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

Genetic (RAPD) Diversity between Oleria onega agarista and Oleria onega ssp. ( Ithomiinae , Nymphalidae, Lepidoptera) in North-Eastern Peru

Oleria onega agarista Felder and Felder and Oleria onega ssp. nov. are two Ithomiinae subspecies from north-eastern Peru, that differ for some morphological and behavioural traits. Two contact zones are known near the town of Tarapoto: Ahuashiyacu, where both subspecies cohabit but do not seem to hybridise, and Estero (near the village of Shapaja), where they apparently hybridise. Genetic differences between the two subspecies and between populations were investigated with random amplified polymorphic DNA (RAPD) markers. Both Cluster and Principal Coordinates Analyses (CCoA and PCoA) performed using these data, provided a clear but weak discrimination between the two subspecies. Genetic diversity is much higher within the populations than between them. Moreover, the geographically more distant populations are grouped together by the genetic data. Morphological traits on the wing patterns of the hybrids are intermediary between the two butterflies subspecies, while RAPDs data place them closer to O. onega agarista than to O. onega ssp. The individuals of the Ahuashiyacu population are clearly separated into two groups, those of O. onega ssp. and O. onega agarista, by both morphology and RAPDs data. Moreover, none of those individuals show RAPD similarity with the hybrids, suggesting that hybridisation has not occurred in this populatio

Mate Choice and Toxicity in Two Species of Leaf Beetles with Different Types of Chemical Defense

Evidence for the use of defensive compounds for sexual purposes is scarce, even though sexual selection might have some importance for the evolution of defensive traits. This study investigates the effect of defense-related traits and body size on mating success in two sister species of leaf beetle differing in their type of chemical defense. Oreina gloriosa produces autogenous cardenolides, whereas O. cacaliae sequesters pyrrolizidine alkaloids from its food plant. Larger O. gloriosa males with more toxin or higher toxin concentration had a mating advantage, likely due to direct or indirect female choice. In the laboratory, particular pairings recurred repeatedly in this species, indicating mate fidelity. O. gloriosa females were also subject to sexual selection, possibly by male choice, because larger females and those with higher toxin concentration mated more readily and more often. In O. cacaliae, in contrast, sexual selection for toxicity and body size was not detected, or at best was much weaker. Because toxicity is heritable in O. gloriosa but environment-dependent in O. cacaliae, individuals of the former species could be choosing well-defended partners with "good genes.” Our study suggests that sexual selection may contribute to the maintenance of heritable defensive trait