Estudo das propriedades térmicas de materiais aplicados em paredes divisórias leves

Para o presente estudo das propriedades térmicas de paredes divisórias leves foi considerada uma parede composta por isolamento (como núcleo) e membranas (como revestimento). Avaliou-se comparativamente o desempenho térmico dos materiais de isolamento aplicados a paredes divisórias: poliestireno expandido (EPS), espuma de poliuretano (PU), estruturas tridimensionais do tipo sandwich em poliéster (3DWK), aglomerados de coco (CKE), fibra de coco (CKF), lã de rocha (RW), fibra reciclados (WF), fibras de sisal (SF), fibras de poliéster (PESF). O objectivo deste estudo é comparar o desempenho térmico dos materiais de isolamento à base de polímeros ou fibras têxteis com os valores de referência das paredes divisórias leves convencionais, produzidas com painéis de gesso cartonado e isolamento em lã de rocha. As conclusões do trabalho permitem quantificar as principais vantagens e desvantagens dos diferentes isolamentos no que diz respeito ao desempenho térmico de divisórias

Characterization of porous acoustic materials applied to lightweight partition walls

The increased need to save material and energetic resources, allied with a growing concern on the environmental issues and incertitude on the evolution of the economy, has impelled minimalist-approaches to Architecture and Engineering, reducing to the minimum necessary expression the building elements. The development of new lightweight materials, most of them composites with fibrous reinforcement systems, has interest for building materials and textile industries. However, these materials still do not have a significant implementation in the building industry or, at least, this implementation is not being made exploring all their potentialities. Non load bearing interior partition walls are thin elements built to divide the indoor space into rooms or other compartments. Porous materials applied in interior partition walls have a significant importance in these building elements because sound insulation is an important requirement. Walls must provide an airborne sound barrier between rooms in a same dwelling and especially between different dwellings, this last issue as a compulsory requirement to fulfil in Portuguese regulations. In the present study it will be considered a lightweight interior partition wall composed by insulation material and layered within two membranes. The process of selecting materials for that interior partition wall is a challenging task. This paper intends to compare results of functional (acoustic and thermal) performance of materials such as expandable polystyrene (EPS), polyurethane foam (PU), Ethylene-vinyl acetate (EVA), 3D warp knitted polyester fabrics (3DWK), Cork (CK), Expanded Cork (CKE), Rockwool (RW), coconut fibber (CCF), silicone (SI), waste fiber (WF), to discuss about their potentialities as insulation or membrane materials applied in interior dividing walls technologies. It also presents a morphological characterization of materials, through microscopic analysis, in order to define the relationship between the morphology and acoustic performance. The results of tests are compared with reference values of rock wool as insulation material - conventionally used in lightweight dividing walls made of plasterboard leaves and light gauge steel framing structure. One of the results of this paper is that a lightweight and thin interior partition wall filled with insulation material present acoustic advantages when compared with a heavyweight interior partition wall with more thickness. The concept of membrane goes back to the Latin word “membrana”, meaning parchment or skin. In previous studies it could be verified that low density makes membrane structures poor thermal and acoustic insulators. However, it is available in the market heavily coated or microperforated membranes that have dampening effect A low density generally also implies a high porosity or a high volume of voids, which leads to a decrease in the thermal conductivity. In previous studies from the same authors, it was concluded that the presence of air gap between insulation materials in a lightweight interior partition can increase the acoustic insulation between 2 to 5 dB, the inclusion of porous materials in the air gap can contribute between 1 to 4 dB in thicknesses till 10cm. The compromise between thermal and acoustic performance should also be attended. However thermal performance is only a requirement for interior partition walls between useful and non useful areas in housing buildings. In this study it will be presented results for different densities of insulation material. In the process of airborne sound transmission between two spaces, should be distinguished: a) direct transmission, that occurs directly through the separation element; or b) marginal transmission - that occurs through other building elements interlocked to the element of separation in study. The direct transmission can occur through joints, cracks or discontinuance of the construction element or through the construction element vibration. The heat transfer coefficient calculation tests were conducted according UNE EN 6946. The sound insulation estimation between locals was conducted according to EN 12354-1. Procedures for measuring the reverberation of a room, the absorption of the covering layers, as well as the sound absorption coefficients of a specimen of sound absorptive material were made according to ASTM C – 423

Characterization of polyester with fiberglass materials as reinforcement in interior dividing walls

Some synthetic fibers present better mechanical performance compared with the natural fibers. Therefor research works were carried out to focus the characterization of polyester and glass fibers to be used as reinforcements in the internal dividing walls. Results from polyester fabrics made of compression with or without fiberglass were obtained

Development of reinforced composite sandwich panels based on 3D fabrics

relative new type of sandwich material was investigated, based on 3D knitted sandwich fabric preforms. Due to the integrally interlacement of both sandwich-fabric the skins by the connection yarns – core debonding resistance of panels and structures based on the perform is very high. [1]. In this work the mechanical performance of sandwich composite panels based on sandwich knitted fabrics is presented and discussed. Different 3D sandwich knitted fabric performs have been produced varying the thickness and the interlacement pattern. Composite panels using these performs have been produced using vacuum infusion technique. Panel thicknesses of 8, 15 and 25 mm, using two resin types – polyester and epoxy – have been produced. Materials thus obtained have been tested in tensile, bending and impact. The results obtained are presented, discussed and compared to models. Various samples of 3D sandwich spacer fabrics using vacuum infusion process have been produced in order to study the impregnation process. The dimensional properties investigated for non-impregnated core structures include cross-threads density, areal mass, yarns linear density, etc. Results obtained show that the mechanical performances vary according to the type of 3D knitted sandwich perform and the type of resin used

Papel de nano-aditivos na funcionalização de argamassas

A manutenção da qualidade do ar no interior dos edifícios é um dos aspetos mais relevantes da construção sustentável e tem forte impacto no nível de conforto dos utilizadores. A introdução de nano-aditivos em materiais de construção permite modificar propriedades fundamentais destes materiais convencionais, com o objetivo de proporcionar novas funcionalidades. Neste trabalho apresentam-se os resultados obtidos com o desenvolvimento de argamassas funcionais que pretendem melhorar a qualidade do ar interior e contribuir para a poupança energética dos edifícios. As formulações foram optimizadas com vista à sua aplicação em construção nova ou reabilitação

A Systematic Review and Meta-Analysis

Background: Autism Spectrum Disorder (ASD) is a neurodevelopmental disorder manifesting as lifelong deficits in social communication and interaction, as well as restricted repetitive behaviors, interests and activities. While there are no specific pharmacological or other physical treatments for autism, in recent years repetitive Transcranial Magnetic Stimulation (rTMS), a technique for non-invasive neuromodulation, has attracted interest due to potential therapeutic value. Here we report the results of a systematic literature review and meta-analysis on the use of rTMS to treat ASD. Methods: We performed a systematic literature search on PubMed, Web of Science, Science Direct, Bielefeld Academic Search, and Educational Resources Information Clearinghouse. Search terms reflected diagnoses and treatment modalities of interest. Studies reporting use of rTMS to treat core ASD or cognitive symptoms in ASD were eligible. Two researchers performed article selection and data extraction independently, according to PRISMA guidelines. Changes in ASD clinical scores or in cognitive performance were the main outcomes. Random effects meta-analysis models were performed. Results: We found 23 eligible reports, comprising 4 case-reports, 7 non-controlled clinical trials, and 12 controlled clinical trials, comparing the effects of real TMS with waiting-list controls (n = 6) or sham-treatment (n = 6). Meta-analyses showed a significant, but moderate, effect on repetitive and stereotyped behaviors, social behavior, and number of errors in executive function tasks, but not other outcomes. Most studies had a moderate to high risk of bias, mostly due to lack of subject- and evaluator-blinding to treatment allocation. Only 5 studies reported stability of these gains for periods of up 6 months, with descriptions that improvements were sustained over time. Conclusions: Existing evidence supports that TMS could be useful to treat some dimensions of ASD. However, such evidence must be regarded with care, as most studies did not adequately control for placebo effects. Moreover, little is known regarding the most effective stimulation parameters, targets, and schedules. There is an urgent need for further randomized, double-blind, sham-controlled trials, with adequate follow-up periods, to test the efficacy of transcranial magnetic stimulation to treat these disorders. Available evidence must be regarded as preliminary and insufficient, at present, to support offering TMS to treat ASD.publishersversionpublishe

Glass fibre content of PP plates and their properties: part II: tensile mechanical properties

Short fibre reinforced polypropylene compounds have been used to produce composites taking advantage of its interesting properties and competitive raw material prices. For the same reason the short glass fibres are the most used reinforcement in injection moulded thermoplastic composites. In injection moulding, varying patterns of fibre orientation are obtained through the thickness direction and along the flow path. Moulding parameters such as injection flow rate or melt-temperature do affect the fibre orientation distributions in mouldings. It has been observed that the type of flow, being dominated by shear stresses (e.g. linear flow) or by extensional stresses (e.g. radial flow) affects the fibre orientation field. Other parameters may have an effect over the fibre orientation such as the fibre length distribution. During processing some degree of fibre breakage in unavoidable. The fibre contents, its length and orientation distributions cause anisotropy on mechanical properties. Efficient reinforcements are obtained in the direction of major orientation of the fibres and when longer fibres are used. In this work the effect of various fibre contents, by volume (0, 10, 20 and 25%) over the anisotropy of mechanical properties of injection moulded rectangular plates is explored. Specimens cut along and across the flow directions are subjected to tensile tests enabling to discuss the anisotropy of tensile mechanical properties.(undefined

Glass fibre contents of PP plates and their properties: part I: Shrinkage and changes in time

In this paper the results from the first part of a study on the glass fibre contents of PP plates and their properties is presented. Focus is made on the effect of the fibre volume fraction and holding pressure on the experimental as-moulded shrinkage in the flow and across flow directions. Data is also presented on the post-moulding shrinkage. For the experimental work, PP with different volume fraction of glass fibre (0, 0.1, 0.2 and 0.25) was used. The mouldings are edge gated flat rectangular plates. The moulding process was continuously monitored with pressure transducers.(undefined