Delamination resistant composites by interleaving bio-based long-chain polyamide nanofibers through optimal control of fiber diameter and fiber morphology

In this work an innovative electrospinning system is proposed that simultaneously has an adequate temperature resistance, a high increase in mode I (þ51%) and mode II (þ96%) delamination performance and can be commercially produced. Interleaving nanofibrous veils can potentially solve the issue of the limited delamination resistance encountered in composite laminates, but industrial upscaling has always been impeded by one or more critical factors. These constraining factors include a limited temperature stability of the nanofibers, a lack in simultaneous mode I and II delamination performance increase and the complexity of the electrospinning system because non-commercial polymers or specialty nanofibers (e.g. coaxial) are required. In this paper, a robust electrospinning system is proposed that is the first to overcome all major hurdles to make nanofiber toughening industrially viable. A new class of nanofibers based on biosourced polyamide 11 and its poly(ether-block-amide) co-polymers is used to deal with those shortcomings. The nanofibers have tuneable diameters down to 50 nm and cross-section morphologies ranging from circular to ribbon-shaped. The key to this work is the fundamental underpinning of the toughening effect using a broad range of interleaves with different mechanical and thermal properties, fiber diameters and fiber morphologies, all produced from the same bio-based base polymer. Generally, round and thin nanofibers performed better than larger and ribbon-like fibers. The relationship between the fiber morphology and the delamination performance is further underpinned using detailed analysis of the fracture surface. Ultimately, this results in a range of optimized nanofibrous veils capable of improving the delamination resistance considerably without suffering from the aforementioned drawbacks

Electrospun nanofibers for skin-contact applications

The use of nanofibers is expanding from academic into industry as these lightweight and highly porous materials are advantageous in many application areas. The main objectives of this roject is to reveal the potential of the bioeconomy in Europe, to decrease the use of fossil-based products, lead to greener and more environmentally friendly growth by fighting against climate change. For this purpose, nonwovens are prepared from bio-based polymers using solution electrospinning method for cosmetics and wound-care applications

Nanofibers for damage resistant composite materials

Fiber reinforced polymer composites are the go-to materialfor designing applications thatrequire a high strength and stiffness at minimal weight such as aerospace structures, wind turbines or ultralight vehicles. However, delamination between the reinforcing plies remains a major occurring failure type.Interleaving electrospun nanofibres between the reinforcing plies has proven to be a viable interlaminar toughening method which significantly limitsthe occurrence of delamination failure in composites. This contributionsgives an overview into the relationship between the electrospun nanofibre properties and the resulting toughenedcomposites

Nanofibre toughening of dissimilar interfaces in composites

Fibre reinforced composite laminates are key engineering materials allowing to design lightweight components with high mechanical properties. Yet they are prone to delamination between the reinforcing plies, which in turn limits the damage resistance of many applications. This is especially true for the interfaces between dissimilar reinforcing plies that are often encountered in actual components, e.g. differences in fibre orientation, fibre material or ply architecture, where high interlaminar stresses can occur. Nanofibrous toughening veils are known to increase the damage resistance when inserted between similar reinforcing plies, but it is currently unknown how they perform when delamination occurs at dissimilar interfaces. Here, the nanofibre toughening of frequently encountered dissimilar interfaces such as occurring between multidirectionally stacked unidirectional fibre plies (+45 degrees/-45 degrees), multistructural stackings (unidirectional versus fabrics) and multimaterial configurations (glass fibres versus carbon fibres) are analysed. These interfaces largely exert their influence on the crack path during delamination and thus alter the effectiveness of nanofibre toughening. Poly(ether-block-amide) nanofibres of the biosourced polyamide 11 family result in a large increase in mode I and mode II interlaminar fracture toughness for all the tested dissimilar interfaces. We show that their effectiveness however depends on the underlying delamination mechanics present in different dissimilar interfaces. (c) 2020 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/)

Silver Nanoparticle-Coated Polyhydroxyalkanoate Based Electrospun Fibers for Wound Dressing Applications

Wound dressings are high performance and high value products which can improve the regeneration of damaged skin. In these products, bioresorption and biocompatibility play a key role. The aim of this study is to provide progress in this area via nanofabrication and antimicrobial natural materials. Polyhydroxyalkanoates (PHAs) are a bio-based family of polymers that possess high biocompatibility and skin regenerative properties. In this study, a blend of poly(3-hydroxybutyrate) (P(3HB)) and poly(3-hydroxyoctanoate-co-3-hydroxy decanoate) (P(3HO-co-3HD)) was electrospun into P(3HB))/P(3HO-co-3HD) nanofibers to obtain materials with a high surface area and good handling performance. The nanofibers were then modified with silver nanoparticles (AgNPs) via the dip-coating method. The silver-containing nanofiber meshes showed good cytocompatibility and interesting immunomodulatory properties in vitro, together with the capability of stimulating the human beta defensin 2 and cytokeratin expression in human keratinocytes (HaCaT cells), which makes them promising materials for wound dressing applications

Electrospun nanofibers for highly toughened fibre reinforced polymer composite laminates

Fiber reinforced polymer composites are the material of choice for designing applications which require a high strength and stiffness at minimal weight such as aerospace structures, wind turbines or ultralight vehicles. However, delamination between the reinforcing plies remains a major problem as it limits further breakthrough of these materials. Recently, interleaving electrospun nanofibres between the reinforcing plies has proven to be a viable interlaminar toughening method which can significantly limit the occurrence of delamination failure in composite materials. This presentation will give a thorough insight into the relationship between the electrospun nanofibre properties and the resulting tough composites, and as such, allow for engineering novel and damage resistant nanofiber toughened composites