Puncture Energy Research Articles

The Use of Machine Learning to Assess the Impact of the Ozonation Process on Selected Mechanical Properties of Japanese Quince Fruits

In this study, selected mechanical properties of fruits of six varieties of Japanese quince (Chaenomeles japonica) were investigated. The influence of their storage time and the applied ozone at a concentration of 10 ppm for 15 and 30 min on water content, skin and flesh puncture force, deformation to puncture and puncture energy was determined. After 60 days of storage, the fruits of the tested varieties showed a decrease in the average water content from 97.94% to 94.39%. No influence of the ozonation process on the change in water content in the fruits was noted. The tests showed a significant influence of ozonation and storage time on the increase in the punch puncture force of the skin and flesh, deformation and puncture energy of the fruits. In order to establish the relationship between storage conditions for various varieties and selected mechanical parameters, a novel machine learning method was employed. The best model accuracy was achieved for energy, with a MAPE of 10% and a coefficient of correlation (R) of 0.92 for the test data set. The best metamodels for force and deformation produced slightly higher MAPE (12% and 17%, respectively) and R of 0.72 and 0.88.

Quasi-static and dynamic stab behavior and damage mechanisms of the spiral/laminated structure of CFRP

Stab resistance depends on the material’s strength and stiffness. Puncture energy is absorbed mainly through fracture and friction in the damaged area. To reduce stress concentrations and diffuse impact energy, this paper proposes a spiral CFRP inspired by spiral grass. Comparison of the puncture resistance of spiral CFRP and laminated CFRP by quasi-static and dynamic puncture. After separating the puncture process into longitudinal piercing and transverse cutting, it was found that spiral CFRP had excellent cutting resistance, with a maximum cutting force 44% higher than laminated CFRP. However, the detachment of the central structure leads to weaker perforation resistance of spiral CFRP than laminated CFRP. Laminated CFRP was found to undergo internal delamination damage after perforation by microscopic characterization and finite element analysis. Spiral CFRP has a helical yarn path and the interface distribution parallel to the impact direction, resulting in a greater susceptibility to delamination damage and rapid spiral crack propagation. The damaged area of spiral CFRP is up to 416% larger than that of laminated CFRP. The structural instability also resulted in a higher penetration depth for spiral CFRP than for laminated CFRP. The composite structure provides better puncture resistance than a single structure. Due to the combined advantages of the passivation of spiral CFRP and the structural stability of laminated CFRP, Sprial/laminated CFRP has the highest puncture resistance, with a maximum puncture load of 1,467 N, and is not penetrated at a puncture energy of 24 J. The spiral structure incorporating crack-inducing and transverse damage resistance could offer a promising approach to developing stab-resistant materials.

Mechanically Interlocked Polyrotaxane Networks with Collective Motions of Multiple Main-Chain Mechanical Bonds.

Type I main-chain polyrotaxanes (PRs) with multiple wheels threaded onto the axle are widely employed to design slide-ring materials. However, Type II main-chain PRs with axles threading into the macrocycles on the polymer backbones have rarely been studied, although they feature special topological structures and dynamic characteristics. Herein, we report the design and preparation of Type II main-chain PR-based mechanically interlocked networks (PRMINs), based on which the relationship between microscopic motion of mechanical bonds on the PRs and macroscopic mechanical performance of materials has been revealed. The representative PRMIN-2 exhibits a robust feature in tensile tests with high stretchability (1680 %) and toughness (47.5 MJ/m3). Moreover, it also has good puncture performance with puncture energy of 22.0 mJ. Detailed rheological measurements and coarse-grained molecular dynamics (CGMD) simulation reveal that the embedded multiple [2]rotaxane mechanical bonds on the PR backbones of PRMINs could undergo a synergistic long-range sliding motion under external force, with the introduction of collective dangling chains into the network. As a result, the synchronized motions of coherent PR chains can be readily activated to accommodate network deformation and efficiently dissipate energy, thereby leading to enhanced mechanical performances of PRMINs.

Mechanically Interlocked Polyrotaxane Networks with Collective Motions of Multiple Main‐Chain Mechanical Bonds

AbstractType I main‐chain polyrotaxanes (PRs) with multiple wheels threaded onto the axle are widely employed to design slide‐ring materials. However, Type II main‐chain PRs with axles threading into the macrocycles on the polymer backbones have rarely been studied, although they feature special topological structures and dynamic characteristics. Herein, we report the design and preparation of Type II main‐chain PR‐based mechanically interlocked networks (PRMINs), based on which the relationship between microscopic motion of mechanical bonds on the PRs and macroscopic mechanical performance of materials has been revealed. The representative PRMIN‐2 exhibits a robust feature in tensile tests with high stretchability (1680 %) and toughness (47.5 MJ/m3). Moreover, it also has good puncture performance with puncture energy of 22.0 mJ. Detailed rheological measurements and coarse‐grained molecular dynamics (CGMD) simulation reveal that the embedded multiple [2]rotaxane mechanical bonds on the PR backbones of PRMINs could undergo a synergistic long‐range sliding motion under external force, with the introduction of collective dangling chains into the network. As a result, the synchronized motions of coherent PR chains can be readily activated to accommodate network deformation and efficiently dissipate energy, thereby leading to enhanced mechanical performances of PRMINs.

Facile Preparation of Tough, Puncture-Resistant Antibacterial Polyrotaxane Hydrogel.

Slide-ring hydrogels containing polyrotaxane structures have been widely developed, but current methods are more complex, in which modified cyclodextrins, capped polyrotaxanes, and multistep reactions are often needed. Here, a simple one-pot method dissolving the pseudopolyrotaxane (pPRX) in a mixture of acrylamide and boric acid to form a slide-ring hydrogel by UV light is used to construct a tough, puncture-resistant antibacterial polyrotaxane hydrogel. As a new dynamic ring cross-linking agent, boric acid effectively improves the mechanical properties of the hydrogel and involves the hydrogel with fracture toughness. The polyrotaxane hydrogel can withstand 1 MPa compression stress and maintain the morphology integrity, showing 197.5 mJ puncture energy under a sharp steel needle puncture. Meanwhile, its significant antibacterial properties endow the hydrogel with potential applications in the biomedical field.

A fluorine-based strong and healable elastomer with unprecedented puncture resistance for high performance flexible electronics

There is usually a trade-off between high mechanical strength and dynamic self-healing because the mechanisms of these properties are mutually exclusive. Herein, we design and fabricate a fluorinated phenolic polyurethane (FPPU) elastomer based on octafluoro-4,4′-biphenol to overcome this challenge. This fluorine-based motif not only tunes interchain interactions through π−π stacking between aromatic rings and free-volume among polymer chains but also improves the reversibility of phenol-carbamate bonds via electron-withdrawing effect of fluorine atoms. The developed FPPU elastomer shows the highest recorded puncture energy (648.0 mJ), high tensile strength (27.0 MPa), as well as excellent self-healing efficiency (92.3%), along with low surface energy (50.9 MJ m−2), notch-insensitivity, and reprocessability compared with non-fluorinated counterpart biphenolic polyurethane (BPPU) elastomer. Taking advantage of the above-mentioned merits of FPPU elastomer, we prepare an anti-fouling triboelectric nanogenerator (TENG) with a self-healable, and reprocessable elastic substrate. Benefiting from stronger electron affinity of fluorine atoms than hydrogen atoms, this electronic device exhibits ultrahigh peak open-circuit voltage of 302.3 V compared to the TENG fabricated from BPPU elastomer. Furthermore, a healable and stretchable conductive composite is prepared. This research provides a distinct and general pathway toward constructing high-performance elastomers and will enable a series of new applications.

Shock absorption and dispersion capability of a novel five-layer mouthguard sheet material.

There is a growing need for a mouthguard sheet material with higher shock absorption and dispersion capacity than those obtained by conventional materials. A five-layer mouthguard sheet material was previously developed using laminated ethylene vinyl acetate and polyolefin copolymer resin. In this study, the shock absorption capacity and dispersion capability of the new sheet material were investigated and compared with those of other materials. Impact testing for the new sheet material showed that the force required to displace the sheet by 1 mm was significantly higher at all thicknesses (p<0.001), whereas the puncture energy and displacement were significantly lower than those for ethylene vinyl acetate (p<0.05). The five-layer mouthguard sheet material successfully absorbed and resisted shock. Therefore, the sheet material potentially increases resistance to applied deformation in teeth and alveolar bone and maintains structure. The five-layer sheet material could expand the range of mouthguard products and help prevent oral trauma.

Preparation and improving mechanism of PBAT/PPC-based micro-layer biodegradable mulch film with excellent water resistance and mechanical properties

The utilization and implementation of biodegradable mulch film represent a highly effective approach to address the persistent pollution caused by non-degradable mulch film. However, the poor water resistance and insufficient mechanical properties strongly restrict its practical application. Here the PBAT/PPC-based multilayer biodegradable mulch films including 3-, 17-, 65-, and 257-layer, were manufactured successfully using a self-developed micro-layer blown film technology. The 65-layer film showed significant improvements in its mechanical and barrier properties, outperforming contrast the blend the film by 148 %, 168 %, and 203 % respectively in terms of puncture energy, tear energy, and water vapor barrier. The results obtained from DSC, WAXD, and SAXS analyses demonstrated a significant similarity in the crystalline structure of PBAT in various micro-layer films and the blend contrast film. Consequently, the robust mechanical and water barrier properties can be attributed to the ultrathin micro-layer structure, which dissipated energy during mechanical breakage by promoting substantial plastic deformation and blocked the water by forming a larger and more continuous phase of high barrier PPC. Briefly, the micro-layer mulch films, based on PBAT/PPC and fabricated using the self-developed micro-layer blown film technology, demonstrate exceptional mechanical strength and water resistance properties. Consequently, this research has the potential to garner interest within the biodegradable mulch film sector.

Post-Ultraviolet-Curing Process Effects on Low-Velocity Impact Response of 3D Printed Polylactic Acid Parts

In this study, polylactic acid (PLA) parts produced with the 3D fused deposition modelling (FDM) technique were cured with ultraviolet irradiation (post-UV-curing) after production, and the low-velocity impact behaviour of the parts was experimentally investigated. Accordingly, PLA parts were subjected to post-UV-curing at 15-, 30-, 45-, and 60-minute periods. The impact behaviour of the specimens produced with production parameters of 200 °C printing temperature, 0.2 mm layer thickness, 50 mm/s printing speed, 100% infill rate, and 45° raster angle was compared with the raw specimens after the post-UV-curing process was applied. As a result of the impact tests, peak force, peak displacement, peak energy, and puncture energy values were obtained from the force-displacement graphs. It has been revealed that the post-UV-curing implementation increases the peak force values of PLA specimens and decreases the displacement values compared to the raw specimens. All specimens' impact behaviour improves with the post-UV-curing process; however, a decreasing trend is entered after 30 min.

Biomimetic supramolecular polyurethane with sliding polyrotaxane and disulfide bonds for strain sensors with wide sensing range and self-healing capability.

To prolong the service life of flexible electronic materials, polymeric matrixes with excellent self-healing capability and integrated mechanical properties are highly desirable, but the balance between the self-healing capability and mechanical properties is a grand challenge. Here, polyrotaxanes as sliding crosslinkers and dynamic disulfide bonds are incorporated into the main chains of polyurethane (PU) via one-pot synthesis, which endows the PU with polydisperse hard/soft segments, high density of self-healing points and energy dissipation. Based on this judicious molecular design, the PU elastomers exhibit exceptional mechanical properties, such as high stretchability (1167% with a tensile strength of 3.49MPa), high fracture energy (20,775Jm-2) and high puncture energy (200.70mJ). Moreover, due to the presence of dynamic reversible hydrogen and disulfide bonds, the elastomer could achieve stress and strain repair efficiencies of 93.98% and 99.21% at 100 ℃ within 1h, respectively. The above-mentioned superiorities enable the bioinspired strain sensors to possess a large sensing range (∼596%), high sensitivity (∼79.98), short response time (∼128ms), along with excellent reliability and self-healing ability. Besides, the strain sensor exhibits remarkable recyclability and prominent reprocessability, which nicely solves the pollution by discarded electronics.

Failure mechanism of weft-knitted insertion fabric/Surlyn resin flexible composite for stab resistance

In this paper, two kinds of aramid fibers were used to prepare weft-knitted insertion fabrics, flexible Surlyn resin as matrix to prepare reinforced weft-knitted insertion fabrics, the effects of hot-pressing temperature, resin content, pressure and holding time on reinforced weft-knitted insertion fabric were explored. Through lamination and co-curing, the effects of the lamination numbers, preparation methods and lamination sequence on the stab resistance of the multilayer system were studied. The results showed that appropriate hot-pressing temperature, resin content, pressure and holding time can improve the stab resistance by improving the permeability of resin in the fabric. However, over high temperatures, pressure and holding time have a negative impact on the stab resistance or flexibility of the composite; high resin content means higher weight, which is not conducive to human wearing. When the area density is similar, the stab resistance of the co-cured composite is the best, followed by the superposition of single-layer composite, finally is the superposition of film and fabric. Weft-knitted insertion fabrics and reinforced weft-knitted insertion fabrics can dissipate puncture energy through shear force, tensile fracture, friction and deformation of yarn or fabric. In addition, composites also have other energy dissipation pathways such as filament compression splitting, fabric/matrix debonding and matrix delamination.

The mechanism of stab resistance of carbon fiber reinforced polymer

In this paper, the puncture resistance of carbon fiber reinforced polymer (CFRP) with different thicknesses under various puncture energy was studied by in-situ observation. The puncture failure process of CFRP was analyzed using a high-speed camera and thin-film pressure sensor in terms of damage image and local pressure change. The experimental results show that the puncture threshold load (PTL) representing material penetration is usually located at the initial loss position of material stiffness. The penetration load can be divided into linear growth and delamination failure zones. Image localization was used to mark the puncture feature points on the puncture force–displacement curve to help characterize the puncture failure process. The theoretical equations of puncture force and displacement before material penetration are proposed and verified by introducing yield stress and friction force, and the correlation between the material thickness and the puncture resistance was proved. In addition, the failure modes and fracture morphology of CFRP after puncture are analyzed and summarized. After puncture impact, fiber fracture, pull out and slip deformation under the action of tensile force and cutting force, and matrix fracture and peel damage. The increase of impact energy leads to a broader range of impact damage but does not change the failure modes.

Biomechanical fracture mechanics of composite layered skin-like materials.

Most protective biological tissues are structurally comprised of a stiff and thin outer layer on top of a soft underlying substrate. Examples include mammalian skin, fish scales, crustacean shells, and nut and seed shells. While these composite skin-like tissues are ubiquitous in nature, their mechanics of failure and what potential mechanical advantages their composite structures offer remains unclear. In this work, changes in the puncture mechanics of composite hyperelastic elastomers with differing non-dimensional layer thicknesses are explored. Puncture behavior of these membranes is measured for dull and sharp conical indenters. Membranes with a stiff outer layer of only 1% of the overall composite thickness exhibit a puncture energy comparable to membranes with a stiff outer layer approximately 20 times thicker. This puncture energy, scaled by its flexural capacity, achieves a local maximum when the top layer is approximately 1% of the total membrane, similar to the structure of numerous mammalian species. The mode of failure for these regimes is also investigated. In contrast with puncture directly beneath sharp tips caused by high stress concentrations, a new type of 'coring' type fracture emerges at large indentation depths, resulting from accumulated tensile strain energy along the sides of the divot as the membrane is deformed with a blunt indenter. These results could enhance the durability and robustness of stretchable materials used for products such as surgical gloves, packaging, and flexible electronics.

Engineered self-healable elastomer with giant strength and toughness via phase regulation and mechano-responsive self-reinforcing

Acquiring simultaneous high strength and toughness, and efficient self-healability of polyurethane (PU) elastomer is of great challenge due to their exclusive dependence on hard segments. Herein, a transparent, puncture-resistant, notch-insensitive, resilient and self-healable elastomer (PDO-IP2.5) with giant tensile strength (29.5 ± 0.9 MPa), excellent toughness (124.9 ± 2.2 MJ/m3), outstanding fracture energy (83.9 kJ/m2), high puncture energy (625 mJ) and balanced self-healing efficiencies (SEs calculated in tensile strength, elongation at break and toughness > 95%) and fast physical wound re-mending (~60 s upon hot airflow) is successfully developed through deliberate phase regulation, i.e. rational design of asymmetric and bulky hard segments and optimization of hard segments content. The resulting loosely-packed hard domains play a pivotal role in conferring self-healability and generating stress-induced crystallization (SIC) of polytetramethylene ether glycol (PTMEG) chains during large deformation, which not only facilitates the chain mobility for heat-responsive dynamic exchange of hydrogen bonds and oxime-carbamate but also dissipate external force during stretching to help the SIC evolution of PTMEG chains. The SIC domains act as physical crosslinking junctions and reinforcing phase, resulting in remarkable strengthening and toughening. This strategy could enlighten researchers in academia and industry to develop strong and tough elastic materials. In the meantime, the unique comprehensive performance of the as-synthesized elastomer confers it with potential practical use in engineer-grade fields of puncture-resistant tire sealant and durable protective coatings.

Investigation on the microstructural characteristics and quasi-static puncture resistance of both domesticated and wild silkworm cocoons

The very thin and lightweight silkworm cocoon has outstanding mechanical properties attributed to its specific composite microstructure. However, the microstructures of the cocoons have not been studied quantitatively, and their anti-puncture performance has not been examined as well. In this study, both domesticated ( Bombyx mori) and wild silkworm cocoons ( Antheraea pernyi, Antheraea mylitta and Samia canningi) were investigated for their microstructures using fractal theory, and their quasi-static puncture resistance was tested and compared. In addition, the effects of cocoon layers and hot-press treatments on the puncture resistance of two cocoon types ( B. mori and A. pernyi) were investigated. The three wild cocoons demonstrated significantly higher fractal dimensions, higher fiber intersectional densities and low porosities, indicating their structures are more optimized. They also displayed better puncture resistance than B. mori. Increased layer numbers could significantly increase the puncture resistance of both cocoon types and A. pernyi showed more remarkable increases. Moreover, the two cocoon types showed optimum puncture resistance after heat treatment with hot-press temperature of 135℃ and pressure of 25 MPa, and A. pernyi showed better puncture resistance after such treatment. Finally, both the maximum puncture force and puncture energy of cocoons displayed a linear increase with the increasing fractal dimensions. The new insights can guide the development of novel protective fiber composites with desirable and predictable anti-puncture performance.

Entanglement Density-Dependent Energy Absorption of Polycarbonate Films via Supersonic Fracture.

The fracture behavior of glassy polymers is strongly coupled to molecular parameters such as entanglement density as well as extrinsic parameters such as strain rate and test temperature. Here we use laser-induced projectile impact testing (LIPIT) to study the extreme strain rate (≈107 s-1) puncture behavior of free-standing polycarbonate (PC) thin films. We demonstrate that changes to the PC molecular mass and the degree of plasticization can lead to substantial changes in the specific puncture energy. We relate these changes to the alteration of the entanglement density of the polymer that determines the underlying failure mechanism as well as the size of the deformation zone.

Fabric Composites Reinforced with Thermally Bonded and Irregularly Aligned Filaments: Preparation and Puncture Resistant Performance.

This study proposes fabric composites with improved static and dynamic puncture via increasing a friction force to restrain the slide of filaments as well as the compression and abrasion between the fibers and the puncture probe. The the bi-layered shell layers of composite fabrics are composed of aramid staple fibers and nylon staple fibers and a layer of low-melting-point polyester (LPET). The nonwoven layer consisting of recycled aramid and nylon staple fibers provides a shear effect to dissipate part of the puncture energy. Reinforcing interlayers include a woven fabric and PET filaments that are circularly aggregated between the surface layers, providing isotropic filament reinforcement and strengthening the resistance against the tip of the puncture probe. The reinforcing filaments may slide after the employment of needle punching, and to compensate for this disadvantage, the LPET layers are used to thermal bond the composite fabrics and the total thickness is controlled at 2 mm. The thermally bonded fabric composites are evaluated in terms of puncture resistance, thereby examining the effects of fabric structure and thermal bonding. According to the test results, the optimal composite structure is the sample N/L/W/F/L/N, which was reinforced by the LPET adhesive layer and irregularly aligned filaments. The sample which used the LPET adhesive layer had a positive influence on static puncture resistance and dynamic puncture resistance, preventing the slide of filaments, but the poor interfacial combination only contributed to limited reinforcement.

Puncture properties of a hybrid continuous-discontinuous sheet moulding compound for structural applications

A novel two-step curing resin system and adapted moulding approach enables the manufacturing of hybrid continuous-discontinuous SMC in a one-shot process. Hybridization led to a significant increase of maximum force (+36%) and puncture energy (+35%) if specimens were punctured in a quasi-static manner. The effect of hybridization was less distinct under dynamic loading (increase of 13% and 7%, respectively), due to a negative rate dependency of the continuous carbon fibre SMC. An increase from 4.4·10−5 m∙s−1 to 4.4 m∙s− 1 resulted in a positive rate dependence of the hybrid SMC with increased maximum force (+33%) and puncture energy (+18%). Important failure mechanisms were inter-bundle and inter-fibre fracture of the continuous SMC and pseudo-delamination (intra-laminar) of the discontinuous component. Delamination took place at both considered loading rates but was more important if hybrid SMC was punctured in a dynamic manner.

Cooking Quality of Lentils Produced under Mediterranean Conditions

Cooking quality (CQ) is the main quality criterion in lentil (Lens culinaris Medik.) and is affected by several factors. Phosphorus fertilization is a common agricultural practice in alkaline P‐poor soils, but studies examining its impact on CQ of lentils are lacking. Four lentil cultivars (three green and one red‐seeded) were tested over two growing seasons, under rainfed Mediterranean conditions, with P as the only nutrient input. The CQ of seeds was estimated using a texture analyzer, and the puncture energy (PE, inversely related to CQ) was calculated. A suite of seed traits (percentage of seed coat weight, 1000‐seed weight, seed softness and protein concentration of hulled and dehulled seeds, and seed coat anatomy) were measured. Moreover, P, K, Na, Ca, and Mg (their sums and ratios) in seeds (hulled and dehulled) were measured to assess their role in CQ. Phosphorus had no significant effect on CQ, but its impact was evident on the chemical composition of the seed coat. Seed coat anatomy was affected only by cultivars. Significant correlations between PE and seed traits for the growth season × cultivar interaction were obtained only for the green‐seeded lentils. In contrast with previous findings, P concentration in hulled seeds was negatively associated with CQ in green lentils; the opposite was evident for Ca. On the other hand, the protein concentration of dehulled seeds was negatively correlated with PE (positively with CQ), indicating that it was the cotyledonary factor influencing CQ by contributing to water absorption.

Mechanical properties and damage evolution of a structural sheet molding compound based on a novel two step curing resin system

A novel two step curing resin system allows for the manufacturing of discontinuous, continuous and hybrid continuous-discontinuous sheet molding compound (SMC) with glass or carbon fibers. In this contribution, the discontinuous component of this innovative hybrid material, a structural glass or carbon fiber SMC, is characterized under quasi-static and dynamic loading conditions. Glass fiber SMC showed a positive loading rate sensitivity. For higher loading rates, maximum force and puncture energy increased significantly for charge (65%/67%) and flow region specimens (73%/64%). Carbon fiber SMC did not show a rate sensitivity. 1D flow of this material during compression molding leads to anisotropic mechanical properties due to fiber orientation. The microstructure of the material significantly influences damage evolution and failure, which was investigated by means of in-situ photography, SEM and μ-CT. The dominant failure mechanisms were interface failure and matrix cracking for the glass and the formation of inter-fiber fracture and inter-granular failure of pseudo-grain like microstructure for the carbon fiber SMC.