Damage behavior of functionally graded kevlar/carbon epoxy nanocomposites reinforced with polyamide 6.6 nanofiber and MWCNTs subjected to low-velocity impact

Abstract

The use of carbon and kevlar fiber-reinforced composite materials continues to grow in high-tech applications such as aerospace engineering. One of the most desired properties in composite structures is a strong interfacial bond between the matrix and the fiber. Nano-material reinforcement is one of the most preferred methods for strengthening the fiber-matrix interfacial bond. In the present research, polyamide 6.6 (PA 6.6) nanofiber and multi-walled carbon nanotubes (MWCNTs) reinforced kevlar fabric (KF), carbon fabric (CF) and epoxy matrix nanocomposite plates were produced by functional grading of these two fabrics. PA 6.6 nanofibers, obtained by electrospinning, were placed between the layers, and 12-layer nanocomposite plates were fabricated using a vacuum-assisted hand lay-up method. In producing MWCNTs reinforced nanocomposite plates, 0.3 wt.% of MWCNTs were added into the epoxy matrix. A comprehensive set of 16 distinct composite plates was manufactured, encompassing unreinforced plates, plates reinforced with MWCNTs, plates reinforced with PA 6.6, and plates reinforced with a combination of PA 6.6 and MWCNTs (PA 6.6-MWCNTs). The impact strengths of the produced composite plates were investigated at energy levels of 20, 40 and 60 J. The effects of reinforcing the composite structure with MWCNTs, PA 6.6, and PA 6.6-MWCNTs, as well as functionally grading KF/CF on impact strength, were investigated in detail. The damages that occurred in the material as a result of the low-velocity impact tests were interpreted by examining the high-resolution camera and optical microscope images. Thus, the nanofiber and nanoparticle reinforcement to composite structure and hybridization effect were evaluated together. With the reinforcement of PA 6.6, MWCNTs and PA 6.6-MWCNTs, the impact strength of the nanocomposite samples increased significantly compared to the unreinforced samples. Moreover, the amount of damage caused by the low-velocity impact test in reinforced samples was significantly reduced.