Role of processing on interlaminar shear strength enhancement of epoxy/glass fiber/multi-walled carbon nanotube hybrid composites

Interlaminar shear strength (ILSS) of hybrid composites made from glass fiber and multi-walled carbon nanotube (MWCNT) modified epoxy is compared with unmodified epoxy/glass fiber composites (control). By combining the techniques of high speed mechanical stirring and ultrasonic agitation, 0.5% MWCNT by weight was dispersed in epoxy to prepare a suspension. Composites were manufactured by both injection double vacuum-assisted resin transfer molding (IDVARTM) and the flow flooding chamber (FFC) methods. Compression shear tests were conducted on the manufactured samples to determine ILSS. The effect of processing history and batch-to-batch variability of materials – glass fiber preform, resin and carbon nanotubes – on ILSS of samples made by both techniques was investigated. Statistical analysis of the measured ILSS values for hybrid composites and their comparison with the control specimens clearly show that hybrid composites made by the FFC process resulted in (i) significant ILSS enhancement relative to the control and to IDVARTM specimens and (ii) better repeatability than the IDVARTM process. A description of both IDVARTM and FFC processes and their role in dispersing the nanotubes between the fabric layers was discussed.