Browsing by Author "Verpoest, Ignaas"
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Item A comparative study of tensile properties of non-crimp 3D orthogonal weave and multi-layer plain weave E-glass composites. Part 1: Materials, methods and principal results(Elsevier Science, 2009-08) Lomov, Stepan V.; Bogdanovich, Alexander E.; Ivanov, Dmitry S.; Mungalov, Dmitri; Verpoest, Ignaas; Karahan, Mehmet; Uludağ Üniversitesi/Teknik Bilimler Meslek Yüksekokulu.; AAK-4298-2021; 8649952500Composites fabricated by VARTM technology with the use of single-ply non-crimp 3D orthogonal woven preforms 3WEAVE (R) find fast growing research interest and industrial applications. It is now well understood and appreciated that this type of advanced composites provides efficient delamination suppression, enhanced damage tolerance, and superior impact, ballistic and blast performance characteristics over 2D fabric laminates. At the same time, this type of composites, having practically straight in-plane fibers, show significantly better in-plane stiffness and strength properties than respective properties of a "conventional" type 3D interlock weave composites. One primarily important question, which has not been addressed yet, is how the in-plane elastic and strength characteristics of this type of composites compare with respective in-plane properties of "equivalent" laminates made of 2D woven fabrics. This 2-part paper presents a comprehensive experimental study of the comparison of in-plane tensile properties of two single-ply non-crimp 3D orthogonal weave E-glass fiber composites on one side and a laminate reinforced with four plies of plain weave E-glass fabric on the other. Results obtained from mechanical testing are supplemented by acoustic emission data providing damage initiation thresholds, progressive cracks observation, full-field surface strain mapping and cracks observation on micrographs. The obtained results demonstrate that the studied 3D non-crimp orthogonal woven composites have considerably higher in-plane ultimate failure stresses and strains, as well as damage initiation strain thresholds than their 2D woven laminated composite counterpart. Part I presents the description of materials used, experimental techniques applied, principal results and their mutual comparisons for the three tested composites. Part 2 describes in detail the experimentally observed effects and trends with the main focus on the progressive damage: detailed results of AE registration, full-field strain measurements and progressive damage observations, highlighting peculiarities of local damage patterns and explaining the succession of local damage events, which leads to the differences in strength values between 2D and 3D composites.Item A comparative study of tensile properties of non-crimp 3D orthogonal weave and multi-layer plain weave E-glass composites. Part 2: Comprehensive experimental results(Elsevier Science, 2009-08) Ivanov, Dmitry S.; Lomov, Stepan V.; Bogdanovich, Alexander E.; Verpoest, Ignaas; Karahan, Mehmet; Uludağ Üniversitesi/Teknik Bilimler Meslek Yüksekokulu.; AAK-4298-2021; 8649952500This Part 2 paper presents results of comparative experimental study of progressive damage in 2D and 3D woven glass/epoxy composites under in-plane tensile loading. As Part 1, this Part 2 work is focused on the comparison of in-plane tensile properties of two non-crimp single-ply 3D orthogonal weave E-glass fibre composites on one side and a laminate reinforced with four plies of E-glass plain weave on the other. The damage investigation methodology combines mechanical testing with acoustic emission registration (that provides damage initiation thresholds), progressive cracks observation on transparent samples, full-field surface strain mapping and cracks observation on micrographs, altogether enabling for a thorough characterisation of the local micro- and meso-damage modes of the studied composites. The obtained results demonstrate that the non-crimp 3D orthogonal woven composites have significantly higher in-plane strengths, failure strains and damage initiation thresholds than their 2D woven laminated counterpart. The growth of transverse cracks in the yarns of 3D composites is delayed, and they are less prone to a yarn-matrix interfacial crack formation and propagation. Delaminations developing between the plies of plain weave fabric in the laminate at certain load level never appear in the 3D woven single-ply composites. (C) 2009 Elsevier Ltd. All rights reserved.Item Compressibility of carbon woven fabrics with carbon nanotubes/nanofibres grown on the fibres(Elsevier, 2011-02-07) Lomov, Stepan V.; Gorbatikh, Larissa; Kotanjac, Zeljko; Koissin, Vitaly; Houlle, Matthieu; Rochez, Olivier; Mezzo, Luca; Verpoest, Ignaas; Karahan, Mehmet; Uludağ Üniversitesi/Teknik Bilimler Meslek Yüksekokulu.; AAK-4298-2021; 8649952500Growth of carbon nanotubes (CNT) or carbon nano-fibres (CNF) on carbon fibrous substrates is a way to increase the fracture toughness of fibre reinforced composites (FRC), with encouraging results reported in the recent years. If these nano-engineered FRC (nFRC) are destined to leave laboratories and enter industrial-scale production, a question of adapting the existing composite manufacturing methods will arise. The paper studies compressibility of woven carbon fibre performs (two types of fabrics) with CNT/CNF grown on the fibres using the CVD method. The results include pressure vs thickness and pressure vs fibre volume fraction diagrams for one and four layers of the fabric. Morphology of the nFRC is studied with SEM. It is shown that the pressure needed to achieve the target fibre volume fraction of the preform increases drastically (for example, from 0.05 MPa to more than 0.5 MPa for a fibre volume fraction of 52%) when CNT/CNF are grown on it. No change in nesting of the fabric plies is noticed. The poor compressibility can lower the achievable fibre volume fraction in composite for economical vacuum assisted light-RTM techniques and increase the pressure requirements in autoclave processing.Item Fatigue tensile behavior of carbon/epoxy composite reinforced with non-crimp 3D orthogonal woven fabric(Elsevier Science, 2011-11-14) Lomov, Stepan Vladimirovitch; Bogdanovich, Alexander E.; Verpoest, Ignaas; Karahan, Mehmet; Uludağ Üniversitesi/Teknik Bilimler Meslek Yüksek Okulu.; AAK-4298-2021; 8649952500An experimental study of the in-plane tension-tension fatigue behavior of the carbon fiber/epoxy matrix composite reinforced with non-crimp 3D orthogonal woven fabric is presented. The results include pre-fatigue quasi-static test data, fatigue life diagrams, fatigue damage progression, and post-fatigue quasi-static test data for the warp- and fill-directional loading cases. It is revealed that the maximum cycle stress corresponding to at least 3 million cycles of fatigue life without failure, is in the range of 412-450 MPa for both loading directions. This stress range is well above the static damage initiation threshold and significantly above the first static damage threshold (determined by the onset of low energy acoustic emission). The second static damage threshold, determined by the onset of high energy acoustic emission and related to the appearance of local debonds and intensive transverse matrix cracking falls within this range. The established correlation between a 3000,000 cycle fatigue stress limit on one side and the second static damage threshold stress on the other is of a high practical importance, because it will significantly reduce the amount of future fatigue tests required for this class of composites. Surprisingly, for equal maximum cycle stress level, the fatigue life under fill-directional loading appears about three times shorter than that under warp-directional loading. The 100,000 cycle, 500,000 cycle and 1000,000 cycle fatigue loading with 450 MPa maximum cycle stress has resulted in so high variations of post-fatigue static modulus, strength and ultimate strain, that no consistent and statistically meaningful trends could have been established; further extensive experimental studies are required to reliably quantify this effect. (C) 2011 Elsevier Ltd. All rights reserved.Item Internal geometry evaluation of non-crimp 3D orthogonal woven carbon fabric composite(Elsevier, 2010-09) Lomov, Stepan Vladimirovitch; Bogdanovich, Alexander E.; Mungalov, Dimitri; Verpoest, Ignaas; Karahan, Mehmet; Uludağ Üniversitesi/Teknik Bilimler Meslek Yüksekokulu.; AAK-4298-2021; 8649952500Measurements of the internal geometry of a carbon fiber non-crimp 3D orthogonal woven composite are presented, including. waviness of the yarns, cross sections of the yarns, dimensions of the yarn cross sections, and local fiber volume fraction. The measured waviness of warp and fill yarns are well below 0.1%. which shows that the fabric termed here "non-crimp" has nearly straight in-plane fibers as-produced, and this feature is maintained after going through all steps of fabric handling and composite manufacturing The variability of dimensions of the yarns is in the range of 4-8% for warp and fill directions, while the variability of the yarn spacing is in the range of 3-4%. These variability parameters are lower than respective ranges of variability of the yarn waviness and the cross-sectional dimensions in typical carbon 2D weave and 3D interlock weave composites, which are also illustrated in this work for comparison.Item Quasi-static tensile behavior and damage of carbon/epoxy composite reinforced with 3D non-crimp orthogonal woven fabric(Elsevier, 2013-08-01) Bogdanovich, Alexander E.; Lomov, Stepan V.; Verpoest, Ignaas; Karahan, Mehmet; Uludağ Üniversitesi/Gemlik Asım Kocabıyık Meslek Yüksekokulu.; AAK-4298-2021; 8649952500This paper presents a comprehensive experimental study and detailed mechanistic interpretations of the tensile behavior of one representative 3D non-crimp orthogonal woven (3DNCOW) carbon/epoxy composite. The composite is tested under uniaxial in-plane tensile loading in the warp, fill and +/- 45 degrees bias directions. An "S-shape" nonlinearity observed in the stress-strain curves is explained by the concurrent contributions of inherent carbon fiber stiffening ("non-Hookean behavior"), fiber straightening, and gradual damage accumulation. Several approaches to the determination of a single-value Young's modulus from a significantly nonlinear stress-strain curve are discussed and the best approach recommended. Also, issues related to the experimental determination of effective Poisson's ratios for this class of composites are discussed, and their possible resolution suggested. The observed experimental values of the warp- and fill-directional tensile strengths are much higher than those typically obtained for 3D interlock weave carbon/epoxy composites while the nonlinear material behavior observed for the +/- 45 degrees-directional tensile loading is in a qualitative agreement with the earlier results for other textile composites. Results of the damage initiation and progression, monitoried by means of acoustic emission, full-field strain optical measurements, X-rays and optical microscopy, are illustrated and discussed in detail. The damage modes at different stages of the increasing tensile loading are analyzed, and the principal progressive damage mechanisms identified, including the characteristic crack patterns developed at each damage stage. It is concluded that significant damage initiation of the present material occurs in the same strain range as in traditional cross-ply laminates, while respective strain range for other previously studied carbon/epoxy textile composites is significantly lower. Overall the revealed advantages in stiffness, strength and progressive damage behavior of the studied composite are mainly attributed to the absence of crimp and only minimal fiber waviness in the reinforcing 3DNCOW preform.