Low velocity failure and integrity assessment of foam core sandwich panels

Impact resistance and energy absorbing capability are of great interest in the design of composite sandwich structures. This paper experimentally studies damage, failure and energy absorption properties of foam core sandwich panels with aluminum and glass fiber reinforced plastic (GFRP) facesheets subjected to low velocity impact. Tests are performed using a drop weight impact tower at different impact velocities. The energy absorbing capabilities of aluminum and composite facesheet sandwich panels with PUR and PS foam core are evaluated by means of absorbed energy-time histories and by specific parameters as normalized absorbed energy, specific energy absorption, and crush force efficiency. Stiffer panels behave better at lower impact velocities, while more ductile ones do better if impact energy is increased

Influence of cell wall curvature radius and adhesive layer on the effective elastic out-of-plane properties of hexagonal honeycombs

Numerical modeling of honeycomb structures in aerospace engineering is too tedious and time consuming. The homogenization of these structures permits to obtain an equivalent orthotropic homogeneous solid and its elastic effective properties and thus realizing very efficient simulations. In a sandwich structure the most important effective constants of the core are the out-of-plane shear moduli G23 and G13. These particular effective constants can be obtained analytically, numerically or, if available, can be taken from the producer's data sheets. In the last case they are generally obtained experimentally, but only for some particular thicknesses of the cores and sandwich faces. The analytical models usually neglect the curvature radius of the cell walls and the adhesive layer influence by using some additional hypotheses. In this paper a general parameterization of commercial honeycombs is first discussed. Then, neglecting the skin effect and considering the rigid skin effect, the out-of-plane properties of the core are obtained using a finite element analysis of a representative volume element. The numerical results are analyzed by comparing them to the ones given by the existing analytical models and/or experimental data and their advantages and pitfalls are discussed and explained. The results provide new insights into understanding the mechanics of honeycombs

Cohesive and XFEM evaluation of adhesive failure for dissimilar single-lap joints

AbstractCohesive Zone Modelling (CZM) and eXtended Finite Element Modelling (XFEM) available in Abaqus® are used together to simulate the behaviour and strength of dissimilar single-lap adhesively bonded joints. A distinct CZM model is also used. Single-lap joints made of aluminium and carbon fibre adherends of different thickness are tested to understand better the behaviour of such dissimilar joints. Local deformation fields are monitored by using the digital image correlation method (DIC). Peeling and shearing strains are investigated, emphasizing that peeling is important in the region where failure is initiated, towards an extremity of the overlap region. The use of dissimilar adherends is reducing the strength and stiffness of the joints as the delamination and pull-out of the carbon fibres reduces the integrity of the joint. The experimental evidence given by DIC is not to be obtained by numerical simulations

The experience of Romanian physiotherapists in the management of postoperative rehabilitation of patients with total hip arthroplasty - content and criteria for completion of physiotherapy sessions

Background: Total hip arthroplasty (THA) is a procedure that removes damaged bone and car-tilage and replaces it with prosthetic components and is performed by orthopedics. Objective: management of post-operative rehabilitation of THA patients in terms of content and comple-tion criteria of physiotherapy sessions. The research aims to explore the experience of Romani-an physiotherapists about the content and completion criteria of physiotherapy sessions in-volved in the management of postoperative rehabilitation after THA. Methods: The method used in this study was a questionnaire-based survey, with 120 Romanian specialists in the field completing an online screening tool that contained, along with a socio-demographic question-naire, a series of questions about their professional experience. Results: One of the most im-portant results of the study is the identification of statistically significant associations between the completion criteria of physiotherapy sessions and three techniques included in the rehabil-itation program after THA: edema management, gait re-education exercises, and exercises to increase hip mobility. Conclusion: The the research revealed that the experience of Romanian specialists regarding postoperative rehabilitation after THA is concordant with the experience of specialists in the field, and can be used to develop and test an individualized therapeutic protocol and to design continuing professional training programs for physiotherapists in Romania

Scoliotic postural alignment in prepubertal children: somatoscopic analysis of anatomical landmarks and development of a working model to limit spinal changes

Background. The study aims to perform a somatoscopic analysis on a sample of 100 prepubertal children aged 10-14 years, girls and boys, who are diagnosed with scoliosis. Somatoscopic as-sessment is one of the most commonly used, therefore we thought that making a way of inter-preting the results could be useful to monitor postural attitude in children diagnosed with sco-liosis. Identifying the early onset of physical impairment in the spine with somatoscopy can be a key factor in maintaining optimal postural status. This approach may help in achieving a way of working that limits the negative effects of scoliosis on the subjects. Materials and methods. The selection of subjects is based on exclusion and inclusion criteria related to age, comorbidi-ties, therapeutic approach, and other criteria. Also, aspects that accompany the growth and de-velopment process of children in this prepubertal period and factors that may disturb this pro-cess are described in detail. Also in this context, we will present basic notions of body posture and etiopathogenesis of the onset of scoliotic deficiencies in children during this period of growth and development. Somatoscopic analysis is performed in the orthostatic position and is based on the identification of anatomical landmarks of the body concerning body posture. Re-sults. From the total analyzed scoliosis, n = 100, 74% are type „C” scoliosis and only 26% are type „S” and in terms of gender, 59% are girls and 41% boys; type „C1” (Cobb angle <100) scoliosis n = 60, with an angulation < 100 are 43.24% stabilized, therefore type „C1” scoliosis are more likely to be stabilized. „S”-type scoliosis with an angulation < 150 is only 3 cases repre-senting 11.53%, and those with an angulation from < 200 to < 400 are number 23 cases 88.64% which concludes that „S” type scoliosis is more aggressive and more difficult to manage. Con-clusions. Our study show that only 13% of the subjects had a regression of the angulation fol-lowing the kinetotherapy program, therefore the main objective remains to stabilize the scoli-osis attitude and limit the effects of this pathology. A regular assessment and somatotopic analysis resulting in a physiotherapy exercises program containing corrective postural postures and postural education is the most beneficial approach to stabilize the postural deficit

ERCP extraction of stones in situs inversus patients; state-of-the-art techniques

Situs inversus totalis (SIT) is a rare congenital disease that causes mirror transposition of the abdomino-thoracic structures. When such patients develop pathologies related to the bile duct, most commonly choledocholithiasis, the optimal diagnostic process can be hampered by the rarity of such a pathology and the lack of medical information on this topic. Once the diagnosis is established, through endoscopic ultrasound and MRCP, the patient is sent to perform ERCP, which requires tailored approaches for each case. We present the case of a 33-year-old patient who was previously documented with SIT. On admission she presented with abdominal pain and fever that started a week before presentation, so antibiotic therapy was initiated. Imaging investigations revealed intrahepatic gallstones, so she underwent ERCP the next day with the identification of an intrahepatic bile lake containing stones within. Naso-biliary drainage was placed and further 2 ERCP procedures followed, with the insertion of 3 plastic biliary stents. The evolution was favorable, until the complete removal of gallstones and remission of clinical symptoms. The patient was carefully monitored in the following two days and the stents were removed, being later discharged and monitored for a period of 6 months in which no biliary/digestive symptoms were noted

Evaluation of patients with a HeartMate 3 left ventricular assist device using echocardiographic particle image velocimetry

Purpose: Poor left ventricular (LV) function may affect the physiological intraventricular blood flow and physiological vortex formation. The aim of this study was to investigate the pattern of intraventricular blood flow dynamics in patients with LV assist devices (LVADs) using echocardiographic particle image velocimetry. Materials and methods: This prospective study included 17 patients (mean age 57 ± 11 years, 82% male) who had received an LVAD (HeartMate 3, Abbott Laboratories, Chicago, Illinois, USA) because of end-stage heart failure and poor LV function. Eleven (64%) patients had ischemic cardiomyopathy, and six patients (36%) had nonischemic cardiomyopathy. All patients underwent echocardiography, including intravenous administration of an ultrasound-enhancing agent (SonoVue, Bracco, Milan, Italy). Echocardiographic particle image velocimetry was used to quantify LV blood flow dynamics, including vortex formation (Hyperflow software, Tomtec imaging systems Gmbh, Unterschleissheim, Germany). Results: Contrast-enhanced ultrasound was well tolerated in all patients and was performed without adverse reactions or side effects. The LVAD function parameters did not change during or after the ultrasound examination. The LVAD flow was on average 4.3 ± 0.3 L/min, and the speed was 5247 ± 109 rotations/min. The quantification of LV intraventricular flow demonstrated substantial impairment of vortex parameters. The energy dissipation, vorticity, and kinetic energy fluctuation indices were severely impaired. Conclusions: Echo particle velocimetry is safe and feasible for the quantitative assessment of intraventricular flow in patients with an LVAD. The intraventricular LV flow and vortex parameters are severely impaired in these patients

Search for dark matter produced in association with bottom or top quarks in √s = 13 TeV pp collisions with the ATLAS detector

A search for weakly interacting massive particle dark matter produced in association with bottom or top quarks is presented. Final states containing third-generation quarks and miss- ing transverse momentum are considered. The analysis uses 36.1 fb−1 of proton–proton collision data recorded by the ATLAS experiment at √s = 13 TeV in 2015 and 2016. No significant excess of events above the estimated backgrounds is observed. The results are in- terpreted in the framework of simplified models of spin-0 dark-matter mediators. For colour- neutral spin-0 mediators produced in association with top quarks and decaying into a pair of dark-matter particles, mediator masses below 50 GeV are excluded assuming a dark-matter candidate mass of 1 GeV and unitary couplings. For scalar and pseudoscalar mediators produced in association with bottom quarks, the search sets limits on the production cross- section of 300 times the predicted rate for mediators with masses between 10 and 50 GeV and assuming a dark-matter mass of 1 GeV and unitary coupling. Constraints on colour- charged scalar simplified models are also presented. Assuming a dark-matter particle mass of 35 GeV, mediator particles with mass below 1.1 TeV are excluded for couplings yielding a dark-matter relic density consistent with measurements