Influence of geometrical features of electrospun nylon 6,6 interleave on the CFRP laminates mechanical properties

Abstract

Twenty plies, woven carbon fiber/epoxy matrix, virgin, and Nylon 6,6 electrospun nanofiber interleaved composite laminate beams are tested under Modes I and II fracture mechanic to assess the effect of nanointerleave on the global behavior of the laminate. Aim of the work is to study the effect of geometrical features of the nanoreinforce on the mechanical response of a laminate subjected to fracture mechanic loads. Nanofiber orientation, nanolayer thickness, and nanofiber diameter have been considered. From the experiments, mechanical parameters have been extracted and used to compare the configurations. The work highlights the importance of an accurate choice of the nanointerleave and showed that thick interleaves may weaken the interface if a high number of voids is left after the curing process, the smaller is the fiber diameter the higher is the energy absorbing capability of the specimens, and that fiber orientation has different effect depending on the loading mode

Compressibility of carbon fabrics with needleless electrospun PAN nanofibrous interleaves

“…Theoretically, by adjusting the thickness of the interleaves and choosing the appropriate nanofiber material the properties of the composite can be tailored from rigid to tough kind of damage. This effect was demonstrated experimentally for Nylon 6.6 interleaves in [16,17]. The toughening effect of polyacrylonitrile (PAN) nanofibrous interleaves in carbon fiber-reinforced structures was proved in [18].…”

Flexural behavior of carbon and glass fiber composite laminates reinforced with Nylon 6,6 electrospun nanofibers

“…The Nylon 6,6 nanofbers electrospun for the experiments here presented, have been already used in other work of the author ( [3,13,14,16]), and proved to maintain their integrity when subjected to the thermal and pressure stresses applied into the autoclave. Furthermore [13,14,16] already proved that Nylon 6,6 nanofibers get completely wet by the resin, during the cure in autoclave. Furthermore, the curing process is monitored by a sacrificial item placed into the autoclave, together with the specimens, with a thermocouple inserted in it to check the real temperature of the resin while it cures, to ensure that the nanofibers do not melt.…”

“…This is due to the fact that Mode II tests aim to load the delaminated interface in shear mode, and thus the effect of the shear is encouraged to be as high as possible (which is something to avoid when testing sample to identify flexural properties). Nanomodified specimens are interleaved with a layer of Nylon 6,6 nanofibers applied in the delaminated interface during the lay-up, as presented in [13].…”

“…Despite the large amount of research dealing with the toughening effect of nanofibers applied into composite interfaces, the effective reinforce mechanism is still a partially uncovered topic. In previous work of Palazzetti [13], a presentation is given on the effect of nanointerleave's geometrical features (such as thickness, fiber diameter and fiber orientation) on woven CFRP Mode I and Mode II loaded specimens. Nanofiber's toughening mechanism has been investigated in [14,15], focusing on the resin interaction with the nanomat, the presence of nanofibers increases the damping of the laminate by friction with the undamaged resin, enabling crack-bridging when the matrix breaks.…”

Electrospun nanofibers as reinforcement for composite laminates materials – A review

“…• in [20,21,23,44] it is shown that mechanical properties of nanomodified samples drop when the nanolayer reaches a certain thickness. It is observed that there is a threshold value on the amount of nanoreinforce after which the compliance of a randomly aligned polymeric nanofibrous mat overcomes the strengthening effect of the same;…”