196,336 research outputs found
RELATIONSHIPS BETWEEN BONE LOSS AND MICROVASCULAR DAMAGE IN PATIENTS WITH SYSTEMIC SCLEROSIS
No full text[FRI0325] RELATIONSHIPS BETWEEN BONE LOSS AND MICROVASCULAR DAMAGE IN PATIENTS WITH SYSTEMIC SCLEROSIS
Authors: B. Seriolo, C. Pizzorni, A. Casabella, G. Zampogna, A. Sulli, M. Cutolo
Session Info: Scleroderma, myositis and related syndromes
Year: 201
Adhesive bonding of a mixed short and continuous carbon-fiber-reinforced Nylon-6 composite made via fused filament fabrication
No full textThis experimental work aims at evaluating the mechanical and failure behavior of adhesive-bonded single-lap joints made of a thermoplastic composite 3D-printed via Fused Filament Fabrication technology. Carbon fiber was selected as the reinforcement and used in the form of both short and continuous fibers embedded in the Nylon-6 matrix, forming the composite?s hybrid structure. An approach based on progressive improvement of surface treatment effectiveness (solvent degreasing, abrasion, and low-pressure plasma) has been adopted to verify how the additively-manufactured composite responds to bonding when increased interfacial adhesion is attained by preparing the outer printed layer. Roughness measurements, wettability evaluations, and XPS analyses have been carried out to assess any modifications of morphology and functionalization exhibited by the different surfaces after treatment. The experimental findings demonstrate that the intrinsic non-homogeneity of 3D-printed composites is emphasized when low-pressure plasma is used, as it generates interfacial bonds between adhesive and adherend that are more effective than the interlaminar ones within the substrate. In this condition, the ultimate resistance of the joint corresponds to that of the base material. In particular, fracturemechanism analysis allowed precise identification of the crack path, highlighting defects and current limitations of the additively-manufactured system and suggesting pivotal aspects to develop in future work to improve joint performance
Ablation treatment of CFRP via nanosecond pulsed Ytterbium-doped fiber laser: Effects of process parameters on surface morphology and shear strength of adhesive bonded joints
No full textAdhesive bonding is the joining technique that provides the maximum exploitation of Carbon Fiber Reinforced Polymers (CFRPs) for structural applications. However, it is necessary to attain a high-strength adhesive bond, achieved by removing surface contaminants, such as mold release agents, and simultaneously generating a surface structure suitable to increase the actual contact surface area. The purpose of the research work presented in this paper is to evaluate the effect of process parameters of a nanosecond pulsed laser pre-bonding surface treatment on the ablation of thermoset matrix CFRP substrates. In particular, the link between the volume of ablated material and the tensile shear strength (TSS) of adhesive bonded joints was evaluated by lap-shear tests, profilometer surveys, and Scanning Electron Microscope (SEM) analysis. ANOVA and regression models were used to highlight the influence of laser parameters, with power emerging as the most significant factor, and energy density proving pivotal for joint strength. Line spacing was also significant, while scanning direction had negligible impact. The key outcomes of the study demonstrated that controlled laser ablation plays a critical role in determining joint performance. A negative correlation was found between TSS and the thickness of ablated material, indicating that excessive ablation weakens the bond. Optimal joint strength was achieved with moderate fiber exposure while maintaining matrix integrity, emphasizing the need for precise control over laser parameters. Fracture surface analyses revealed distinct failure mechanisms, ranging from cohesive failure within the adhesive layer to interfacial failure at the fiber-matrix boundary, depending on the ablation conditions. The findings provide clear guidelines for optimizing laser surface treatments to enhance the structural performance of CFRP adhesive joints in practical applications
FRI0288 Nailfold capillaroscopic pictures in a cohort of undifferentiated connective tissue disease (UCTD) patients and in those that move to systemic lupus erythematosus
No full textLow pressure plasma treatment of CFRP substrates for adhesive bonding: an investigation of joint durability under severe temperature-moisture conditioning
No full textThis work reports a quantitative evaluation of the aging behavior of adhesively bonded joints manufactured using a toughened epoxy adhesive applied on CFRP substrates. Low-pressure plasma (LPP) treatment was employed, adopting air and pure oxygen as process gases and varying working parameters such as power and exposure time. A preliminary testing campaign was performed under standard laboratory conditions to evaluate shear strength of single-lap joints (SLJ), comparing effectiveness of LPP treatments to a traditional mechanical abrasion of the adherends. Even at this early stage, experimental findings highlighted how this physical method provides for competitive performance over abrasion, resulting in a remarkable enhancement of the shear resistance. Four sets of LPP-treatment conditions were selected and then subjected to accelerated aging (consisting of 56 cycles of 5 h at T = 70 °C, RH>90% and 5 h at T = −40 °C each). Their behavior was compared to that of abraded joints, employed as a reference. To assess the durability of the CFRP-epoxy adhesive system under accelerated aging conditions, tensile shear strength (TSS) testing and wedge cleavage test (WT) were performed in parallel. The experimental results showed that low-pressure plasma treatment of the CFRP substrates results in increased short-term quality of the adhesive joint as well as in enhancement of its durability even under severe aging conditions
Low-pressure plasma treatment of CFRP substrates for epoxy-adhesive bonding: an investigation of the effect of various process gases
No full textThis work reports a systematic and quantitative evaluation of the effects induced on the adhesive properties of carbon fiber reinforced polymer (CFRP) substrates by various vacuum cold-plasma treatments. In particular, surface activation of the CFRP substrates was performed using several combinations of exposure time, plasma power, and processing gas (air, O-2, Ar and N-2). By comparing these plasma treatments with conventional techniques of abrasion and peel ply, it was possible to substantially increase the performance of the adhesively bonded joints made by overlapping the CFRP substrates with a structural epoxy resin. On each differently treated surface, measurements of roughness and of wettability were performed, allowing the evaluation of the increase in surface energy after the plasma treatment. XPS analyses allowed the identification of the chemical state of the substrates and showed an in-depth functionalization of the outer layer of the CFRP material. The experimental results show that an engineered plasma treatment of the CFRP substrates allows one to modify the surface morphology and both wetting and chemical activation properties of the treated surfaces, resulting in an increased mechanical shear strength of the joints
Influence of silica aerogel filler on strength-to-weight ratio of carbon/epoxy composite made by vacuum resin infusion
No full textCapillaroscopy
No full textCapillaroscopy is the most reliable way to distinguish between primary and secondary Raynaud's phenomenon (RP) through identification of an early pattern of systemic sclerosis (SSc). The presence of giant capillaries and microhaemorrhages on nailfold videocapillaroscopy (NVC) is sufficient to identify the scleroderma pattern (early), and an increase in these features and the addition of loss of capillaries (active pattern) is followed by neo-angiogenesis, fibrosis and 'desertification' (late pattern). The sensitivity of the American College of Rheumatology's classification criteria for SSc increases from 67% to 99% with the addition of these specific NVC abnormalities. Based on the appearance of the scleroderma pattern on NVC, almost 15% of patients shift from primary to secondary RP over a mean follow-up period of 29.4 ± 10 months. Follow-up by NVC (every 6 months) is suggested for RP patients. A scoring system for NVC changes is available, and scores change significantly during follow-up of SSc patients. Several other NVC patterns have also been identified, such as in dermatomyosistis, systemic lupus eythaematosus, mixed connective tissue disease and antiphospholipid syndrome. © 2008 Elsevier Ltd. All rights reserved
Laser surface pre–treatment of polyolefin substrates for adhesive bonding
No full textAdhesive bonding offers many advantages over mechanical fastening, but requires accurate surface preparation, which is widely recognized as the key step to producing reliable and durable adhesive bonds. The use of laser cleaning processes helps to increase the reactivity of the topmost layers of substrates, without affecting the bulk material properties. These methods are often applied to treat polymers, which are generally characterized by high chemical inertia, very low surface energy values and, consequently, poor adhesive properties and this is particularly true for polyolefins. Furthermore, laser treatment provides an alternative to the polluting and less accurate practices such as manual abrasion and primer. In this paper the effect of different laser pre-treatments on polypropylene (PP) and high density polyethylene (HDPE) substrates was studied, by microscopic investigation and single lap- shear tests. As a comparison, untreated and primer treated specimens were also included in the experimental campaign. The results show that laser treatment significantly affected the substrates' surface and the mechanical properties of adhesive bonded joints. Finding the optimal combination of the working parameters, it is possible to enhance the strength of both untreated and primer-treated joints
Assessment of treatment effects on digital ulcer and blood perfusion by laser speckle contrast analysis in a patient affected by systemic sclerosis
No full textLaser speckle contrast analysis (LASCA) is a good tool to evaluate the variation in peripheral blood perfusion during long-term follow-up and is able to safely monitor digital ulcer evolution in scleroderma patients. It evaluates blood perfusion in different areas within the skin lesions and surrounding them during standard treatment
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