Specific Toughness Research Articles

Revealing the role of multi-scale fibers in the compressive behavior of a novel ultra-high performance concrete subjected to elevated temperatures

Ultra-high performance concrete has received widespread attention due to its excellent performance. However, the mechanical properties can seriously degrade at high temperatures. To improve the thermal resistance, cenospheres and multi-scale fibers such as polyethylene fiber, steel fiber, calcium sulfate whisker, carbon fiber, and carbon nanotubes, are added to develop a type of ultra-high performance (MSFUHPC) in this work. The effects of cenospheres and multi-scale fibers on peak strain, compressive strength, Young's modulus, specific toughness and stress-strain curve are studied at various temperatures (25 °C, 200 °C, 400 °C, 600 °C, and 800 °C) through uniaxial compression tests. Additionally, mercury intrusion porosimetry tests and scanning electron microscope tests are used to discuss the effect of cenospheres and multi-scale fibers on the microstructure. The results demonstrate that both CE and multi-scale fiber can reduce the thermal damage of MSFUHPC. The multi-scale fiber can significantly improve the mechanical strength of the material, while CE has the opposite effect. It is found that microscale and nanoscale fibers have negligible effect on the specific toughness, while the effect of CE on specific toughness depends on the temperature and its content. Results show that the incorporation of multi-scale fibers effectively decreases the fraction of large pores while simultaneously refining the pore structure and enhancing the proportion of gel pores. Furthermore, the stress-strain relationship of MSFUHPC is established by considering the influence of multi-scale fiber content and high temperature.

Mitigating the brittle behavior of compression cast concrete using polypropylene fibers

Compression casting enhances mechanical properties, durability, and microstructure of concrete while reducing cement usage and carbon emissions. However, its brittleness restricts its widespread use. This study aims to mitigate the brittleness of compression cast concrete (CCC) through fiber reinforcement. Eleven concrete mixes with varied volumetric ratios (0, 0.05, 0.1, 0.15, 0.2, and 2 %) and aspect ratios (250, 313, and 396) of polypropylene fibers were prepared. Both compressed and uncompressed specimens were analyzed for compressive stress-strain behavior, compressive strength, modulus of elasticity, toughness, specific toughness, and microstructure. Results show that CCC specimens have steeper and shorter descending segments on their compressive stress-strain curves than uncompressed concrete, indicating brittleness. Adding polypropylene fibers significantly reduces this brittleness by enhancing the post-peak compressive stress-strain behavior of CCC. Fiber reinforced CCC specimens exhibit significant enhancements in compressive strength, modulus of elasticity, and toughness (up to 68 %, 34 %, and 38 % respectively) compared to uncompressed plain concrete. Mercury intrusion porosimetry, scanning electron microscopy, and backscattered electron imaging confirm that compression casting strengthens the interfacial transition zone of both plain and fiber reinforced CCC. Proposed empirical models accurately forecast the modulus of elasticity, compressive strength, and peak compression strain for both types of CCC. Comparisons with existing models show that Nematzadeh and GB50010–2010 models effectively predict the ascending part of the compressive stress-strain curves of plain and fiber reinforced CCC. These findings affirm that polypropylene fibers effectively reduce the brittleness of CCC, promoting its practical application.

Compression behavior of lightweight corrugated composite Sandwich panels with smart facesheets reinforced by shape memory alloy wires: an experimental study

AbstractThis paper presents an experimental examination of the compression demeanor of lightweight corrugated core composite (CCC) sandwich panel and corrugated core smart composites (CCSC) sandwich panels subjected to quasi‐static edgewise compression loading. The existence of shape memory alloy (SMA) wires and pre‐strain percentages of SMA are the indicators studied in this article. The fabrication procedure presented and the appraisement of the mechanical properties of the CCC and CCSC sandwich panels are expressed. The core geometry of samples is trapezoid corrugated made of aluminum. The facesheets are four layers of woven glass fiber/ epoxy laminated composite. For evaluation of the efficacy of the presence of SMA wires on mechanical specifications of sandwich panels, three SMA wires with various pre‐strain percentages (0%, 3%, and 6%) are embedded in each composite facesheet. Mechanical properties of all types of CCC and CCSC sandwich panels such as maximum force, critical damage force, specific strength, absorb energy, specific toughness, Young's modulus, and specific stiffness were evaluated. Results showed that the CCC sandwich panel has higher mechanical specifications than the CCSC sandwich panels with 0% and 3% pre‐strain. Also, increasing pre‐strained SMA wires improves all mechanical parameters of CCSC sandwich panels. CCSC sandwich panel with 6% pre‐strain has the highest compression properties than other sandwich panels. Maximum Force, Critical Damage Force, Specific Strength, Absorbed Energy, Specific Toughness, Young's Modulus, and Specific Stiffness of CCSC sandwich panel with 6% pre‐strain are 14.73 kN, 13.6 kN, 9.55 MPa/g, 26.61 kJ, 0.346 MJ/m3g, 4395 MPa and 0.61 kN/mm g, respectively.Highlights Lightweight CCC sandwich panel and CCSC sandwich panel manufactured. Compression behavior of CCC sandwich panel and CCSC sandwich panel evaluated. Pre‐strained SMA wires improves energy absorption of CCSC sandwich panels. Higher specific toughness was obtained with 6% pre‐strain SMA. Presence of SMA wires with no pre‐strain cannot improve the specific strength.

Incorporation of Finasteride-Loaded Microspheres into Personalized Microneedle for Sustained Transdermal Delivery.

Although finasteride (FNS) tablets are considered the most effective drug for the treatment of androgenetic alopecia (AGA), their clinical applications are limited due to the associated side effects including decreased libido, breast enlargement, and liver dysfunction. In this study, we have developed a personalized microneedle (PMN) with a double-layer structure that incorporates FNS-loaded microspheres (MPs) to accommodate irregular skin surfaces. This design enables the sustained release of FNS, thereby reducing potential side effects. The needle body was synthesized with high-strength hyaluronic acid (HA) as the base material substrate. The backing layer utilized methacrylate gelatin (GelMA) with specific toughness, enabling PMN to penetrate the skin while adapting to various skin environments. The length of PMN needles (10 × 10) was approximately 600 μm, with the bottom of the needles measuring about 330 μm × 330 μm. The distance between adjacent tips was around 600 μm, allowing the drug to penetrate the stratum corneum of the skin. The results of the drug release investigation indicated the sustained and regulated release of FNS from PMN, as compared to that of pure FNS and FNS-MPs. Further, the cytotoxicity assay demonstrates that PMS displays good cytocompatibility. Altogether, this mode of administration has immense potential for the development of delivery of other drugs, as well as in the medical field.

Covalently cross-linked ultrastrong SiO2-loaded polyvinyl alcohol fibers via microfluidic spinning.

Polyvinyl alcohol (PVA) fiber materials have gained immense recognition due to their good biocompatibility and wide applications. However, methods allowing the synergistic enhancement of mechanical strength and toughness of PVA fibers still remain a key challenge. To this end, we developed covalently cross-linked ultrastrong SiO2-loaded polyvinyl alcohol fibers via a microfluidic spinning chemistry strategy. The thermal stretching and annealing processes not only promote the ordered arrangement of molecules, but also facilitate the ring opening reaction and increase crystallinity. Thus, the resulting fiber has a high tensile strength of 866 MPa, a specific toughness of 288 J g-1 and a tensile strain of 80%. This work provides a covalent cross-linking reinforcement method to prepare ultrastrong composite fibers assisted by microfluidic spinning chemistry and thermal stretching, which would lead to the fabrication of mechanically strong fiber materials through a simple pathway.

Ionic Liquid Directed Spinning of Cellulose Aerogel Fibers with Superb Toughness for Weaved Thermal Insulation and Transient Impact Protection.

Aerogel fibers, combining the nanoporous characteristics of aerogels with the slenderness of fibers, have emerged as a rising star in nanoscale materials science. However, endowing nanoporous aerogel fibers with good strength and high toughness remains elusive due to their high porosity and fragile mechanics. To address this challenge, this paper reports supertough aerogel fibers (SAFs) initially started from ionic-liquid-dissociated cellulose via wet-spinning and supercritical drying in sequence. The supertough nanoporous aerogel fibers assembled with cellulose nanofibers exhibit a high specific surface area (372 m2/g), good mechanical strength (30 MPa), and large elongation (107%). Benefiting from their high strength and elongation, the resultant cellulose nanoporous aerogel fibers show ultrahigh toughness up to 21.85 MJ/m3, much outperforming the known aerogel materials in the literature. Moreover, the toughness of this nanoporous aerogel fiber is 7.4 times higher than that of human knee ligaments, and its specific toughness is comparable to that of commonly used solid polyester fibers. In addition, we also verified the weavability, desirable thermal insulation performance, and supertoughness to resist the transient impact of SAFs. The long-sought strategy to simultaneously resolve the strength and toughness of nanoporous aerogel fibers, in combination with the biodegradable nature of the cellulose, provides multifaceted opportunities for broad potential applications, including lightweight wearable textiles and beyond.

Ultrafast volumetric assembly of layered nanocomposites at dynamic gelation interface

Biomimetic learning has boosted the development of layered nanocomposites with superior mechanical properties, fast ion conduction, high barrier capacities, and high conductivities, resulting in numerous practical applications in artificial structural materials, energy storage, filtration, and electromagnetic shielding. These outstanding properties arise from the highly oriented layered structure. Convenient fabrication and complex shapes are required for practical applications. However, conventional strategies, including ice templating, vacuum filtration, and electromagnetic induction, are constrained by time-consuming fabrication and sample shapes, restricting their extension to large-scale applications. Here, we present a facile, universal, and scalable strategy for fabricating layered nanocomposites using ion diffusion-induced directional gelation. This ultrafast volumetric production, including controllable thickness growth with no size restriction, results from continuous gelation and convenient post-processing, whose fabrication rate is 21.7 times that of ice templating, 13.2 times that of vacuum filtration, and 3.1 times that of electromagnetic induction. Furthermore, layered alumina/epoxy nanocomposites were prepared with superior specific strength (2.9 MPa m1/2/(Kg/m3)) and specific toughness (96.2 MPa/(Kg/m3)), demonstrating the validity of our strategy for layered structures. Moreover, our approach can be extended to other material systems and arbitrary shapes for multifunctional applications in wearable devices, sensors, and anti-corrosion coatings.

Experimental study on compression failure characteristics of basalt fiber-reinforced lightweight aggregate concrete: Influences of strain rate and structural size

This paper presents systematic experimental investigations on the combined influences of loading strain rate and structural size on uniaxial-compression failure characteristics of LAC and basalt fiber-reinforced lightweight aggregate concrete (BFLAC), in terms of workability, failure morphology, deformation curve, failure strength, elastic modulus and energy absorption, with a special focus on the size-dependence of strain rate effect. Results indicate that the uniaxial-compression strength, elastic modulus, compression toughness as well as specific toughness are increased when the basalt fibers with 0.3% volume content is added in LAC, which can be ascribed to the synergistic effect of three working modes of basalt fibers in restricting the crack propagation and fracture failure. As the strain rate increases, specimens with larger size perform a stronger strain rate effect, resulting in that the influence of structural size on uniaxial-compression failures is weakened. The addition of basalt fibers can also weaken the size-dependence on uniaxial-compression strength, compression toughness and specific toughness, which contributes to the promotion and application of basalt fibers in LAC, especially for large-scale engineering structures. The dynamic increase factor (DIF) empirical formulas of LAC and BFLAC with various structural sizes have been obtained, which can provide a reasonable reference for structure safety design and numerical computation of LAC and BFLAC.

AI-assisted Design, 3d Printing, and Evaluation of Architecture Polymer-concrete Composites (APCC) With High Specific Flexural Strength and High Specific Toughness

AI-assisted Design, 3d Printing, and Evaluation of Architecture Polymer-concrete Composites (APCC) With High Specific Flexural Strength and High Specific Toughness

Experimental investigation on static compressive toughness of steel fiber rubber concrete

Abstract Recycled rubber particles can be produced by using waste tires. Adding recycled rubber particles to concrete can form rubber concrete (RC). RC can not only reduce the amount of natural sand and reduce the cost of concrete but also improve the static compressive toughness of concrete. Adding steel fiber into RC can improve the strength of concrete. In order to study the compressive toughness of steel fiber rubber concrete (SFRC), rubber particles washed with NaOH are added to steel fiber reinforced concrete. This can enhance the bonding performance between the recycled rubber particles and concrete. The volume ratio of recycled rubber is 5, 10, and 15%. Prismatic and cubic test blocks were prepared and their compressive tests were carried out. The results show that the stress interaction between the rubber particles and steel fiber in concrete significantly improves the compressive strength, elastic modulus, and stress–strain relationship of concrete. The compressive toughness and ductility of concrete are improved. When the content of rubber particles is 15–20%, the compressive toughness of SFRC is improved most obviously. Through experiments, the toughness index and specific toughness of rubber steel fiber reinforced concrete are calculated, which explores a new way and method for studying the compressive toughness of similar recycled material concrete.

Effects of nano-SiO2 modification on rubberised mortar and concrete with recycled coarse aggregates

Abstract With the recent acceleration of industrialisation and urbanisation, increasing quantities of demolished construction waste and waste tyres are being produced. The production of recycled coarse aggregate (RCA) and rubber particles from this waste, for use as partial or full replacements of normal aggregate in cement concrete, is attracting attention as a solution to the problem of solid waste management. However, the greater incidence of defects in RCA and rubber particles than in normal aggregate limits their application in construction industries. This study evaluated an economic and environmental approach to optimise the performance of rubberised concrete with RCA. Two types of nanomaterials, nano-SiO2 (NS) solution and NS sol–gel, were used to pretreat RCA and rubber. The effect of the treatment time on the physical properties of the RCA was tested, and the mechanical properties of the rubberised mortar prepared with pretreated rubber were investigated. In addition, a compression test for the rubberised recycled aggregate concrete (RRAC) was designed using the Taguchi method. The effects of four factors (water–cement ratio, rubber content, rubber size, and aggregate treatment) on the stress–strain curve, compressive strength, elastic modulus, specific toughness, and failure patterns of RRAC were also analysed. The results showed that the NS-treated RCA exhibited lower water absorption rate and better mechanical properties. Moreover, the NS-modified rubber enhanced the compressive and flexural strengths of the rubberised mortar by 35 and 17%, respectively. Interestingly, it was found that simultaneous treatment of both RCA and rubber could negatively affect RRAC. Scanning electron microscopy indicated that NS improved the interfacial transition zone separating RCA and rubber from the cement matrix, whereas the pretreated RCA tended to bond with the pretreated rubber in RRAC.

Mechanical response of shape-recovering metamaterial structures fabricated by additive manufacturing

Three different metamaterial structures were fabricated using stereolithography 3D printing and a shape recovering material. Mechanical properties and recovery efficiency were assessed after compression testing. All three structures exhibited similar initial specific compressive moduli, while the highest specific toughness was observed for the stretch-dominated structure. The three metamaterial structures were re-tested after shape recovery. Significant strengthening was observed for all structures, with the bend-stretch-dominated structure strengthening to the highest degree. This strengthening phenomenon was characterized as strain hardening. It was found that the strengthening is highly geometry dependent. The geometry with stretch-dominated behavior exhibited the highest mechanical properties after a second test was performed. Improvements in specific toughness of up to 67% were observed after the second compressive test.

Ecological and evolutionary distances from neighbouring plants do not influence leaf herbivory by chewing insects in a Neotropical savanna

ABSTRACT Background Coexisting plant species frequently exhibit marked differences in leaf damage caused by chewing insects. Such variation in leaf herbivory has often been attributed to interspecific differences in leaf defensive traits, leaf nutritional quality and leaf abundance. Aims We aimed to investigate the hypothesis that plants surrounded by more similar neighbours tend to exhibit higher levels of herbivory than plants surrounded by less similar neighbours. Methods We sampled 27 tree and shrub species in 49 plots of 10 m2 located in a Neotropical savanna. For each of the 815 plants sampled, we quantified leaf damage, specific leaf area, leaf toughness, height, and conspecific abundance. We analysed the relationship between herbivory levels and plant traits comparing each individual with its neighbouring plants. The effect of phylogenetic similarity was addressed using the mean phylogenetic distance between a focal plant individual and its neighbours (i.e., the phylogenetic isolation). Results Leaf herbivory damage ranged from zero to 29.6%. We found that phylogenetic isolation, specific leaf area, plant height, and plant abundance were not related to differences in leaf herbivory at the individual level in a neighbourhood. Conclusions Our findings show that leaf herbivory damage of individual plants was not consistently influenced either by phylogenetic or by trait similarity with neighbours.

Axial Stress-Strain Performance of Recycled Aggregate Concrete Reinforced with Macro-Polypropylene Fibres

The addition of macro-polypropylene fibres improves the stress-strain performance of natural aggregate concrete (NAC). However, limited studies focus on the stress-strain performance of macro-polypropylene fibre-reinforced recycled aggregate concrete (RAC). Considering the variability of coarse recycled aggregates (CRA), more studies are needed to investigate the stress-strain performance of macro-polypropylene fibre-reinforced RAC. In this study, a new type of 48 mm long BarChip macro-polypropylene fibre with a continuously embossed surface texture is used to produce BarChip fibre-reinforced NAC (BFNAC) and RAC (BFRAC). The stress-strain performance of BFNAC and BFRAC is studied for varying dosages of BarChip fibres. Results show that the increase in energy dissipation capacity (i.e., area under the curve), peak stress, and peak strain of samples is observed with an increase in fibre dosage, indicating the positive effect of fibre addition on the stress-strain performance of concrete. The strength enhancement due to the addition of fibres is higher for BFRAC samples than BFNAC samples. The reduction in peak stress, ultimate strain, toughness and specific toughness of concrete samples due to the utilisation of CRA also reduces with the addition of fibres. Hence, the negative effect of CRA on the properties of concrete samples can be minimised by adding BarChip macro-polypropylene fibres. The applicability of the stress-strain model previously developed for macro-synthetic and steel fibre-reinforced NAC and RAC to BFNAC and BFRAC is also examined.

A comparative study of nano-fillers to improve toughness and modulus of polymer-derived ceramics

Brittleness is a major limitation of polymer-derived ceramics (PDCs). Different concentrations of three nanofillers (carbon nanotubes, Si3N4 and Al2O3 nanoparticles) were evaluated to improve both toughness and modulus of a commercial polysilazane (PSZ) PDC. The PSZs were thermally cross-linked and pyrolyzed under isostatic pressure in nitrogen. A combination of mechanical, chemical, density, and microscopy characterizations was used to determine the effects of these fillers. Si3N4 and Al2O3 nanoparticles (that were found to be active fillers) were more effective than nanotubes and improved the elastic modulus, hardness, and fracture toughness (JIC) of the PDC by ~ 1.5 ×, ~ 3 ×, and ~ 2.5 ×, respectively. Nanotubes were also effective in maintaining the integrity of the samples during pyrolysis. The modulus and hardness of PDCs correlated positively with their apparent density; this can provide a fast way to assess future PDCs. The improvement in fracture toughness was attributed to crack deflection and bridging observed in the micro-indentation cracks in the modified PDCs. The specific toughness of the modified PDCs was 4 × higher than that of high-purity alumina, and its specific modulus reached that of commercially available technical ceramics. These PDCs can also easily take different shapes and therefore are of interest in protective armor, propulsion, thermal protection, device packaging and biomaterial systems.

Experimental and analytical study of hybrid fiber reinforced concrete prepared with basalt fiber under high temperature

SummaryThe usage of mineral basalt fibers is a relatively novel and popular topic nowadays due to its abundant availability, low cost, and higher temperature resistance. In addition, the establishment of analytical models is beneficial because the experimental work is more time‐consuming and expensive. Therefore, in this study, the inorganic mineral basalt fibers with different length and content in hybrid fiber concrete composite are investigated to assess its suitability at room temperature and under high temperature. In addition, a new analytical model for stress‐stain curve of hybrid fiber concrete composite is developed and compared with the models in previous studies. The microstructure examination is also conducted after exposure to high temperature to explore the fiber morphology and interaction with matrix. The substantial improvement was indicated by addition of basalt fiber in hybrid fiber concrete for stress‐strain response, peak stress, elastic modulus, peak strain, ultimate stain, toughness, and specific toughness at room temperature and at 850°C. It was revealed that the basalt fiber had demonstrated overall good appropriateness in the hybrid fiber concrete composite for all the compressive properties. Moreover, the proposed analytical model could be useful for prediction of analytical behavior from experimental data under high temperature for the research and design purposes.

Nacreous aramid-mica bulk materials with excellent mechanical properties and environmental stability.

SummaryLow density, high strength and toughness, together with good environmental stability are always desirable but hardly to achieve simultaneously for man-made structural materials. Replicating the design motifs of natural nacre clearly provides one promising route to obtain such kind of materials, but fundamental challenges remain. Herein, by choosing aramid nanofibers and mica microplatelets as building blocks, we produce a nacreous aramid-mica bulk material with a favorable combination of low density (∼1.7 g cm−3), high strength (∼387 MPa) and toughness (∼14.3 MPa m1/2), and impressive mechanical stability in some harsh environments, including acid/alkali solutions, strong ultraviolet radiation, boiling water, and liquid nitrogen, standing out from previously reported biomimetic bulk composites. Moreover, the obtained material outperforms other bulk nacre-mimetics and most engineering structural materials in terms of its specific strength (227 MPa/[Mg m−3]) and specific toughness (8.4 MPa m1/2/[Mg m−3]), making it a new promising engineering structural material for different technical fields.

Mechanical Behavior of Steel Fiber-Reinforced Lightweight Concrete Exposed to High Temperatures

The mechanical characteristics of steel fiber-reinforced lightweight concrete (SFLWC) under high temperatures are studied in this paper. Different concrete matrices, including all-lightweight concrete (ALWC) and semi-lightweight concrete (SLWC), and different steel fibers with hooked ends and crimped shapes are considered as objects. In addition, normal-weight limestone aggregates concrete (NWC), no-fiber ALWC, and SLWC were tested after high-temperature treatment as a control group. The temperature effects on the splitting tensile strength, ultrasonic pulse velocity, compressive stress–strain curve, elastic module, peak strain, and axial compressive strength of the SFLWC were investigated. The results showed that, with increasing exposure temperature, both the axial compressive strength and the elastic modulus decreased, while the axial peak strain has a certain increase, and hence the stress–strain curves were gradually flattened. The toughness of all the concretes increased first and then reduced with increasing temperature, while the specific toughness of all the concretes increased with the increase in temperature. Compared with NWC and SLWC, ALWC had a better capacity to resist high temperatures, especially temperatures > 400 °C. Adding steel fibers can improve the capacity of energy absorption, specific toughness, and residual splitting tensile strength of lightweight concrete (LWC) before and after it is exposed to high temperatures. Based on a regression analysis, a segmented constitutive equation for LWC and SFLWC under uniaxial compression was derived from fitting the experimental findings, and the fitting curve agrees well with the test results.

Crack propagation and toughening mechanisms of bio-inspired artificial spicules fabricated by additive manufacturing technique

In this study, for the first time, we produced synthetic spicule-inspired structures (SISs) by 3D printing technology to improve both strength and toughness of brittle rigid resin. The SISs with 0.375 mm cylinder wall thickness without cores showed an improvement of 21%, 1450%, 6000% and 68% in flexural strength, strain, specific toughness and buckling stress (compared to the control samples), respectively. The Shear test results showed that SISs, provide a structure with better dispersing stress. Changing the architecture of solid rods to spiculic structures led to stopping and deflecting the crack path, and subsequently prevented catastrophic failure in these structures. Therefore, SISs can offer a novel and promising approach to increase the strength and flexibility of these brittle materials.

(Invited) 3D Printing of Soft-Matter Mono Pump in Infant Ventricular Assist Device (VAD) for Blood Pumping

We want to develop a soft-matter Mono pump for infant Ventricular Assist Device (VAD). In this research, we have developed the Mono pump, which is made of soft materials and hard materials to study the effect of applying the soft materials to the Mono pump. The stator of the 3D printed Mono pump was made with biocompatible soft materials called Inter Cross-linking Network (ICN) gels. We believe that ICN gels have not only specific toughness and low friction but also excellent biocompatibility that can prevent blood cell trauma and the transplant rejection. Moreover, the rotor is made of hard materials using commercial resin or filament based 3D printers, (Form 2 and Flashforge Creator). Finally, we will compare the practical and theoretical displacement from the flow rate measurement to implement the best performance of the Mono pump in practical use. Figure 1