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Thomas Keller

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Publications associées (309)

A novel fatigue life prediction methodology based on energy dissipation in viscoelastic materials

Thomas Keller, Ghazaleh Eslami

This paper introduces a new fatigue life prediction methodology for viscoelastic materials in the tension-tension fatigue loading region. The model was established based on the total amount of energy dissipated during fatigue loading, and offers two main a ...

ELSEVIER SCI LTD2021

Origami-inspired carbon fiber-reinforced composite sandwich materials - Fabrication and mechanical behavior

Thomas Keller, Yuntong Du

A folding fabrication method inspired by origami for carbon fiber-reinforced composites to fabricate three-dimensional structures is presented. PMI foams serve as substrates, making it possible to manufacture this kind of origami-inspired composite sandwic ...

ELSEVIER SCI LTD2021

Mechanical properties of a balsa wood veneer structural sandwich core material

Thomas Keller, Anastasios Vassilopoulos, Niloufar Vahedi

Balsa wood is an appropriate core material for structural sandwich applications due to its high strength- and stiffness-to-weight ratios. However, the mechanical properties vary considerably owing to the inherent scattering of natural wood materials. One a ...

2020

Experimental investigation of mesoscale variability of clear spruce mechanical properties in the radial direction

Thomas Keller, Anastasios Vassilopoulos, Alireza Farajzadeh Moshtaghin, Steffen Franke

The aim of this work is the investigation of mesoscale/local variability in mechanical properties of clear timber in the radial direction. Clear Norway spruce wood, Picea abies, was used for cutting specimens of different lengths with a small cross-section ...

2020

Optimization of multi-directional fiber architecture for resistance and ductility of bolted FRP profile joints

Thomas Keller, Lulu Liu, Xin Wang

In view of the low structural efficiency of bolted joints in pultruded fiber-reinforced polymer (FRP) profiles with mainly unidirectional (UD) fiber architecture, off-axis plies were considered as an effective way to improve bolted joint performance. An ex ...

ELSEVIER SCI LTD2020

Resistance and ductility of FRP composite hybrid joints

Thomas Keller, Lulu Liu, Xin Wang

An experimental investigation of the load-bearing behavior and ductility of FRP hybrid double-lap joints composed of both adhesively-bonded and bolted connection parts was conducted. Amongst other things, the effects of the adherends’ fiber architecture (u ...

2020

Thermomechanical characterization of a balsa-wood-veneer structural sandwich core material at elevated temperatures

Thomas Keller, Anastasios Vassilopoulos, Chao Wu, Niloufar Vahedi

The tensile, compressive and shear behavior of standardized specimens cut from a veneered balsa wood used as structural sandwich core was investigated at ambient temperatures of up to 250 degrees C. The average moisture content was 9.1%. The specimens' res ...

ELSEVIER SCI LTD2020

Energy dissipation in adhesive and bolted pultruded GFRP double-lap joints under cyclic loading

Thomas Keller, Sonia Yanes Armas, Ghazaleh Eslami

Fiber-reinforced polymer (FRP) structures, due to their low mass, are valuable alternatives to traditional steel or concrete structures in seismic areas. However, to resist seismic actions, FRP structures must be able to dissipate a significant amount of i ...

2020

Stress ratio effect on tension-tension fatigue behavior of angle-ply GFRP laminates

Thomas Keller, Anastasios Vassilopoulos

The effect of the stress ratio (R = sigma(min)/sigma(max)) on the fatigue behavior of (+/- 45)(2s) angle-ply glass/epoxy composite laminates was investigated by comparing their mechanical, thermal, and optical properties under the stress ratio of 0.5 with ...

2019

Modeling of fatigue behavior based on interaction between time- and cyclic-dependent mechanical properties

Thomas Keller, Anastasios Vassilopoulos

A general constitutive equation was established using the theory of viscoelasticity in order to consider the interaction of the time- and cyclic-dependent mechanical properties of laminated composites. This equation was solved for two specific loading patt ...

2019

Durability of adhesively bonded joints between pultruded GFRP adherends under hygrothermal and natural ageing

Thomas Keller, Joào Pedro Girâo Meireles de Sousa

This paper presents an experimental and numerical study about the durability of adhesively bonded joints between pultruded glass fibre reinforced polymer (GFRP) adherends for civil engineering applications. Single lap joint (SLJ) specimens were manufacture ...

ELSEVIER SCI LTD2019

Two-dimensional quasi-static debonding in GFRP/balsa sandwich panels

Thomas Keller, Anastasios Vassilopoulos, Aida Cameselle Molares

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 ...

2019

Numerically-based method for fracture characterization of Mode I-dominated two-dimensional delamination in FRP laminates

Thomas Keller, Anastasios Vassilopoulos, Aida Cameselle Molares

A new numerically-based method suitable for determining the total strain energy release rate (SERA) involved in two-dimensional (2D) Mode I-dominated delamination under opening loads in FRP laminates is presented. The method is based on the mutual dependen ...

2019

Influence of curved delamination front on R-curve of DCB specimen

Thomas Keller, Anastasios Vassilopoulos, Zhengwen Jiang

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 ...

ELSEVIER SCI LTD2019

Temperature effect on fatigue behavior of basalt fiber-reinforced polymer composites

Thomas Keller, Anastasios Vassilopoulos, Xing Zhao, Xin Wang

In this study, the temperature effect on the static and tension–tension fatigue behavior of basalt fiber‐reinforced epoxy polymer (BFRP) composites is investigated. The S–N curves, energy dissipation, stiffness degradation, and displacement increment with ...

Wiley2019

Stress mitigation for adhesively bonded photovoltaics with fibre reinforced polymer composites in load carrying applications

Thomas Keller, Yu Bai

Structural loads, especially in-plane compression, may cause local buckling and debonding of the photovoltaic (PV) cells that are mechanically integrated with structural members and this may lead to degradation in their electrical performance. This paper p ...

ELSEVIER SCI LTD2019

Creep effects on tension-tension fatigue behavior of angle-ply GFRP composite laminates

Thomas Keller, Anastasios Vassilopoulos, Abdolvahid Movahedirad

Angle-ply (±45)2S glass/epoxy composite specimens have been subjected to pure creep and tension-tension constant amplitude fatigue loading interrupted at max by creep intervals lasting for 2 or 48 hours in order to examine the effects of creep loading on ...

2019

Two-dimensional fatigue debonding in GFRP/balsa sandwich panels

Thomas Keller, Anastasios Vassilopoulos, Aida Cameselle Molares

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 fatigu ...

2019

Ductile adhesively-bonded timber joints - Part 1: Experimental investigation

Thomas Keller, Anastasios Vassilopoulos, Myrsini Angelidi

In the field of timber load-bearing structures, adhesive bonding is a promising joining technique that may increase the structural stiffness and capacity of timber joints and structures. The use of ductile adhesives may furthermore allow designing ductile ...

2018

Fatigue damage in angle-ply GFRP laminates under tension-tension fatigue

Thomas Keller, Anastasios Vassilopoulos

2018

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