Publications by Georgios Pappas

Crack propagation in CFRP laminates under mode I monotonic and fatigue loads: A methodological study

John Botsis, Charlie Joseph Simon Blondeau, Georgios Pappas

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 ...

ELSEVIER SCI LTD2021

Monitoring of Torque Induced Strain in Composite Shafts with Embedded and Surface-Mounted Optical Fiber Bragg Gratings

John Botsis, Georgios Violakis, Georgios Pappas

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 wi ...

2021

Variations on R-curves and traction-separation relations in DCB specimens loaded under end opening forces or pure moments

John Botsis, Georgios Pappas

In this work the differences in R-curve response 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 momen ...

PERGAMON-ELSEVIER SCIENCE LTD2020

Experiments and numerical modelling on angle-ply laminates under remote mode II loading

John Botsis, Charlie Joseph Simon Blondeau, Georgios Pappas

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 degrees, +/- 45 ...

ELSEVIER SCI LTD2020

Towards a geometry independent traction-separation and angle relation due to large scale bridging in DCB configuration

John Botsis, Georgios Pappas

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 ...

ELSEVIER SCI LTD2020

Design optimization of a CFRP-aluminum joint for a bioengineering application

John Botsis, Georgios Pappas

Lightweight design demands and complexity requirements of modern high-end structures in aerospace, automotive, sports and bioengineering can be successfully covered by a combination of fiber reinforced polymers (FRPs) with metallic components. Conventional ...

2019

Micromechanical study on the origin of fiber bridging under interlaminar and intralaminar mode I failure

John Botsis, Georgios Pappas, Fernando Naya Montans

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 spec ...

ELSEVIER SCI LTD2019

Runaway electron beam control

Basil Duval, Stefano Coda, Diego Carnevale, Georgios Pappas, Joan Decker, Umar Sheikh, Cristian Galperti, Filippo Bagnato, Gergely Papp

Post-disruption runaway electron (RE) beams in tokamaks with large current can cause deep melting of the vessel and are one of the major concerns for ITER operations. Consequently, a considerable effort is provided by the scientific community in order to t ...

IOP PUBLISHING LTD2019

A comparative study of mode I delamination behavior of unidirectional glass fiber-reinforced polymers with epoxy and polyurethane matrices using two methods

John Botsis, Georgios Pappas

The mode I delamination behavior of a unidirectional glass-fiber reinforced polymer with a prototype elasto-plastic polyurethane matrix (GF/PU) was investigated and compared with that of glass/epoxy (GF/EP) using double cantilever beam specimens. Fracture ...

PERGAMON-ELSEVIER SCIENCE LTD2019

Individualized lightweight structures for biomedical applications using additive manufacturing and carbon fiber patched composites

Georgios Pappas, Mirko Meboldt

Combining additive manufacturing (AM) with carbon fiber reinforced polymer patched composites unlocks potentials in the design of individualized, lightweight biomedical structures. Arising design opportunities are geometrical individualization of structure ...

2019

Influence of ply-angle on fracture in antisymmetric interfaces of CFRP laminates

John Botsis, Charlie Joseph Simon Blondeau, Georgios Pappas

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 dif ...

ELSEVIER SCI LTD2019

The influence of through-thickness reinforcement geometry and pattern on delamination of fiber-reinforced composites: Part I - Experimental results

John Botsis, Véronique Michaud, Georgios Pappas

This experimental study reports effect of tuft geometry i.e., standard tufts and loops milled-down, and tufting pattern on Mode I interlaminar fracture in a GFRP. Standard tufting geometry is responsible for an increase in fracture resistance by 3.5-6 time ...

Elsevier2018

The influence of through-thickness reinforcement geometry and pattern on delamination of fiber-reinforced composites: Part II - Modeling

John Botsis, Véronique Michaud, Georgios Pappas

This article reports modeling techniques and results based on experimental Mode I characterization of a layered woven GFRP material with tufting reinforcement. Standard tuft and loop-less geometries are investigated on three different areal patterns to eva ...

Elsevier2017

Studies on Traction Separation Relations in Fracture of Layered Composites : Experiments and Modeling

Georgios Pappas

Layered fiber reinforced composite materials are prone to fracture in planes parallel to the direction of fibers leading to extensive delamination or intralaminar fracture. This phenomenon of crack propagation is frequently accompanied by significant incre ...

EPFL2017

Intralaminar fracture of unidirectional carbon/epoxy composite: experimental results and numerical analysis

John Botsis, Georgios Pappas

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 com ...

Elsevier2016

Large scale fiber bridging in mode I intralaminar fracture. An embedded cell approach

John Botsis, Luis Pablo Canal Casado, Georgios Pappas

Fiber reinforced composites can develop large scale bridging upon mode I fracture. This toughening mechanism depends on the constituents and the geometry of the specimen, and is especially important in unidirectional laminates when fracture is parallel to ...

Elsevier2016

Characterization of intralaminar mode I fracture of AS4/PPS composite using inverse identification and micromechanics

John Botsis, Luis Pablo Canal Casado, Georgios Pappas

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 q ...

Elsevier2016