John Botsis
École Polytechnique Fédérale de Lausanne
Composite numberOpticsFinite element methodComposite materialEpoxyBridging (networking)Glass fiberMaterials scienceOptical fiberFiber optic sensorStrain energy release rateResidual stressFiber Bragg gratingFracture (geology)Fracture mechanicsStructural engineeringDelaminationBendingStress (mechanics)Fracture toughness
222Publications
37H-index
4,028Citations
Publications 203
Newest
#1Maria Konstantaki (FORTH: Foundation for Research & Technology – Hellas)H-Index: 19
#2Georgios Violakis (FORTH: Foundation for Research & Technology – Hellas)H-Index: 4
Last. Stavros Pissadakis (FORTH: Foundation for Research & Technology – Hellas)H-Index: 24
view all 12 authors...
In this study, silica glass, optical fiber Bragg gratings (FBGs) are used for torque-induced strain monitoring in carbon fiber reinforced polymer (CFRP) hollow shafts toward the development of a methodology for structural load monitoring. Optical fibers with gratings are embedded during shaft manufacturing, by an industrial filament winding process, along different orientations with respect to its central axis and surface mounted after production. Experimental results are supported by numerical ...
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#1C. BlondeauH-Index: 2
#2G. PappasH-Index: 8
Last. John BotsisH-Index: 37
view all 3 authors...
Abstract Delamination in composite materials is often accompanied by fiber bridging that increases resistance to crack growth. Here, delamination of two unidirectional carbon/epoxy systems was studied under monotonic and displacement-controlled fatigue loading. One material (CP004) presented a random distribution of fiber clusters and matrix-rich zones while the other (SE-84) had an ordered microstructure. The results showed that monotonic and fatigue delamination of CP004 presented similarities...
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#1N. Pichler (EPFL: École Polytechnique Fédérale de Lausanne)H-Index: 2
#2Miguel González Herráez (EPFL: École Polytechnique Fédérale de Lausanne)H-Index: 12
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...
3 CitationsSource
#1Miguel González Herráez (EPFL: École Polytechnique Fédérale de Lausanne)H-Index: 12
#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...
2 CitationsSource
#1G. Pappas (EPFL: École Polytechnique Fédérale de Lausanne)H-Index: 8
#2John Botsis (EPFL: École Polytechnique Fédérale de Lausanne)H-Index: 37
Abstract In this work the differences in R-curve responfigse and traction-separation relations due to a finite damage zone or large-scale bridging (LSB) in mode I fracture on double cantilever beams (DCB) were investigated under end opening forces (EOF) and pure moments (PM). To realize PM loading, a novel test-rig was designed, built and used to test adhesive joints with metallic substrates and unidirectional carbon fiber reinforced polymer (CFRP) specimens. In the adhesive joints, no pronounce...
3 CitationsSource
#1Miguel González Herráez (EPFL: École Polytechnique Fédérale de Lausanne)H-Index: 12
#2N. Pichler (EPFL: École Polytechnique Fédérale de Lausanne)H-Index: 2
Last. John Botsis (EPFL: École Polytechnique Fédérale de Lausanne)H-Index: 37
view all 3 authors...
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...
2 CitationsSource
#1G. Pappas (EPFL: École Polytechnique Fédérale de Lausanne)H-Index: 8
#2John Botsis (EPFL: École Polytechnique Fédérale de Lausanne)H-Index: 37
Abstract Traction-separation relations due to large scale bridging in composites are very important in modeling their fracture response. Several works demonstrated that such relations are dependent upon the specimen's stiffness and loading conditions. Experimental data and micromechanics of bridging suggested that, in addition to the crack opening displacement (COD), the local curvature can be used as an additional kinematic parameter to incorporate the stiffness dependence on traction-separatio...
2 CitationsSource
#1S. Kohler (EPFL: École Polytechnique Fédérale de Lausanne)H-Index: 2
#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 Thin-ply composites were shown to exhibit significantly delayed transverse cracking, but the linear onset of damage scaling with ply thickness reported by Amacher et al. (2014) did not correspond to the established LEFM based in situ strength model. This study further investigates this experimental behaviour by simultaneously comparing in situ free edge crack observation with acoustic emission measurements as well as performing ex-situ X-ray tomography observations of crack propagation....
7 CitationsSource
#1C. Blondeau (EPFL: École Polytechnique Fédérale de Lausanne)H-Index: 2
#2G. Pappas (EPFL: École Polytechnique Fédérale de Lausanne)H-Index: 8
Last. John Botsis (EPFL: École Polytechnique Fédérale de Lausanne)H-Index: 37
view all 3 authors...
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-inde...
12 CitationsSource
#1F. Naya (EPFL: École Polytechnique Fédérale de Lausanne)H-Index: 9
#1F. Naya (EPFL: École Polytechnique Fédérale de Lausanne)H-Index: 1
Last. John Botsis (EPFL: École Polytechnique Fédérale de Lausanne)H-Index: 37
view all 3 authors...
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...
15 CitationsSource