Microscale material variability and its effect on longitudinal tensile failure of unidirectional carbon fibre composites

This paper deals with modelling the effect of local fibre volume fraction variability, fibre misalignment and fibre strength variability on the longitudinal tensile strength of unidirectional plies with finite element analysis. Variability is accounted for by generating spatially-correlated fields of fibre misalignment and volume fraction. This information is then translated into local mechanical properties and orientations in finite element models of the ply, which are virtually tested in longitudinal tension. Monte Carlo simulations were performed to evaluate the effect of different sources of material variability, i.e. local fibre strength, fibre volume fraction and misalignment. Ply strength predictions lowered when including the variability of local volume fraction and fibre misalignment in the modelling, showing a better agreement with experiments for the carbon/epoxy system investigated

Micro-mechanical modelling of longitudinal compression in unidirectional composites: effect of misalignment

Unidirectional composites exhibit their best performances when loaded in the longitudinal direction, exploiting the high stiffness and strength of the reinforcements. In longitudinal compression, the strength is significantly lower if compared to tension. This is due to the inherent material imperfections, such as fibre misalignment, that trigger the formation of kink bands and micro-buckling of fibres under compression. The phenomena involved in longitudinal compression are very complex. According to some authors, failure is governed by the matrix yielding and the fibre-matrix debonding, promoted by fibre misalignment. Predictive models in the literature consider these phenomena to capture the kink band formation. In this work, a micromechanical model based on finite elements is used to simulate the longitudinal compressive behaviour of a unidirectional composite. The microstructure is generated based on an algorithm, extended to include misalignment. The features of the model are: i) fibre-matrix interfaces modelled with cohesive elements, ii) matrix plasticity and damage, to account for the non-linear behaviour of the matrix; iii) sinusoidal misalignment and iv) random geometrical arrangement in the transverse direction. The results of this investigation are compared with other similar works in the literature, both with finite element and analytical formulations. The results of this work are the first part of a broader research, aimed to investigate more realistic 3D misalignments and its effect on compressive strength

Evaluation of tomato rootstock in Sicilian greenhouse growing conditions

[EN] Greenhouse tomato production is one of the most important agriculture Italian vegetable production which is of interest for all the country¿s regions, focusing on southern Italy. The critical point of breeders for this crop is to obtain a high level of sustainability needed in organic farming. The aim of the present work was the evaluation of 21 genotypes of tomato rootstocks originated by several crosses aimed to transfer interesting resilience traits such as Fusarium oxysporum f. sp. radicis-lycopersici (FORL), Tomato mosaic virus (ToMV) and Tomato spotted wilt virus (TSWV) producing interspecific and intraspecific hybrids. The genotype `Creativo¿ F1 hybrid was chosen as a control grafted and as scion for the grafted plants. The plants were grown inside the greenhouse at single stem till the eighth truss at 3 plants m¿2 crop density and were placed following randomized blocks experimental design. Tomato genotypes were characterized for their yield traits such as the trusses weight, fruit number truss¿1, red and green fruits truss¿1 and cumulative production until the eighth truss; only eight trusses were considered for the phenotypical analysis. Fruit (longitudinal and transversal) and plant (stem and basal stem) diameters were calculated and compared. Tomato phenotyping was followed by the qualitative analysis of trusses with chromatic parameters (a*, b*, L*) and soluble solids content. The results showed significant variations among genotypes: rootstock cross BT04060 × BT00120 registered the higher yield and single fruits weight (908.28 g) followed by BT2510 × BT00250 (861.36 g) and BT02220 × BT00230 (853.29 g). The higher fruits number truss¿1 value was registered in BT2510 × BT00250 and was 12.19. The present work is included in Horizon 2020 BRESOV (Breeding for Resilient, Efficient and Sustainable Organic Vegetable production) project.The present work was funded and performed within the BRESOV H2020 project (Grant Agreement nr. 774244).Treccarichi, S.; Infurna, M.; Malgioglio, G.; Arena, D.; A. Ruffino; Prohens Tomás, J.; Branca, F. (2022). Evaluation of tomato rootstock in Sicilian greenhouse growing conditions. Acta Horticulturae. 1354:129-136. https://doi.org/10.17660/ActaHortic.2022.1354.17129136135

Prediction of tensile stiffness and failure of carbon fibre composite laminae: a multi-scale non-deterministic approach

status: Unpublishe

A viviparous mutant of maize exhibiting permanent water stress symptoms

In maize vivipary, the precocious germination of the seed while it is still attached to the ear is a reliable phenotype for the identification of mutants impaired in the biosynthesis or response to abscisic acid (ABA). Here we present the characterization of a new allele of vp10, a gene encoding for a cofactor (MoCo) required for the last step of ABA biosynthesis. The lesion in this gene leads to a reduction in the endogenous ABA level. Embryonic messenger RNAs of the ABA inducible genes glb1, lea3, and rab17 are barely detectable, although their level increases when stimulated by exogenous ABA administration. These findings confirm that the mutant can be ascribed to a defect in ABA biosynthesis. In the absence of water stress, mutant plants grow like wild-type siblings; however when mutant tissues are exposed to air they differ from non-mutant ones by showing a higher rate of water loss, of transpiration and of stomatal conductance. These events are restored to almost normal values by adding exogenous ABA. All these defects are ascribable to an impairment in the regulation of stomatal opening since, in contrast to wild-type, some of the mutant stomata exhibit partially or totally open rims. The defect in ABA biosynthesis is also associated with loss of regulation of the expression of rab17 and rab28, two genes expressed in vegetative tissues under abiotic stress. These genes are constitutively expressed in the mutant plant tissues independently of the water regime applied. Thus this mutant may provide a tool for the study of molecular mechanisms underlying drought-stress responses in crop plants

THE MOTIVATION OF COLLABORATORS IN FAMILY MICRO COMPANIES: CYBERCAFÉ

<div><p>ABSTRACT Purpose: The purpose of this study is to analyze the motivation of collaborators based on the Maslow pyramid, in order to have an approach to the subject of motivation in family micro-businesses, such as cybercafé, where business is income from computer systems and the internet. Originality/value: This paper is original to find solutions to the existent gap in motivating collaborators of micro family business dedicated to the service of renting computers for the Internet. The main implication is to generate proposals for the improvement of labor motivation in the aforementioned family micro-enterprises. Design/methodology/approach: A questionnaire elaborated on the scale of Likert is applied to diagnose motivation and job satisfaction starting from the Maslow pyramid. With a sample of 7 employees, who work in the company mentioned above, the questionnaire was applied to Google forms. Summary of key results: The results presented by the study of job motivation in cybercafé are not favorable to the company, due to the representativeness showed by the “indifferent” option chosen by the employees in the scenarios presented in the questionnaire. This can create uncertainty due to the impartiality or to some extent insecurity in the employee when choosing the option “indifferent”. Findings: Labor motivation in the family micro-business partners may be a little complex to address under the Maslow theory, and in general, that of any models, which have been developed, because of to the environment, in which these family companies are set up and operate.</p></div