Analytical and numerical study concerning the behaviour of single-sided bonded patch repairs

Adhesive bonded joints are used in the assembling of structural parts, especially of those which are made from dissimilar materials. Lightweight fibre reinforced polymer composites and other adhesive bonded components represent a major proportion of a modern aircraft. Bonded patch repair technology has been widely used to repair cracked thin-walled structures to extend their service life, because a correctly executed repair significantly enhances the structural performance.In practice, the single-sided bonded patch repair is the most used because a good solution like the double-sided repair may not be an option if the access to the structure is only available from one side.This paper presents a relatively simple and effective design procedure for the single strapped bonded joints. Also, the influence of various geometrical parameters of the joint is evaluated. The analytical development is validated based on nonlinear finite element analyses

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

Pegylation of phenothiazine – A synthetic route towards potent anticancer drugs

Introduction Cancer is a big challenge of the 21 century, whose defeat requires efficient antitumor drugs. Objectives The paper aims to investigate the synergistic effect of two structural building blocks, phenothiazine and poly(ethylene glycol), towards efficient antitumor drugs. Methods Two PEGylated phenothiazine derivatives were synthetized by attaching poly(ethylene glycol) of 550 Da to the nitrogen atom of phenothiazine by ether or ester linkage. Their antitumor activity has been investigated on five human tumour lines and a mouse tumor line as well, by determination of IC50. The in vivo toxicity was determined by measuring the LD50 in BALB/c mice by the sequential method and the in vivo antitumor potential was measured by the tumours growth test. The antitumor mechanism was investigated by complexation studies of zinc and magnesium ions characteristic to the farnesyltransferase enzyme, by studies of self-aggregation in the cells proximity and by investigation of the antitumor properties of the acid species resulted by enzymatic cleavage of the PEGylated derivatives. Results The two compounds showed antitumor activity, with IC50 against mouse colon carcinoma cell line comparable with that of the traditional antitumor drugs 5-Fluorouracil and doxorubicin. The phenothiazine PEGylation resulted in a significant toxicity diminishing, the LD50 in BALB/c mice increasing from 952.38 up to 1450 mg/kg, in phenothiazine equivalents. Both compounds inflicted a 92% inhibition of the tumour growth for doses much smaller than LD50. The investigation of the possible tumour inhibition mechanism suggested the nanoaggregate formation and the cleavage of ester bonds as key factors for the inhibition of cancer cell proliferation and biocompatibility improvement. Conclusion Phenothiazine and PEG building blocks have a synergetic effect working for both tumour growth inhibition and biocompatibility improvement. All these findings recommend the PEGylated phenothiazine derivatives as a valuable workbench for a next generation of antitumor drugs

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

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

Periodontal status and inflammatory markers in gingival crevicular fluid of patients with periodontitis and colorectal cancer

Objectives. The present pilot study was carried out to evaluate the periodontal status, the levels of interleukin-6 and tumor necrosis factor alpha in gingival crevicular fluid on hospitalized patients with colorectal cancer. Materials and Methods. The sample of our study was represented by 74 patients with colorectal cancer. They were assigned to one of the two study groups, based on cancer’s stages, as follows: (i) stage III-IV: 51 patients (A-group); (ii) stage I-II: 23 patients (B-group). For each participant periodontal parameters were recorded and gingival crevicular fluid samples were collected and immunologically assessed. Results. Statistically significant differences were found between the two groups, regarding probing pocket depth, clinical attachment loss, bleeding on probing, interleukin-6 and tumor necrosis factor alpha. In A-group, statistically significant correlations were found between the inflammatory markers and probing pocket depth and between their levels and bleeding on probing. In B-group, statistically significant correlation was found between the levels of interleukin-6 and bleeding on probing. Conclusions. Our results suggest an association between the severity of periodontitis, the studied immunologic inflammatory markers and colorectal cancer’s severity

Childbearing intentions in a low fertility context: the case of Romania

This paper applies the Theory of Planned Behaviour (TPB) to find out the predictors of fertility intentions in Romania, a low-fertility country. We analyse how attitudes, subjective norms and perceived behavioural control relate to the intention to have a child among childless individuals and one-child parents. Principal axis factor analysis confirms which items proposed by the Generation and Gender Survey (GGS 2005) act as valid and reliable measures of the suggested theoretical socio-psychological factors. Four parity-specific logistic regression models are applied to evaluate the relationship between the socio-psychological factors and childbearing intentions. Social pressure emerges as the most important aspect in fertility decision-making among childless individuals and one-child parents, and positive attitudes towards childbearing are a strong component in planning for a child. This paper also underlines the importance of the region-specific factors when studying childbearing intentions: planning for the second child significantly differs among the development regions, representing the cultural and socio-economic divisions of the Romanian territory

Universal scaling of c-axis dc conductivity for the underdoped hightemperature cuprate superconductors

Coexistence of the "metallic-like" in-plane and the "semiconducting-like" out-of-plane (caxis) dc conductivities ({\sigma}c), generating a huge anisotropy in the underdoped hightemperature cuprate superconductors (HTCS), defies our current understanding of metal. In this report we present an intrinsic doping dependence of {\sigma}c. We find that the {\sigma}c for the underdoped HTCS is universally scaled to the {\sigma}c at the optimal doped-hole concentration. The universal scaling behavior suggests that there are three intrinsic processes contribute to {\sigma}c: (i) the doping-dependent-activated gap; (ii) the exponential doping dependences and (iii) the tunneling between adjacent CuO2 block layers. They are the essential underlying characteristics of the c-axis transport for all HTCSs.Comment: 14 pages, 3 figures. Accepted for the publication in Solid State Communication

Evaluation of appendicitis risk prediction models in adults with suspected appendicitis

Background Appendicitis is the most common general surgical emergency worldwide, but its diagnosis remains challenging. The aim of this study was to determine whether existing risk prediction models can reliably identify patients presenting to hospital in the UK with acute right iliac fossa (RIF) pain who are at low risk of appendicitis. Methods A systematic search was completed to identify all existing appendicitis risk prediction models. Models were validated using UK data from an international prospective cohort study that captured consecutive patients aged 16–45 years presenting to hospital with acute RIF in March to June 2017. The main outcome was best achievable model specificity (proportion of patients who did not have appendicitis correctly classified as low risk) whilst maintaining a failure rate below 5 per cent (proportion of patients identified as low risk who actually had appendicitis). Results Some 5345 patients across 154 UK hospitals were identified, of which two‐thirds (3613 of 5345, 67·6 per cent) were women. Women were more than twice as likely to undergo surgery with removal of a histologically normal appendix (272 of 964, 28·2 per cent) than men (120 of 993, 12·1 per cent) (relative risk 2·33, 95 per cent c.i. 1·92 to 2·84; P < 0·001). Of 15 validated risk prediction models, the Adult Appendicitis Score performed best (cut‐off score 8 or less, specificity 63·1 per cent, failure rate 3·7 per cent). The Appendicitis Inflammatory Response Score performed best for men (cut‐off score 2 or less, specificity 24·7 per cent, failure rate 2·4 per cent). Conclusion Women in the UK had a disproportionate risk of admission without surgical intervention and had high rates of normal appendicectomy. Risk prediction models to support shared decision‐making by identifying adults in the UK at low risk of appendicitis were identified

Design of a compact six-component force and moment sensor for aerodynamic testing

The measurement of steady and fluctuating forces acting on a body in a flow is one of themain tasks in wind-tunnel experiments. Usually, a multi-component strain gauge force and momentsensor (also known as balance) is used to generate signals which are processed by means of anadequate instrumentation.To design a wind-tunnel balance, the specifications of the load ranges and the available space (for theplacement of the balance inside or outside the model) are required. The main challenge is to conceivethe elastic element of the sensor as a monolithic part with a relative simple geometry and to identifythe adequate placement of strain gauges to maximize the measuring sensitivities and to diminish theinter-influence of the components.This paper describes the design of a six-component force/moment sensor which is compact, has highmeasuring sensitivities, and can be used either as internal or as external balance in the aerodynamictesting