Lateral Indentation of a Thin Elastic Film

Indentation is a standard, widely used technique in mechanical assays and theoretical analysis. It unveils the fundamental modes of deformation and predicts the response of the material under more complex...

Effect of Pectin on the Characteristics of Edible Film from Pink Ear Emperor (Lethrinus lentjan) Gelatin

Edible film is a thin layer used to coat food. One of the biopolymers that can be used as a base for the edible film is fish gelatin. Gelatin can be obtained from the skin of Lethrinus lentjan. However, edible film is usually brittle if only gelatin is used, so other materials, such as pectin, are needed to form an elastic film. This study aims to determine the effect of pectin addition on the characteristics of the edible film. The method used in this research was the experimental method with five treatments of pectin concentration (0%, 0.2%, 0.25%, 0.3%, 0.35%). Physical and chemical characteristics (thickness, tensile strength, elongation, water vapor transmission, and moisture content) of edible films were analyzed. The results showed that different concentrations of pectin significantly affected the characteristics of edible film. The best characteristics of edible film (0.12 mm thickness, 15.40 MPa tensile strength, 26.50% elongation, 6.99 gram/m2 24 h water vapor transmission rate, and 8.745% moisture content) were obtained as 0.2% pectin added in making the gelatin-based edible film.

The interface competitive debonding of a bilayer elastic film on a rigid substrate

Different from the system of a single-layer elastic film on a rigid substrate, it is difficult to determine which interface will debond in a bilayer or multilayer film-substrate system. A peeling model of a bilayer elastic film on a rigid substrate is established in the present paper, in order to predict which interface debonding occurs first. The interfacial competitive debonding mechanism is theoretically analyzed with the help of the beam bending theory. A criterion of which interface debonding occurs first is proposed. It is found that the interfacial debonding path is mainly controlled by five dimensionless parameters, i.e., the strength ratio and the critical separation distance ratio of the upper and lower interfaces, the Young's modulus ratio and the thickness ratio of the upper and lower films, and the possible initial cantilever length for ease of loading. The corresponding competitive debonding map is well obtained. From the map, which interface debonds first can be easily predicted. It is interesting to find that the interfacial debonding path can be well tuned by any one of the five parameters. The results of the finite element calculation further confirm the theoretical predictions. The present work can not only provide a theoretical method to determine the interfacial debonding path but also be helpful for the optimal design of multilayer film-substrate systems in practical applications.

Analysis of Embedded Optical Interferometry in Transparent Elastic Grating for Optical Detection of Ultrasonic Waves

In this paper, we propose a theoretical framework to explain how the transparent elastic grating structure can be employed to enhance the mechanical and optical properties for ultrasonic detection. Incident ultrasonic waves can compress the flexible material, where the change in thickness of the elastic film can be measured through an optical interferometer. Herein, the polydimethylsiloxane (PDMS) was employed in the design of a thin film grating pattern. The PDMS grating with the grating period shorter than the ultrasound wavelength allowed the ultrasound to be coupled into surface acoustic wave (SAW) mode. The grating gaps provided spaces for the PDMS grating to be compressed when the ultrasound illuminated on it. This grating pattern can provide an embedded thin film based optical interferometer through Fabry–Perot resonant modes. Several optical thin film-based technologies for ultrasonic detection were compared. The proposed elastic grating gave rise to higher sensitivity to ultrasonic detection than a surface plasmon resonance-based sensor, a uniform PDMS thin film, a PDMS sensor with shearing interference, and a conventional Fabry–Perot-based sensor. The PDMS grating achieved the enhancement of sensitivity up to 1.3 × 10−5 Pa−1 and figure of merit of 1.4 × 10−5 Pa−1 which were higher than those of conventional Fabry–Perot structure by 7 times and 4 times, respectively.

The Mechanical Mechanism and Influencing Factors of Ice Adhesion Strength on Ice-Phobic Coating

Ice accretion can cause problems on polar ships, ocean platforms, and in other marine industries. It is important to understand the interface debonding behavior between ice and the surface of equipment. In this work, we created a mechanical model to analyze the interface debonding behavior between a square-based ice cuboid and an elastic coating base, using contact mechanics and fracture mechanics. Three-dimensional (3D) finite element (FE) simulation was used to simulate the interface debonding for normal and shear separation. A bilinear cohesive zone model (CZM) was used to simulate the interface between the ice cuboid and the elastic coating. We investigated the effect of the elastic modulus E of an elastic film on the critical detachment force Fc for normal and shear separation. The results showed that Fc increases with an increase of the elastic modulus of the elastic film. When E exceeds a certain level, Fc achieves a constant value and then remains stable. Finally, a series of epoxy/polydimethylsiloxane (PDMS) interpenetrating polymer-network (IPN) gel coatings with different elastic moduli were prepared. The ice tensile and shear adhesion strengths (σice and τice) of the coatings were measured. The results were roughly consistent with the results of the numerical simulation when E < 1 MPa.

ДОСЛІДЖЕННЯ ВПЛИВУ СТИРОЛ-АКРИЛОВИХ ПОЛІМЕРІВ НА ФІЗИКО-МЕХАНІЧНІ І ГІГІЄНІЧНІ ВЛАСТИВОСТІ БАВОВНЯНОЇ ТКАНИНИ

The purpose of the work is to study the effect of styrene-acrylic polymer coatings on the change in physical, mechanical and hygienic properties of cotton fabric. Aqueous dispersions of styrene-acrylic polymers (Lacrytex 640, Akratam AS 02.1, Tubifast AS 4010) were selected as the object of study. The processing of cotton fabric was carried out by the method of impregnation with varying a concentration of the studied polymers in finishing bath from 50 g/l to 150 g/l, followed by drying and heat setting. Standardized methods for studying the properties of textile materials were applied. The effect of polymer coatings on the physical and mechanical properties of cotton fabric was evaluated by the indicators of weight gain, thickness and rigidity. The hygienic properties of treated cotton fabric were characterized by hygroscopicity and breathability. The paper presents the results of a study of the dependence of physical, mechanical and hygienic properties of cotton fabric on the type and concentration of styrene-acrylic dispersions used. According to the results of the experiment, it was found that the acrylic copolymer Lacrytex 640 increases the elastic properties of treated fabric in the entire concentration range studied. It was determined that the greatest decrease in air permeability is typical for fabric samples coated on the basis of Akratam AS 02.1 dispersion. The hygroscopicity of cotton textile material with an increase in a concentration of the studied styrene-acrylic polymer dispersions from 50 g/l to 100 g/l decreases slightly (by 2%). It is proved that the styrene-acrylic copolymer Tubifast AS 4010 due to the formation of highly elastic film provides a soft handle and high hygienic properties of cotton fabric. The obtained experimental results are of practical value in the development of new finishing compositions for textile materials.

Exploring Mechanical Properties of Nanometer-thick Elastic Film through Micro-drop Impinging on Large-area Suspended Graphene

In this work, dependence of effective Young’s modulus on the thickness of suspended graphene was confirmed through a drop impingement method. Large area suspended graphene (LSG) layers with diameter up...

The crystallization and mechanical properties of poly(4-methyl-1-pentene) hard elastic film with different melt draw ratios

To study the effect of the melt-draw ratios (MDRs) on the structure and properties of the poly(4-methyl-1-pentene) (PMP) film, the crystal structure evolution and mechanical properties of the PMP film with an MDR of 40–160 were characterized using scanning electron microscopy, differential scanning calorimetry, wide-angle X-ray scattering, and mechanical test. The results show that with the increase of MDR, the spherulite to platelet transition occurs in the PMP. When the MDR exceeds 100, a parallel platelet structure appears. Due to the side chains, with the increase of MDR, the distribution density of tie chains in PMP decreases and the entanglement density of amorphous chains increases. This leads to a decrease in the yield strength and the strain hardening becomes noticeable. Although the crystalline network becomes loose due to the decrease in tie chain density, the elastic recovery (ER) value still increases with the increase of MDR. This result indicates that the entanglement density of the amorphous region greatly contributes to the ER.