Vibroacoustic performance of fiber metal laminates with delamination

In the present work, the numerical assessment of vibroacoustic (VA) performance of fiber metal laminates (FML) with mid-plane center delamination is presented. A fluid structure interaction study has been done using finite element method (FEM). Experimental validation is performed on an aluminium (AL) panel for verifying the correctness of finite element (FE) idealization procedure to simulate the fluid-structure interaction. Delamination is introduced in the FE model of FML panel and VA analysis is subsequently carried out. Sound transmission loss (STL) is computed on the panel with center delamination and without delamination. The overall sound pressure level (OASPL) shows that the presence of delamination (40% in total area) in FML has not changed the total energy of the transmitted sound when compared to aluminium and composites. However, in the narrow frequency bands (150–200 Hz, 200–250 Hz), the sound transmission nature has been significantly affected due to local delamination modes participating in the fluid-structure interaction process

Influence of active stiffening on dynamic behaviour of piezo-hygro-thermo-elastic composite plates and shells

The active stiffening and active compensation analyses are carried out to present the influence of active stiffness on the dynamic behaviour of piezo-hygro-thermo-elastic laminates. A coupled piezoelectric finite element formulation involving a hygrothermal strain field is derived using the virtual work principle and is employed in a nine-noded field consistent Lagrangian element. The closed-loop system is modelled with elastic stiffness, active stiffness introduced by isotropic actuator lamina and geometric stiffness due to stresses developed by hygrothermal strain. Through a parametric study, the influence of active stiffening and active compensation effects on the dynamics of cross-ply and angle-ply laminated plates and shells are highlighted. The active stiffening on thin shells is significantly influenced by boundary effects and the actuator efficiency further decreases with increase in curvature. The reduction in natural frequencies of cross-ply laminates due to hygrothermal strain is actively compensated by active stiffening; however, it is observed that the actuator performance reduces significantly with increase in curvature particularly in angle-ply laminates, which demands the use of directional actuators. The active stiffening and active compensation effects are low in moderately thick piezo-hygro-thermo-elastic plates and shells, which are less influenced by boundary conditions

Vibroacoustic Performance of Fiber Metal Laminates with Delamination

In the present work, the numerical assesment of vibroacoustic (VA) performance of Fibre Metal Laminates (FML) with mid-plane center delamination is presented. A fluid structure interaction study has been done using Finite Element Method (FEM). Experimental validation is performed on aluminium panel for verifying the correctness of Finite Element idealization procedure to simulate the fluid-structure interaction. Delamination is introduced in the FE model of FML panel and VA analysis is subsequently carried out. Sound Transmission Loss (STL) is computed on the panel with center delamination and without delamination. The Over All Sound Pressure Level (OASPL) shows that the presence of delamination (40% in total area) in FML has not changed the total energy of the transmitted sound, when compared to aluminium and composites. However, in the narrow frequency bands (150-200 Hz, 200-250 Hz) the sound transmission nature has been significantly affected due to local delamination modes, participating in the fluid-structure interaction process

The influence of biofilms on carbapenem susceptibility and patient outcome in device associated K. pneumoniae infections : insights Into phenotype vs genome-wide analysis and correlation

Klebsiella pneumoniae is one of the leading causes of nosocomial infections. Carbapenem-resistant K. pneumoniae are on the rise globally. The biofilm forming ability of K. pneumoniae further complicates patient management. There is still a knowledge gap on the association of biofilm formation with patient outcome and carbapenem susceptibility, which is investigated in present study. K. pneumoniae isolates from patients admitted in critical care units with catheters and ventilators were included. K. pneumoniae (n = 72) were subjected to 96-well plate biofilm formation assay followed by MBEC assay for subset of strong biofilm formers. Whole genome sequencing and a core genome phylogenetic analysis in comparison with global isolates were performed. Phenotypic analyses showed a positive correlation between biofilm formation and carbapenem resistance. Planktonic cells observed to be susceptible in vitro exhibited higher MICs in biofilm structure, hence MICs cannot be extrapolated for treatment. The biofilm forming ability had a significant association with morbidity/mortality. Infections by stronger biofilm forming pathogens significantly (p < 0.05) resulted in fewer “average days alive” for the patient (3.33 days) in comparison to those negative for biofilms (11.33 days). Phylogenetic analysis including global isolates revealed clear association of sequence types with genes for biofilm formation and carbapenem resistance. Known hypervirulent clone-ST23 with wcaG, magA, rmpA, rmpA2, and wzc with lack of mutation for hyper-capsulation might be poor biofilm formers. ST15, ST16, ST307, and ST258 (reported global high-risk clones) were wcaJ negative indicating the high potential of biofilm forming capacity. Genes wabG and treC for CPS, bcsA and pgaC for adhesins, luxS for quorum sensing were common in all clades in addition to genes for aerobactin (iutA), allantoin (allS), type I and III fimbriae (fimA, fimH, and mrkD) and pili (pilQ and ecpA). This study is the first of its kind to compare genetic features of antimicrobial resistance with a spectrum covering most of the genetic factors for K. pneumoniae biofilm. These results highlight the importance of biofilm screening to effectively manage nosocomial infections by K. pneumoniae. Further, data obtained on epidemiology and associations of biofilm and resistance genetic factors will serve to enhance our understanding on biofilm mechanisms in K. pneumoniae

Optimising intraperitoneal gentamicin dosing in peritoneal dialysis patients with peritonitis (GIPD) study

Background: Antibiotics are preferentially delivered via the peritoneal route to treat peritonitis, a major complication of peritoneal dialysis (PD), so that maximal concentrations are delivered at the site of infection. However, drugs administered intraperitoneally can be absorbed into the systemic circulation. Drugs excreted by the kidneys accumulate in PD patients, increasing the risk of toxicity. The aim of this study is to examine a model of gentamicin pharmacokinetics and to develop an intraperitoneal drug dosing regime that maximises bacterial killing and minimises toxicity

Paediatric multisystem inflammatory syndrome temporally associated with SARS-CoV-2 (PIMS-TS): Prospective, national surveillance, United Kingdom and Ireland, 2020.

Background: Paediatric Multisystem Inflammatory Syndrome temporally associated with SARS-CoV-2 (PIMS-TS), first identified in April 2020, shares features of both Kawasaki disease (KD) and toxic shock syndrome (TSS). The surveillance describes the epidemiology and clinical characteristics of PIMS-TS in the United Kingdom and Ireland. Methods: Public Health England initiated prospective national surveillance of PIMS-TS through the British Paediatric Surveillance Unit. Paediatricians were contacted monthly to report PIMS-TS, KD and TSS cases electronically and complete a detailed clinical questionnaire. Cases with symptom onset between 01 March and 15 June 2020 were included. Findings: There were 216 cases with features of PIMS-TS alone, 13 with features of both PIMS-TS and KD, 28 with features of PIMS-TS and TSS and 11 with features of PIMS-TS, KD and TSS, with differences in age, ethnicity, clinical presentation and disease severity between the phenotypic groups. There was a strong geographical and temporal association between SARS-CoV-2 infection rates and PIMS-TS cases. Of those tested, 14.8% (39/264) children had a positive SARS-CoV-2 RT-PCR, and 63.6% (75/118) were positive for SARS-CoV-2 antibodies. In total 44·0% (118/268) required intensive care, which was more common in cases with a TSS phenotype. Three of five children with cardiac arrest had TSS phenotype. Three children (1·1%) died. Interpretation: The strong association between SARS-CoV-2 infection and PIMS-TS emphasises the importance of maintaining low community infection rates to reduce the risk of this rare but severe complication in children and adolescents. Close follow-up will be important to monitor long-term complications in children with PIMS-TS. Funding: PHE

MAV structures and smart materials applications

Micro air vehicles are tiny flying objects, which have potential applications in multiple fields. Though13; Propulsion and Control related issues are the critical areas for MAV, structural configuration poses equally a13; challenging task for the development of strategic MAVx2019;s. As weight becomes stringent design parameter, highly13; flexible but very light weight materials are used in some of the flying MAVx2019;s. However, we have made an13; attempt to use composite materials, along with low density materials like balsa to build NAL-MAV, named13; Black Kite. Even though, stresses, or frequencies coupling with aerodynamics are not being considered13; seriously, aeroelastic stability such as gust needs attention naturally, while attitude of MAV is addressed.13; Therefore, proper structural analysis is essential, in order to optimize the weight by retaining the aerodynamic13; configuration

Evolution based statistical optimization technique to design the smart structural system for large aerospace structures

A numerical approach for genetics based statistical optimization technique is used to design the smart structural system for aerospace structures. An evolutionary based optimization technique like genetic algorithm (GA) has come into prominence. The reason for developing evolution based algorithm for optimization is for its robustness and randomness. Other numerical tools that are used for optimization are generally gradient based algorithm, where there is possibility of occurrence for a local optimum value. The GA developed is a niche-micro GA, where termination criteria are set in order to restart the algorithm. Stage-wise multiple objective functions and multiple termination criteria are incorporated to improve the computational effort. The current approach is very much robust to design a smart structural system through optimization for its maximum structural performance. In order to achieve maximum structural performance for the smart structural system, it is necessary to appropriately position the active elements. Here the genetic algorithm is amalgamated with finite element to perform a statistical based optimization to locate the position and size of active structural elements i.e. actuators/sensors. Majorly, nowadays the actuators and sensors that are preferred for smart structures design (i.e. Piezo patches, Piezo composite, SMA wire, SMA composite etc) develop induced strain under an external applied field. It becomes necessary to optimize the smart structures using the following parameters such as static strains, modal dynamic strains, size of the actuators/sensors, induced strain etc. A scaled T-Tail model is taken as an illustration to carry out the GA analysis for the location and sizing of PZT actuator/sensor. The structural parameters such as static strains, modal dynamic strains and geometry details are taken from NASTRAN and then interfaced with MATLAB to perform the statistical optimization analysis

Bending behavior of piezo-hygrothermo-elastic smart laminated composite flat and curved plates with active control

The actuation and sensing behavior of piezo-hygrothermo-elastic flat and curved plates with active control is presented. A finite element procedure involving coupled piezoelectric field with hygrothermal strain is derived using first order shear deformation theory and is implemented in a nine-noded Lagrangian plate element. The accuracy of the element to model the piezoelectric, pyroelectric, hygroelastic, and thermoelastic behaviors of flat and doubly curved plates is validated with standard benchmark problems. The directional actuation that represents the piezoelectric anisotropy is introduced in the analysis and a comparison is made with isotropic actuation to control the thermal and moisture induced deformation in the laminated plates. Numerical studies are carried out with different fiber orientations to capture the influence of piezoelectric anisotropy on the actuation and sensing characteristics of the active lamina. The directionally actuated piezoelectric lamina that has a reduced piezoelectric capability in transverse direction is efficient, if property tailored along the fiber directions. However, it is observed that the isotropic actuation has the potential to control the thermal and moisture developed deflection in angle-ply and cross-ply laminates. The actuator lamina is efficient if placed on the top of curved laminates in controlling the deflection

Design, development and ground testing of hingeless elevons for MAV using piezoelectric composite actuators

A design methodology is presented to develop the hingeless control surfaces for MAV using adhesively bonded Macro Fiber Composite (MFC) actuators. These actuators have got the capability to deflect the trailing edge surfaces of the wing to attain the required maneuverability, besides achieving the set aerodynamic trim condition. A scheme involving design, analysis, fabrication and testing procedure has been adopted to realize the trailing edge morphing mechanism. The stiffness distribution of the composite MAV wing is tailored such that the induced deflection by piezoelectric actuation is approximately optimized. Through ground testing, the proposed concept has been demonstrated on a typical MAV structure. Electromechanical analysis is performed to evaluate the actuator performance and subsequently aeroelastic and 2D CFD analyses are carried out to see the functional requirements of wing trailing edge surfaces to behave as elevons. Efforts have been made to obtain the performance comparison of conventional control surfaces (elevons) with morphing wing trailing edge surfaces. A significant improvement in lift to drag ratio is noticed with morphed wing configuration in comparison to conventional wing. Further, it has been shown that the morphed wing trailing edge surfaces can be deployed as elevons for aerodynamic trim applications