Interplay of Fracture and Martensite Transformation in Microstructures:A Coupled Problem

We are witnessing a tremendous transition towards a society powered by net-zero carbon emission energy, with a corresponding escalating reliance on functional materials (FM). In recent years, the application of FM in multiphysics environments has brought new challenges to the mechanics and materials research communities. The underlying mechanism in FM, which governs several fundamental characteristics, is known as martensitic phase transformation (MPT). When it comes to the application of FM in the multiphysics context, a thorough understanding of the interplay between MPT and fracture plays a crucial role in FM design and application. In the present work, a coupled problem of crack nucleation and propagation and multivariant stress-induced MPT in elastic materials is presented using a finite element method based on Khachaturyan’s microelasticity theory. The problem is established based on a phase-field (PF) approach, which includes the Ginzburg–Landau equations with advanced thermodynamic potential and the variational formulation of Griffith’s theory. Therefore, the model consists of a coupled system of the Ginzburg–Landau equations and the static elasticity equation, and it characterizes evolution of distributions of austenite and two martensitic variants as well as crack growth in terms of corresponding order parameters. The numerical results show that crack growth does not begin until MPT has grown almost completely through the microstructure. Subsequent to the initial formation of the martensite variants, the initial crack propagates in such a way that its path mainly depends on the feature of martensite variant formations, the orientation and direction upon which the martensite plates are aligned, and the stress concentration between martensite plates. In addition, crack propagation behavior and martensite variant evaluations for different lattice orientation angles are presented and discussed in-detail

Factors influencing patient satisfaction with dental appearance and treatments they desire to improve aesthetics

Background: We assessed factors influencing patients’ satisfaction with their dental appearance and the treatments they desired to improve dental aesthetics. Methods: A cross-sectional study was performed out among 235 adult patients who visited the Hospital Universiti Sains Malaysia dental clinic. A structured, interviewer-guided questionnaire was used to identify patient satisfaction with their general dental appearance, cosmetic elements and desired treatments. Results: The 235 patients consisted of 70 males (29.8%) and 165 females (70.2%), of mean age 31.5 years (SD 13.0). Of these patients, 124 (52.8%) were not satisfied with their general dental appearance. In addition, 132 patients (56.2%) were not happy with the color of their teeth, 76 (32.3%), regarded their teeth were poorly aligned, 62 (26.4%), as crowded and 56 (23.4%) protruded. Dissatisfaction with tooth color was significantly higher in female than in male patients (odds ratio [OR] of 1.99 (95% confidence interval [CI] 1.13-3.50). Tooth whitening was the treatment most desired by patients (48.1%). Results of multiple logistic regression analysis showed that patient dissatisfaction with general dental appearance was significantly associated with female gender (OR = 2.18; 95% CI: 1.18-4.03), unhappiness with tooth color (OR = 3.05; 95% CI: 1.74-5.34) and the opinion that their teeth protruded (OR = 2.91, 95% CI: 1.44-5.91)

Natural frequency analysis of continuously graded carbon nanotube-reinforced cylindrical shells based on third-order shear deformation theory

Based on the third-order shear deformation theory (TSDT), the investigation of the free vibration response of a continuously graded carbon nanotube-reinforced (CGCNTR) cylindrical shell is presented. The volume fractions of randomly oriented straight single-walled carbon nanotubes are assumed to be graded in the thickness direction. An embedded carbon nanotube in a polymer matrix and its surrounding inter-phase is replaced with an equivalent fiber for predicting the mechanical properties of the carbon nanotube/polymer composite. The Mori–Tanaka scheme as an accurate micromechanics model is used for estimating the homogenized material properties of nanocomposites reinforced with equivalent fibers. The equations of motion and the associated boundary conditions are derived using the Hamilton’s principle based on TSDT. The discretization of the system by means of the Generalized Differential Quadrature Method leads to a standard linear eigenvalue problem. Detailed parametric studies have been carried out to study the impacts of the various types of equivalent fiber distribution, different boundary conditions and geometrical parameters on the vibration characteristics of CGCNTR cylindrical shells. The interesting finding of the present study is that the graded CNT volume fractions with symmetric distribution through the shell thickness have high capabilities to reduce or increase the natural frequency in comparison with uniformly and asymmetric CNT distribution. </jats:p

Manufacturable insight into modelling and design considerations in fibre-steered composite laminates : State of the art and perspective

The advent of novel robot-assisted composite manufacturing techniques has enabled steering of fibre paths in the plane of the lamina, leading to the emergence of the socalled variable angle tow (VAT) composite laminates. These laminates, with spatially varying fiber angle orientations, provide the designer with the ability to tailor the pointwise stiffness properties of VAT composites with substantially more efficient structural performance over conventional straight fibre laminates. As the application of fibresteered composite laminates has reached an unprecedented scale in both academia and industry in recent years, a reflection upon the state-of-the-art advancements in the modelling, design, and analysis of these advanced structures becomes vital for successfully shaping the future landscape. Motivated by the gap and shortcomings in the available review works, in the present paper, firstly underlying fibre placement technologies including tailored fiber placement (TFP), continuous tow shearing (CTS), and automated fibre placement (AFP) are presented and discussed in detail. Afterwards, mathematical models of reference fibre path in fibre--steering technology will be reviewed, followed by providing a discussion on the manufacturing limitations and constraints of the AFP process. Then, design considerations in constructing a ply with multiple courses are elaborated and key techniques to fill the entire layer with several courses are reviewed. This review is then followed by an introduction to the continuity and smoothness of fiber paths. Furthermore, a description on the material and geometric uncertainties is elaborated. Last but not least, the plate and shell laminate theories, which establish the fundamental core of the modelling and design of VAT composite structures, will be discussed

One-year clinical evaluation of a glass carbomer fissure sealant, a preliminary study

Glass Carbomer® is a new generation of restorative material developed from glass-ionomer cements with possiblity of gradual mineralization into fluorapatite. The aim of this clinical trial was to investigate the retention of Glass Carbomer® fissure sealant after 12 months, in comparison to a commonly used conventional resin-based sealant. Forty-eight teeth in 24 patients [mean (SD) =8 (2.3) years] with well-delineated fissure morphology were randomly divided into two equal groups and sealed with Bis-GMA resin-based Helioseal F (group A, Ivoclar Vivadent, Liechtenstein) and Glass Carbomer (group B, Glass Carbomer® Sealant, Glass Carbomer Products, Leiden, Netherlands) using the split mouth design. Materials were placed and set according to the manufacturer’s instructions using a polymerization unit Bluephase 16i (Vivadent, Liechtenstein). Complete sealant retentions in both groups were 100% and 75% after 6 and 12 months of clinical service, respectively. There were there were no secondary caries lesions in both groups after 6 months; two new carious lesions were detected in both groups after 12 months. The MannWhitney U test revealed no significant difference between the two groups at both evaluations points (P>0.05). Glass Carbomer® material showed a similar retention rate when compared with a resin-based sealant. Future studies are required to examine the long-term performance of Glass Carbomer® sealants