper, a brief review of the fiber-matrix interphase/interface region is given for carbon- and glass-fiber composites. The interphase/interface region is discussed interms of the fiber interphase (FI), the matrix (MI), and the FI-MI interface as originally proposed by Drzal. The schematic model of interphase deformation behavior originally given by Bascom is reconstructed to include research results from Drzal. To systematically probe adhesion at the FI-MI interface, functionalized self-assembled monolayers (SAMs) using bonding and non-bonding C11-type trichlorosilanes are prepared using the research of Menzel & Heise and Cave & Kinloch as a guide. Results from this research are compared with short chain bonding and non-bonding silanes prepared by aqueous and non-aqueous deposition process. Sharpe's and Drzal's original assumption about the factors that contribute to adhesion in the fiber-matrix and the mathematical equation proposed by Nardin & Ward were used to interpret the data. For the non-bonding short-chain silane deposited by aqueous deposition, 90 % of the bonding was found to be due to mechanical interlocking, with the remaining adhesion due to physicochemical interactions. For the bonding short-chain silane deposited by aqueous deposition, the interface strength relative to the non-bonding short-chain silane increased by 31 %. However the interfacial shear strength (IFSS) of this system was approximately 40 % lower than the comparable bonding SAMs interface. This difference was interpreted in terms of the propensity of the C3-alkylamine to form cyclic ring structures in the MI region as described by Ishida, Koenig, et al. The SAM's data also indicates that (70 to 85) % of the maximum IFSS is obtained with (25 to 50) % of the surface covered with functional groups. This suggests that steric hindrance, due to the size of the DGEBA molecules, restrict access to the functional groups on the surface. Therefore, only 35 % of the surface functional groups are accessible for bonding in the DGEBA/m-PDA epoxy resin system.
Citation: Composite Interfaces
Issue: No. 6
Pub Type: Journals
adhesion, carbon fiber, glass fiber, interface, interface strength, interphase, matrix, self-assembled monolayer, silane coupling agent