Mechanical Properties Of Products Research Articles

Critical length prediction for fiber breaking in injection molded of long-fiber reinforced thin-walled products

Fiber length is one of the vital factors in determining the properties of long fiber reinforced thermoplastics (LFRT). However, many factors may generate fiber breakage in the injection molding process of LFRT, such as friction, melt shear, injection rate, etc. Especially for thin-walled products, owing to the relatively narrow mold cavity and frozen layer near the mold wall, it’s usually difficult for the fibers to move freely with the melt, leading to fiber breakage under the shear stress of the flow field eventually. In such a situation, the existing buckling breakage model based on the assumption fibers immersed in the flow field being in an unconstrained state is no longer applicable. In this paper, a new model for calculating the critical length of constrained fiber in thin-walled injection molded products is developed. A typical long glass fiber reinforced polypropylene thin-walled product was employed to verify the reliability of the model. The high-precision fiber length analyzer was used to calculate the fiber length distribution at different distances from the injection port. At the same time, the length distribution at the corresponding position was predicted via the model. The average prediction accuracy in the three sampling sections is 87.8%, 91.4% and 83.6%, respectively. The results show that the proposed model can effectively predict the fiber length distribution of injection molded thin-walled products. This conclusion provides important support for further accurate calculation of the mechanical properties of products.

Issues in the design of tissue-engineered collagen constructs and some approaches to their solution: A review

This review article analyzes modern literature sources on the design of bioinks and tissue-engineered constructs on the basis of soluble forms of collagen, including gelatin. The choice of soluble forms of collagen as a biopolymer basis for bioinks and this type of constructs is determined by their unique biocompatibility, bioresorbability, as well as the presence of adhesive sites (motifs) for binding cells with their subsequent proliferation and organ or tissue maturation. However, the poor mechanical properties of products derived from soluble collagens, rapid biodegradation, tendency to lose the solubility of highly viscous solutions when stored or with pH increase limit their application in tissue engineering. The use of more stable low-viscosity collagen solutions does not enable the creation of dimensionally stable tissue-engineered constructs. It is shown that the introduction of various water-soluble biocompatible polymeric additives into hydrogels on the basis of soluble collagens allows the above-mentioned problems to be solved, as well as providing a means to customize the required characteristics of bioinks and tissue-engineered constructs. The additives that improve their characteristics include biopolymers: silk sericin and fibroin, as well as alginates and fibrinogen, which can form cross-links in the presence of Ca2+. This type of crosslinking is shown to further improve the performance of these constructs. All of these biopolymers are commercially available. The article comparatively analyzes approaches to stabilizing the shape, improving the mechanical properties, and adjusting the bioresorption time of 3D printed tissue-engineered constructs during organ or tissue maturation.

Simulation of voltage characteristics of vapor-gas shell during electrolyte-plasma treatment

Electrolytic plasma processing (EPT) is a method of surface treatment of materials based on the use of plasma and an electrolytic solution. This abstract discusses the principle of action, main applications and potential benefits of EPТ. The EPТ technique involves immersing the object being treated in an electrolytic solution, after which an electric current is applied, causing decomposition of the solution and the formation of a plasma cloud at the surface of the material being processed. Exposure to plasma and chemically active components of the solution makes it possible to modify the surface of the material, improving its properties, such as adhesion, strength and corrosion resistance. EPТ is widely used in a variety of industries, including metalworking, electronics, medical equipment and food processing. The advantages of the method include high efficiency, the ability to process complex shapes and materials, as well as environmental safety due to the absence of the use of chemically aggressive substances. Electrolytic plasma processing is a promising direction in the field of surface modification of materials with a wide range of potential applications. In this paper, theoretical studies of vapor-gas shell formation in the near-surface region of structural steels in the cathodic heating mode of electrolyte-plasma treatment were considered. The technology of electrolyte-plasma hardening, providing the required mechanical properties of products, which are often subjected to wear, temperature and force effects, was investigated. Based on the results of theoretical studies, mathematical calculations of voltage, current density, and dependence graphs were made to obtain a model of vapor-gas shell formation in the process of cathodic heating. Modeling of calculations of vapor-gas shell formation in the process of cathodic heating was carried out with the help of Maple program.

The influence of low-temperature shear on crystallization of shish-kebab of unimodal/ bimodal C4 short-chain branching polyethylene

The shish crystal, a crucial structure in the formation of shish-kebab crystals, has drawn widespread attention due to its highly oriented chain arrangement, significantly enhancing the mechanical properties of products. This study utilizes polyethylene samples with longer C4 short branches, employing in-situ synchrotron SAXS/WAXD to investigate the influence of short branch length and content on the formation of shish-kebab crystals in unimodal and bimodal polyethylene under low-temperature shear conditions (with supercooling degrees of 13.5 °C and 10.5 °C). The results reveal that the presence of C4 short-chain branching affects system crystallization, but low-temperature shear induces stronger mechanical action on the melt, resulting in better-oriented lamellar crystals compared to high-temperature shear (superheat degrees of 22.5 °C and 19.5 °C), achieving higher orientation. This achieves the control of shish-kebab crystal generation through the stretched network mechanism. Both types of samples with different C4 short-chain branching contents generate shish-kebab crystals during the shear stage, with relatively higher short-chain branching content inducing more shish crystal formation but with less regular structure. The bimodal polyethylene exhibit higher proportions and absolute amounts of final shish crystals compared to the unimodal polyethylene, indicating that high molecular weight portions are conducive to shish crystal generation under shear. The result demonstrates the feasibility of generating shish-kebab crystals during the low-temperature shear process of PE in the presence of C4 branches using the stretched network mechanism under shear flow conditions. Moreover, controlling the degree of entanglement of molecular chains by adjusting shear temperature, branch content, and branch length can modulate two formation mechanisms of shish crystals—coil-stretch transition mechanism at high temperature and stretched network mechanism at low-temperature.

Mechanical properties of products made of corrosion-resistant steels during additive growth by laser sintering and electric arc surfacing

The mechanical properties of products made from 10Х12Н10Т and 08Х18Н9 corrosion-resistant steels are studied during additive growth of powder particles by laser sintering (SLM method) and electric arc surfacing (WAAM method). It is shown that the tensile strength of products obtained by the SLM method is higher than that of rolled samples obtained by the WAAM method. Additional heat treatment of products reduces the tensile strength, but increases ductility properties, especially when manufactured using the WAAM method. An assessment of the influence of structure porosity on the mechanical properties of the metal is given. Keywords:additive growth, corrosion-resistant steels, SLM and WAAM methods, mechanical properties, heat treatment uru.40@mail.ru

Machine learning optimization of bio-sandcrete brick modelling using response surface methodology

In this study, raw grinded groundnut shell (RGGNS) was used as a fine aggregate in the brick industry to reuse agricultural waste in building materials. In this study, an experimental approach was used to examine a new cement brick with raw groundnut shells integrated with compressive strength, water absorption and dry density optimization utilizing response surface methodology (RSM). The raw ground-nut shell content improved the fine aggregate performance of the 40%, 50%, and 60% samples. The 28-day high compressive strength with the raw ground-nut shell was 6.1 N/mm2 maximum, as needed by the technical standard. Samples made from 40%, 50%, and 60% raw groundnut shells yielded densities of 1.7, 2.2, and 1.9 kg/cm3 for groundnut shell (GNS) brick, respectively. A product's mechanical properties meet the IS code standard’s minimum requirements. RSM was then utilized to develop a model for the addition of raw groundnut shell to concrete. R-square and Adeq precision values indicated that the results are highly significant, and equations for predicting compressive strength, water absorption, and dry density have been developed. In addition, optimization was performed on the RSM findings to determine the efficiency optimization of the model. Following the optimization results, experiments were conducted to determine the applicability of the optimized model.

Study of the Effect of Selective Laser Melting Parameters on the Structure and Physico-Mechanical Properties of a Blank Made of Stainless Chromium-Nickel Steel

Currently, there are a number of additive technologies that are used in various industries (laser fusion of powder materials, electron beam melting, etc.). The formation of metal structures and products by methods of additive technologies occurs by adding a new layer of material and its further melting (sintering), ensuring the adhesion of each subsequent layer with the previous one in accordance with digital model data. The advantages of using and developing additive technologies include the possibility of using a wide range of materials, obtaining finished products with complex geometries, restoring and repairing damaged structures, as well as the possibility of applying protective and anticorrosive coatings. Metal powder materials with specified physical and mechanical properties are of crucial importance in additive manufacturing. The main requirements for such powders include requirements for their shape and size. The preferred particle shape is spherical, as it provides a more compact installation in a given volume and the necessary fluidity of the material, which is due to the low resistance in the supply systems of powder materials in 3D printers. The aim of the work is to study the influence of the parameters of the SLM printing process on the structure and mechanical properties of products made of 12Cr18Ni10Ti alloy. Samples obtained by selective laser melting were subjected to pycnometric and metallographic analysis. Based on the obtained microstructure images, a digital porosity analysis of the work piece under study was performed in the Thixomet Pro software package. The microhardness and acoustic characteristics were also measured over the entire section of the work piece under study. It was revealed that with an increase in the distance from the substrate (0...112 mm) in the transverse and longitudinal sections, the tendency remains to decrease the density values and increase the volume fraction of pores. It is shown that the acoustic parameter Dc can be used to control changes in the physical and mechanical properties of stainless chromium-nickel steel blanks obtained by selective laser melting.

FINE-GRAINED CONCRETE BASED ON WASTE FROM THERMAL POWER PLANTS AND METALLURGICAL ENTERPRISES EAST KAZAKHSTAN REGION

The relevance of industrial processing of waste from thermal power engineering and mining and metallurgical complex (MMC) enterprises in order to obtain effective concrete is due to the need to obtain building materials with improved characteristics and low cost, on the one hand, and the problem of catastrophic volumes and condition of man-made waste stored in the East Kazakhstan region, - with another. The purpose of the article is to analyze methods for producing effective fine-grained concrete solutions with the addition of waste from thermal power engineering and mining enterprises located in Eastern Kazakhstan. The article describes the features and scope of application of fine-grained concrete mortars. The need, possibilities and prospects for using technogenic waste for the production of building materials, products and structures have been studied. Compositions of fine-grained concrete were selected based on technogenic raw materials - ash and slag waste and metallurgical slag. The study showed that the introduction of fly ash and metallurgical slag into concrete improves the physical and mechanical properties of products with significant savings in cement. The applicability of the studied technogenic raw materials in fine-grained concrete has been proven, resulting in a wide range of applications for the material. The study showed that based on the obtained indicators of strength, frost resistance, abrasion, corrosion resistance, resistance to alternate wetting and drying and other improved characteristics, these concretes can be recommended for the production of small-piece concrete products (curbs, artificial paving stones, paving slabs, side stones, facing slabs, concrete tiles, etc.) and in road construction. The mobility of fine-grained concrete mortar allows it to be used for sealing seams and cracks in monolithic concrete and in the installation of reinforced cement structures, including large ones. A significant environmental effect from the processing of technogenic deposits in the East Kazakhstan region is shown.

EXPERIMENTAL STUDY OF SAMPLES MANUFACTURED FROM CRUSHED POLYMER WASTE ON A 3D PRINTER WITH A SCREW EXTRUDER

The article conducts an experimental study of samples made from crushed polymer waste on a 3D printer with a screw extruder. General information about the experimental study is given. An analysis of literary sources on the study of mechanical properties of products manufactured by FDM technology on 3D printers was carried out. Two 3D printers were chosen for the production of experimental prototypes, one of which prints with filament, the other with granules or crushed polymer waste. The equipment for determining the accuracy of printed samples has been selected. The measuring part of the tearing machine for taking tensile diagrams of polymer samples has been improved. A strain gauge for force measurement and an optical encoder for displacement measurement are installed in it. A digital electronic system for data collection from sensors based on the Arduino Uno microcontroller was developed. Software for experimental data processing was created. The general view of the experimental setup is given. It is proposed to use uniaxial tension to evaluate the mechanical characteristics of the test samples printed on a 3D printer. Current international standards for tensile testing of plastics are described. To determine the mechanical tensile characteristics, samples in the shape of a blade were made from polymer materials ABS and TPU. The parameters for printing test samples made from these materials are set. With the use of the developed installation, the failure diagrams of samples (blades) made of crushed polymer waste and filament of ABS and TPU plastics with different amounts of internal filling were obtained. In the form of tables, the values of the mechanical characteristics of the samples produced by the 3D printing method from ABS and TPU polymers with different internal filling obtained during the uniaxial tensile test are presented. A photo of the places of breakage of ABS plastic blades, taken using a digital camera, is given. An analysis of the structure of the samples was carried out on them. Experimental test samples were made using two 3D printers to determine the accuracy of 3D printing. Measurements were made in different planes of the test cube using a digital electronic caliper. The obtained results were compared with the created model. Ways to improve print accuracy are described.

Carbon Fiber 3D Printing: Technologies and Performance—A Brief Review

Additive manufacturing is evolving in the direction of carbon fiber 3D printing, a technology that combines the versatility of three-dimensional printing with the exceptional properties of carbon fiber. This work aims to provide a brief review of the main methodologies used in carbon fiber 3D printing, focusing particularly on the two most widespread types: continuous fiber printing and short fiber printing. In the context of continuous fiber printing, the process of embedding a continuous carbon fiber into a polymer matrix will be examined, resulting in the achievement of high-performance lightweight structural components. On the other hand, short fiber printing involves the use of short carbon fibers mixed in turn with polymeric materials, with the advantage of having greater ease of processing and obtaining highly performing components with large-scale economic investments that are lower in cost than additive manufacturing using continuous fiber printing. Furthermore, this work will conduct an evaluation of the mechanical properties of products printed using both technologies, focusing on key aspects, such as strength, stiffness, weight, and resistance to mechanical stress. The specific advantages and challenges associated with each printing technique will also be analyzed.

Influence of deformation degree on grains size and borders between them in metal alloys during cold rolling of sheets

The internal structure of metal products was investigated and it was identified that it affects quality and workability of equipment parts. Changes that occur in metal products structure during cold treatment by pressure, which lead to changes in physical and mechanical properties of products, have been analyzed. It was established that grains and borders between them, which determine internal structure of metal products, change their shape and size during cold rolling, depending on percentage reduction value. It is offered to consider grain borders as amorphous layer. Methodology has been developed to study influence of deformation degree during cold rolling to grain size of metal internal structure and intergranular layer volume. Intergranular surface area, its volume and part of surface volume from metal volume were determined. Parameters of internal structure of low-carbon steel were calculated depending on reduction value during cold rolling. According to study results, interconnection between grains size and deformation degree was established; and percentage reduction influence to grain size and borders between them was determined, obtaining a minimum standard grain size with percentage reduction of over 80 %; yield strength and its growth for metal alloy during cold rolling are established, which allows controlling the strength of steel by adjusting the grain size and their junction surface. It is shown that with an increase in deformation degree, yield strength of metal product material increases in hyperbolic dependence, and fraction of amorphous layer and strength properties of low-carbon steel change almost equally in exponential functions. It is revealed that during cold rolling, it is possible to control internal properties of obtained product by adjusting reduction value.

Study on the hot isostatic pressing post-treatment of FDM-3D printed continuous carbon fiber reinforced composites

The use of continuous carbon fiber reinforced composites (CCFRC) in fused deposition modelling (FDM)-3D printing can significantly improve the mechanical properties of products. However, compared with the products of traditional fiber placement technology, the mechanical properties of FDM-3D printed CCFRC have a big gap. In this paper, finite element analysis (FEA) and Tsai-Wu failure criterion were used to simulate the interlaminar shear failure and tensile failure of the model with staggered arranged polyamide 6 (PA6) layers and continuous carbon fiber (CCF) layers. The post-treatment processes of CCFRC were also simulated. The FEA models were FDM-3D printed and hot isostatic pressing (HIP) post-treated with the aim of improving the mechanical properties of the CCFRC. The effects of various HIP parameters including temperature, pressure and post-treatment time on interlaminar shear strength (ILSS) and tensile strength were studied. It was found that the ILSS and tensile strength were increased maximally by 64.47 % and 27.55 % under HIP as compared to the pristine samples. The mechanical properties of CCFRC after HIP treatment can be further improved compared with annealing treatment without pressure. Studying the variations in isostatic pressure and selecting the optimal pressure level to achieve the most effective enhancement can offer a novel approach for post-treatment FDM-3D printing.

Non-contact assessment of porosity in metal 3D printed parts by vibration spectra

Volumetric porosity as a common defect in metal 3D printing (3DP) that can significantly impede the mechanical properties of products. Traditional methods of porosity control (microscopy) and non-destructive testing (computed tomography) usually are not applicable at the production site. In this study, sensitivity of three examined testing modalities based on acoustic methods and vibration analysis to changes in the volumetric porosity of 3DP parts was examined. Test objects were cylindrical specimens made of AlMg powder by 3DP with a gradually dosed porosity from 0.5 to 4.0%. Ultrasonic testing by through transmission showed the best accuracy using ultrasound velocity and pulse intensity parameters. Shifts of resonant frequency and spectral density and appearance of side harmonics were the manifestations of increased porosity using vibration approaches. The method comprising a loudspeaker as a vibration exciter and an optoelectronic device for remote sensing of vibration is the most attractive from the point of view of application to objects of complex geometry.

Microconvection of MHD solarized nanofluid in the presence of double slip and surface suction

Refrigeration systems are becoming more efficient as a result of nanofluids. Cooling and heating process improvements can lead to enhanced industrial efficiency, reduced processing times, energy conservation, and improved heating and cooling processes. A study is being conducted on the effects of magnetohydrodynamics (MHD) in nanofluids by adding double slip and thermal radiation to the governing model. It is numerically simulated using bvp4c code in MATLAB. Analyzing temperature, concentration, and velocity requires the evaluation of multiple parameters. A more uniform distribution of temperatures can be achieved by increasing the Biot number, thermal radiation, and thermophoretic motion parameters. The use of suction is an effective method of controlling the rate of temperature reduction in various manufacturing processes. A product's mechanical properties and overall quality can be enhanced if one is able to control how quickly it cools during the process of melting and condensing raw materials. As a consequence of the emergence of quadratic and linear slip factors, the flow velocity decreases. A distinguishing feature of this research is the use of boundary conditions that are tailored to the geometry that is being investigated.

Оцінка підходів до прогнозування властивостей синтетичного чавуну у ливарному виробництві

An overview of approaches to assessing the dependence of the mechanical properties of products made of synthetic iron smelted in induction crucible furnaces on the content of carbon and the content of silicon in its chemical composition, as well as on the carbon equivalent, the degree of eutecticity, and the ratio of the carbon content to the silicon content is given. The statistical parameters of the percentage distributions of the specified elements in the chemical composition of cast irons with lamellar graphite produced in accordance with the requirements of DSTU 8833-2019 were analyzed. The values ​​of the carbon equivalent of the chemical state of these cast irons and the values ​​of their degree of eutecticity were calculated according to common formulas for determining these indicators using the Monte Carlo method and using a probabilistic approach taking into account the content of each element in the chemical composition of cast iron. It is emphasized that, from a probabilistic point of view, the values ​​of the carbon equivalent and the degree of eutecticity may not coincide in different batches of cast iron, even with the same values ​​of the percentage content of chemical elements in its composition. It is shown that with an increase in the carbon equivalent and the degree of eutecticity, the strength and hardness of cast iron produced in accordance with DSTU 8833-2019 decrease. As the carbon content and carbon equivalent increase, the ratio of carbon content to silicon content decreases. In industrial batches of cast iron brake pads and «Khanin wedge» manufactured in accordance with GOST 30249-97 and GOST 34503-2018, the hardness of these products does not depend on the carbon equivalent due to the small range of the carbon equivalent values. Keywords: foundry products, cast iron, chemical composition, carbon equivalent, ratio of carbon content to silicon content, degree of eutecticity, hardness, strength

Оптимизация выбора схемы 3D-печати функциональных объектов из композиционных материалов

<p>The implementation of priority areas for the development of the Economy of the Russian Federation, the digital transformation of production, the improvement and development of new designs used at domestic enterprises in the aviation and rocket and space industries, energy, mechanical engineering and others, is largely associated with the use of polymer composite materials (CM), which provide optimal physical and mechanical characteristics of structures (functional objects). As reinforcing elements of CM, carbon fibers are widely used, because they have high specific strength. At the same time, the mechanical properties of products significantly depend on the direction of the fibers. One of the promising directions for the manufacture of objects from CM, which makes it possible to create structures of complex shape, is 3D printing technology. The use of 3D printing makes it possible to obtain structures with spatial reinforcement along specified trajectories. This is due to the fact that continuous carbon fiber reinforced polymer composite (CFRT) is used for printing. This allows full control over the location of the fibers during the printing process, which allows you to arrange 100% of the fibers in accordance with the required operating conditions of the object. However, practically unexplored are issues related to the optimization of the process of 3D printing of functional objects from CM by the method CFRT 3D printing in terms of controlling the location of fibers during printing, allowing to take into account the criteria for the destruction of the composite. This work is devoted to this goal, which proposes general approaches to setting and solving the problem of optimizing the selection of a 3D-printing scheme.</p>

Hardness and modulus programmable tuning for silicone 3D printing device and experiment

PurposeThe purpose of this study was to fabricate silicone products that had different hardnesses and moduli, thus partially addressing the limitations of homogeneous materials whose deformation depends on altered structure or dimensions, and to provide new dimensions for the design of silicone soft structures.Design/methodology/approachA soft material three-dimensional printing platform with a dual-channel printing capability was designed and built. Using the material extrusion method, material screening was first performed using single-channel printing, followed by dual-channel-regulated printing experiments on products having different hardness and modulus values.FindingsThe proportion of additives has an effect on the accuracy of the printed product. Material screening revealed that Sylgard 527 and SE 1700 could be printed without additives. The hardness and mechanical properties of products are related to the percentage in their composition of hard and soft materials. The hardness of the products could be adjusted from 26A to 42A and the Young’s modulus from 0.875 to 2.378 Mpa.Originality/valueExisting silicone products molded by casting or printing are mostly composed of a single material, whose uniform hardness and modulus cannot meet the demand for differentiated deformation in the structure. The existing multihardness silicone material printing method has the problems of long material mixing time and slow hardness switching and complicated multi-extrusion head switching. In this study, a simple, low-cost and responsive material extrusion-based hardness programmable preparation method for silicone materials is proposed.

Influence of Carbon Content on the Formation of a Contact Interparticle Surface during Hot Post-Pressing

Introduction. The technology for producing hot-formed powder steel is one of the most energy-intensive in powder metallurgy, which includes a large number of operations. The study of the influence of technological modes on the final properties of the part is an urgent task. Developed by the scientific team under the leadership of Yu. G. Dorofeev at the end of the XX century, the technology of manufacturing hot-formed powder steels is currently one of the main ones in the production of high-density products. However, the use of new materials that improve the mechanical properties of products requires a modern approach to analyzing the quality of interparticle splicing of powder particles. The influence of the following technological factors on the formation of qualitative interparticle splicing was established: the blank density, the granulometric composition of the initial charge, the temperature and holding time of the blank during heating, the ratio of its dimensions, the deformation rate. The study objective is to analyze the effect of a graphite-containing component on the mechanical properties of hot-formed powder alloys due to the formation of high-quality interparticle splicing.Materials and Methods. The work used domestic and foreign powders produced by PAO Severstal and the Swedish company Höganäs with the addition of carbon GC-1 (GOST 4404-78). Hot stamping was carried out on a crank press of the K2232 model with a maximum force of 1600 kN. The heating temperature of the workpieces varied between 800-1200 ºC.Results. As a result of the experiments, the influence of the sintering duration on the mechanical properties of materials was established. The reason for the change in mechanical properties are local inclusions of graphite, which did not have time to homogenize as a result of prolonged sintering. Technological modes of hot stamping for steels have been developed that affect the preservation or destruction of the pre-formed contact interparticle surface.Discussion and Conclusion. The studies have shown that additional hot plastic deformation contributes to the formation of intracrystalline fusion on the entire contact surface. The addition of graphite to the charge improves splicing for alloyed iron powder and practically does not affect the use of alloyed and unalloyed iron powder.

Study of Typical Functional Failure and Mechanical Properties of Non-absorbable Suture Anchor

To study the mechanical properties related to the typical functional failure modes of non-absorbable suture anchor in clinical use, and to support product design, development and verification. By retrieving the database of relevant adverse events, the typical functional failure modes of non-absorbable suture anchor were summarized, and the influencing factors of functional failure were further analyzed by studying the mechanical properties related to functional failure. The publicly available test data was retrieved for verification and provided reference for the researchers. The typical functional failure modes of non-absorbable suture anchor include anchor failure, suture failure, fix loosening, inserter failure, which are related to the mechanical properties of products, such as screw-in torque and break torque of screw-in anchors, insertion force of knock-in anchors, suture strength, pull-out force before and after system fatigue test and elongation of sutures after fatigue test. Enterprises should pay attention to improving the mechanical performance level of products through material, structural design and the suture weaving process to ensure the safety and effectiveness of products.

Personal Perspective on Strain-Induced Polymer Crystallization.

Semicrystalline polymer materials are commonly strong yet tough after processed through fiber spinning, film stretching (or blowing), and plastic molding (or foaming), which are fundamentally related with strain-induced crystallization. This paper provides a personal perspective on thermodynamics and kinetics aspects of strain-induced polymer crystallization, mainly based on the author's recent research experience. The thermodynamic studies include homopolymers, random copolymers, solution polymers, and blend polymers. The kinetic studies cover three sequential crystallization stages, i.e., crystal nucleation, crystal growth, and postgrowth. The thermodynamic driving forces join with the kinetic barriers to determine the crystal nucleation mechanisms and the structure evolution at the molecular level, which yield unique polymer crystal morphologies from lamellar crystals to shish-kebab crystals and eventually fibril crystals. The resulting semicrystalline structures were discussed with their implications for the mechanical properties of products. Some future studies were briefly proposed.