Abstract Laminated composites are prone to fracture at layer interfaces. Such damage impairs their structural response and engenders important constraints in design. In this work, the influence of ply orientation on crack growth resistance was studied for three different antisymmetric interfaces and compared to a unidirectional reference one, using double cantilever beam specimens with equivalent stiffness, loaded under mode I conditions. Fracture toughness at initiation was found interface-independent. In all angle-ply specimens, distinct slow and fast phases of crack propagation were observed. Crack increments due to fast growth, were characterized using experimental energy release rates and verified from fracture surface analysis. The slow propagation phases were accompanied by large scale bridging involving intra-ply growth in the adjacent plies, with toughness increasing inversely with the angle. Mechanistic investigations suggest a consistent fracture pattern in terms of the interface angle. For each interface angle, a single traction-separation relation, obtained from the experimental energy release rate and crack opening displacements, was sufficient to model two consecutive slow propagation phases. These relations were used in 2D cohesive element models to predict very well the loading history.
#1F. Naya(EPFL: École Polytechnique Fédérale de Lausanne)H-Index: 1
#1F. Naya(EPFL: École Polytechnique Fédérale de Lausanne)H-Index: 9
Last. John Botsis(EPFL: École Polytechnique Fédérale de Lausanne)H-Index: 37
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Abstract Fiber reinforced polymers (FRPs) subjected to mode I fracture show important toughening due to the development of large scale bridging (LSB). Experimental studies of this phenomenon in unidirectional carbon/epoxy laminates using double cantilever beam specimens, demonstrate important differences in R-curve response for inter- and intralaminar fracture. Post fracture observation of composite’s cross-section pointed out dissimilar fiber bundle size and shape, as the main origin of their d...
Abstract Delamination migration is particularly critical in multi-directional composite laminates and is often observed in different loading scenarios and components. Further understanding on the migration mechanism, especially the similarities and differences in the quasi-static and fatigue delamination migrations, is important for the design of composite structures. In this study, the process of delamination migration under mode I quasi-static and fatigue loadings was experimentally investigat...
Abstract Obvious R-curve behavior exists in multidirectional carbon fiber reinforced polymers (CFRP) laminates under mode I loading, in which the plateau fracture toughness represents the steady-state delamination growth behavior. By decomposing the fracture toughness into the fracture work for pure delamination at the interface and that for the intra-ply damage of adjacent layers, a mechanism-based correlation between the plateau value of interface mode I fracture toughness in multidirectional ...
#1Guillaume Frossard(EPFL: École Polytechnique Fédérale de Lausanne)H-Index: 3
#2Joël Cugnoni(EPFL: École Polytechnique Fédérale de Lausanne)H-Index: 26
Last. John Botsis(EPFL: École Polytechnique Fédérale de Lausanne)H-Index: 37
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Abstract Fiber bridging is one of the main toughening mechanisms in mode I interlaminar and intralaminar fracture of laminated composites. Intact fibers exert closing forces on both faces of the crack, restraining crack propagation. An effective identification procedure is required to characterize bridging tractions and to develop accurate prediction models. The method proposed in this work is based on the resistance (R)-curve and assumes fiber bridging tractions decreasing non-linearly with res...
Abstract In this paper, the role of interface fiber angle on the bridging traction of double cantilever beam (DCB) specimens is investigated experimentally. In order to eliminate the effect of the remote ply orientation on the bridging traction during delamination initiation and propagation, DCB specimens with stacking sequences of [0 11 /θ//0 12 ] where θ = 0, 30, 45 and 90 were considered. An experimental test set-up was established for measuring the Initial crack tip opening displacement (ICT...
#1B.Y. Chen(NUS: National University of Singapore)H-Index: 15
#2Tong Earn Tay(NUS: National University of Singapore)H-Index: 34
Last. Vincent B. C. Tan(NUS: National University of Singapore)H-Index: 45
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Abstract This paper presents a numerical study of the delamination migration in angle-ply laminates observed in experiments reported in the literature, where the delamination originally propagates along the lower, 0 ∘ / 60 ∘ interface and later migrates onto the upper, 60 ∘ / 0 ∘ interface. The recently-developed Floating Node Method (FNM) is used for modelling this problem. The initiation and propagation of both delamination and matrix cracks are modelled within the FNM elements. Experimentally...
Last. Xiaojing Gong(University of Toulouse)H-Index: 11
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The influence of ply orientation on the resistance to mode I delamination of multidirectional composite laminates can be assessed by Double Cantilever Beam (DCB) tests. However, one difficulty is to uncouple the global and local effects due to the stacking sequence, which is necessary for a conclusive analysis. In the present work six multidirectional DCB specimens were designed so as to obtain an uncoupled fully isotropic elastic behavior, with the same properties for the entire laminate and th...
#1G. Pappas(EPFL: École Polytechnique Fédérale de Lausanne)H-Index: 8
#2Luis P. Canal(EPFL: École Polytechnique Fédérale de Lausanne)H-Index: 11
Last. John Botsis(EPFL: École Polytechnique Fédérale de Lausanne)H-Index: 37
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Abstract A detailed experimental-numerical study of large scale bridging during intralaminar fracture of AS4/PPS uniaxial thermoplastic composite is reported. Identification of bridging tractions is carried out using: (a) An inverse identification method based on quasi-distributed strain data from fiber Bragg gratings, FE modeling and optimization; both small and large displacements are considered in the simulations resulting in negligible differences between the bridging tractions and of about ...
#1Xiaofei Hu(DUT: Dalian University of Technology)H-Index: 15
#2B.Y. Chen(NUS: National University of Singapore)H-Index: 15
Last. Tong Earn Tay(NUS: National University of Singapore)H-Index: 34
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Abstract Progressive damage and failure in composites are generally complex and involve multiple interacting failure modes. Depending on factors such as lay-up sequence, loading and specimen configurations, failure may be dominated by extensive matrix crack-delamination interactions, which are very difficult to model accurately. The present study further develops an integrated extended finite element method (XFEM) and cohesive element (CE) method for three-dimensional (3D) delamination migration...
#1G. Pappas(EPFL: École Polytechnique Fédérale de Lausanne)H-Index: 8
#2John Botsis(EPFL: École Polytechnique Fédérale de Lausanne)H-Index: 37
Abstract Fracture of carbon fiber reinforced polymers (CFRPs) is dominated by large scale fiber bridging which acts as a very important toughening mechanism. The objective of this paper is to investigate the intralaminar Mode I fracture in a unidirectional CFRP composite in double cantilever beam specimens with thickness H = 6, 10 and 14 mm with a symmetric intralaminar precrack introduced by a thin diamond wire saw. Optical fibers with 10 multiplexed Bragg grating sensors are glued onto the upp...
#1A Raimondo(TU Delft: Delft University of Technology)
#2I Urcelay Oca(TU Delft: Delft University of Technology)
Last. Chiara Bisagni(TU Delft: Delft University of Technology)H-Index: 25
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The standard experimental procedures for determining the interlaminar fracture toughness are designed for delamination propagation in unidirectional specimens. However, in aerospace structural comp...
#1M.F. Abd Rased(UTM: Universiti Teknologi Malaysia)H-Index: 1
#2Sung Ho Yoon(Kumoh National Institute of Technology)H-Index: 1
Abstract This study focused on the delamination fracture behavior of asymmetrical stacking sequences of CFRP laminates subjected to different loading directions in double cantilever beam (DCB), end-notched flexure (ENF), and mixed-mode bending (MMB) tests. CFRP laminates with three different stacking sequences mimicking the winding angles of filament wound structures were considered. As the stacking sequences were asymmetrical, flipped and non-flipped specimens were tested to examine the effects...
Last. Jianyu Zhang(Chongqing University)H-Index: 25
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Abstract Large scale fiber bridging in composite laminates is one of the most common toughening mechnisms, exerting a close-force on the crack surfaces to restrain the delamination propagation. To account for the effect of the fiber bridging in delamination simulation, a physically semi-analytical method based on the Euler-Bernoulli beam theory considering the bridging stress is presented. The mode I energy release rate for every crack length is explicitly expressed in terms of the external load...
Abstract R-curve and traction-separation relation are commonly used to characterize the fiber bridging, which is significant toughening mechanism in composite laminates. Current investigations are mainly focused on unidirectional laminates. However, the dependence of the R-curve and traction-separation relation on the stacking sequence is still lack of comprehensive studies. Here, the effect of stacking sequence on the R-curve and traction-separation relation in unidirectional and multidirection...
#1Chen Liu(DUT: Dalian University of Technology)H-Index: 2
#2Ruixiang Bai(DUT: Dalian University of Technology)H-Index: 10
Last. Cheng Yan(QUT: Queensland University of Technology)H-Index: 42
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Abstract Interlaminar fracture toughness is an important parameter to characterize the delamination performance of carbon fiber-reinforced epoxy laminates. In this study, the mode-I fracture toughness of interlaminar interfaces with different local ply angles were studied by experiments and numerical simulations. A set of double cantilever beam specimens of T800 carbon fiber/EH104 epoxy were prepared according to the ASTM-D5528–01 standard, where four specimens had straight ply interfaces (0°//0...
Last. John Botsis(EPFL: École Polytechnique Fédérale de Lausanne)H-Index: 37
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Abstract Multidirectional laminates are very often used in advanced structures. However, the existing data in the literature regarding their fracture response is not conclusive. In this work, the fracture response of a + 45 ∘ / / − 45 ∘ interface is investigated under remote mixed mode loading and compared to a 0 ∘ / / 0 ∘ layout. Several experiments were conducted under three mode mixities ϕ = 0.15 , 0.35 and 0.65 as well as pure modes I ( ϕ = 0 ) and II ( ϕ = 1.0 ) following the established st...
Last. Eric Martin(University of Bordeaux)H-Index: 23
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Abstract This paper proposes an experimental study whose goal is to validate the concept of Fully-Uncoupled Multi-Directional (FUMD) specimens for delamination tests. In order to reduce the likelihood of delamination jump, a glass/epoxy UD-fabric composite was used to fabricate double cantilever beam specimens. Mode I tests were performed with standard UD specimens and with FUMD specimens having the following delamination interfaces: 0 ° //0 ° , 0 ° //15 ° , 0 ° //30 ° , 0 ° //45 ° and -45 ° //4...
#2N. Pichler(EPFL: École Polytechnique Fédérale de Lausanne)H-Index: 2
Last. John Botsis(EPFL: École Polytechnique Fédérale de Lausanne)H-Index: 37
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Abstract Delamination is a well-known damage mode exhibited by laminated composites which has been extensively studied in unidirectional laminates (UD). In this work, a novel strategy consisting of the introduction of a small interlaminar defect to enhance the fracture resistance to delamination of UD composites is presented. This toughening concept is based on the simultaneous propagation of multiple interlaminar cracks along different interfaces. A preliminary numerical study showed that the m...
Last. Jianyu Zhang(Chongqing University)H-Index: 25
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Abstract Delamination of composite laminates under mode I loading is usually accompanied by large scale fiber bridging. Characterization of the bridging-traction law is of significant importance in delamination simulations to account for the effect of fiber bridging in such situation. This paper proposed a semi-analytical methodology to determine the bridging-traction law of composite laminates under mode I loading. The enhanced beam theory is physically improved by considering the bending-exten...
#2N. Pichler(EPFL: École Polytechnique Fédérale de Lausanne)H-Index: 2
Last. John Botsis(EPFL: École Polytechnique Fédérale de Lausanne)H-Index: 37
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Abstract Delamination is a very frequent damage mechanism that affects the integrity of laminated composites. In this study, the effect of ply orientation on crack growth resistance was analyzed for three different anti-symmetric interfaces ( ± 30 ° , ± 45 ° and ± 60 ° ) and compared to a unidirectional baseline under remote mode II loading. Fracture toughness at initiation was the same regardless of the ply orientation, nevertheless, the energy dissipated during crack propagation increased with...