Breaking Strain Research Articles

Effect of the Addition of Oil Palm Mesocarp Fibers on the Physical and Mechanical Properties of a Polyester Matrix Composite

This work focuses on the assessment of oil palm mesocarp fibers as reinforcement in a composite material with an unsaturated polyester matrix. Several volume ratios of OPMF reinforcement (0 to 15%) were used, the fibers being distributed randomly. The resulting composite was characterized on the physical and mechanical aspects. Physically, the true and apparent densities were determined as well as the porosity rate. It appears that the addition of fibers further lightens the composite and increases the porosity. The water absorption rate of the different composites samples was evaluated. The more fibers the composite contains, the higher its water absorption rate. On the mechanical aspect, the bending modulus of elasticity, bending stress at break, and breaking strain were evaluated through a three-point bending test on all combinations. The same parameters were also evaluated for certain combinations by a unidirectional tensile test. It appears from this mechanical characterization that the volume fraction of 5% reinforcement has the highest specific modulus. Impact tests were performed on samples of this combination using several sizes of reinforcing fibers. Impact resistance is enhanced as the size of the inclusion increases. The Halpin-Tsai micromechanical model for randomly distributed short fiber composites was used for the inverse approach determination of the theoretical moduli of the matrix and OPMF, then in a direct approach to determine the elastic modulus of the composite at 7.5% reinforcement.

Twisted graphene fibre based breathable, wettable and washable anti-jamming strain sensor for underwater motion sensing

Wearable electronics have promising applications in human–machine interfaces and Internet of Things. Recent reported wearable sensing techniques are implemented mainly by either encapsulated packaging approaches or deposition of conductive nanomaterials onto flexible textiles. However, such fabrication technologies sacrifice the physical comfort, washability and wettability which are the essential elements to wearables. In this paper, we report a continuous twisted graphene fibre with high tensile strength (369 MPa) and remarkable breaking strain (48.5%), as well as stable electrical and mechanical performances under cyclic washing and chronic wetting. The as-prepared twisted graphene fibre is woven into a pure fabric-based breathable, wettable and washable strain sensor with outstanding sensitivity (gauge factor = 63) to strain while negligible sensitivity upon bend, pressure, temperature and humidity. The strain sensor displays undifferentiated high performance of sensitivity, stability and durability both in air and water, enabling its precise detection of human motions in complex external environment.

The information content of tensile tests of human hair (wet) is limited: Variables mainly cluster in just two principal components

Tensile testing of keratin fibres, such as wool and hair, in the wet state is a well established tool in the academic as well as applied portfolio of mechanical analyses. For the tensile curve of a hair fibre, fourteen material-specific stress-, strain, and work-related variables were identified. Analysing twelve samples of cosmetically untreated hair, we show that the variables show good precision and a satisfactory degree of homogeneity across samples. Correlation analysis shows strong relationships between essentially all variables. Some strong correlations were in fact expected. However, their actual extent is very surprising, including even rather dissimilar variables (e.g., elastic-vs break-modulus). This observation led us to investigate whether variables may be clustered into a number of groups in order to define a set of underlying orthogonal factors, using Factor Analysis. The results show that 87% of data variance can be accounted for by just two factors, which we refer to as ‘stress-’ and ‘strain’- factor, respectively. The tensile properties of untreated hair (wet) are thus well described by just any pair of strong variables from each factor, such as elastic modulus and break strain. We hypothesize that similar principles may also be applicable for treated hair. This type of approach and its implications may also have relevance for other epidermal appendages (nails, claws, horn, etc) or even more generally for other biological composite materials, such as skin, tendon and bone.

Conductive ionogel with underwater adhesion and stability as multimodal sensor for contactless signal propagation and wearable devices

Gathering information and giving feedback on it happen all the time for the human and animals. Soft materials such as hydrogels are often chosen as sensors due to their portability and wearability. However, these materials previously reported have various defects, such as poor underwater adhesion, underwater swelling, unstable underwater conductivity. Herein, a hydrophobic ionogel is prepared by ion-dipole and ion-ion interactions between fluorine-rich poly (ionic liquid) and ionic liquid, and covalent cross-linking. The conductive ionogel shows adjustable mechanical property (fracture strength: 0.24–0.52 MPa, break strain: 210% to 360%), underwater adhesion (693 KPa to plastic), optical transparency (81%, 2 mm), temperature tolerance and suitable conductivity (10−5-10−4 S/cm). Thus, the ionogel is used as s multimodal sensor no matter in the air or in aquatic environment. Based on the mechanism of electron transport path change, the ionogel sensor can recognize different objects entering water, and even different objects touching ice, such as hands, tweezers and aluminum foil, and send messages out of the water by Morse code. Even more, the standing posture and touching between two persons can be recorded by ionogel sensor. And the ionogels can be served as temperature sensor, containing wide operating temperature window (0–80 °C) and high detecting accuracy (0.2 °C). Therefore, the ionogel has vital important applications in non-contact signal propagation and wearable devices.

Grafting alkynyl groups on the surface of nano‐aramid fibers towards flame retardant thermoplastic polyurethane

AbstractIn this work, para‐aramid fibers were dispersed into para‐aramid nanofibers (ANF) by deprotonation process, and then modified by 3‐chloropropyne (PC) via covalent bonding interaction. The resultant nanofiber (ANF‐PC) as a flame retardant was blended with thermoplastic polyurethane (TPU) to obtain fire‐retardant TPU nanocomposites. The addition of 0.250 wt% ANF‐PC reduced the peak heat release rate, total heat release, total smoke release, and peak CO release rate of TPU by 47.7%, 31.5%, 16.4%, and 45.1%, respectively. The char yield of TPU/ANF‐PC0.250 was increased from 7.7% (TPU/ANF0.250) to 13.7%. The flame‐retardant effect of ANF‐PC in TPU composites can be attributed to its carbonization effect in the condensed phase, which increased the char yields and graphitization degree of char residue. In addition, the presence of ANF‐PC increased the tensile strength and breaking strain of TPU by 645% and 578% compared to untreated ANF, due to the improved dispersion state of ANF‐PC.

Enhancement of Wear Resistance on H13 Tool and Die Steels by Trace Nanoparticles

In order to improve the impact toughness and wear resistance of the tool and die steels, this study innovatively prepared strengthened H13 steels with different contents of single-phase TiC and dual-phase TiC + TiB2 through in situ nanoparticle/Al master alloys at room temperature. The microstructure evolution and mechanical properties as well as wear resistance were investigated. Results indicate that the H13 steel with 0.02 wt.% dual-phase TiC + TiB2 nanoparticles has a more uniform and finer microstructure, and the mechanical properties and wear resistance are significantly improved. The yield strength, maximum tensile strength, breaking strain, uniform elongation, product of strength plasticity, and unnotched and U-notched impact toughness of H13 steel with 0.02 wt.% dual-phase TiC + TiB2 are higher than that of H13 steel. In addition, the volume wear rate, maximum scratch depth and width reach 7.1 × 10−11 m3/m, 6050 nm and 90 μm, respectively, which are reduced by 44.5%, 30.1% and 45.5% compared with that of H13 steel. Refining the microstructure and improving impact toughness and wear resistance of H13 tool steel through trace nanoparticles can provide important inspiration for industrial applications.

Preparation and Property of a Three‐Dimensional Nitrogen‐Doped Graphene‐Fe3+/P(AA‐co‐DMA) Hydrogel

AbstractIn this study, a three‐dimensional nitrogen‐doped graphene (3DNG)‐Fe3+/poly(acrylic acid‐co‐N,N‐dimethylacrylamide) (3DNG‐Fe3+/P(AA‐co‐DMA)) hydrogel with strong flexibility and excellent self‐healing property was prepared. The 3DNG‐Fe3+/P(AA‐co‐DMA) hydrogel was characterized by Fourier transform infrared spectrometer (FT‐IR), scanning electron microscope (SEM). The specific surface area and pore size distribution of the 3DNG‐Fe3+/P(AA‐co‐DMA) hydrogel were measured by using Brunauer‐Emmett‐Teller (BET) method. The experimental results demonstrate that when 6 mol% FeCl3 was added, the breaking strain of Fe3+/P(AA‐co‐DMA) hydrogel reaches 1149 %, and the tensile strength reaches 689 kPa. Furthermore, the recovery degree of Fe3+/P(AA‐co‐DMA) hydrogel was almost 100 % after 24 h. The supercapacitors based on 3DNG‐Fe3+/P(AA‐co‐DMA) hydrogel have a specific capacitance value of 231.8 F g−1 at 1 A⋅g−1, and conductivity is 0.053 S⋅cm−1. When the power density is 5 kW kg−1, the energy density of the device is 38.7 Wh kg−1.

Tensile properties of all-polymeric syntactic foam composites: Experimental characterization and mathematical modelling

All-polymer syntactic foams are studied under large strain cyclic and monotonic tensile loading in order to reveal their tensile stress-strain behaviour, recoverability, tensile strength, and elongation at break. The syntactic foam under study here consists of hollow thermoplastic microspheres (HTMs) of two distinct grades (551 and 920), with distributions of mean-wall thicknesses and diameters, embedded inside a polyurethane matrix in various volume fractions. Cyclic loading-unloading curves are recorded, revealing the level of viscoelasticity exhibited by the materials (which becomes a stronger effect with increasing volume fractions of HTMs) and indicating the level of repeatability of loading under large strain. Samples are also subjected to monotonic tensile loading in order to study their elongation at break. Higher volume fractions of HTMs increase the stiffness of the material and whilst it is observed that the materials are highly elastic over a wide range of tensile strains, damage arises at lower levels of strain for more highly filled materials. The HTM syntactic foams thus exhibit lower breaking strains compared to the neat matrix, which is attributed to matrix-microsphere interfacial debonding. Furthermore, by employing optimization techniques, linear elastic properties of the microspheres and an average shell thickness of the 551 grade are inferred by comparing experimental results to predictions from the Generalized Self-Consistent Method, incorporating polydispersity data on the size distribution of the microspheres. These results complement previous work which involved direct experimental measurements of the 920 grade shell thickness. Results also indicate that the characterization of microsphere properties is not critically dependent on access to high resolution microsphere diameter distribution data, provided that an accurate representative mean diameter is known. Finally, the thermal degradation of the samples is studied by using thermogravimetric analysis (TGA) which reveals that HTMs can be added to a polyurethane matrix without significantly affecting the thermal stability of the matrix material.

Molecular Mechanisms Involved in Thermally Induced Gel Formation of Japanese Codling Meat Paste during a Two-Step Heating Procedure

We analyzed changes in the rheological properties of Japanese codling (Physiculus japonicus) meat paste during the following two-step heating procedure: first preheating at 0–70 °C with 5 or 10 °C intervals and subsequent secondary main heating at 85 °C. Changes in the breaking strength and breaking strain rate showed roughly three phases associated with preheating temperatures of 0–25, 30–50, and 55–70 °C. The most prominent change was observed for preheated gels with preheating from 30 to 55 °C, where the myosin polymerization rate was high. The increase in the preheating temperature from 0 to 25 °C was accompanied by a gradual decrease in protein solubilization and a rapid increase in myosin polymerization for preheated gels, suggesting that gel formation occurred even at low preheating temperatures. Dynamic viscoelasticity measurements indicated that structural changes in myosin other than polymerization also participate in gel formation. Moreover, NH4Cl, an inhibitor of transglutaminase, reduced myosin polymerization in meat paste.

An experimental study on compressive properties of high density polyethylene-nano alumina-groundnut shell hybrid composites

In recent years, bio-fibers have become increasingly popular as reinforcements for thermoplastics and thermosets. Research into the use of natural fibers such flax, bamboo, sisal, hemp, and jute as reinforcing elements in the production of various composites has been considerable. Groundnut shell particles and refractory alumina powder were combined with high density polyethylene (HDPE) polymer matrix to create new bio-based composites in this study. The results were promising. Composite boards were synthesized by with HDPE with randomly distributed nano alumina and groundnut shell particles with volume percentages of 95:0:5, 95:2.5:2.5 and 95:5:0. ASTM standards were used to evaluate the compressive, shore hardness and water intake characteristics of the composites. The highest compressive load, compressive strength, increase in area, maximum displacement, displacement at break and compressive strain were analyzed for the specimen having HDPE, nano alumina and groundnut shell particles proportion 95:2.5:2.5. Using HDPE, nano alumina, and groundnut shell particles, Possibly a composite might be produced that could replace wood in many settings.

A colorless, transparent and mechanically robust polyurethane elastomer: synthesis, chemical resistance and adhesive properties

In this work, a transparent, mechanically strong and chemically resistant XDI-PUE adhesive was fabricated, which exhibited a remarkable tensile stress of 21.0 MPa with a break strain of 1608%. XDI-PUE also showed good chemical resistance towards toluene and NaOH aqueous solution.

A review of Thermal, Physical, electrical properties of spider silk and their experimental setups

Spider silk, a natural fibre is found to be stronger than steel and has displayed a huge scope for application. It is essential to understand the thermal, physical, and electrical properties of spider silk for most of its engineering applications. The accumulation of literature over the decades in this field indicates that Spider silk has attracted researchers from various fields such as ecology, zoology, biotechnology, biomechanics, and engineering. Our current review focuses on the recent studies of the thermal, physical, and electrical properties of silk. Effect of super contraction and effect of relative humidity on spider silk has been discussed. Stresses produced in the silk are strongly influenced by the relative humidity in its surroundings. For 50% or greater relative humidity conditions, increase in stress in the silk was observed. Breaking stress and Young's modulus of the silk can increase with the increase in reeling speed. The tension tests could be conducted with low force as low as 10-3N/sec and as high as 1700 N/sec using the TAQ800DMA machine. The silk can have high shear rigidity and torsional stability. Web capture abilities are not affected due to change in temperature but the physical properties of the silk can considerably change. Increase in temperature can cause decrease in stiffness and breaking strain of the silk. The silk is primarily found to behave as an electrical insulator but can conduct electricity when doped with certain materials such as gold.

Mechanical and fatigue behaviour of artificial ligaments (ALs)

A flexible biologic band, ACL is the most injured and ruptured ligament in the knees of humans and animals. This research aims to produce synthetic anterior cruciate ligaments (ACLs) and compare these ligaments' mechanical and fatigue life properties with the natural ACL and commercial synthetic grafts. Artificial ligaments were designed as a core-sheath type structure. The core consisted of straight, parallel yarns and the sheath was a tubular fabric produced by weaving or braiding techniques from polyester or Vectran® yarns. The mechanical properties of the resulting artificial ligaments (AL) were tested before and after the fatigue test and compared to those of the natural ACL and commercial artificial ACLs in the market. Results showed that all ligaments had sufficient tensile strength, and they retained it after the fatigue test. If constructed sheath and core parts were from the same type of yarns, the breaking load of ligaments was higher. The breaking strain and stiffness of woven structures, particularly with Vectran cores, were better than braided ones. After the fatigue test, the breaking strain and stiffness of AL structures with a braided sheath or polyester core were improved. This finding suggests that to prevent the laxity of knee preconditioning of the ligament is necessary if the fabric structure or yarn inherently has high breaking strain and low stiffness. Overall, this study shows that a variety of suitable candidates for replacing ruptured anterior cruciate ligaments could be developed by carefully combining the fatigue-resistant yarns with leno, narrow, and braided structures.

A novel biodegradable poly(propylene carbonate) with enhanced thermal and mechanical properties by incorporating tannic acid

AbstractIt is a challenge to simultaneously enhance the thermo‐oxidative stability, mechanical properties and biodegradability of biodegradable polymer. In this work, by incorporating tannin acid, a natural compound with polyphenol hydroxyl, a biodegradable poly(propylene carbonate) (PPC) with improved thermo‐oxidative stability and biodegradability was successfully prepared. Besides, due to the existence of plentiful hydrogen bond between PPC and tannic acid (TA), the composite exhibits an obviously improved Young's modulus and yield strength while retaining a high break strain (>350%). The improved comprehensive properties should be ascribed to the abundant polyphenol hydroxyl in TA, which can consume oxygen, enhance the hydrophilia of PPC/TA composites and constructing plentiful hydrogen bond with PPC. We envision that this work offers a facile route to prepare PPC with high thermo‐oxidative stability, mechanical properties, and biodegradability, and will promote the practical use of PPC.

Preparation, characterization, and gel characteristics of nanoemulsions stabilized with dextran-conjugated clam Meretrix meretrix linnaeus protein isolate

In this study, the stability and flavor characteristics of nanoemulsions prepared with dextran-conjugated Meretrix meretrix clam protein isolate were studied by characterizing particle size, polydispersity index, zeta potential, turbidity, microstructure, e-tongue, e-nose and HS-GC-IMS. Compared with the NCPI (CPI nanoemulsions) and NCPI-Dex Mix (CPI-Dex Mix nanoemulsions), the NCPI-Dex Con (CPI-Dex Con nanoemulsions) has better stability and flavor. The breaking strength and breaking strain of clam sausages were significantly (P > 0.05) affected by the addition of NCPI-Dex Con. The gel strength with 8% NCPI-Dex Con was the highest (5122.08 g‧mm), a 51.07% increase compared with the control group (3390.58 g‧mm). The clam sausages supplemented with the 8% NCPI-Dex Con had the highest sensory score, with the densest and the most uniform gel structure. Therefore, CPI-Dex Con stabilized nanoemulsions could effectively improve the gel property and flavor of the clam sausages.

Mechanically Robust Flexible Multilayer Aramid Nanofibers and MXene Film for High-Performance Electromagnetic Interference Shielding and Thermal Insulation.

In order to overcome the various defects caused by the limitations of solid metal as a shielding material, the development of electromagnetic shielding materials with flexibility and excellent mechanical properties is of great significance for the next generation of intelligent electronic devices. Here, the aramid nanofiber/Ti3C2Tx MXene (ANF/MXene) composite films with multilayer structure were successfully prepared through a simple alternate vacuum-assisted filtration (AVAF) process. With the intervention of the ANF layer, the multilayer-structure film exhibits excellent mechanical properties. The ANF2/MXene1 composite film exhibits a tensile strength of 177.7 MPa and a breaking strain of 12.6%. In addition, the ANF5/MXene4 composite film with a thickness of only 30 μm exhibits an electromagnetic interference (EMI) shielding efficiency of 37.5 dB and a high EMI-specific shielding effectiveness value accounting for thickness (SSE/t) of 4718 dB·cm2 g−1. Moreover, the composite film was excellent in heat-insulation performance and in avoiding light-to-heat conversion. No burning sensation was produced on the surface of the film with a thickness of only 100 μm at a high temperature of 130 °C. Furthermore, the surface of the film was only mild when touched under simulated sunlight. Therefore, our multilayer-structure film has potential significance in practical applications such as next-generation smart electronic equipment, communications, and military applications.

PH-Responsive and degradable polyurethane film with good tensile properties for drug delivery in vitro

In this paper, we synthesized a new type of pH-responsive block polyurethane (PMCU) through the condensation polymerization of N-methyldiethanolamine (MDEA), poly(ε-caprolactone) and 4,4′-dicyclohexylmethane diisocyanate. The chemical structure of the PMCU were characterized, and the influence of MDEA content on the physicochemical properties of the casted PMCU films were studied detailly. The tensile test demonstrated the good tensile properties of the PMCU films with the breaking strain of 983–425% and the ultimate strength of 11.7–31.2 MPa. The tertiary amine groups and polyester segments endowed the material with pH sensitivity and hydrolytic degradability, respectively. The pH responsiveness of the films was confirmed from the enhanced equilibrium swelling ratio (ESR) with decreasing pH value of the medium, and the ESR in acidic condition (pH 1.5) was much higher than that in neutral (pH 7.0) and basic (pH 12.0) conditions. The studies of drug sustained-release in vitro at different pH indicated a pH-dependent release efficiency, which was closely related with the ESR and almost unaffected by the slow hydrolytic degradation. In addition, the cytotoxicity assay showed that the PMCU had good cytocompatibility to L929 cells. This study showed that pH-responsive promising platform for targeted drug delivery in the biomedical areas.

Dynamic Nanoconfinement Enabled Highly Stretchable and Supratough Polymeric Materials with Desirable Healability and Biocompatibility.

Lightweight polymeric materials are highly attractive platforms for many potential industrial applications in aerospace, soft robots, and biological engineering fields. For these real-world applications, it is vital for them to exhibit a desirable combination of great toughness, large ductility, and high strength together with desired healability and biocompatibility. However, existing material design strategies usually fail to achieve such a performance portfolio owing to their different and even mutually exclusive governing mechanisms. To overcome these hurdles, herein, for the first time a dynamic hydrogen-bonded nanoconfinement concept is proposed, and the design of highly stretchable and supratough biocompatible poly(vinyl alcohol) (PVA) with well-dispersed dynamic nanoconfinement phases induced by hydrogen-bond (H-bond) crosslinking is demonstrated. Because of H-bond crosslinking and dynamic nanoconfinement, the as-prepared PVA nanocomposite film exhibits a world-record toughness of 425± 31MJ m-3 in combination with a tensile strength of 98MPa and a large break strain of 550%, representing the best of its kind and even outperforming most natural and artificial materials. In addition, the final polymer exhibits a good self-healing ability and biocompatibility. This work affords new opportunities for creating mechanically robust, healable, and biocompatible polymeric materials, which hold great promise for applications, such as soft robots and artificial ligaments.

Effect of Crosslinkers on Optical and Mechanical Behavior of Chiral Nematic Liquid Crystal Elastomers.

Chiral nematic (N*) liquid crystal elastomers (LCEs) are suitable for fabricating stimuli-responsive materials. As crosslinkers considerably affect the N*LCE network, we investigated the effects of crosslinking units on the physical properties of N*LCEs. The N*LCEs were synthesized with different types of crosslinkers, and the relationship between the N*LC polymeric system and the crosslinking unit was investigated. The N*LCEs emit color by selective reflection, in which the color changes in response to mechanical deformation. The LC-type crosslinker decreases the helical twisting power of the N*LCE by increasing the total molar ratio of the mesogenic compound. The N*LCE exhibits mechano-responsive color changes by coupling the N*LC orientation and the polymer network, where the N*LCEs exhibit different degrees of pitch variation depending on the crosslinker. Moreover, the LC-type crosslinker increases the Young’s modulus of N*LCEs, and the long methylene chains increase the breaking strain. An analysis of experimental results verified the effect of the crosslinkers, providing a design rationale for N*LCE materials in mechano-optical sensor applications.

Bioinspired, Strong, and Tough Nanostructured Poly(vinyl alcohol)/Inositol Composites: How Hydrogen-Bond Cross-Linking Works?

Spider silk-inspired hydrogen-bond (H-bond) cross-linking has recently been shown to enable polymers, e.g., poly(vinyl alcohol) (PVA), to achieve high strength in combination with large ductility and great toughness by adding small H-bond cross-linkers. Unfortunately, the correlation of H-bond cross-linking to the microstructure and mechanical performances of the resultant polymers remains unclear. Herein, we prepare strong and tough nanostructured PVA composites with inositol (IN) molecules as cross-linkers. The addition of 1.0 wt % of IN increases the yield strength (σy) of PVA up to 148 MPa (by ∼31%), in combination with appreciable increases in the break strain (by 250%) and toughness (by 3.6-fold) because of dynamic physical cross-linking and crystalline grain refinement. We show that there exists a close but simple correlation between the H-bond cross-linking density (ne) and σy, the chain movement (e.g., glass transition temperature (Tg), relaxation activation energy (Ea)) and the crystalline grain size (L), namely, σy ∝ ne, Tg, Ea, and 1/L. This work casts light on the governing effect of H-bonding cross-linking on the microstructure and mechanical properties of PVA and unveils its correlation to mechanical properties, chain dynamics, and crystallization for the first time. These exciting findings open up many new opportunities for creating strong, tough, and ductile polymeric materials.