Rubbery nanofibers via blend and emulsion electrospinning for structural modification of composite laminates
Topic(s) : Material science
Co-authors :
Emanuele MACCAFERRI (ITALY), Laura MAZZOCCHETTI (ITALY), Tiziana BENELLI (ITALY), Tommaso Maria BRUGO (ITALY), Andrea ZUCCHELLI (ITALY), Loris GIORGINI (ITALY)Abstract :
Thermosetting Fiber Reinforced Polymer (FRP) laminates are valid for reducing components’ weight while retaining high specific mechanical properties. However, their laminar structure leads to an intrinsic delamination weakness triggered by out-of-plane loads (impacts), fatigue, or a combination thereof.
Adding tougheners to the bulk resin is a well-known solution to limit delamination by increasing the interlaminar fracture toughness. However, the addition of tougheners, such as rubbers, may result in a loss (even significant) of the laminate’s thermomechanical properties. On the contrary, the modification of localized interlaminar regions where stresses are concentrated the most (holes, free edges, etc.) limits the overall impact on the other materials’ properties.
The integration of electrospun nanofibrous mats represents a valid solution for improving delamination resistance and, in some cases, even the material damping, with reduced impact on the laminate’s strength and stiffness.
Besides common nanomats, mainly made of Nylons and polycaprolactone (PCL), rubber-based nanofibrous mats have been recently proposed for hindering delamination. While the latter are very promising nanomaterials, shaping rubbers straightforwardly into nanofibers is prevented by their low glass transition temperature (Tg): just the formation of a bulk film can be attained due to the rubber cold flow. Two main different approaches can be addressed for maintaining the nanofibrous structure: i) coaxial electrospinning and ii) single-needle electrospinning of polymeric blends. The first approach, besides requiring a more complicated electrospinning setup, provides poor control over the produced nanofibers due to feeding two distinct solutions (the “core” rubber solution and the “shell” one containing a polymer with a Tg higher than room temperature). The second way exploits the common and simple single-needle electrospinning process, enabling even precise control of the rubber content in the nanofiber.
The present work aims to illustrate the production and use of rubber-based nanofibers to improve some structural properties, such as the interlaminar fracture toughness, of FRP laminates. Single-needle electrospinning of Nitrile Butadiene Rubber (NBR) mixed with suitable thermoplastic polymers is exploited to fabricate the rubbery mats. In particular, blend electrospinning of NBR and PCL and emulsion electrospinning of NBR and a polyaramid are effective approaches for obtaining stable nanomats without the need for a crosslinking step. In addition, the effect of their integration into epoxy Carbon FRP (CFRP) laminates on delamination resistance is investigated. Results demonstrate that rubbery nanofibers can significantly improve the interlaminar fracture toughness (up to 4-5 times) with limited impact on the other laminates’ thermal and mechanical properties, paving the way for their use for improving the service life and safety of components made of composite laminates.
Adding tougheners to the bulk resin is a well-known solution to limit delamination by increasing the interlaminar fracture toughness. However, the addition of tougheners, such as rubbers, may result in a loss (even significant) of the laminate’s thermomechanical properties. On the contrary, the modification of localized interlaminar regions where stresses are concentrated the most (holes, free edges, etc.) limits the overall impact on the other materials’ properties.
The integration of electrospun nanofibrous mats represents a valid solution for improving delamination resistance and, in some cases, even the material damping, with reduced impact on the laminate’s strength and stiffness.
Besides common nanomats, mainly made of Nylons and polycaprolactone (PCL), rubber-based nanofibrous mats have been recently proposed for hindering delamination. While the latter are very promising nanomaterials, shaping rubbers straightforwardly into nanofibers is prevented by their low glass transition temperature (Tg): just the formation of a bulk film can be attained due to the rubber cold flow. Two main different approaches can be addressed for maintaining the nanofibrous structure: i) coaxial electrospinning and ii) single-needle electrospinning of polymeric blends. The first approach, besides requiring a more complicated electrospinning setup, provides poor control over the produced nanofibers due to feeding two distinct solutions (the “core” rubber solution and the “shell” one containing a polymer with a Tg higher than room temperature). The second way exploits the common and simple single-needle electrospinning process, enabling even precise control of the rubber content in the nanofiber.
The present work aims to illustrate the production and use of rubber-based nanofibers to improve some structural properties, such as the interlaminar fracture toughness, of FRP laminates. Single-needle electrospinning of Nitrile Butadiene Rubber (NBR) mixed with suitable thermoplastic polymers is exploited to fabricate the rubbery mats. In particular, blend electrospinning of NBR and PCL and emulsion electrospinning of NBR and a polyaramid are effective approaches for obtaining stable nanomats without the need for a crosslinking step. In addition, the effect of their integration into epoxy Carbon FRP (CFRP) laminates on delamination resistance is investigated. Results demonstrate that rubbery nanofibers can significantly improve the interlaminar fracture toughness (up to 4-5 times) with limited impact on the other laminates’ thermal and mechanical properties, paving the way for their use for improving the service life and safety of components made of composite laminates.