Preliminary results in synchrotron X-ray diffraction measurements of rubber composites structure before and after exposure to hydrogen

In future years, fuel cells are expected to represent a promising technology as a source of heat and electricity in buildings and of electrical power for vehicles, since fossil fuels are exhausting and significantly degrade air quality. It is well known that, when exposed to a hydrogen environment, hydrogen embrittlerment may affect materials such as iron and steel. But these are not the only materials that are used for hydrogen equipment. In particular, the rubber materials used for O\u2013rings that seal high pressure hydrogen gas equipment show problems of internal fracture, called blister fracture, when the gas is rapidly decompressed. As many different kinds of fillers can be used, in this work we started to investigate the influence of the type of filler on the rubber composites structure, by means of X-ray diffraction measurements performed at the Elettra synchrotron radiation facility in Trieste. In this preliminary study, three kinds of samples were analyzed before and after exposure to hydrogen: Sulphur vulcanized EPDM, Peroxide vulcanized EPDM and Sulphur vulcanized NBR. While Peroxide vulcanized samples did not show significant differences in the diffraction pattern, changes could be detected in the cristalline form of Sulfure vulcanized rubber

A possible new approach in the prediction of late gestational hypertension: The role of the fetal aortic intima-media thickness

The aim was to determine the predictive role of combined screening for late-onset gestational hypertension by fetal ultrasound measurements, third trimester uterine arteries (UtAs) Doppler imaging, and maternal history. This prospective study on singleton pregnancies was conducted at the tertiary center of Maternal and Fetal Medicine of the University of Padua during the period between January 2012 and December 2014. Ultrasound examination (fetal biometry, fetal wellbeing, maternal Doppler study, fetal abdominal aorta intima-media thickness [aIMT], and fetal kidney volumes), clinical data (mother age, prepregnancy body mass index [BMI], and parity), and pregnancy outcomes were collected. The P value <0.05 was defined significant considering a 2-sided alternative hypothesis. The distribution normality of variables were assessed using Kolmogorov–Smirnoff test. Data were presented by mean (±standard deviation), median and interquartile range, or percentage and absolute values. We considered data from 1381 ultrasound examinations at 29 to 32 weeks’ gestation, and in 73 cases late gestational hypertension developed after 34 weeks’ gestation. The final multivariate model found that fetal aIMT as well as fetal umbilical artery pulsatility index (PI), maternal age, maternal prepregnacy BMI, parity, and mean PI of maternal UtAs, assessed at ultrasound examination of 29 to 32 weeks’ gestation, were significant and independent predictors for the development of gestational hypertension after 34 weeks’ gestation. The area under the curve of the model was 81.07% (95% confidence interval, 75.83%–86.32%). A nomogram was developed starting from multivariate logistic regression coefficients. Late-gestational hypertension could be independently predicted by fetal aIMT assessment at 29 to 32 weeks’ gestation, ultrasound Doppler waveforms, and maternal clinical parameters

Evaluation of fibre lenght distribution in a short glass fibre reinforced PA-6

The aim of this work is to evaluate the fibre length distribution in a polyamide reinforced by short glass fibre. The fibre length and the fibre orientation distributions strongly influence the mechanical properties of short fibre reinforced composites. The sample investigated is a 30GFPA6 (polyamide-6 reinforced by 30 % by weight glass fibre), extracted from an injection-moulded plate. The digital reconstruction of the three-dimensional structure of the sample was obtained by synchrotron radiation micro-computed tomography (micro-CT), a high spatial resolution non-destructive technique. One global and one local method have been tested for the automatic evaluation of the fibre length distribution in our sample. The global method is based on the mean fibre length distribution computed from the Star Length Distribution (SLD), a morphological parameter. The local method is based on a 3D skeletonize function. The results are discussed in the light of the experimental data available in literature

PRELIMINARY DESIGN OF AN X-RAY IMAGING SYSTEM FOR THE BONE STRUCTURAL INDEX EVALUATION

Osteoporosis (OP) is a very common disease in which the bones become weak and are more likely to break. Despite the huge costs in the EU and worldwide, the majority of individuals who have sustained an osteoporosis-related fracture or who are at high risk of fracture are left untreated. In effect, OP is a silent disease, with bones deteriorating without warning until fracture, and the current screening modalities are not significantly better than age alone, also because they consider only the bone quantity (bone mineral density, BMD) and the clinical risk factors, but disregard the bone quality, that is the structural soundness of the trabecular arrangement, which can be evaluated by simulations on virtual models. While 3D models can only be used in research because of high costs, an alternative approach based on the acquisition of planar hand radiograms for bone behaviour simulations, and the use of a Structural Index, SI, for bone quality ranking, have been developed at the University of Trieste. In this work, we discuss the preliminary design of a portable low dose X-ray hand scanner to be used as a low cost, user-friendly device (Fig.1) for imaging the trabecular pattern in the proximal phalanges of the non-dominant hand and for providing a radiogram suitable for the SI evaluation

PRELIMINARY DESIGN OF AN X-RAY IMAGING SYSTEM FOR THE BONE STRUCTURAL INDEX EVALUATION

Osteoporosis (OP) is a very common disease in which the bones become weak and are more likely to break. Despite the huge costs in the EU and worldwide, the majority of individuals who have sustained an osteoporosis-related fracture or who are at high risk of fracture are left untreated. In effect, OP is a silent disease, with bones deteriorating without warning until fracture, and the current screening modalities are not significantly better than age alone, also because they consider only the bone quantity (bone mineral density, BMD) and the clinical risk factors, but disregard the bone quality, that is the structural soundness of the trabecular arrangement, which can be evaluated by simulations on virtual models. While 3D models can only be used in research because of high costs, an alternative approach based on the acquisition of planar hand radiograms for bone behaviour simulations, and the use of a Structural Index, SI, for bone quality ranking, have been developed at the University of Trieste. In this work, we discuss the preliminary design of a portable low dose X-ray hand scanner to be used as a low cost, user-friendly device (Fig.1) for imaging the trabecular pattern in the proximal phalanges of the non-dominant hand and for providing a radiogram suitable for the SI evaluation

ELASTICITY of SHORT FIBRE REINFORCED POLYAMIDE: MORPHOLOGICAL AND NUMERICAl ANALYSIS OF FIBRE ORIENTATION EFFECTS

The fatigue behaviour of injection moulded short fibre reinforced polymers depends upon fibre orientation, as shown in experiments conducted with notched specimens injected through different injection gates. The different fatigue behaviour is mainly related to the different local elastic properties, as determined by the different fibre orientation patterns, resulting into different strain distributions. In order to quantify the relationship between fibre orientation and elastic constants, the Cell Method was applied to volumes extracted from the specimens, reconstructed by micro-tomography

MODELLING ELASTICITY OF INJECTION MOULDED SHORT FIBRE REINFORCED POLYMERS: COMPARISON BETWEEN EXPERIMENTAL AND ANALYTICAL APPROACHES

In this work we analysed a sample of short fibre reinforced polyamide extracted from an injection moulded plate. We derived local values of the elastic constants by two different numerical methods, one based on simulation and one based on the reconstruction of the sample's microstructure by micro - CT. Results were compared in terms of moduli of elasticity, assuming an orthotropic material model. Fibre orientation was first simulated by process simulation and results were checked against experimental data obtained by the optical section method. Then, fibre orientation data were used for micro-mechanical modelling of the elastic behaviour by means of mean field homogenisation tools. The experimentally based approach was based on micro computed tomography reconstructions of the inner structure of samples extracted from the injection moulded plate. Using numerical models based on the Cell Method, the elastic behaviour of the reconstructed volume was simulated and results were compared with analytical models based on process simulations and homogenization

Analisi dell’anisotropia microstrutturale in materiali compositi rinforzati con fibre corte

Synchrotron light microtomography has proved to be particularly efficient in order to analyze the microstructural characteristics in terms of reinforce fibre distribution and orientation in glass fibre reinforced composites. The spatial distribution of fibre within the polymeric matrix could be detected even in case of fibre characterized by a small diameter (10 micrometers average diameter). Differences in orientation distribution within a sample could be measured using the Mean Intercept Length (MIL) and the fabric tensor. The results presented herein refer to a sample of a 30% by weight glass fibre reinforced polyamide 6, extracted form a thin plate

Studio del danneggiamento mediante tomografia in luce del sincrotrone: impatto di un cono d’ombra sulla qualità finale delle ricostruzioni

Un’accurata osservazione della geometria tridimensionale di cricche e difetti è necessaria per lostudio dei meccanismi alla base del processo di danneggiamento. I metodi convenzionali utilizzati a questoscopo sono distruttivi o non possiedono una sufficiente risoluzione. Le tecniche di imaging che utilizzano laluce di sincrotrone, ed in particolare la microtomografia (micro-CT) a raggi X, invece, uniscono i vantaggi di unatecnica non distruttiva ad un’elevata risoluzione spaziale e risultano quindi particolarmente interessanti. Unlimite all’applicazione di questa tecnica è costituito dalla propensione della cricca a richiudersi una volta rimossoil carico che ha provocato il danneggiamento, superabile attraverso l’impiego di un dispositivo in grado diesercitare un carico di trazione durante l’acquisizione dei dati. Facendo riferimento al set-up sperimentale dellalinea SYRMEP di Elettra, il sincrotrone di Trieste, e tralasciando per il momento i vincoli legati a pesi eingombri, è possibile pensare di inserire tra camera di ionizzazione e CCD una macchina per prove di trazionemono-colonna commerciale, in grado di mantenere aperto il difetto per tutta la durata della tomografia. Inquesto lavoro viene valutato l’impatto di questo vincolo sulla qualità finale delle ricostruzioni