000186379 001__ 186379
000186379 005__ 20190509132438.0
000186379 0247_ $$2doi$$a10.5075/epfl-thesis-5728
000186379 02470 $$2urn$$aurn:nbn:ch:bel-epfl-thesis5728-4
000186379 02471 $$2nebis$$a9769875
000186379 037__ $$aTHESIS
000186379 041__ $$aeng
000186379 088__ $$a5728
000186379 245__ $$aMixed-Mode Static and Fatigue Failure Criteria for Adhesively-Bonded FRP Joints
000186379 260__ $$bEPFL$$c2013$$aLausanne
000186379 269__ $$a2013
000186379 336__ $$aTheses
000186379 502__ $$aI. Smith (président), B.R. Blackman, A. Brunner, A. Nussbaumer
000186379 520__ $$aFiber-reinforced polymer (FRP) composites are increasingly used in many load-bearing
 structures. Joints are the most critical structural elements as they often become the weak links
 in engineering structures. Bonding and bolting are two of the main joining techniques used for
 composite elements but, although bolted and bonded joints have their advantages and
 disadvantages, adhesively-bonded joints are often preferred. This is thanks to their better
 performance in terms of cost-effective structures with uniformly distributed stresses without
 the need for cutting fastener holes that result in high stress concentrations in the FRP
 adherends at the edges of the holes. In addition, due to the absence of stress concentrations,
 adhesively-bonded joints exhibit better fatigue behavior. However, the efficient and reliable
 use of adhesively-bonded joints requires a thorough understanding of their failure
 mechanisms under mixed-mode quasi-static and fatigue loading conditions. In real structural
 applications, failure of adhesively-bonded joints occurs due to crack initiation and
 propagation under varying mixed-mode ratios. Since it is difficult to describe this progressive
 fracture in a structural joint, fracture joints with constant mode-mixity ratios are used to
 determine the strain energy release rates for crack initiation and propagation. Subsequently,
 mixed-mode failure criteria based on the determined strain energy release rates can be
 established and used to model/predict the fatigue and fracture behaviors of structural joints.
 The main objectives of this thesis were to understand the fracture and fatigue behaviors of
 adhesively-bonded FRP fracture joints under Mode I, Mode II, and mixed-Mode I/II loading
 conditions and, consequently, develop mixed-mode static and fatigue failure criteria
 applicable to structural joints. To fulfill these objectives a combined experimental-analytical-numerical study was undertaken. Double cantilever beam (DCB-Mode I), end-load split
 (ELS-Mode II), and mixed-mode bending (MMB-Mode I/II) specimens were examined under
 quasi-static and constant amplitude fatigue loading. Analytical approaches were used to
 determine the strain energy release rates under quasi-static and fatigue loading, whereas
 phenomenological models were developed to characterize the fatigue and fracture behaviors
 of the joints. A new approach designated the “extended global method” was established and
 applied for the analysis of the quasi-static and fatigue experimental data and the fracture mode
 partitioning in the mixed-mode experiments.
 In parallel, non-linear finite element models were developed to simulate the quasi-static
 fracture behavior and investigate the effects of both the existing asymmetry and the observed
 fiber bridging on the fracture behavior of the examined joints. The bridging zone was modeled by zero-thickness cohesive elements. An exponential traction-separation description of the cohesive zone model was shown to appropriately model the fiber bridging and calculate its
 contribution to the fracture energy under quasi-static loading. The FE models were
 successfully employed for the separation of the fracture parameters, i.e. strain energy released
 at the crack tip (Gtip) and the amount of energy released along the crack-bridging zone (Gbr),
 in the quasi-static mixed-mode failure criterion for crack propagation.
 In addition to the studies on the quasi-static fracture behavior of the joints, a new
 phenomenological fatigue crack growth formulation for the modeling and prediction of Rratio
 effects on the Mode I fatigue behavior of adhesively-bonded joints was also derived. The
 model was used for prediction of the fatigue behavior of the examined joints under different
 R-ratios. The results proved that the model could accurately simulate the fatigue behavior of
 the examined joints and was also capable of predicting behavior exhibited under unseen
 loading conditions, i.e. the R-ratios used for estimating the model parameters were different
 from those used for validating its prediction capability.
 The experimental results and numerical analyses combined with the phenomenological
 models were used to establish mixed-mode static and fatigue failure criteria for crack
 initiation and crack propagation for the adhesively-bonded joints. The derived mixed-mode
 failure criteria can be used for simulating/predicting the crack initiation and progressive crack
 propagation in structural joints comprising the same adhesive and adherends.
000186379 6531_ $$aadhesively-bonded joints
000186379 6531_ $$apultruded GFRP
000186379 6531_ $$afiber bridging
000186379 6531_ $$afatigue
000186379 6531_ $$afracture
000186379 6531_ $$afailure criterion
000186379 6531_ $$acohesive zone element
000186379 6531_ $$afinite element
000186379 700__ $$0242002$$g189944$$aShahverdi, Moslem
000186379 720_2 $$aKeller, Thomas$$edir.$$g121845$$0240002
000186379 720_2 $$aVasilopoulos, Anastasios$$edir.$$g172705$$0241999
000186379 8564_ $$uhttps://infoscience.epfl.ch/record/186379/files/EPFL_TH5728.pdf$$zn/a$$s14786622$$yn/a
000186379 909C0 $$xU10234$$0252002$$pCCLAB
000186379 909CO $$pthesis-bn2018$$pDOI$$pENAC$$ooai:infoscience.tind.io:186379$$qDOI2$$qGLOBAL_SET$$pthesis
000186379 917Z8 $$x108898
000186379 917Z8 $$x108898
000186379 917Z8 $$x108898
000186379 917Z8 $$x108898
000186379 918__ $$dEDST$$cIIC$$aENAC
000186379 919__ $$aCCLAB
000186379 920__ $$b2013$$a2013-5-14
000186379 970__ $$a5728/THESES
000186379 973__ $$sPUBLISHED$$aEPFL
000186379 980__ $$aTHESIS