Abstract
Carbon Fiber Reinforced Polymers (CFRPs) are widely used where high mechanical performance and lightweight are required. However, they suffer from delamination and low damping, severely affecting laminate reliability during the service life of components. CFRP laminates modified by rubbery nanofibers interleaving is a recently introduced way to increase material damping and to improve delamination resistance. In this work, nitrile butadiene rubber/poly(ε-caprolactone) (NBR/PCL) blend rubbery nanofibrous mats with 60 wt% NBR were produced in three different mat grammages (5, 10 and 20 g/m2) via single-needle electrospinning and integrated into epoxy CFRP laminates. The investigation demonstrated that both mat grammage and positioning affect CFRP tanδ behaviour, evaluated by dynamic mechanical analysis (DMA) tests, as well as the number of nano-modified interleaves. Double cantilever beam (DCB) tests were carried out to assess the mat grammage effect on the interlaminar fracture toughness. Results show an outstanding improvement of GI,R for all the tested reinforced laminates regardless of the mat grammage (from +140% to +238%), while the effect on GI,C is more dependent on it (up to +140%). The obtained results disclose the great capability of NBR/PCL rubbery nanofibrous mats at improving CFRP damping and interlaminar fracture toughness. Moreover, CFRP damping can be tailored by choosing the number and positioning of the nano-modified interleaves, besides choosing the mat grammage.
Highlights
Composite laminates, such as high-performance Carbon Fiber Reinforced Polymers (CFRPs), may need improved properties to replace conventional metallic materials in specific fields
Preliminary data suggested that a high number of nano-modifications and a high amount of nitrile butadiene rubber (NBR) lead to a significant improvement of the composite damping, thanks to nitrile butadiene rubber/poly(ε-caprolactone) (NBR/PCL) mixing with the epoxy resin
CFRP laminates nano-modified via rubbery nanofibers interleaving is a recently introduced way to increase material damping and improved delamination resistance in well localized composite regions of a composite
Summary
Composite laminates, such as high-performance Carbon Fiber Reinforced Polymers (CFRPs), may need improved properties to replace conventional metallic materials in specific fields. The simplest methods involve mixing uncrosslinked “liquid” rubber with resin precursors or the addition of already crosslinked rubbery particles, adding up to 20 wt% of toughener [1,2,3,4,5]. This usually implies the modification of the whole resin bulk, requiring a new formulation for each specific case. Another viable solution is the integration of viscoelastic films between laminae [6,7,8]. While it represents a simple and economical solution, the use of bulk layers negatively affects laminate stiffness and strength, besides determining significant weight and size increase [9]
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