Plásticos reforçados a base de tecidos híbridos: efeitos da anisotropia e geometria normativa na caracterização mecânica e da fratura

As most current studies, reinforced plastics have been, in recent years, a viable alternative in building structural elements of medium and large, since the lightness accompanied by high performance possible. The design of hybrid polymer composites (combination of different types of reinforcements) may enable structural applications thereof, facing the most severe service conditions. Within this class of composite materials, reinforced the underlying tissues hybrid high performance are taking space when your application requires high load bearing and high rigidity. The objective of this research work is to study the challenges in designing these fabrics bring these materials as to its mechanical characterization and fracture mechanisms involved. Some parameters associated with the process and / or form of hybridization stand out as influential factors in the final performance of the material such as the presence of anisotropy, so the fabric weave, the process of making the same, normative geometry of the specimens, among others. This sense, four laminates were developed based hybrid reinforcement fabrics involving AS4 carbon fiber, kevlar and glass 49-E as the matrix epoxy vinyl ester resin (DERAKANE 411-350). All laminates were formed each with four layers of reinforcements. Depending on the hybrid fabric, all the influencing factors mentioned above have been studied for laminates. All laminates were manufactured industrially used being the lamination process manual (hand-lay-up). All mechanical characterization and study of the mechanism of fracture (fracture mechanics) was developed for laminates subjected to uniaxial tensile test, bending in three and uniaxial compression. The analysis of fracture mechanisms were held involving the macroscopic, optical microscopy and scanning electron microscopy

Adição de geomanta e tecido não tecido de polipropileno em cimentos geopoliméricos de pega rápida

Geopolymers are cementing materials that depict a number of advantages compared to Portland cement. Contrary to the latter, geopolymers are synthesized at room temperature, thus significantly reducing the emission of CO2 to the atmosphere. Moreover, the composition and synthesis reactions can be tailored to adjust the setting time of the material as well as its compressive mechanical strength. It is then possible to produce geopolymeric cements with short setting times and high compressive strength, although relatively brittle. The objective of the present study was to produce and characterize composite materials by reinforcing fastsetting geopolymeric matrixes with polypropylene geosynthetics (geomats and geotextiles) in an attempt to improve the toughness and tensile strength of the cementing material. Geosynthetics have been increasingly used to reinforce engineering structures, providing higher strength and better toughness. In particular, polypropylene nonwoven and geomats depict other attractive properties such as low density, durability, impact absorption and resistance to abrasion. Fast-setting geopolymers were then synthesized and reinforced with polypropylene nonwoven and geomats. The mechanical strength of the materials, reinforced or not, was characterized. The results showed that relatively short setting times and adequate flowing behavior were achieved by adjusting the composition of the geopolymer. In addition, it is possible to improve the fracture resistance of geopolymeric cements by adding polypropylene geosynthetics. The best results were achieved by reinforcing geopolymer with polypropylene TNT

Capacidade de absorção de energia de tubos de compósitos submetidos à compressão

Structures capable of absorbing large amounts of energy are of great interest, particularly for the automotive and aviation industries, to reduce tbe impact on passengers in the case of a collision. The energy absorption properties of composite materials structures can be tailored, thus making these structures an appealing option a substitute of more traditional structures in applications where energy absorption is crucial. ln this research, the influence of some parameters, which affect the energy absorption capacity of composite material tubes, was investigated. The tubes were fabricated by hand lay-up, using orthophthalic polyester resin and a plain weave E-glass fabric Test specimens were prepared and tested under compression load. The ínfluence of the following parameters on the specific energy absorption capacity of the tubes was studied: fiber configuration (0/90º or ± 45°), tube cross-section (circular or square), and processing conditions (with or without vacuum). The results indicated that circular cross-section tubes with fibers oriented at 0/90º presented the highest level of specific energy absorbed. Further, specimens from tubes fabricated under vacuum displayed higher energy absorption capacity, when compared with specimens from tubes fabricated without vacuum. Thus, it can be concluded that the fabrication process with vacuum produce composite structures with better energy absorption capacity

Análise do desempenho térmico de sistema constutivo de concreto com EPS como agregado graúdo

In the last decades there was a concentrate effort of researchers in the search for options to the problem of the continuity of city development and environmental preservation. The recycling and reuse of materials in industry have been considerate as the best option to sustainable development. One of the relevant aspects in this case refers to the rational use of electrical energy. At this point, the role of engineering is to conceive new processes and materials, with the objective of reducing energy consumption and maintaining, at the same time the benefits of the technology. In this context, the objective of the present research is to analyze quantitatively the thermal behavior of walls constructed with concrete blocks which composition aggregates the expanded polystyrene (EPS) reused in the shape of flakes and in the shape of a board, resulting in a “light concrete”. Experiments were conducted, systematically, with a wall (considerate as a standard) constructed with blocks of ordinary concrete; two walls constructed with blocks of light concrete, distinct by the proportion of EPS/sand; a wall of ceramic bricks (“eight holes” type) and a wall with ordinary blocks of cement, in a way to obtain a comparative analysis of the thermal behavior of the systems. Others tests conducted with the blocks were: stress analysis and thermal properties analysis (ρ, cp e k). Based on the results, it was possible to establish quantitative relationship between the concentration (density) of EPS in the constructive elements and the decreasing of the heat transfer rate, that also changes the others thermal properties of the material, as was proved. It was observed that the walls of light concrete presents better thermal behavior compared with the other two constructive systems world wide used. Based in the results of the investigation, there was shown the viability of the use of EPS as aggregate (raw material) in the composition of the concrete, with the objective of the fabrication of blocks to non-structural masonry that works as a thermal insulation in buildings. A direct consequence of this result is the possibility of reduction of the consume of the electrical energy used to climatization of buildings. Other aspect of the investigation that must be pointed was the reuse of the EPS as a raw material to civil construction, with a clear benefit to reducing of environmental problems

Compósito de poliuretano de mamona e vermiculita para isolação térmica

They are in this study the experimental results of the analysis of thermal performance of composite material made from a plant matrix of polyurethane derived from castor oil of kernel of mamona (COF) and loading of clay-mineral called vermiculite expanded. Bodies of evidence in the proportions in weight of 10%, 15% and 20% were made to determine the thermal properties: conductivity (k), diffusivity (ά) and heat capacity (C), for purposes of comparison, the measurements were also performed the properties of polyurethane of castor without charge and also the oil polyurethane (PU), both already used in thermal insulation. Plates of 0.25 meters of material analyzed were manufactured for use as insulation material in a chamber performance thermal coverage. Thermocouples were distributed on the surface of the cover, and inside the material inside the test chamber and this in turn was subjected to artificial heating, consisting of a bank of incandescent lamps of 3000 w. The results obtained with the composite materials were compared with data from similar tests conducted with the camera alone with: (a) of oil PU, (b) of COF (c) glass wool, (d ) of rock wool. The heat resistance tests were performed with these composites, obtaining temperature limits for use in the range of 100 º C to 130 º C. Based on the analysis of the results of performance and thermal properties, it was possible to conclude that the COF composites with load of expanded vermiculite present behavior very close to those exhibited by commercial insulation material

Efeitos da radiação uv, temperatura e vapor aquecido nos compósitos poliméricos: monitoramento, instabilidade estrutural e fratura

The application of composite materials and in particular the fiber-reinforced plastics (FRP) has gradually conquered space from the so called conventional materials. However, challenges have arisen when their application occurs in equipment and mechanical structures which will be exposed to harsh environmental conditions, especially when there is the influence of environmental degradation due to temperature, UV radiation and moisture in the mechanical performance of these structures, causing irreversible structural damage such as loss of dimensional stability, interfacial degradation, loss of mass, loss of structural properties and changes in the damage mechanism. In this context, the objective of this thesis is the development of a process for monitoring and modeling structural degradation, and the study of the physical and mechanical properties in FRP when in the presence of adverse environmental conditions (ageing). The mechanism of ageing is characterized by controlled environmental conditions of heated steam and ultraviolet radiation. For the research, it was necessary to develop three polymer composites. The first was a lamina of polyester resin reinforced with a short glass-E fiber mat (representing the layer exposed to ageing), and the other two were laminates, both of seven layers of reinforcement, one being made up only of short fibers of glass-E, and the other a hybrid type reinforced with fibers of glass-E/ fibers of curaua. It should be noted that the two laminates have the lamina of short glass-E fibers as a layer of the ageing process incidence. The specimens were removed from the composites mentioned and submitted to environmental ageing accelerated by an ageing chamber. To study the monitoring and modeling of degradation, the ageing cycles to which the lamina was exposed were: alternating cycles of UV radiation and heated steam, a cycle only of UV radiation and a cycle only of heated steam, for a period defined by norm. The laminates have already undergone only the alternating cycle of UV and heated steam. At the end of the exposure period the specimens were subjected to a structural stability assessment by means of the developed measurement of thickness variation technique (MTVT) and the measurement of mass variation technique (MMVT). Then they were subjected to the mechanical tests of uniaxial tension for the lamina and all the laminates, besides the bending test on three points for the laminates. This study was followed by characterization of the fracture and the surface degradation. Finally, a model was developed for the composites called Ageing Zone Diagram (AZD) for monitoring and predicting the tensile strength after the ageing processes. From the results it was observed that the process of degradation occurs Abstract Raimundo Nonato Barbosa Felipe xiv differently for each composite studied, although all were affected in certain way and that the most aggressive ageing process was that of UV radiation, and that the hybrid laminated fibers of glass-E/curaua composite was most affected in its mechanical properties

Utilização de RNA´s na construção do diagrama de vida constante de probabilidade de materiais compósitos

The static and cyclic assays are common to test materials in structures.. For cycling assays to assess the fatigue behavior of the material and thereby obtain the S-N curves and these are used to construct the diagrams of living constant. However, these diagrams, when constructed with small amounts of S-N curves underestimate or overestimate the actual behavior of the composite, there is increasing need for more testing to obtain more accurate results. Therewith, , a way of reducing costs is the statistical analysis of the fatigue behavior. The aim of this research was evaluate the probabilistic fatigue behavior of composite materials. The research was conducted in three parts. The first part consists of associating the equation of probability Weilbull equations commonly used in modeling of composite materials S-N curve, namely the exponential equation and power law and their generalizations. The second part was used the results obtained by the equation which best represents the S-N curves of probability and trained a network to the modular 5% failure. In the third part, we carried out a comparative study of the results obtained using the nonlinear model by parts (PNL) with the results of a modular network architecture (MN) in the analysis of fatigue behavior. For this we used a database of ten materials obtained from the literature to assess the ability of generalization of the modular network as well as its robustness. From the results it was found that the power law of probability generalized probabilistic behavior better represents the fatigue and composites that although the generalization ability of the MN that was not robust training with 5% failure rate, but for values mean the MN showed more accurate results than the PNL model

Laminados compósitos de PRFV: efeitos da descontinuidade geométrica e do envelhecimento ambiental acelerado

The growing demand in the use of composite materials necessitates a better understanding of its behavior related to many conditions of loading and service, as well as under several ways of connections involved in mechanisms of structural projects. Within these project conditions are highlighted the presence of geometrical discontinuities in the area of cross and longitudinal sections of structural elements and environmental conditions of work like UV radiation, moisture, heat, leading to a decrease in final mechanical response of the material. In this sense, this thesis aims to develop studies detailed (experimental and semi-empirical models) the effects caused by the presence of geometric discontinuity, more specifically, a central hole in the longitudinal section (with reduced cross section) and the influence of accelerated environmental aging on the mechanical properties and fracture mechanism of FGRP composite laminates under the action of uniaxial tensile loads. Studies on morphological behavior and structural degradation of composite laminates are performed by macroscopic and microscopic analysis of affected surfaces, in addition to evaluation by the Measurement technique for mass variation (TMVM). The accelerated environmental aging conditions are simulated by aging chamber. To study the simultaneous influence of aging/geometric discontinuity in the mechanical properties of composite laminates, a semiempirical model is proposed and called IE/FCPM Model. For the stress concentration due to the central hole, an analisys by failures criteria were performed by Average-Stress Criterion (ASC) and Point-Stress Criterion (PSC). Two polymeric composite laminates, manufactured industrially were studied: the first is only reinforced by short mats of fiberglass-E (LM) and the second where the reinforced by glass fiber/E comes in the form of bidirectional fabric (LT). In the conception configurations of laminates the anisotropy is crucial to the final mechanical response of the same. Finally, a comparative study of all parameters was performed for a better understanding of the results. How conclusive study, the characteristics of the final fracture of the laminate under all conditions that they were subjected, were analyzed. These analyzes were made at the macroscopic level (scanner) microscope (optical and scanning electron). At the end of the analyzes, it was observed that the degradation process occurs similarly for each composite researched, however, the LM composite compared to composite LT (configurations LT 0/90º and LT ±45º) proved to be more susceptible to loss of mechanical properties in both regarding with the central hole as well to accelerated environmental aging

Descontinuidade na seção transversal em laminados compósitos poliméricos: efeitos e propriedades

The growing demand in the use of composite materials necessitates a better understanding its behavior to many conditions of loading and service, as well as under several ways of connections involved in mechanisms of structural projects. It is know that most of the structural elements are designed with presence of geometric discontinuities (holes, notches, etc) in their longitudinal sections and / or transversals, and that these discontinuities affect the mechanical response of these elements. This work has aims to analyze a study of the mechanical response, when in the presence geometric discontinuity, of polymer matrix composite laminates (orthophthalic polyester) to the uniaxial tensile test. The geometric discontinuity is characterized by the presence of a center hole in the transversal section of the composite. In this study, different kinds of stacking sequences are tested, with and without the presence of the hole, so as to provide better understanding of the mechanical properties. This sense, two laminates were studied: the first is only reinforced by with seven layers short mats of fiberglass-E (CM) and the second where the reinforcement of fiberglass-E comes in the form of bidirectional fabric (CT), with only four layers. The laminate CT has the presence of anisotropy (sense of continuous fibers with respect to the applied load) as the main parameter influencing its mechanical behavior, behavior this, not observed for the CM. In addition to the mechanical properties was also studied the fracture characteristics developed in each composite laminated. The results also showed that the presence of the hole in the transversal section decreased the ultimate strength of laminates and changed the final characteristic of fracture in all kinds of composite laminated studied

Metodologia, Sistema de Codificação e Ferramenta de software para Modelagem de Móveis Modulados

On this research we investigated how new technologies can help the process of design and manufacturing of furniture in such small manufacturers in Rio Grande do Norte state. Google SketchUp, a 3D software tool, was developed in such a way that its internal structures are opened and can be accessed using SketchUp s API for Ruby and programs written in Ruby language (plugins). Using the concepts of the so-called Group Technology and the flexibility that enables adding new functionalities to this software, it was created a Methodology for Modeling of Furniture, a Coding System and a plugin for Google s tool in order to implement the Methodology developed. As resulted, the following facilities are available: the user may create and reuse the library s models over-and-over; reports of the materials manufacturing process costs are provided and, finally, detailed drawings, getting a better integration between the furniture design and manufacturing process

Estudo da presença de entalhes semicirculares em compósitos poliméricos híbridos

Composite materials have a wide application in various sectors, such as the medical field in the manufacture of prostheses, in automotive and aerospace. Thus it is essential to the development of new composite and a better understanding in the face of various loading conditions and service. Several structural elements are manufactured in the presence of geometric discontinuity (notch, hole, etc ) in their longitudinal sections and/or cross-cutting, and these affect the mechanical response of these elements. The objective is to study the mechanical response of laminated polymer matrix hybrid composites reinforced with glass fiber/jute in a uniaxial tensile test. The mechanical response takes in account both the influence of the presence of a geometric discontinuity (semicircular notches) and the orientation of fibers in the layers (anisotropy). The semicircular notches are located in longitudinal section (with a reduction in cross section) of the same. In this analysis, the anisotropy is characterized by types of configurations (with different orientations of fibers in the outer layers). A comparative study of mechanical properties with and without the presence of notches is developed. Both configurations consist of four layers of woven jute fiber bidirectional and a central layer of bidirectional woven glass fibers. In addition to the mechanical properties was also studied the characteristics of the fracture developed in each composite laminate. The results showed that in the comparative study, the anisotropy and the presence of semicircular notches directly influences the mechanical behavior of laminates composites, mainly in reducing the tensile strength, and well as the final characteristics of the fracture

Avaliação do comportamento tribológico de compósitos poliéster/fibra de vidro utilizando resíduos de poliéster/fibra de vidro e carbonato de cálcio como carga

The use of composite materials and alternative is being increased every day, as it becomes more widespread awareness that the use of renewable and not harmful to the environment is part of a new environmentally friendly model. Since its waste (primarily fiberglass) can not be easily recycled by the difficulty that still exists in this process, since they have two phases mixed, a polymeric matrix thermoset difficult to recycle because it is infusible and phase of fiber reinforcements. Thermoset matrix composites like Polyester + fiberglass pose a threat due to excessive discharge. Aiming to minimize this problem, aimed to reuse the composite Polyester + fiber glass, through the wastes obtained by the grinding of knifes and balls. These residues were incorporated into the new composite Polyester/Fiberglass for hot compression mold and compared tribological to composites with filler CaCO3, generally used as filler, targeting a partial replacement of CaCO3 by such waste. The composites were characterized by thermal analysis (TGA, DSC and DMA), by the surface integrity (roughness determination, contact angle and surface energy), mechanical properties (hardness) and tribological tests (wear and coefficient of dynamic friction) in order to evaluate the effect of loads and characterize these materials for applications that can take, in the tribological point of view since waste Polyester + fiberglass has great potential for replacement of CaCO3

Resposta térmica de um compósito PEEK+PTFE+Fibra de carbono+grafite

Composites based on PEEK + PTFE + CARBON FIBER + Graphite (G_CFRP) has increased application in the top industries, as Aerospace, Aeronautical, Petroleum, Biomedical, Mechanical and Electronics Engineering challenges. A commercially available G_CFRP was warmed up to three different levels of thermal energy to identify the main damage mechanisms and some evidences for their intrinsic transitions. An experimental test rig for systematize a heat flux was developed in this dissertation, based on the Joule Effect. It was built using an isothermal container, an internal heat source and a real-time measurement system for test a sample by time. A standard conical-cylindrical tip was inserted into a soldering iron, commercially available and identified by three different levels of nominal electrical power, 40W (manufacturer A), 40W (manufacturer B), 100W and 150W, selected after screening tests: these power levels for the heat source, after one hour of heating and one hour of cooling in situ, carried out three different zones of degradation in the composite surface. The bench was instrumented with twelve thermocouples, a wattmeter and a video camera. The twelve specimens tested suffered different degradation mechanisms, analyzed by DSC (Differential Scanning Calorimetry) and TG (Thermogravimetry) techniques, Scanning Electron Microscopy (SEM) and Energy-Dispersive X-Rays (EDX) Analysis. Before and after each testing, it was measured the hardness of the sample by HRM (Hardness Rockwell M). Excellent correlations (R2=1) were obtained in the plots of the evaporated area after one hour of heating and one hour of cooling in situ versus (1) the respective power of heat source and (2) the central temperature of the sample. However, as resulting of the differential degradation of G_CFRP and their anisotropy, confirmed by their variable thermal properties, viscoelastic and plastic properties, there were both linear and non-linear behaviour between the temperature field and Rockwell M hardness measured in the radial and circumferential directions of the samples. Some morphological features of the damaged zones are presented and discussed, as, for example, the crazing and skeletonization mechanism of G_CFRP

Desenvolvimento de têxteis técnicos para reforço de compósitos poliméricos

Materials denominated technical textiles can be defined as structures designed and developed with function to fulfill specific functional requirements of various industrial sectors as are the cases of the automotive and aerospace industries. In this aspect the technical textiles are distinguished from conventional textile materials, in which the aesthetic and of comfort needs are of primordial importance. Based on these considerations, the subject of this dissertation was established having as its main focus the study of development of textile structures from aramid and glass fibers and acting in order to develop the manufacture of composite materials that combine properties of two different structures, manufactured in an identical operation, where each structure contributes to improving the properties of the resulting composite material. Therefore were created in laboratory scale, textile structures with low weight and different composition: aramid (100%), glass (100%) and aramid /glass (65/35%), in order to use them as a reinforcing element in composite materials with polyester matrix. These composites were tested in tension and its fracture surface, evaluated by MEV. Based on the analysis of mechanical properties of the developed composites, the efficiency of the structures prepared as reinforcing element were testified by reason of that the resistance values of the composites are far superior to the polyester matrix. It was also observed that hybridization in tissue structure was efficient, since the best results obtained were for hybrid composites, where strength to the rupture was similar to the steel 1020, reaching values on the order of 340 MPa

Compósito Polimérico Híbrido: Comportamento Mecãnico, Descotinuidade Geométrica e Resistência Residual

The growing demand in the use of hybrid composite materials makes it essential a better understanding of their behavior face of various design conditions, such as the presence of geometric discontinuities in the cross section of structural elements. This way, the purpose of this dissertation is a study of the mechanical response (strength and stiffness), modes (characteristics) of fracture and Residual Strength of an hybrid polymeric composite with and without a geometric discontinuity in its longitudinal section (with a reduction in the cross section) loaded by uniaxial tension. This geometric discontinuity is characterized by central holes of different diameters. The hybrid composite was fabricated as laminate (plate) and consisting of ortho-tereftalic polyester matrix reinforced by 04 outer layers of Jute fibers bidirectional fabrics and 01 central layer of E-glass bidirectional fabric. The laminate was industrially manufactured (Tecniplas Nordeste Indústria e Comércio Ltda.), obtained by the hand lay-up technique. Initially, a study of the volumetric density of the laminate was made in order to verify its use in lightweight structures. Also were performed comparative studies on the mechanical properties and fracture modes under the conditions of the specimens without the central hole and with the different holes. For evaluating the possible influence of the holes in the structural stability of the laminate, the Residual Strength of the composite was determined for each case of variation in hole diameter. As a complementary study, analyses of the macroscopic final fracture characteristic of the laminates were developed. The presence of the central hole of any sizes, negatively changed the ultimate tensile strength. Regarding the elastic modulus, moreover, the difference found between the specimens was within the range of tests displacement, showing the laminate stability related to the stiffness