A continuum damage model to simulate failure in composite plates under uniaxial compression

Experimental investigations and numerical simulations are performed in order to numerically predict the buckling behaviour of thin composite laminated specimens. Experiments are aimed at two objectives: the first is to completely characterize the carbon/epoxy material under simple loading configurations, the second is to test this material in buckling and post-buckling situations. The data collected with the first campaign of experiments are used to obtain the strength parameters required to define a damage model based on the failure theory by Tsai-Wu. This model is implemented in a Finite Element (FE) code and numerical simulations of buckling are executed for unidirectional and cross-ply laminates; results are in good agreement with experiments both in terms of determination of the critical loads and prediction of failure during post-buckling

Thermo-Mechanical Behaviour of Flax-Fibre Reinforced Epoxy Laminates for Industrial Applications

The present work describes the experimental mechanical characterisation of a natural flax fibre reinforced epoxy polymer composite. A commercial plain woven quasi-unidirectional flax fabric with spun-twisted yarns is employed in particular, as well as unidirectional composite panels manufactured with three techniques: hand-lay-up, vacuum bagging and resin infusion. The stiffness and strength behaviours are investigated under both monotonic and low-cycle fatigue loadings. The analysed material has, in particular, shown a typical bilinear behaviour under pure traction, with a knee yield point occurring at a rather low stress value, after which the material tensile stiffness is significantly reduced. In the present work, such a mechanism is investigated by a phenomenological approach, performing periodical loading/unloading cycles, and repeating tensile tests on previously \u201cyielded\u201d samples to assess the evolution of stiffness behaviour. Infrared thermography is also employed to measure the temperature of specimens during monotonic and cyclic loading. In the first case, the thermal signal is monitored to correlate departures from the thermoelastic behaviour with the onset of energy loss mechanisms. In the case of cyclic loading, the thermoelastic signal and the second harmonic component are both determined in order to investigate the extent of elastic behaviour of the materia

Using FEM simulation to predict structural performances of a sailing dinghy

The use of finite element method (FEM) tools is proposed to investigate the structural response of an eco-sustainable sailing yacht to different loading conditions, typical of those acting during regattas. The boat is, in particular, a 4.60 m dinghy with the hull and the deck made of an hybrid flax\ue2\u80\u93cork sandwich and internal reinforcements made of marine plywood. A preliminary activity has consisted in the refitting of an existing model in order to reduce the hull weight and to improve performances during manoeuvrings. These tasks have been interactively simulated in the virtual environment of the boat CAD model, where longitudinal and transversal reinforcements were enlightened and the maximum beam reduced. At the same time, results of FEM simulations on the modified model were analysed in order to verify the structural integrity. Shape modifications have been applied to the real model in laboratory and the resulting hull has been instrumented with strain gauges and tested under rigging conditions to validate the numerical procedure. Finally, the FEM model was used to predict the response of the boat to loading systems typical of sailing conditions

Neoadjuvant therapy for breast cancer

Objective: To evaluate the frequency of neoadjuvant therapy (NT) in women with stage I–III breast cancer in Italy and whether it is influenced by biological characteristics, screening history, and geographic area. Methods: Data from the High Resolution Study conducted in 7 Italian cancer registries were used; they are a representative sample of incident cancers in the study period (2009–2013). Included were 3546 women aged <85 years (groups <50, 50–69, 70–64, and 75+) with stage I–III breast cancer at diagnosis who underwent surgery. Women were classified as receiving NT if they received chemotherapy, target therapy, and/or hormone therapy before the first surgical treatment. Logistic models were built to test the association with biological and contextual variables. Results: Only 8.2% of women (290 cases) underwent NT; the treatment decreases with increasing age (14.5% in age <50 and 2.2% in age 75+), is more frequent in women with negative receptors (14.8%), HER2-positive (15.7%), and triple-negative (15.6%). The multivariable analysis showed the probability of receiving NT is higher in stage III (odds ratio [OR] 3.83; 95% confidence interval [CI] 2.83–5.18), luminal B (OR 1.87; 95% CI 1.27–2.76), triple-negatives (OR 1.88; 95% CI 1.15–3.08), and in symptomatic cancers (OR 1.98; 95% CI 1.13–3.48). Use of NT varied among geographic areas: Reggio Emilia had the highest rates (OR 2.29; 95% CI 1.37–3.82) while Palermo had the lowest (OR 0.41; 95% CI 0.24–0.68). Conclusions: The use of NT in Italy is limited and variable. There are no signs of greater use in hospitals with more advanced care

Big Bang nucleosynthesis revisited via Trojan Horse Method measurements

Nuclear reaction rates are among the most important input for understanding the primordial nucleosynthesis and therefore for a quantitative description of the early Universe. An up-to-date compilation of direct cross sections of 2H(d,p)3H, 2H(d,n)3He, 7Li(p,alpha)4He and 3He(d,p)4He reactions is given. These are among the most uncertain cross sections used and input for Big Bang nucleosynthesis calculations. Their measurements through the Trojan Horse Method (THM) are also reviewed and compared with direct data. The reaction rates and the corresponding recommended errors in this work were used as input for primordial nucleosynthesis calculations to evaluate their impact on the 2H, 3,4He and 7Li primordial abundances, which are then compared with observations.Comment: 22 pages, 7 figures, accepted for publication in The Astrophysical Journa

The durability of carbon fiber/epoxy composites under hydrothermal ageing

Studies on fibre reinforced composites are now receiving greater attention. Industrial applications have been successful in areas like aerospace, automobile, marine, construction and sporting goods. The first generation of epoxy resins for use in carbon fibre composites are able to achieve optimized high stiffness modules and high heat resistance by a high crosslink density, reached through thermal curing. However, these formulations can be very toxic and brittle with low crack resistance, which was a major disadvantage for structural applications. In the last years the use of ionizing radiation as alternative to thermal curing has been proposed as an environmentally friendly process. Furthermore, in order to enhance toughness mechanical requirements for their applications, the formulation generally consists of blends of epoxy resins and engineering thermoplastics. In terms of durability (service life and reliability), in these materials it depends on different environmental conditions (temperature, moisture, etc.), and it is very important to know how their properties are modified after the exposure to different temperature and moisture absorption cycles. In this work carbon fibre composites produced by ionizing radiation induced curing of the epoxy based matrices have been subjected to thermal and moisture absorption ageing and the influence of these treatments on the thermal and mechanical properties has been investigated through dynamic mechanical thermal analysis and mechanical fracture toughness tests

Technical Solutions and Standards Upgrade for Photovoltaic Systems Operated over 1500 Vdc

This paper deals with photovoltaic (PV) systems with operating voltage increased over the value 1500 V in DC, which represents the limit of the current solutions and the actual standard for the PV plant at utility-scale level. The increase of the DC voltage is aimed at reducing the cable energy losses, the number of components and to optimise the layout of the plants, increasing the competitiveness of Medium Voltage PV (MVPV) solutions with rated powers of hundreds of megawatt. The analysis carried out has identified the possible solutions to adopt in order to reach this target and has remarked that today the International Standards are not covering all the aspects of the technical solutions to be introduced in a MVPV plant. This paper indicates the key issues to be addressed by new Standards on some components in order to enable the deployment of MVPV solutions. Finally, the characteristics of an installation at 1500 V DC and some results of tests carried out on the isolation system of a 1500 V PV plant are discussed

Nuove varianti di Bronchite Infettiva negli allevamenti avicoli siciliani

Avian Infectious Bronchitis (IB) is a disease caused by a Coronavirus, included in Coronaviridae family. The disease, endemic in Italy, affects both broilers and laying hens. It represents one of the main health issue in sicilian poultry farms. The presence of new antigenic variants makes problematic the implementation of an adequate prophylaxis through the use of appropriate vaccines. The present work aims to study the spread of IB strains in Sicily by serological and biomolecular tests in order to investigate the presence of "historical" strains as well as new strains and to carry out the genotyping of viruses isolated. The serological results show that the used vaccination protocols are able to develop an adequate antibody titre along all production steps both laying hens and broilers. The virological results underline the presence of QX strain in a broilers farm. This is a strain widespread in Italy but never reported in the regional territory

Direct Reactions with Exotic Nuclei, Nuclear Structure and Astrophysics

Intermediate energy Coulomb excitation and dissociation is a useful tool for nuclear structure and astrophysics studies. Low-lying strength in nuclei far from stability was discovered by this method. The effective range theory for low-lying strength in one-neutron halo nuclei is summarized and extended to two-neutron halo nuclei. This is of special interest in view of recent rather accurate experimental results on the low-lying electric dipole strength in $^{11}$Li. Another indirect approach to nuclear astrophysics is the Trojan horse method. It is pointed out that it is a suitable tool to investigate subthreshold resonances.Comment: 8 pages, 2 figures, Proceedings of the Erice School on 'Radioactive Beams, Nuclear Dynamics and Astrophysics' to be published in 'Prog. Part. Nucl. Phys.