دانلود رایگان مقاله لاتین تقویت smc از سایت الزویر
عنوان فارسی مقاله:
خصوصیات غیر مخرب جهت گیری فیبر در تقویت SMC به عنوان ورودی برای طراحی بر اساس شبیه سازی
عنوان انگلیسی مقاله:
Non-destructive characterization of fiber orientation in reinforced SMC as input for simulation based design
سال انتشار : 2016
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مقدمه انگلیسی مقاله:
1. Introduction
The mixing of fibers and polymers to form composites opens new ways for designing lightweight materials substituting traditionally used steel alloys or iron sheets in aviation and car industry [1]. Composite materials are traditionally regarded as materials that can save energy in large structures and components associated with transportation. Some of the most interesting applications of fiber reinforced composite materials are those where they are used to protect lives or property by absorbing energy in impacts or crashes [2,3]. Impact is considered as one of the most dangerous damage sources of fiber reinforced polymeric composite structures, as it can lead to significant reduction on the strength and stiffness of the structures. However, the damage can often not be detected from mere surface inspection of the component, thus causing great security risks to the structures.Among various composite systems, the sheet molding compounds (SMCs) have been increasingly used for structural applications because of their excellent processibility and versatility in manufacture and desirable mechanical properties for engineering design. SMCs are high strength glass or carbon reinforced thermoset molding materials processed by thermocompression. SMC composites combine glass or carbon fiber and unsaturated polyester/vinylester modified resins to produce a high-strength molding compound [4,5]. The rapid increase in applications of short- and long-fiber reinforced SMCs as safety-relevant parts and components has resulted in significant concern over the failure behavior of the material. In this context, many experimental studies have been performed to measure the mechanical response of SMCs to a variety of loading conditions such as crash impact [6–8], fluctuating temperature environments [9,10] or different strain rates [11,12]. While such experiments provide data for a useful analytic description of the studied material behavior and for deriving constitutive equations that can be used in numerical studies, they do not provide any detailed microstructural information about fiber orientation in different layers of the SMC material. Recently, with the rapid development of computer speed and computational methods, such as the Discrete Element Method (DEM) and the Finite Element Method (FEM), numerical simulations on multiscales, taking into account different structural features of materials not only on the macroscopic, but also on the microscopic scale, have become feasible [13–16]. Thus, for numerical simulations, a better understanding of the connection between the spatial distribution of microscopic fibers, controlling the macroscopic performance, has become a major issue. Knowing the composition of the precursors as well as the production process of fiber reinforced composites provides broad qualitative information about the microstructure, for instance fiber volume fraction, preferred fiber direction or layers within the microstructure. However, quantitative image analysis is needed in order to go beyond mere qualitative descriptions of composite materials and to obtain detailed local microstructural information that can be used as input for numerical simulation tools [17]. In particular, local deviations from the expected fiber content or direction have to be taken into account when designing parts. Also, enhanced virtual component design before manufacturing a single part requires quantitative image analysis: The software packages for computer aided design need as input not only the material properties of the components but also microstructural features that have to be acquired image analytically. Traditional approaches in materialography are based on lightmicroscopic 2D images of microsections and provide measurements of fiber volume fraction and its local variation. There exists a variety of methods for the so-called binarization, i.e., the separation of an image into foreground (fibers) and background areas [18,19]. Anisotropy can be quantified using linear contact or chord length distributions [20]. 3D fiber directions can be estimated from 2D microsections using the elliptical shape of fiber cross-sections [21,22]. However, this approach requires individual fibers to be segmented, i. e. identified as individual objects within the image, and that the resolution is high enough to reliably measure the cross-sectional shape. Fiber directions in fiber reinforced SMC have been studied as early as 1986 using the high X-ray absorption contrast of lead doped glass fibers in radiographs [23]. Advani provides a comprehensive overview of early orientation analysis methods [24]. Confocal laser scanning microscopy allows to image layers up to a depth of about 30 lm and was used to decrease the error in orientation measurements based on the shape of elliptical cross-sections [25,26]. In SMC composites, bundles formed of long fibers have to be analyzed. Thus methods thriving on the segmentation of individual fibers are not applicable and approaches for determining local fiber directions without segmentation of individual fibers have to be considered. Le et al. [5] segmented individual bundles manually exploiting high lateral and gray value resolutions achieved by synchrotron radiation computed tomography. The so-called chord length transform and the method based on axis and moments of inertia thrive on ideas from mathematical morphology [27,28]. A refinement of the latter method has been used by Viguié et al. [29] to segment and individually analyze fiber bundles in an SMC sample imaged by micro computed tomography (lCT). Krause et al. deduced local directions from first order derivatives (gradients) subsumed in the structure tensor [30]. The Hessian matrix of second partial derivatives yields the local fiber direction as the direction corresponding to its lowest eigenvalue [31,32]. In this paper, scanning acoustic microscopy (SAM) and lCT are combined with a local orientation analysis method based on anisotropic Gaussian filters [33,34,32] since this method is particularly well suited for large, rather roughly resolved images of fiber reinforced SMC. This paper introduces this method for the first time in an application setting, shows its robustness, and its applicability to images from very different sources. In particular, analysis results based on SAM and lCT are found to be comparable. The method based on anisotropic Gaussian filters is particularly well-suited for the SMC samples considered here as it (a) allows to extract the local fiber orientation information without error-prone and tedious segmentation of individual fibers or fiber bundles, (b) is robust with respect to noise [32] and not well defined edges, and (c) can be computed very efficiently for orientation distributions concentrated in a plane [34]. From the local fiber orientation distribution, a measure for anisotropy is deduced, which can be directly correlated with the observed fatigue strength of the specimens thus experimentally confirming rules of thumb on the relation of the degree to which the fibers are oriented and mechanical behaviour. The organization of the paper is as follows: A short description of the material studied is followed by a summary of the imaging techniques used. Subsequently, we describe the measurement of fiber orientation in the material samples and the fatigue tests. The agreement of the experimental results – image analytically determined fiber orientation and cumulative fatigue strength – is emphasized in a dedicated section just before the final conclusions.
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کلمات کلیدی:
Determination of the orientation of short glass fibers in sheet molding ... onlinelibrary.wiley.com/doi/10.1002/pc.750080204/abstract by H Kau - 1987 - Cited by 28 - Related articles Abstract. A computer based semiautomatic procedure has been developed to measure the fiber orientation on the surface of Sheet Molding Compound (SMC) ... Predicting mold flow for unsaturated polyester resin sheet molding ... onlinelibrary.wiley.com/doi/10.1002/pc.750010105/full by RJ Silva‐Nieto - 1980 - Cited by 40 - Related articles Presented at 34th Annual Conference: SPI Reinforced Plastics/Composites ... Improved products can be obtained from sheet molding compounds (SMC) if due regard ... without substantially altering the initial fiber orientation of the SMC matrix. Handbook of Materials Selection - Page 374 - Google Books Result https://books.google.com/books?isbn=0471359246 Myer Kutz - 2002 - Technology & Engineering The third material is sheet molding compound (SMC), which contains chopped ... Composites reinforced with randomly oriented fibers tend to have lower volume ... Expression Method of Fiber Orientation Distribution in Fiber ... https://www.jstage.jst.go.jp/article/jsms1963/39/436/39_436_38/_article Keywords: Fiber orientation distribution function, Fiber reinforced composite, ... of fiber orientation for the fiber composite, and the mold flow of fibers in SMC ... Searches related to orientation in reinforced SMC bmc polymer frp manufacturing process ppt frp moulding process frp material properties
