New Application Field of Polyethylene Oxide: PEO Nanofibers as Epoxy Toughener for Effective CFRP Delamination Resistance Improvement

Abstract

Delamination is the most severe weakness affecting all composite materials with a laminar structure. Nanofibrous mat interleaving is a smart way to increase the interlaminar fracture toughness: the use of thermoplastic polymers, such as poly(ε-caprolactone) and polyamides (Nylons), as nonwovens is common and well established. Here, electrospun polyethylene oxide (PEO) nanofibers are proposed as reinforcing layers for hindering delamination in epoxy-based carbon fiber-reinforced polymer (CFRP) laminates. While PEO nanofibers are well known and successfully applied in medicine and healthcare, to date, their use as composite tougheners is undiscovered, resulting in the first investigation in this application field. The PEO-modified CFRP laminate shows a significant improvement in the interlaminar fracture toughness under Mode I loading: +60% and +221% in G I,C and G I,R , respectively. The high matrix toughening is confirmed by the crack path analysis, showing multiple crack planes, and by the delamination surfaces, revealing that extensive phase separation phenomena occur. Under Mode II loading, the G II enhancement is almost 20%. Despite a widespread phase separation occurring upon composite curing, washings in water do not affect the surface delamination morphology, suggesting a sufficient humidity resistance of the PEO-modified laminate. Moreover, it almost maintains both the original stiffness and glass transition temperature ( T g ), as assessed via three-point bending and dynamic mechanical analysis tests. The achieved results pave the way for using PEO nanofibrous membranes as a new effective solution for hindering delamination in epoxy-based composite laminates.

The Mechanical Properties of Nanocomposites Reinforced with PA6 Electrospun Nanofibers

“…The addition of micro- or nanofillers to polymer materials has been used to achieve the desired mechanical and thermal characteristics [ 4 , 5 , 6 , 7 , 8 ]. Nanofiber-reinforced composite laminates can have a higher tensile strength [ 9 ], interlaminar fracture toughness [ 10 , 11 ], resistance to delamination [ 12 , 13 ] under static, impact, and fatigue loads. These characteristics depend on the polymer, chemical, physical, and mechanical parameters, as well as the additives.…”

Rubber-enhanced polyamide nanofibers for a significant improvement of CFRP interlaminar fracture toughness

“…8 G,H). Moreover, the flat planes, still reminiscent of brittle matrix fracture, are completely lost, as already observed when the nanomodification is carried out through polyethylene oxide (PEO) 46 , NBR/PCL blend 32 and NBR/Nomex mixed 33 nanofibers. By contrast, such planes are visible when the mats are impregnated by the 3.0 wt% NBR solution, highlighting that the matrix toughening is lower.…”

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Figure 7 Comparison of Mode I energy release rate of tested composites with literature data: ( A ) G I initiation, and ( B ) G I propagation. Legend: circles identify the laminates tested in the present work (solid black circle, reference; black circles, plain Nylon 66 mats; blue circles, mats impregnated with the 3.0 wt% NBR solution; red circles, mats impregnated with the 7.0 wt% NBR solution); yellow polyamide nanofibers 26 ; green, NBR/PCL nanofibers 32 ; spent fucsia, NBR/Nomex nanofibers 33 ; dark blue, PEO nanofibers 46 ; grey, “other” nanofiber types 26 .

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Preparation and Characterization of Simvastatin-Loaded PCL/PEG Nanofiber Membranes for Drug Sustained Release

“…The mechanical properties of NFMs were characterized as shown in Figure 5 and Table 3 . The tensile behavior exhibited by the three different NFMs is common, as reported in different literature [ 41 , 42 , 43 ]. It could be seen from Figure 5 that during the stretching process, the beginning of the curve was a straight line, where the elastic deformation was first triggered until the stress exceeded the elastic limit and entered the yielding phase.…”