Abstract A numerical investigation was carried out in order to simulate experimental results previously obtained concerning two-dimensional (2D) in-plane crack propagation in laminated glass fiber-reinforced polymer (GFRP) plates. The laminated plates were designed with an embedded circular pre-crack and subjected to quasi-static out-of-plane loads. In order to study the transition from standard fracture mechanics tests, where the crack propagates only in one dimension (1D), to 2D scenarios, additional double cantilever beam (DCB) experiments were carried out on the same material system. Three-dimensional finite element models were developed for the simulation of the experimental fracture responses and cohesive elements were used to take into account the fracture mechanisms acting on the fracture process zone. Compared to the 1D DCB specimens, a much higher value of the total strain energy release rate (SERR) was obtained for the 2D plates, which was correlated to their higher flexural stiffness and to the stress stiffening effect caused by the stretching of their deformed part. Furthermore, and based on the numerical results, it was proved that the area of the fully developed fiber-bridging in the plates can be directly obtained from the experimental compliance vs crack area curves.
Last. Thomas Keller(EPFL: École Polytechnique Fédérale de Lausanne)H-Index: 45
view all 3 authors...
Abstract The 2D delamination behavior of composite laminates under quasi-static out-of-plane opening loading has been experimentally investigated. A circular embedded pre-crack was introduced in the center and at the midplane of the laminates. To investigate the effect of the fiber architecture on the fracture behavior, six different types of fabrics were selected. Increasing load–displacement curves were obtained due to the increasing crack front length during propagation. During the loading pr...
Compression After Impact (CAI) strength is critical to the safety and weight of carbon fibre aircraft. In this paper, the standard aerospace industry practice of using separate analyses and tests for panel buckling and CAI strength is challenged. Composite panels with a range of stacking sequences were artificially delaminated and subject to compression testing in a fixture that allowed local sublaminate and global panel buckling modes to interact. Compared to panels without delamination, intera...
A quasi-static progressive damage model for prediction of the fracture behaviour and strength of adhesively bonded fibre-reinforced polymer joints is introduced in this paper. The model is based on the development of a mixed-mode failure criterion as a function of a master R-curve derived from the experimental results obtained from standard fracture mechanics joints. Consequently, the developed failure criterion is crack-length and mode-mixity dependent, and it takes into account the contributio...
Abstract A cohesive zone model (CZM) is proposed to assess the thickness scaling effect associated with fiber bridging during fracture. The CZM was developed through a multi-scale simulation approach and utilizes an embedded cell model of the Double Cantilever Beam (DCB) that explicitly accounts for the bridging bundles on the fracture plane. In particular, micromechanical simulations of failure were carried out, for varying arms thickness, in order to determine the homogenized fracture behavior...
#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
view all 3 authors...
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 ...
Abstract Quasi-brittle materials such as fibre-reinforced composite materials develop a relatively large Fracture Process Zone where material toughening mechanisms such as matrix cracking, fibre-bridging and fibre pull-outs take place. The damage onset and damage propagation are well defined from a cohesive model point of view, although no standard procedure has been yet developed to characterize the translaminar Cohesive Law. The present work proposes an objective inverse method for obtaining t...
#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
view all 4 authors...
Abstract In this work, the influence of ply thickness on strain energy release rate (ERR) in delamination of carbon-epoxy laminates is addressed. Specimens with three ply thicknesses: 0.030, 0.075 and 0.150 mm are tested. While the ERR at onset of crack propagation is independent of ply thickness, the plateau level is much lower in thin-ply laminates than in thicker ply ones. This effect is attributed to changes in microstructure, caused by the tow spreading process involved in the fabrication o...
Abstract Polymer-based laminated composite materials can fail by delamination. Cohesive zone development occurs during delamination, where dissipation mechanisms take place. Within a numerical framework, a fine discretization is needed along the cohesive zone length to accurately capture the non-linear stress distribution. Knowing the cohesive zone length beforehand is important for meshing purposes. This paper presents a literature review of existing analytic expressions. The limitations and ra...
#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...
Typical damage modes in light honeycomb sandwich structures include face sheet/core disbonding and core fracture, both of which can pose a threat to the structural integrity of a component. These damage modes are of particular interest to aviation certification authorities since several in-service occurrences, such as rudder structural failure and other control surface malfunctions, have been attributed to face sheet/core disbonding. Extensive studies have shown that face sheet/core disbonding a...
Last. Thomas Keller(EPFL: École Polytechnique Fédérale de Lausanne)H-Index: 45
view all 3 authors...
Abstract The two-dimensional (2D) delamination growth in fiber-reinforced polymer (FRP) laminates with in-plane isotropy under Mode I loading condition was numerically investigated using finite element analyses. Two sizes of plate models were developed, focusing on different fracture stages. Cohesive elements were employed to simulate the fracture behavior in the presence of large-scale bridging (LSB). The influences of the pre-crack shape/area, loading zone shape/area and fracture resistance we...
This paper is focused on mode I delimitation of a unidirectional glass fibre reinforced polymer (GFRP) composite. The aim is to propose an accurate and simple characterisation of three cohesive zone models (CZM)—bilinear, trilinear, and potential—from the measurement of the load-displacement curve during a double cantilever beam experimental test. For that, a framework based on the equivalent linear elastic fracture mechanics (LEFM) R-curve is here proposed, which has never before been developed...
In this paper, the effect of cable indent shape on the shear behavior of concrete-cable attachment surface has been investigated using PFC2D. Firstly, calibration of PFC was performed using the Brazilian experimental test and uniaxial compression test to reproduce the concrete sample. After calibration of PFC2D, punch shear tests were simulated by creating a rectangular concrete model in PFC2D. Numerical models with a dimension of 100mm *100 mm were prepared. cable with different indent shape wa...
Abstract Investigations of the fatigue performance of composite materials have accompanied their introduction in several engineering domains since the 1950s. An abundance of publications have emerged dealing with the experimental investigation of the fatigue performance of composites under different loading and environmental conditions, as well as the development of theories for the modeling of the fatigue behavior and/or prediction of the fatigue life of the materials systems under consideratio...
Last. Thomas Keller(EPFL: École Polytechnique Fédérale de Lausanne)H-Index: 45
view all 3 authors...
Abstract An experimental investigation of the two-dimensional (2D) debonding behavior of GFRP/balsa sandwich panels with embedded circular disbonds at the face sheet/core interface subjected to out-of-plane fatigue loads was conducted. The constant amplitude fatigue experiments were performed under load control and different R-ratios. Two face sheet configurations were investigated: a pure woven ply layup (SPA) and a combination of continuous filament mat (CFM) and woven plies (SPB). For the lat...
#1Hao Long(CAS: Chinese Academy of Sciences)H-Index: 4
#2L. H. Liang(CAS: Chinese Academy of Sciences)H-Index: 15
Last. Yueguang Wei(PKU: Peking University)H-Index: 17
view all 3 authors...
Abstract Cohesive zone models have been widely used to model interface crack initiation and propagation both in single-material media and bi-material systems. For single-material media with cohesive elements inserted into interface among segments, in order to ensure that the introduction of interface cohesive zone models does not affect the mechanical properties of single-material media before the softening stage of cohesive zone models, a selection criterion of stiffness of cohesive elements is...
Last. Thomas Keller(EPFL: École Polytechnique Fédérale de Lausanne)H-Index: 45
view all 3 authors...
Abstract The two-dimensional (2D) debonding behavior of GFRP/balsa sandwich panels presenting embedded circular disbonds at the face sheet/core interface was experimentally investigated. The bottom of the panels was fixed and out-of-plane quasi-static tensile loads were applied to open the crack. Two different face sheet configurations were studied. The first consisted of a pure woven ply layup while in the second, layers of continuous filament mat (CFM) were placed above and below the woven pli...
Last. Thomas Keller(EPFL: École Polytechnique Fédérale de Lausanne)H-Index: 45
view all 5 authors...
Abstract A new numerically-based method suitable for determining the total strain energy release rate (SERR) involved in two-dimensional (2D) Mode I-dominated delamination under opening loads in FRP laminates is presented. The method is based on the mutual dependence of the load vs opening displacement curves slope exhibited after the full development of the fracture process zone (FPZ) and the total SERR involved in the delamination process. The equation relating these parameters is derived from...