Elucidating the effect of cohesive zone length in fracture simulations of particulate composites

The influence of the cohesive zone length on the crack driving force is quantified and analyzed in a representative system of particles dispersed in a matrix of a composite material. For heterogeneous material systems, e.g. particulate composites, it is known that as a crack approaches the particles, the crack driving force may increase ...

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

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...

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

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....

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

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,...

Flexible, printed, Pb-free piezo-composites for haptic feedback systems

While most of the work on piezoelectric composites focuses on methods to reduce the dielectric constant of the composite (for better sensor and energy harvesting performance), for haptic feedback and actuator applications the opposite is desirable. We present here a study of the effect of adding a second ceramic phase (BaTiO3 nanoparticles)...

Flexible Lead-Free Piezoelectric Composite Materials for Energy Harvesting Applications

Vibrational piezoelectric energy harvesters are being investigated to replace batteries in embedded sensor systems. The energy density that can be harvested depends on the figure of merit, d₃₃g₃₃, where d₃₃ and g₃₃ are the piezoelectric charge and voltage coefficient. Commonly used piezoelectric...

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

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...

Self-healing of Al₂O₃ containing Ti microparticles

This work explores the possibility of using embedded micron-sized Ti particles to heal surface cracks in alumina and to unravel the evolution of the crack filling process in case of pure solid-state oxidation reactions. The oxidation kinetics of the Ti particles is studied and the results are applied in a simple model for crack-gap filling....

Thermo – mechanical properties of SPS produced self-healing thermal barrier coatings containing pure and alloyed MoSi₂ particles

Yttria – partially stabilised zirconia (YPSZ) MoSi₂ composites have been designed to prolong the lifetime of the matrix by self – healing cracks during thermal cycling. The healing reaction at high temperatures is based on the decomposition of MoSi₂, leading to a volumetrically expanding reaction product, which seals the...

Self-healing thermal barrier coating systems fabricated by spark plasma sintering

The present paper focuses on the Spark Plasma Sintering (SPS) manufacturing of a new type of self-healing thermal barrier coating (TBC) and a study of its thermal cycling behaviour. The ceramic coating consists on an Yttria Partially Stabilized Zirconia (YPSZ) matrix into which healing agents made of MoSi₂-Al₂O<sub>3<...

Routes to Make Natural Rubber Heal: A Review

This review outlines latest developments in the field of self-healing rubbers and elastomers, analyzing their potential application to natural rubber (NR). Different validated healing concepts are presented and the possibilities of applying them to NR are discussed. Research in this field should aim at modifying the chemical structure of NR...

Healing of a glass fibre reinforced composite with a disulphide containing organic-inorganic epoxy matrix

We report the development of an intrinsic healing glass fibre reinforced polymer (GFRP) composite based on a disulphide-containing organic-inorganic thermoset matrix. Thermomechanical experiments showed that the newly developed matrix has a combination of a Young's modulus value in the range of (800–1200 MPa), the ability to multiple...

Non-destructive monitoring of delamination healing of a CFRP composite with a thermoplastic ionomer interlayer

A comparative study is performed on the monitoring of delamination healing in CFRP-ionomer sandwich composites by non-destructive techniques and destructive compression testing. Artificial delaminations of various areal dimensions and nature were introduced during production of the composites. The extent of the delamination and the healing...

Setup for EMI Shielding Effectiveness Tests of Electrically Conductive Polymer Composites at Frequencies up to 3.0 GHz

Conductive polymer composites have been receiving increased interest both from the scientific community and industry with a special focus on electromagnetic interference (EMI) shielding applications. In this paper, we present the design, EM wave simulation, and validation through S-parameters measurements of an EMI shielding effectiveness (SE...

Poling piezoelectric (K,Na,Li)NbO₃-polydimethylsiloxane composites

Composites of aligned (K,Na,Li)NbO₃ (KNLN) piezoceramic particles in a PDMS polymer matrix are presented as promising materials for flexible sensors and energy harvesters. Their ease of processing is matched with a relatively high damage tolerance and piezoelectric performance at low dielectric loss. To maximize piezoelectric...

Flexible Piezoelectric Touch Sensor by Alignment of Lead-Free Alkaline Niobate Microcubes in PDMS

A highly sensitive, lead-free, and flexible piezoelectric touch sensor is reported based on composite films of alkaline niobate K_0.485Na_0.485Li_0.03NbO₃ (KNLN) powders aligned in a polydimethylsiloxane (PDMS) matrix. KNLN powder is fabricated by solid-state sintering and consists of microcubes. The...

In-situ poling and structurization of piezoelectric particulate composites

Composites of lead zirconate titanate particles in an epoxy matrix are prepared in the form of 0–3 and quasi 1–3 with different ceramic volume contents from 10% to 50%. Two different processing routes are tested. Firstly a conventional dielectrophoretic structuring is used to induce a chain-like particle configuration, followed by curing the...

Healing of Early Stage Fatigue Damage in Ionomer/Fe₃O₄ Nanoparticle Composites

This work reports on the healing of early stage fatigue damage in ionomer/nano-particulate composites. A series of poly(ethylene-co-methacrylic acid) zinc ionomer/Fe3O4 nanoparticle composites with varying amounts of ionic clusters were developed and subjected to different levels of fatigue loading. The initiated damage was healed upon localized...