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Synergistic Toughening of Epoxy through Layered Poly(ether imide) with Dual-Scale Morphologies

Teuwen, Julie J.E. (author), Farooq, U. (author), Alderliesten, R.C. (author), Dransfeld, C.A. (author)

Toughness of epoxies is commonly improved by adding thermoplastic phases, which is achieved through dissolution and phase separation at the microscale. However, little is known about the synergistic effects of toughening phases on multiple scales. Therefore, here, we study the toughening of epoxies with layered poly(ether imide) (PEI) structures...

journal article 2023

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Using an industry instrument to trigger the improvement of the transversal competency learning outcomes of engineering graduates

Leandro Cruz, M. (author), Saunders-Smits, Gillian (author)

To assist in resolving the perceived lack of transversal competencies (TCs) of engineering graduates by industry, this study investigates the characteristics of transforming an existing industry TC instrument for use in engineering education. The instrument consists of 36 nuanced sub-competencies with the corresponding definitions and...

journal article 2022

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The effect of stacking sequence and circumferential ply drop locations on the mechanical response of type IV composite pressure vessels subjected to internal pressure: A numerical and experimental study

Nebe, M. (author), Johman, A. (author), Braun, C. (author), van Campen, J.M.J.F. (author)

Type IV composite pressure vessels represent the current state-of-the-art for compressed gaseous hydrogen storage in fuel cell electric vehicles. A combination of highly demanding safety regulations and the need for cost competitive solutions make the topic of CPVs particularly challenging. Given the elevated material price of carbon fiber,...

journal article 2022

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The effectiveness of an activity to practise communication competencies: A case study across five European engineering universities

Leandro Cruz, M. (author), Sá, Sofia (author), Mesquita, Diana (author), Lima, Rui M. (author), Saunders-Smits, Gillian (author)

Although accreditation bodies emphasise communication competencies development in engineering curricula due to its importance for future engineers, the focus is often mainly on oral presentation and written reports. A communication activity was created to practice and reflect on students’ communication competencies including describing...

journal article 2021

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Exploring the effectiveness and the transversal competency retention of a game-based learning activity one year after student participation

Leandro Cruz, M. (author), Saunders-Smits, Gillian (author)

Most studies in engineering education focus on the effectiveness of the teaching interventions and what transversal competencies engineering students gain from those interventions immediately after they take place. This study explores the effectiveness of an existing game-based learning activity and the competency retention of the participating...

journal article 2021

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Estimating the true piezoelectric properties of BiFeO₃ from measurements on BiFeO₃-PVDF terpolymer composites

Tuluk, A. (author), Mahon, T.R. (author), van der Zwaag, S. (author), Groen, W.A. (author)

BiFeO₃ is an interesting multiferroic material with potential use in sensors and transducers. However, the high coercive field and low dielectric strength of this material make the poling process extremely difficult. Poling becomes a lot easier if the ceramic particles are incorporated in a non-conductive polymer with comparable...

journal article 2021

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Deterioration of the piezoelectric properties of (Bi_0.5Na_0.5)TiO₃ when using Na₂CO₃ as a sintering aid: A crystallographic and microstructural study

Mahon, T.R. (author), Giannopoulos, D. (author), van der Zwaag, S. (author), Groen, W.A. (author)

In this work, we present the impact of using Na₂CO₃ as a sintering aid and grain growth agent on the crystal structure, microstructure, and piezoelectric properties of (Bi_0.5Na_0.5)TiO₃ ceramics. The addition of Na₂CO₃ leads to a substantial increase in the grain size...

journal article 2021

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Effect of single-side stroke limiter on cantilever-based piezoelectric energy harvesting from low frequency vibrations

Giannopoulos, D. (author), Chen, Yu Chen (author), van der Zwaag, S. (author), Groen, W.A. (author)

Piezoelectric transducers which rely on oscillating cantilever-type beams to harvest mechanical energy locally available in environments have been of great interest as a substitute for batteries. Most of the research efforts focus mostly on designs which aim at resonance matching to achieve maximum energy output without taking the mechanical...

journal article 2021

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Comparison of first-year student conceptions of their future roles as engineers between Belgium, Ireland, and The Netherlands

Saunders-Smits, Gillian (author), Craps, Sofie (author), Carthy, Darren (author), Langie, Greet (author)

Recent research by KU Leuven showed that 33% of the engineering graduates in Flanders changed jobs in the first year, with 60% of those citing job content as a reason. Also, industry often reports that recent graduate hires lack the right skills for the job. It appears that students seem to enter the labour market less prepared both in...

journal article 2021

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Testing the Validity and Reliability of an Instrument Measuring Engineering Students' Perceptions of Transversal Competency Levels

Leandro Cruz, M. (author), van den Bogaard, M.E.D. (author), Saunders-Smits, Gillian (author), Groen, W.A. (author)

Contribution: This study reports on a reliable and valid instrument that measures engineering students' perceptions of their competency levels. A better understanding of students' needs in engineering curricula will support the development of engineering students' transversal competencies. Background: Prior research has investigated how...

journal article 2020

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Effect of topological imperfections on the electro-mechanical properties of structured piezoelectric particulate composites

van Kempen, S. E. (author), Khanbareh, H. (author), Groen, W.A. (author), Hol, J.M.A.M. (author), van der Zwaag, S. (author)

A novel method based on the Virtual Particle Mori–Tanaka (VPMT) is developed to predict the effective electro-elastic properties, d₃₃ and g33, of structured piezoelectric particulate composites with improved accuracy by means of a single parameter related to the spatial distribution of imperfectly aligned rod-like PZT particles....

journal article 2020

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Harnessing Plasticity in an Amine-Borane as a Piezoelectric and Pyroelectric Flexible Film

Zhang, Yan (author), Hopkins, Margaret A. (author), Liptrot, David J. (author), Khanbareh, Hamideh (author), Groen, W.A. (author), Zhou, Xuefan (author), Zhang, Dou (author), Bao, Yinxiang (author), Zhou, Kechao (author), Bowen, Chris R. (author), Carbery, David R. (author)

We demonstrate that trimethylamine borane can exhibit desirable piezoelectric and pyroelectric properties. The material was shown to be able operate as a flexible film for both thermal sensing, thermal energy conversion and mechanical sensing with high open circuit voltages (>10 V). A piezoelectric coefficient of d₃₃≈10–16 pC N...

journal article 2020

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Effect of particle contact on the electrical performance of NTC-epoxy composite thermistors

Deutz, D.B. (author), van der Zwaag, S. (author), Groen, W.A. (author)

As demand rises for flexible electronics, traditionally prepared sintered ceramic sensors must be transformed into fully new sensor materials that can bend and flex in use and integration. Negative temperature coefficient of resistance (NTC) ceramic thermistors are preferred temperature sensors for their high accuracy and excellent stability,...

journal article 2020

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Fabrication of piezoelectric composites using high-temperature dielectrophoresis

Khaliq, J. (author), Hoeks, Theo (author), Groen, W.A. (author)

In this paper, we present a method to create a highly sensitive piezoelectric quasi 1–3 composite using a thermoplastic material filled with a piezoelectric powder. An up-scalable high-temperature dielectrophoresis (DEP) process is used to manufacture the quasi 1–3 piezoelectric polymer-ceramic composites. For this work, thermoplastic cyclic...

journal article 2019

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A large displacement orthotropic viscoelastic model for manufacturing-induced distortions in Fibre Metal Laminates

Abouhamzeh, M. (author), Sinke, J. (author), Benedictus, R. (author)

Distortions and residual stresses are predicted in Fibre Metal Laminates (FMLs) under large deformations. A new modelling procedure is presented for small and large deformation analysis of thermo-viscoelastic problems of orthotropic materials. The material model is implemented in a finite element package which can be used for cure and/or...

journal article 2019

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Evaluation of the mechanical performance of a composite multi-cell tank for cryogenic storage: Part II – Experimental assessment

Tapeinos, I. (author), Rajabzadeh, Aydin (author), Zarouchas, D. (author), Stief, Malte (author), Groves, R.M. (author), Koussios, S. (author), Benedictus, R. (author)

This study focuses on the understanding of the thermal and structural behavior of an innovative Type IV multi-spherical composite-overwrapped pressure vessel through an experimental assessment that consists of hydrostatic testing at ambient conditions and pressure cycling with a cryogenic medium (LN₂). During hydro-burst testing at...

journal article 2019

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The effect of the intrinsic electrical matrix conductivity on the piezoelectric charge constant of piezoelectric composites

Stuber, V.L. (author), Mahon, T.R. (author), van der Zwaag, S. (author), Groen, W.A. (author)

Polymer-piezoceramic composites have drawn a lot of attention for sensor and energy harvesting applications. Poling such materials can be difficult due to the electric field getting mostly distributed over the low dielectric constant matrix. During this process, the electrical matrix conductivity plays a vital role. This work shows how two...

journal article 2019

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Composite layup effect on the failure mechanism of single lap bonded joints

Kupski, J.A. (author), Teixeira De Freitas, S. (author), Zarouchas, D. (author), Camanho, P. P. (author), Benedictus, R. (author)

Single lap bonded joints with four different composite adherend stacking sequences were tested and numerically simulated. The aim was to evaluate the effect of the layups on the quasi-static tensile failure of the bonded joints. The study shows that increasing the adherends bending stiffness postpones the damage initiation in the joint....

journal article 2019

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Systematic multiparameter design methodology for an ultrasonic health monitoring system for full-scale composite aircraft primary structures

Ochôa, Pedro (author), Groves, R.M. (author), Benedictus, R. (author)

The successful utilization of guided wave-based structural health monitoring (SHM) for detailed quantitative diagnostic of damage in composite aircraft primary structures depends on the excitation frequency, geometry, and positioning of the piezoelectric transducers. This study proposes a novel methodology to consistently define those parameters...

journal article 2019

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Depolarization of multidomain ferroelectric materials

Zhao, Dong (author), Lenz, Thomas (author), Gelinck, Gerwin H. (author), Groen, W.A. (author), Damjanovic, Dragan (author), de Leeuw, D.M. (author), Katsouras, Ilias (author)

Depolarization in ferroelectric materials has been studied since the 1970s, albeit quasi-statically. The dynamics are described by the empirical Merz law, which gives the polarization switching time as a function of electric field, normalized to the so-called activation field. The Merz law has been used for decades; its origin as domain-wall...

journal article 2019