Assessment of interfacial adhesion between carbon fiber and epoxy by transverse fiber bundle and single fiber fragmentation tests

This work concentrates on contrasting interfacial normal strength (INS) and interfacial shear strength (ISS) results separately from the transverse fiber bundle (TFB) test and traditional microscopic test and analyzing the similarities and differences for these two test approaches. Four kinds of carbon fibers were employed to prepare specimens with the same epoxy resin. The interfacial properties of these fiber-matrix system were investigated by both the TFB test and single fiber fragmentation (SFF) test. For the TFB test, the multiscale approach based on the highly efficient Generalized Method of Cells (GMC) was adopted to describe the failure and interphase behavior of TFBC specimen. The macroscopic structural level for the TFBC was discretized by the FE method using Abaqus. In the GMC micromechanics model, a discrete interphase was included apart from the fiber and matrix. The progressive failure process was simulated and the micro interfacial stress was exported for discussion. The INS was successfully determined by the correlation of the experimental and analytical results. For the SFF test, the fragmentation method was combined with acoustic emission (AE) analysis and the IFS was calculated based on the classic Kelly-Tyson model. Furthermore, the IFS results from the SFF test and the INS results from the TFB test were contrasted. Both tests show the same trend, but differs in the specific values. The coefficient of variation (CV) of TFB test was much lower than that of SFF test. The TFB test may be an alternative for the assessment of interfacial strength.