1,721,415 research outputs found
Acoustic emission and damage mode correlation in textile reinforced PPS composites
Full text linkThe paper applies the cluster analysis methodology to thermoplastic Polyphenylene sulphide (PPS) carbon woven composites. The experimental quasi-static tensile tests were assisted by: a digital camera for digital image correlation (DIC) evaluation of the full field strain; a digital camera for local damage observation; acoustic emission (AE) sensors for measurement of the acoustic emission features during loading. The experimental data and the subsequent cluster analyses of the AE events show a similar distribution of the AE clusters for the considered thermoplastic carbon composites and other thermoset woven composites described in the literature. The boundaries of those clusters are different for some extent, while a typical damage mechanism, namely transverse cracks inside the yarns, was clearly correlated to the first cluster with lower amplitude and lower frequency acoustic events
Fatigue limit: Is there a link to the quasi-static damage?
No full textThe paper presents experimentally and numerically observed relations of the fatigue life limit and the quasi-static damage threshold, which provide rough estimation for the design strains to use under fatigue strength requirements and allow planning of the fatigue testing programs to minimize the amount of costly and time-consuming experiments with low loads and high number of cycles
Fatigue of Textile and Short Fiber Reinforced Composites
No full textThis book covers several aspects of the fatigue behavior of textile and short fiber reinforced composites. The first part is dedicated to 2D and 3D reinforced textile composites and includes a systematic description of the damage evolution for quasi-static and tensile-tensile fatigue loadings. Acoustic emissions and digital image correlation are considered in order to detect the damage modes’ initiation and development. The acoustic emission thresholds of the quasi-static loading are connected to the ‘fatigue limit’ of the materials with distinctions for glass and carbon reinforcements.
The second part is devoted to the fatigue behavior of injection molded short fiber reinforced composites. Experimental evidence highlighting the dependence of their fatigue response on various factors: fiber and matrix materials, fiber distribution, environmental and loading conditions are described. A hybrid (experimental/simulations) multi-scale method is presented, which drastically reduces the amount of the necessary experimental data for reliable fatigue life predictions
Physics-informed machine learning for loading history dependent fatigue delamination of composite laminates
No full textFiber bridging has retardation effect on Mode I fatigue delamination, making the damage loading history dependent. This research creates a physics-informed machine learning (ML) model for characterizing this fatigue delamination propagation. After a training, the model can predict fatigue crack growth rate for a given crack length, accounting for a certain amount of bridging fibers. Mode I fatigue experiments were first performed to obtain sufficient data for the ML. A semi-empirical Paris-type correlation determines fatigue damage evolution with bridging retardation. This correlation was integrated as a physical constraint into the physics-informed neural networks (PINNs). PINNs demonstrate excellent performance: the predictions of the delamination fall within a narrow scatter band of 1.5 times by crack growth rate, outperforming both the non-physics-informed ML model and the Paris-type correlation. The proposed ML model can be applied for the development, characterization and comparison of composite materials, and for composite structure design and life evaluation
Modelling the damage evolution in unidirectional all-carbon hybrid laminates
No full textHybrid reinforcements for composites have been extensively studied and adopted to overcome the lack of ductility via pseudo-ductility. Thin-ply all-carbon interlayer hybrid laminates have attracted attention for their peculiar pseudo-ductile tensile response. At the same time, conventional thick plies have been barely considered. This work developed a finite element model to simulate the complex tensile damage scenario of unidirectional thin- and thick-ply all-carbon interlayer hybrid laminates. The damage modes intended in the numerical model were fragmentation in the low-elongation (LE) plies, and delamination of LE and high-elongation (HE) ply interfaces. Thin- and thick-ply hybrid laminates were modelled and compared to available experiments. The numerical model was also adopted to simulate different layups to predict the effect of LE thickness fraction on the pseudo-ductile tensile behaviour and the evolution of damage modes. As suggested in the literature, the results allowed us to depict the damage mode map of the considered hybrid laminates. The map distinguishes the allcarbon hybrid laminate configurations with pseudo-ductile and brittle tensile responses
Fatigue of hybrid fibre-reinforced plastics
No full textUnderstanding the fatigue behaviour of hybrid fibre-reinforced plastics is desirable for exploiting their features in safe, durable and reliable industrial components. The fatigue performance of hybrid composites has not been extensively investigated yet. The paper presents an overview of the available knowledge on the fatigue of hybrid fibre-reinforced plastics, and, more specifically, reports the fatigue behaviour of a quasi-isotropic pseudo-ductile all-carbon fibre interlayer hybrid composite by experimental measurements and observations, with emphasis on the damage development. The fatigue conditions are tension-tension stress- and strain controlled cyclic loading. The results include fatigue life for different maximum stress and strain levels, stiffness evolution and damage observations by X-ray micro-computed tomography. The studied hybrid all-carbon fibre quasi-isotropic composite exhibits pseudo-ductility in quasi-static testing. For stress controlled fatigue, the fatigue load over the limit of elastic response is not sustained. Contrary to that, the composite retains its load-carrying ability in the pseudo-ductile regime for a strain-controlled regime, albeit with lowered stiffness
Carbon fibre sheet moulding compounds with high in-mould flow: linking morphology to tensile and compressive properties
Full text linksponsorship: The research leading to these results has been performed within the framework of the FiBreMoD project and has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 722626. YS acknowledges FWO Flanders for his postdoctoral fellowship. SVL holds the Toray Chair at KU Leuven, the support of which is acknowledged. SP acknowledges her Research Fellowship of the Royal Academy of Engineering on "Multiscale discontinuous composites for high-volume and sustainable applications" (2015-2019). The authors also acknowledge Mitsubishi Chemical Carbon Fiber and Composites GmbH for providing material and related information. The micro-CT images have been acquired on the X-ray computed tomography facilities at KU Leuven, maintained under the supervision of Prof M. Wevers and financed by the Hercules Foundation and the Research Council of KU Leuven (project C24/17/052); help of Dr Jeroen Soete and of technician Johan Vanhulst is gratefully acknowledged. The authors acknowledge Marco Alves (Imperial College London) for several useful discussion on CT analysis of TBDC. The technicians of KULeuven Bart Pelgrims and Kris Van de Staey are acknowledged for their help with the tensile and compressive tests. (European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant|722626, FWO Flanders, Toray Chair at KU Leuven, the Royal Academy of Engineering, Hercules Foundation, Research Council of KU Leuven|C24/17/052)status: Published onlin
Morphological and Mechanical Quantification of Porous Structures by Means of Micro-CT (Morfologische en mechanische kwantificatie van poreuze structuren met behulp van micro-CT)
No full textSuitable characterization techniques for porous structures are required to (i) understand and to be able to simulate, via finite elements (FE), the structure-properties relationships and (ii) understand the relationship between the morphology and mechanical behaviour on one hand, and the failure mechanisms on the other hand. X-ray microfocus computed tomography (micro-CT) offers a solution as it provides a means to acquire a complete 3D set of images of the structure visualizing the internal architecture at the microscopic level in a non-destructive way. Additionally, the micro-CT images enable subsequent image analysis, resulting in an extensive 3D quantitative description of the morphology that cannot be obtained by other methods. But, one has to be aware of the fact that micro-CT images are inherently subjected to artefacts and that the image quality and accuracy depend on multiple factors. For example, the acquisition settings (target material, tube voltage and filter material) influence the X-ray spectra and hence also the image quality. The spatial resolution strongly influences the accuracy of the micro-CT images and as a result also the morphological analysis. Closely related to the latter, the material architecture has a significant influence on the micro-CT image accuracy, which is also affected by the material type.
In a first part of this study, systematic, fast and user-independent protocols have been developed both for acquisition parameter optimization and for image accuracy validation, and the influence of the different factors mentioned above on the image accuracy has been investigated. As a result, when applying these protocols, the micro-CT user should know, for different material types and architectures, what the capabilities and limitations of micro-CT are for morphological assessment of porous structures.
In a second part, this knowledge has been applied and the use of micro-CT has been expanded to the mechanical characterization of porous structures by combining micro-CT imaging and 3D image analysis with in-situ mechanical loading, FE analysis and local strain mapping as this combination allows to (i) provide in-situ and experimentally the mechanical properties, (ii) link the mechanical properties to the morphology, (iii) investigate the morphological changes under compressive loading, (iv) feed and validate a FE model which can be applied for the prediction of the mechanical properties that cannot readily be determined experimentally and (v) predict the failure modes by using experimental local strain mapping
Micro-CT based structure tensor analysis of fibre orientation in random fibre composites versus high-fidelity fibre identification methods
No full textThe fibre orientation distribution controls the mechanical properties of random fibre composites. Generally accepted methods for its characterisation involve identification of fibres or their ellipsoidal cross sections as individual objects, requiring high image resolution and high computational resources. This paper investigates whether structure tensor analysis can be an alternative and whether it can work with lower resolution images. Micro-computed X-ray tomography images of random glass fibre/polypropylene injection moulded composites were processed using ellipsometry on 2D slices, 3D fibre identification (Avizo software) and analysis of the structure tensor (VoxTex software). The images had resolutions of 1.4, 3.2, 8 and 16 µm per pixel, compared to an average glass fibre diameter of 17 µm. All the methods yielded similar results for high-resolution images (1.4 and 3.2 µm). The high-fidelity, direct identification of fibres failed for low-resolution images, but the structure tensor analysis still yielded results close to the high-resolution scans.sponsorship: The research visit of RK to KU Leuven has been funded by Skoltech. LM is an Early Stage Researcher in the Marie Sklodowska-Curie European Training Network FiBreMoD, funded by Horizon 2020 program of European Commission, research and innovation programme under the Marie Sklodowska-Curie grant agreement No 722626. The work is partially funded by SIM/VLAIO (Flanders) in T4G project running in NANOFORCE program and is supported by Toray Chair for Composite Materials @ KU Leuven, held by SL. The micro-CT images have been acquired on the X-ray computed tomography facilities at KU Leuven, maintained under the supervision of Prof. M. Wevers and financed by the Hercules Foundation and the KU Leuven Research Council (project C24/17/052). The authors are grateful for discussions with Dr. Ilya Straumit for the VoxTex calculations. (Skoltech, Horizon 2020 program of European Commission, research and innovation programme|722626, SIM/VLAIO (Flanders) in T4G project running in NANOFORCE program, Toray Chair for Composite Materials @ KU Leuven, Hercules Foundation, KU Leuven Research Council|C24/17/052, Marie Curie Actions (MSCA)|722626)status: Publishe
Micro-scale numerical study of fiber/matrix debonding in steel fiber composites
No full textsponsorship: The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: The work reported here was funded by SIM and IWT (Flanders) in the framework of NANOFORCE program (MLM project) and The Scientific and Research Council of Turkey, project number 115C082. S.V. Lomov holds Toray Chair for Composite Materials at KU Leuven, support of which is acknowledged. (SIM (Flanders), IWT (Flanders), Scientific and Research Council of Turkey|115C082, Toray Chair for Composite Materials at KU Leuven)status: Publishe
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