Abstract The influence of curved delamination front on mode-I fracture toughness of adhesively-bonded composite joint is investigated using double cantilever beam (DCB) with an adhesive layer. The model of curved delamination front is converted to the model of straight crack front based on the principle of equivalent crack area. With visual deviation λ v and non-uniformity coefficient β , the effect of curved delamination front can be incorporated into determination of fracture toughness for DCB specimens. Then, the parametric analyses concerning λ v are studied with virtual crack closure technique (VCCT). Meanwhile, the practical formulas of λ v are put forward.
Last. Kongjian Shen(SEU: Southeast University)H-Index: 5
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Abstract The mode-I fracture behavior and non-uniformity coefficient β of an adhesively bonded joint composed of Glass Fiber-reinforced Polymer (GFRP) laminates are investigated using double cantilever beam (DCB) specimens with an adhesive layer. First, the opening displacement of the DCB is solved using the elastic foundation beam method considering the impact of the displacement and the rotation angle of the crack tip. The fracture toughness G Ic is calculated using the compliance method throu...
#1S.A. Hashim(Glas.: University of Glasgow)H-Index: 6
#1S.A. Hashim(Glas.: University of Glasgow)H-Index: 3
Last. J.A. Nisar(Glas.: University of Glasgow)H-Index: 2
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The paper investigates the failure and behaviour of metal/composite double lap shear (DLS) joints where the composite is the inner/loaded adherend, using multi-scale modelling techniques. The unidirectional (UD) composite is based on glass fibre and vinyl ester resin moulded by pultrusion. The multi-scale models include a long overlap DLS joint (macro), small shear and tensile laminate joints (meso) and fibre–matrix resin models (micro). The macro- and meso-scale joints/models were mechanically ...
Abstract A number of different experimental methods are used at two independent laboratories to evaluate the influence of layer thickness on the fracture properties of one batch of a crash resistant epoxy adhesive. Both mode I and II are considered. Novel, as well as state of the art methods are used. In mode I, the Double Cantilever Beam (DCB) and two versions of the Tapered Double Cantilever Beam (TDCB) specimens are utilized; in mode II, two versions of the End Notch Flexure (ENF) and the End...
Last. Thomas Keller(EPFL: École Polytechnique Fédérale de Lausanne)H-Index: 45
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The fatigue response of adhesively-bonded pultruded GFRP double-lap joints was investigated under different loading patterns and experimental results were obtained for three different applied load ratios: R = 0.1, R = 10, and R = -1. The fatigue life of the examined joint configuration is affected by the different loading type, generally being shorter for tensile loads and longer when compressive loads were applied. The dominant failure mode was a fiber-tear failure that occurred in the mat laye...
#1Mahmood M. Shokrieh(IUST: Iran University of Science and Technology)H-Index: 53
#2M. Heidari-Rarani(IUST: Iran University of Science and Technology)H-Index: 16
Last. Majid R. Ayatollahi(IUST: Iran University of Science and Technology)H-Index: 65
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Abstract In this research, a Timoshenko beam (TB) resting on two-parametric (or Pasternak) elastic foundation (PEF) is developed for determination of strain energy release rate (SERR) of mode-I delamination in multidirectional double cantilever beam (DCB) specimens. Based upon the compliance approach, a closed-form solution is obtained for SERR versus delamination length, applied load, effective mechanical properties, and geometrical dimensions of DCB specimen. The required effective flexural mo...
Abstract This work covers the problems encountered in correctly determining mode I interlaminar fracture toughness of composite materials. Pure mode I tests were performed on double cantilever beam (DCB) specimens composed by quasi-homogeneous and uncoupled multidirectional (MD) laminates using 16 or 26-ply: [α/−α 2 /α/−α/α 2 /−α] sym or anti-sym and [0/α/−α/0 2 /−α/0/α/0 2 /α/−α/0] sym , with α = 0°,15°,30°,45°,90°. A finite element analysis shows that the non-uniformity ratio β=(G Imax −G Iav....
Abstract This paper presents the results of an experimental investigation conducted to characterize the joint strengths, peel stresses and failure modes in adhesively bonded double-strap and supported single-lap glass fiber-reinforced polymer (GFRP) joints. The joints were composed of pultruded GFRP adherends having the same stiffness as the members that would be used in FRP bridge decks. The design parameters investigated in the study were adhesive type, adhesive layer thickness and overlap len...
A fiber-reinforced polymer (FRP) composite cellular deck system was used to rehabilitate a historical cast iron thru-truss structure (Hawthorne St. Bridge, Covington, VA). The most important characteristic of this application is reduction in self-weight, which raises the live load-carrying capacity of the bridge by replacing the existing concrete deck with an FRP deck. This bridge is designed to HL-93 load and has a 22.86 m clear span with a roadway width of 6.71 m. The panel-to-panel connection...
Abstract The energy release rate in delamination of angle-ply laminated double cantilever composite beam specimens was calculated using the compliance equation, and interlaminar cohesive strengths were obtained. Instead of the traditional approach of a beam on an elastic foundation, a second-order shear-thickness deformation beam theory (SSTDBT) was considered. The equilibrium equations were obtained using the principle of minimum total potential energy and the system of ordinary differential eq...
#1Lucas F. M. da Silva(Faculdade de Engenharia da Universidade do Porto)H-Index: 26
#1Lucas F.M. da Silva(Faculdade de Engenharia da Universidade do Porto)H-Index: 2
Last. Robert D. Adams(UoB: University of Bristol)H-Index: 65
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Abstract The authors have previously developed a novel joint that consists of two adhesives, one better at low temperatures (−55 °C) and the other for high temperatures (200 °C). They have shown that this technique enables the design of a joint with a higher load capacity than a joint with only one adhesive, especially for dissimilar adherends. They studied the case of a double-lap joint where the outer adherends were titanium and the inner adherend was a carbon fibre-reinforced bismaleimide. Ho...
Last. Xiaojing Gong(University of Toulouse)H-Index: 1
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Abstract Strain energy release rate (SERR) along a linear crack front of a multidirectional composite DCB specimen shows an obviously non-uniform distribution, which causes the fracture toughness GIavg measured by experiments smaller than the real GIC, and so leading to a lower estimation of fracture toughness. In this study, based on the numerical model a novel semi-empirical closed-form formula was proposed for determination of pure mode I fracture toughness of a multidirectional composite DCB...
Last. Thomas Keller(EPFL: École Polytechnique Fédérale de Lausanne)H-Index: 45
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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...
Abstract The pure mode-I, pure mode-II and the mixed-mode I/II fracture behavior of the adhesively-bonded pultruded GFRP/steel joint were experimentally investigated by using double cantilever beam (DCB) test, and four-point end-notched flexure (4ENF) test combined with four-point single leg bending (4SLB) test, respectively. The extended global method (EGM) was employed to obtain closed-form analytical solutions of mode-II fracture toughness for the 4ENF specimen and mixed-mode I/II fracture to...
This paper presents an experimental evaluation of influence of the elastic couplings on the fracture toughness as well as on delamination initiation and propagation in carbon/epoxy composite laminates. For this purpose the mode I double cantilever beam (DCB) tests according to the American Society for Testing and Materials (ASTM) D5528 Standard were performed on specimens with different delamination interfaces and specific lay-ups composition exhibiting the bending-twisting (BT) and the bending-...
Abstract This work investigated the evolution of the non-uniform distribution of Mode-I strain energy release rate (SERR) along a straight pre-crack front of double cantilever beams (DCB), caused by the anticlastic deformation and the longitudinal free-edge effects. A modified DCB specimen with a curved pre-crack front was introduced in order to alleviate this problem and produce an uniform SERR distribution at the initiation and propagation stages. The first order optimization method was used t...
Last. Tuck Wah Ng(Monash University, Clayton campus)H-Index: 16
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The ability to conduct en-route centrifugation of samples improves quality and timeliness in the pre-analytical phase. This is demonstrated here on a quadcopter whereby the propellers were adapted to house and apply centrifugal forces to sample-containing capillary tubes instead of incorporating a centrifuge. Tests revealed the ability of the method to separate non-homogenized milk into a cream portion and a skim milk portion, and human whole blood into plasma, buffy coat, and red blood cell com...
Last. Ugo Galvanetto(UNIPD: University of Padua)H-Index: 28
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Abstract The paper presents an effective and accurate way to couple FEM meshes to peridynamic grids and uses it to solve 1D, 2D and 3D problems in static and dynamic conditions. Crack propagation with crack branching problems is also solved. An adaptive algorithm is presented which allows to transform FEM nodes into peridynamic nodes. In this way a new computational technique is produced which equips standard FEM with the capability to effectively and efficiently describe 3D problems with crack ...
Abstract Fatigue crack propagation for copper/epoxy molding compound interfaces is modeled in this work by conducting cyclic loading on double cantilever beam test specimens. The continued increase in mechanical compliance of test specimens as the crack propagates through hundreds of cycles is used to determine the crack length and thus, the crack growth rate per cycle which is used to determine the Paris’ law constants as a function of strain energy release rate range. When monotonic debonding ...
Abstract We analyse edge effects in two common adhesive joint fracture configurations, namely the single and the double cantilever beam tests. Several experiments were performed studying the crack front vicinity for deflection and crack front morphology using light scanning and microscopy techniques. To understand the findings a finite element model is used to determine the energy release rate at the crack front, particularly in the vicinity of free edges. Two approaches - an inverse procedure a...
#1J.A. Pascoe(TU Delft: Delft University of Technology)H-Index: 10
#2René Alderliesten(TU Delft: Delft University of Technology)H-Index: 31
Last. Rinze Benedictus(TU Delft: Delft University of Technology)H-Index: 34
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Abstract The available models for the prediction of fatigue crack growth in adhesive bonds rely on the similitude principle. In most cases, one of three similitude parameters based on the strain energy release rate (SERR) is used; i.e. G max , ( Δ G ) 2 , or Δ G . In all cases it is usually observed that keeping the similitude parameter constant, and changing the R-ratio, results in a different crack growth rate. In this paper it is shown that this apparent ‘R-ratio’ effect is caused because the...