Search results for "Composites"
showing 10 items of 1905 documents
Advanced Strategies and Materials for Reinforcing Normal and Disturbed Regions in Brick Masonry Columns
2016
This work presents the results of an experimental investigation on the behavior of 42 solid clay brick masonry columns internally strengthened by fiber-reinforced polymer (FRP) fabrics or stainless steel grids placed in horizontal mortar joints. In some cases, every course, and in other cases, alternate courses were reinforced with steel grids, carbon, and basalt FRP fabrics. Monotonic compressive loading tests were carried out under concentric and eccentric loads. Eccentric tests were carried out by loading the specimens on a reduced area with respect to the entire cross section, producing a disturbed region (D-region). A detailed characterization of the constituent materials was made expe…
Experimental investigation on the effect of mortar grade on the compressive behaviour of FRCM confined masonry columns
2018
Abstract The use of Fiber Reinforced Cementitious Mortar (FRCM) systems for structural retrofitting of masonry structures has become increasingly popular in the last years, due to the capability of this technique in overcoming some of the drawbacks related to the adoption of resin-based composites. Recent studies investigated on the effect of FRCM wraps on the compressive behaviour of concrete members and demonstrated as the application of mortar-based composites allows increasing the strength and, above all, the ductility of the column. The main difference with FRP confined columns is related to the different post-peak behaviour, characterized by a softening branch. Differently, few studie…
Comparative experimental analysis on the compressive behaviour of masonry columns strengthened by FRP, BFRCM or steel wires
2017
Abstract In the last decade, several studies have investigated the application of Fibre Reinforced Polymer (FRP) wraps to masonry piers in order to provide a confinement effect and enhance compressive strength and ductility. Although this technique has proved to be quite effective, various drawbacks arise when organic resins are used to bind fibres. To solve these problems, different techniques have been developed to be used as alternative methods for enhancing the structural performances of weak masonry columns. Among these, the use of Basalt Fibre Reinforced Cementitious Matrix (BFRCM) wrapping, or the application of steel wires at mortar joints. This paper presents the results of an expe…
Influence of different parameters on drug release from hydrogel systems to a biomembrane model. Evaluation by differential scanning calorimetry techn…
2000
A comparative study on the drug release capacity of four water swellable polymeric systems was carried out by differential scanning calorimetry (DSC). The polymeric systems chosen were alpha,beta-polyaspartahydrazide (PAHy) crosslinked by glutaraldehyde (GLU) (PAHy-GLU) or by ethyleneglycoldiglycidylether (EGDGE), (PAHy-EGDGE), polyvinylalcohol (PVA) crosslinked by glutaraldehyde (PVA-GLU) and alpha,beta-poly(N-hydroxyethyl)-DL-aspartamide (PHEA) by gamma irradiation (PHEA-gamma matrices). The degree of crosslinking for PAHy-GLU, PAHy-EGDGE and PVA-GLU samples was about 0.4 and 0.8. These hydrogels were characterized as free of drugs and were loaded with diflunisal (DFN) (approximately 2.5%…
Micromechanisms of load transfer in a unidirectional carbon fibre–reinforced epoxy composite due to fibre failures. Part 1: Micromechanisms and 3D an…
2006
This study gives a detailed analysis of load distributions around fibre breaks in a composite and the mechanisms involved in load transfer. In contrast to other studies reported in the literature the analysis considers different configurations of composite damage from the failure of a few fibres to the failure of many. The model considers the elastic case with and without debonding at the broken fibre/matrix interface. In this way, the usual limitations of the finite element approach are overcome so as to take into account the numbers and interactions of broken fibres whilst maintaining an evaluation of the various fields involved, in particular the stress fields associated with fibre failu…
Minimal intervention in dentistry: Which is the best approach for silorane composite restoration repairs?
2021
Made available in DSpace on 2021-06-25T10:28:11Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-04-01 Background: This study aimed to evaluate surface treatments, adhesives and composites for repairing silorane based restorations. Material and Methods: One hundred and twenty truncated cones (2 mm smaller diameter and 4 mm larger diameter) made of silorane composite were divided in 12 groups according with the surface treatment (diamond bur and oxide aluminum abrasion), the adhesive (Adper Scothbond Multipurpose (3M ESPE), Ecusit (Voco) and Filtek P90 Adhesive (3M ESPE)). Each group was subdivided in two according with the composite used for repair (methacrylate and silorane). The rep…
Hydrothermal ageing of polylactide/sisal biocomposites. Studies of water absorption behaviour and Physico-Chemical performance
2014
An accelerated hydrothermal degrading test was designed in order to analyse the synergic effect of water and temperature on PLA/sisal biocomposites with and without coupling agent. As well, the physicochemical properties of biocomposites were monitored along the hydrothermal test by means of Scanning Electron Microscopy, Size Exclusion Chromatography and Differential Scanning Calorimetry. The addition of fibre induced higher water absorption capability and promoted physical degradation, as observed in the surface topography. During the processing of biocomposites and throughout the hydrothermal ageing, a reduction of molecular weight due to chain scission was found. As a consequence, a fast…
Carbon Fiber Composites Cured by γ-Radiation-Induced Polymerization of an Epoxy Resin Matrix
2008
The use of ionizing radiation in order to initiate polymerization of suitable monomers has found increased interest in the last two decades due to its several advantages. In this work, carbon fiber composites through gamma radiation polymerization of epoxy matrices have been produced for aerospace and advanced automotive applications. Composite samples were produced by irradiation at room temperature using different radiation doses and, as reference, thermal curing of the same epoxy resin formulations was also carried out. Furthermore, some irradiated samples were subjected to postirradiation thermal curing to complete the polymerization reactions. The properties of the cured materials were…
Local structure of ball-milled LaNi5 hydrogen storage material by Ni K-edge EXAFS
2010
Abstract Local structure of the nanostructured LaNi5 hydrogen storage alloys, prepared by ball-milling, has been studied using Ni K-edge extended X-ray absorption fine structure spectroscopy. Results indicate that the ball-milling up to 100 h results in the production of nanoparticles characterized by large atomic disorder and slightly reduced unit-cell volume, compared to the bulk LaNi5. High temperature annealing appears to help in partial recovery of atomic order in the ball-milled samples; however, long-time ball-milled samples retain large disorder even after the high temperature annealing. The results suggest that the large disorder and the reduced unit-cell volume might be causing a …
Wavelet and fractal approach to surface roughness characterization after finish turning of different workpiece materials
2009
In this paper, the surface profiles generated in longitudinal turning operations were characterized using continuous wavelet transform (CWT) and normalized fractal dimension Dn. In the comparative analysis, some characteristic roughness profiles after the turning of different workpiece materials, such as C45 medium carbon steel, nodular cast iron and hardened (55 HRC) high-strength alloy steel were selected. For wavelet characterization, both Morlet and ‘Mexican hat’ analyzing wavelets, which allow the assessment of extrema and frequency distribution, were utilized. The results of the CWT as a function of profile and momentary wavelet length are presented. It is concluded that CWT can be us…