1,721,059 research outputs found
Influence of Material Uncertainty on the Damage Resistance and Tolerance of Stiffened Composite Panels
No full textStochastic Approach to Damage Resistance Analysis of Stiffened Composite Panels
No full textComposite materials exhibit complex phenomena associated with damage onset, and are characterized by significant uncertainties in their material properties. The development of damage resistance design methodology, especially for damage induced by low velocity impacts in aircraft structures, have allowed a more efficient management of the damage in composites. In this paper a probabilistic approach has been adopted in order to evaluate the impact of the material properties scattering on the damage resistance of a composite panel. Furthermore two different composite panels have been investigated and compared in order to detect, based on a probabilistic approach, the one exhibiting the best performances in terms of damage resistance
INFLUENCE OF MATERIAL UNCERTAINTY ON THE DAMAGE RESISTANCE AND TOLERANCE OF STIFFENED COMPOSITE PANELS
No full textComposite materials exhibit complex phenomena associated with damage onset and propagation. In particular damages induced by low velocity impacts represent a main concern in aircraft structures, which may be subjected to hail impact, tools dropped during maintenance, or foreign object damage during landing and takeoff. The heterogeneous and anisotropic nature of composites allows for several modes of failure, however it has been observed that the most dangerous and unpredictable one is the delamination, which can considerably reduce the inplane compressive strength of the laminates. The development of damage resistance and damage tolerance design methodologies have allowed a more efficient management of the damage in composites. However these methodologies strongly depend on composite material properties, which are affected by an intrinsic uncertainty. In this paper the effect of the material properties scatter on the damage resistance and the damage tolerance of composites will be assessed by using a probabilistic approach
Characteristics of viral pneumonia in the COVID-19 era: an update
No full textInfluenza virus, rhinovirus, and adenovirus frequently cause viral pneumonia, an important cause of morbidity and mortality especially in the extreme ages of life. During the last two decades, three outbreaks of coronavirus-associated pneumonia, namely Severe Acute Respiratory Syndrome, Middle-East Respiratory Syndrome, and the ongoing Coronavirus Infectious Disease-2019 (COVID-19) were reported. The rate of diagnosis of viral pneumonia is increasingly approaching 60% among children identified as having community-acquired pneumonia (CAP). Clinical presentation ranges from mild to severe pneumonitis complicated by respiratory failure in severe cases. The most vulnerable patients, the elderly and those living with cancer, report a relevant mortality rate. No clinical characteristics can be useful to conclusively distinguish the different etiology of viral pneumonia. However, accessory symptoms, such as anosmia or ageusia together with respiratory symptoms suggest COVID-19. An etiologic-based treatment of viral pneumonia is possible in a small percentage of cases only. Neuraminidase inhibitors have been proven to reduce the need for ventilatory support and mortality rate while only a few data support the large-scale use of other antivirals. A low-middle dose of dexamethasone and heparin seems to be effective in COVID-19 patients, but data regarding their possible efficacy in viral pneumonia caused by other viruses are conflicting. In conclusion, viral pneumonia is a relevant cause of CAP, whose interest is increasing due to the current COVID-19 outbreak. To set up a therapeutic approach is difficult because of the low number of active molecules and the conflicting data bearing supportive treatments such as steroids
Thermo Mechanical Design Methodologies
No full textDuring the Preliminary Design Phase, a simplified model has been developed in order to make fast the optimization process of thermal protection systems thicknesses.
It is adopted to minimize the weight of the thermal protection systems by choosing the best configuration that fits a given set of requirements.
It is mainly suitable for axisymmetric geometries in which axial conduction/diffusion phenomena can be neglected
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