Adherend thickness effect on the tensile fracture toughness of a structural adhesive using an optical data acquisition method

Adhesive bonding is nowadays a serious candidate to replace methods such as fastening or riveting, because of attractive mechanical properties. As a result, adhesives are being increasingly used in industries such as the automotive, aerospace and construction. Thus, it is highly important to predict the strength of bonded joints to assess the feasibility of joining during the fabrication process of components (e.g. due to complex geometries) or for repairing purposes. This work studies the tensile behaviour of adhesive joints between aluminium adherends considering different values of adherend thickness (h) and the double-cantilever beam (DCB) test. The experimental work consists of the definition of the tensile fracture toughness (GIC) for the different joint configurations. A conventional fracture characterization method was used, together with a J-integral approach, that take into account the plasticity effects occurring in the adhesive layer. An optical measurement method is used for the evaluation of crack tip opening and adherends rotation at the crack tip during the test, supported by a Matlab® sub-routine for the automated extraction of these quantities. As output of this work, a comparative evaluation between bonded systems with different values of adherend thickness is carried out and complete fracture data is provided in tension for the subsequent strength prediction of joints with identical conditions.

Tensile fracture characterization of adhesive joints by standard and optical techniques

The use of adhesive joints has increased in recent decades due to its competitive features compared with traditional methods. This work aims to estimate the tensile critical strain energy release rate (GIC) of adhesive joints by the Double-Cantilever Beam (DCB) test. The J-integral is used since it enables obtaining the tensile Cohesive Zone Model (CZM) law. An optical measuring method was developed for assessing the crack tip opening (δn) and adherends rotation (θo). The proposed CZM laws were best approximated by a triangular shape for the brittle adhesive and a trapezoidal shape for the two ductile adhesives.

Bone turnover markers for early detection of fracture healing disturbances: A review of the scientific literature

Imaging techniques are the standard method for assessment of fracture healing processes. However, these methods are perhaps not entirely reliable for early detection of complications, the most frequent of these being delayed union and non-union. A prompt diagnosis of such disorders could prevent prolonged patient distress and disability. Efforts should be directed towards the development of new technologies for improving accuracy in diagnosing complications following bone fractures. The variation in the levels of bone turnover markers (BTMs) have been assessed with regard to there ability to predict impaired fracture healing at an early stage, nevertheless the conclusions of some studies are not consensual. In this article the authors have revised the potential of BTMs as early predictors of prognosis in adult patients presenting traumatic bone fractures but who did not suffer from osteopenia or postmenopausal osteoporosis. The available information from the different studies performed in this field was systematized in order to highlight the most promising BTMs for the assessment of fracture healing outcome.

Influence of casting condition on the anisotropy of the fracture properties of Steel Fibre Reinforced Self-Compacting Concrete (SFRSCC)

Identification of the tensile constitutive behaviour of Fibre Reinforced Concrete (FRC) represents an important aspect of the design of structural elements using this material. Although an important step has been made with the introduction of guidance for the design with regular FRC in the recently published fib Model Code 2010, a better understanding of the behaviour of this material is still necessary, mainly for that with self-compacting properties. This work presents an experimental investigation employing Steel Fibre Self-Compacting Concrete (SFRSCC) to cast thin structural elements. A new test method is proposed for assessing the post-cracking behaviour and the results obtained with the proposed test method are compared with the ones resulted from the standard three-point bending tests (3PBT). Specimens extracted from a sandwich panel consisting of SFRSCC layers are also tested. The mechanical properties of SFRSCC are correlated to the fibre distribution by analysing the results obtained with the different tests. Finally, the stress-crack width constitutive law proposed by the fib Model Code 2010 is analysed in light of the experimental results.

Parametric analysis of different compact tension specimens for fracture toughness characterisation in woven composite materials

Estudi elaborat a partir d’una estada a l’ Imperial College London, entre juliol i novembre de 2006. En aquest treball s’ha investigat la geometria més apropiada per a la caracterització de la tenacitat a fractura intralaminar de materials compòsits laminats amb teixit. L’objectiu és assegurar la propagació de l’esquerda sense que la proveta falli abans per cap altre mecanisme de dany per tal de permetre la caracterització experimental de la tenacitat a fractura intralaminar de materials compòsits laminats amb teixit. Amb aquesta fi, s’ha dut a terme l’anàlisi paramètrica de diferents tipus de provetes mitjançant el mètode dels elements finits (FE) combinat amb la virtual crack closure technique (VCCT). Les geometries de les provetes analitzades corresponen a la proveta de l’assaig compact tension (CT) i diferents variacions com la extended compact tension (ECT), la proveta widened compact tension (WCT), tapered compact tension (TCT) i doubly-tapered compact tension (2TCT). Com a resultat d’aquestes anàlisis s’han derivat diferents conclusions per obtenir la geometria de proveta més apropiada per a la caracterització de la tenacitat a fractura intralaminar de materials compòsits laminats amb teixit. A més, també s’han dut a terme una sèrie d’assaigs experimentals per tal de validar els resultats de les anàlisis paramètriques. La concordança trobada entre els resultats numèrics i experimentals és bona tot i la presència d’efectes no previstos durant els assaigs experimentals.

Minimal invasive surgery for coronoid fracture: technical note.

Operative treatment of coronoid fracture often requires a large dissection of soft tissue, resulting in elbow stiffness and functional limitation. The authors present a minimal invasive, safe technique, useful in the case of isolated coronoid fracture associated with elbow dislocation. This technique does not require soft tissue dissection and allows an early unlimited resumption of sports activities.

Which screening strategy using BMD measurements would be most cost effective for hip fracture prevention in elderly women? A decision analysis based on a Markov model.

INTRODUCTION: Hip fractures are responsible for excessive mortality, decreasing the 5-year survival rate by about 20%. From an economic perspective, they represent a major source of expense, with direct costs in hospitalization, rehabilitation, and institutionalization. The incidence rate sharply increases after the age of 70, but it can be reduced in women aged 70-80 years by therapeutic interventions. Recent analyses suggest that the most efficient strategy is to implement such interventions in women at the age of 70 years. As several guidelines recommend bone mineral density (BMD) screening of postmenopausal women with clinical risk factors, our objective was to assess the cost-effectiveness of two screening strategies applied to elderly women aged 70 years and older. METHODS: A cost-effectiveness analysis was performed using decision-tree analysis and a Markov model. Two alternative strategies, one measuring BMD of all women, and one measuring BMD only of those having at least one risk factor, were compared with the reference strategy "no screening". Cost-effectiveness ratios were measured as cost per year gained without hip fracture. Most probabilities were based on data observed in EPIDOS, SEMOF and OFELY cohorts. RESULTS: In this model, which is mostly based on observed data, the strategy "screen all" was more cost effective than "screen women at risk." For one woman screened at the age of 70 and followed for 10 years, the incremental (additional) cost-effectiveness ratio of these two strategies compared with the reference was 4,235 euros and 8,290 euros, respectively. CONCLUSION: The results of this model, under the assumptions described in the paper, suggest that in women aged 70-80 years, screening all women with dual-energy X-ray absorptiometry (DXA) would be more effective than no screening or screening only women with at least one risk factor. Cost-effectiveness studies based on decision-analysis trees maybe useful tools for helping decision makers, and further models based on different assumptions should be performed to improve the level of evidence on cost-effectiveness ratios of the usual screening strategies for osteoporosis.

Comparison of two osteoporotic fracture management pathways: experience at 1 year

Introduction: Osteoporosis presenting as low-impact fractures to traumatology units is often undiagnosed and under-treated. Results from the Osteocare study in Lausanne (a nurse based intervention, passive pathway) showed that only 19% of patients received management for osteoporosis, and in the literature [1], the rate is between 10-25%. We have evaluated a different management concept, based on the systematic assessment of patients with osteoporotic fractures during and after hospitalization (active pathway). Methods: Inpatients admitted to the Department of Musculoskeletal Medicine for a fragility fracture were identified by a nurse according to a predefined questionnaire and were then clinically evaluated by a doctor. Based on the results, a management plan was proposed to the patients. Patients could choose between follow up either by their GP or by the Centre of Bone Disease of the CHUV. For patients who chose follow-up in our Centre, we assessed their adherence to medical follow-up 1 year inclusion. The results of patients who had been evaluated in our cohort between the 1 November 2008 and the 1 December 2009 were analysed. Results: 573 inpatients received specific management of their osteoporotic fracture over 18 months. The mean age was 77 y (31-99), 81% were women (203 hip fractures, 40 pelvis fractures, 101 arm fractures, 57 vertebral fractures, 63 ankle fractures, and 25 others sites). During the study period, 303 patients received a proposition of a specific treatment. 39 (13%) chose a follow up with the GP, 19 (6%) dead and 245 (81%) preferred a follow up in our Centre. After 1 year, 166 (67%) patients are under follow up in our outpatient clinic. Conclusion: With an active clinical pathway that starts during the hospitalization, consisting on a nursing evaluation followed by a medical consultation by an expert in osteoporosis, the adherence increased from 19% to 67% in terms of follow up. These results lead us to propose a consultation with a doctor experienced in osteoporosis after all osteoporotic fractures.

Prise en charge des troubles oculomoteurs après effraction iatrogène de l'orbite au cours d'interventions sinusiennes endoscopiques [Management of motility disorders secondary to iatrogenic orbital fracture during endoscopic sinus surgery.]

PURPOSE: Orbital wall fracture may occur during endoscopic sinus surgery, resulting in oculomotor disorders. We report the management of four cases presenting with this surgical complication. METHODS: A non-comparative observational retrospective study was carried out on four patients presenting with diplopia after endoscopic ethmoidal sinus surgery. All patients underwent full ophthalmologic and orthoptic examination as well as orbital imaging. RESULTS: All four patients presented with diplopia secondary to a medial rectus lesion confirmed by orbital imaging. A large horizontal deviation as well as limitation of adduction was present in all cases. Surgical management consisted of conventional recession-resection procedures in three cases and muscle transposition in one patient. A useful field of binocular single vision was restored in two of the four patients. CONCLUSION: Orbital injury may occur during endoscopic sinus surgery and cause diplopia, usually secondary to medial rectus involvement due to the proximity of this muscle to the lamina papyracea of the ethmoid bone. Surgical management is based on orbital imaging, duration of the lesion, evaluation of anterior segment vasculature, results of forced duction testing and intraoperative findings. In most cases, treatment is aimed at the symptoms rather than the cause, and the functional prognosis remains guarded.

Freeze-fracture study of Trichomonas vaginalis

The freeze-fracture technique was used to analyse the organization of the plasma membrane, as well as membranes of cytoplasmic organelles, of the pathogenic protozoan Trichomonas vaginalis. Rosettes formed by 4 to 14 intramembranous particles were seen on the fracture faces of the membrane lining the anterior flagella as well as in fracture faces of the plasma membrane enclosing the anterior region of the protozoan and in cytoplasmic organelles. Special organization of the membrane particles were also seen in the region of association of the recurrent flagellum to the cell body.