Tensile Fracture Surfaces Research Articles

Mechanical and Aging Properties of Hydrogenated Epoxidized Natural Rubber and Its Lifetime Prediction.

Natural rubber (NR) has restricted its application due to its potential for thermal- and oil-resistant materials. The weakness of NR can be eliminated by chemical modification to enhance aging properties. Formic acid and hydrogen peroxide have been used to prepare partially epoxidized natural rubber (ENR) in the latex state. Its residual unsaturated units were then modified using hydrazine and hydrogen peroxide to obtain hydrogenated ENR (HENR). 1H-NMR characterized the resulting products. NR and modified NRs were compounded and then vulcanized using a conventional milling process. This paper compares NR, ENR having 49.5% epoxide group content, and HENR having 49.5% epoxide group content and 24% hydrogenation degree in terms of tensile, thermal, oil, and ozone properties. Morphology and lifetime prediction were studied. Overall results show that the tensile strength of the HENR composite (14.7 MPa) was 79 and 71% lower than that of ENR (18.6 MPa) and NR (20.8 MPa) composites, respectively. In contrast, the modulus at 100% elongation of the HENR composite (2.0 MPa) was 167 and 200% higher than that of ENR (1.2 MPa) and NR (1.0 MPa) composites, respectively. Morphological studies of the tensile fractured surface of the vulcanizates, using scanning electron microscopy, confirmed a shift from ductility failure to brittle with the presence of the epoxide groups and low unsaturated bonds in the backbone chain. The results demonstrated that HENR could act as an ideal material, providing better thermal, oil, and ozone resistances while maintaining the mechanical properties of the rubber. The kinetic analyses of the thermal degradation of NR, ENR, and HENR were studied using thermogravimetric analysis (TGA) at three heating rates. Kissinger–Akahira–Sunose (KAS) was employed to calculate the activation energy (Ea). The obtained data were used to predict the lifetime under the established temperature range and 0.05 conversion level. Overall, the results represented that HENR had a longer lifetime than NR and ENR for a temperature range between 25 and 200 °C, indicating that HENR had excellent thermal stability than NR and ENR. Therefore, the HENR should extend the applications to include gaskets and seals, especially for the automotive and oil industries.

Evaluation of tensile properties and fracture surface morphology of woven fabric-polymer composites filled with micro SiC and Al2O3 particulates

The current research aims to study the influence of hybridisation on the tensile and fracture surface morphology of plain weave glass fibre/epoxy composites. The polymer resin is primarily filled with inorganic particles such as silicon carbide and alumina, and the corresponding modified resin is termed as effective matrix. This effective matrix is further reinforced by plain weave glass fibre to fabricate the hybrid composite. Elastic properties of the composites are estimated after developing Micro-mechanical-model-based formulation considering different analytical model like Mori-Tanaka, Paul, Ishai-Cohen model along with equivalent modulus theory. Experiments are conducted to estimate the elastic constants and post-tensile fractured surface morphology of these composites. The tensile modulus predicted using Mori-Tanaka and equivalent modulus theory matches well with the experiments and found to be in good convergence compared to the other models. Detailed analyses of the fractured surface of the tensile samples express the positive effect of hybridisation on the tensile and failure behaviour. It is found that the tensile strength and elastic modulus of the composites increase with an increase in particulate content.

Synthesis, Microstructural Characterization, Mechanical, Fractographic and Wear Behavior of Micro B4C Particles Reinforced Al2618 Alloy Aerospace Composites

In the current studies an investigations were made to know the effect of 63 micron sized B4C particles addition on the mechanical and wear behavior of aerospace alloy Al2618 metal composites. Al2618 alloy with different weight percentages (2, 4, 6 and 8 wt. %) of 63 micron sized B4C particles reinforced composites were produced by stir cast process. These synthesized composites were tested for various mechanical properties like hardness, compression strength and tensile behavior along with density measurements. Further, microstructural characterization was carried by SEM/EDS and XRD analysis to know the micron sized particles distribution and phases. Wear behavior of Al2618 alloy with 2 to 8 wt. % of B4C composites were studied as per ASTM G99 standards with varying loads and sliding speeds. By adding 63 micron sized B4C particles hardness, compression and tensile strength of Al2618 alloy was enriched with slight decrease in elongation. Further, wear resistance of Al2618 alloy was enriched with the accumulation of B4C particles. As load and speed on the specimen increased, there was increase in wear of Al2618 alloy and its composites. Various tensile fracture surface morphology and worn surface behavior was observed by SEM analysis.

Microstructural and mechanical characterization of Cu/Sn SLID bonding utilizing Co as contact metallization layer

Most micro-electro-mechanical systems (MEMS) devices contain fragile moving parts, which poses challenges in process integration of interconnection methods requiring wet-chemistry, such as solid-liquid interdiffusion bonding (SLID). These sensitive MEMS structures can be protected from either the wet-chemistry or plated metals during chemical/electro-chemical plating of SLID interconnection materials; however, this is a complex process. Hence, our previous research has investigated employing a physically deposited contact metallization on the wafers containing functional devices instead of chemically deposited layers (such as electrochemical Cu). Co is a plausible contact metallization layer for Cu-Sn SLID bonding, as it is chemically compatible with Cu–Sn systems. Furthermore, it can positively impact the mechanical reliability of the intermetallic compounds (IMCs) due to the stabilizing of the HT-hexagonal Cu6Sn5 phase down to room temperature and suppressing the Cu3Sn phase formation and subsequent void formation. However, it is critical to control Co thickness to achieve a stable bond based on our previous research on Co bulk in contact with Cu-Sn electroplated silicon chips. To utilize Co as a contact metallization layer for wafer-level Cu-Sn SLID bonding, it is necessary to define appropriate metal layers in the contact metallization stack. Consequently, the present study investigated four different contact metallization stacks including A) 40nmTi/100 nm Co, B) 40 nm Ti/200 nm Mo/100 nm Co, C) 40 nm Ti/500 nm Co, and D) 40 nm Ti/200 nm Mo/500 nm Co. More specifically, we evaluated the microstructural formation and evolution and mechanical performance of the joints. Our study revealed that the Ti/Mo/100 nm Co contact metallization stack for (4 µm)Cu/(2 µm)Sn SLID bonding is composed of IMCs (Cu,2.5at%Co)6Sn5 and Cu3Sn without remaining Sn. Moreover, the joint contained a negligible number of voids even after long-time annealing at 150 °C. Our analysis of the mechanical properties of the joint showed that 1) the tensile fracture surface exhibited a mixture of ductile and brittle fractures, and 2) the Young’s modulus of (Cu,2.5at%Co)6Sn5 was higher than Cu6Sn5, while hardness of (Cu,2.5at%Co)6Sn5 and Cu6Sn5 were comparable. By employing a Ti/Mo/100 nm Co contact metallization stack, the current study was able to produce 25 µm and 10 µm void free (4 µm Cu/2 µm Sn) microbumps.

Damping of micro- and nanocellulose reinforced PA610 composites and influences of moisture absorption

Composites consisting of bio-based polyamide 610 (PA610) reinforced with micro- and nano-cellulose were manufactured by melt compounding followed by injection molding. The resulting composites had fiber sizes ranging from nanoscale to 100 µm at 2.5 %, 5 % and 10 % fiber mass fractions. These composites were mechanically characterized by tensile tests followed by scanning electron microscopy to examine the tensile fracture surface. The primary focus of the work was the damping behavior of these nanocomposites, which was found to be substantial. Damping was characterized using the damping ratio extracted from the measured decay of mechanical vibrations. Cellulose nanocrystal-reinforced PA610 at 10 % mass fraction was found to produce a 210 % increase in damping ratio compared to control PA610. Larger fiber sizes and lower mass fractions resulted in smaller, but significant, increases in damping. Comparison to cellulose reinforced polypropylene composites showed that PA610/cellulose composites produced significantly greater relative damping. Additionally, since both cellulose and PA610 are hydrophilic materials, a study was made on the effects of moisture absorption on the damping. It was found that the pronounced effect of the filler on damping was diminished by absorbed moisture and did not return after removing moisture from the samples. The origin of the damping increase and the effects of moisture were discussed in the article.

Investigation of Rock Burst Mechanism under Thermomechanical Coupling Conditions Based on Rock Mechanical Tests

Abstract The thermomechanical (TM) coupling effects of rock bursts have attracted considerable attention from researchers owing to the high geothermal and geostresses in deep tunnels in regions such as Western China. To study the brittleness and rock burst mechanism under TM conditions, various tests, such as splitting, uniaxial compression, rock burst tendency, and rock burst physical model tests, were conducted at temperatures ranging from 20°C to 80°C. The results revealed that, when granite samples were heated, their tensile strengths decreased in the splitting tests. Their peak stresses and the corresponding strains increased; their macroscopic tensile fracture surfaces became more evident; and the microcosmic tensile properties of intergranular fractures became prominent under uniaxial compression. Rock burst physical model tests and acoustic emission monitoring results revealed that, at higher temperatures, the fracture degree and failure range were larger, the energy was higher and more concentrated during failure, and failure occurred earlier. The brittleness index B, rock burst tendency Wet, and σθ/σc all exhibited a clear increasing tendency with an increase in temperature. The rock burst mechanism, considering the temperature effect, can be summarized as follows: the increase in brittle tensile fracture components and geostress caused by temperature increasing is conducive to the rapid release of energy, which will promote the occurrence of rock burst. The researching result is of great academic value and practical significance for the prevention, design, and safe construction of rock burst in deep high geothermal tunnels.

Bioinspired Multi-Metal Structures Produced via Direct Ink Writing

Bioinspired Multi-Metal Structures (MMSs) combine distinct properties of multiple materials, benefiting from improved properties and providing superior designs. Additive Manufacturing (AM) exhibits enormous advantages in applying different materials and geometries according to the desired functions at specific locations of the structure, having great potential in fabricating multi-materials structures. However, current AM techniques have difficulty manufacturing 3D MMSs without material cross-contamination flexibly and reliably. This study demonstrates a reliable, fast, and flexible direct ink writing method to fabricate 3D MMSs. The in-situ material-switching system enables the deposition of multiple metallic materials across different layers and within the same layer. 3D Fe–Cu MMSs with complex geometries and fine details are fabricated as proof of concept. The microstructures, chemical and phase compositions, and tensile fracture surfaces of the Fe–Cu interfaces indicate a well-bonded interface without cracks, delamination, or material cross-contamination. We envision this novel method making other metallic combinations and even metal-ceramic components. It paves the way for manufacturing 3D MMSs using AM and establishes the possibilities of numerous MMSs applications in engineering fields.

A crack-free and high-strength Al-Cu-Mg-Mn-Zr alloy fabricated by laser powder bed fusion

Laser Powder Bed Fusion (LPBF) is considered as one of the most current additive manufacturing technologies that could prepare customized and complex parts. There have been challenges for LPBF-fabricating 2xxx (Al–Cu) alloy because that own alloy elements cause large solidification ranges and hot cracking is susceptible to generate during solidification. In this study, a crack-free and high-strength Al–Cu–Mg–Mn–Zr alloy was designed and manufactured by LPBF. The results showed that the laser energy density has an important effect on microstructure and density, and it was sufficient to melt the alloy powder and deliver high-quality builds at 333 J/mm3. The microhardness, tensile strength, and yield strength of the LPBF-fabricated Al–Cu–Mg–Mn–Zr alloy increased with increasing laser energy density. In addition, the tensile fracture surfaces exhibited mixed brittle and ductile fracture features at low energy density values (231–358J/mm3). The ductile fracture was observed at higher energy density values (>463J/mm3). When the laser density was set at 500 J/mm3, the LPBF-fabricated alloy exhibited high relative density (99.88%) and the most optimal mechanical properties, with microhardness of 141.5 Hv, tensile strength of 343.9 MPa, yield strength of 311.0 MPa, and elongation of 6.1%. After solution treatment at 560 °C for 2 h and water quenching, the Al–Cu–Mg–Mn–Zr alloy exhibits the excellent mechanical properties with ultimate tensile strength of 483.6 MPa, yield strength of 365.5 MPa, and elongation of 13.4%.

Novel approach to recycled carbon fiber suitability assessment for additive technologies

This article presents a new approach to suitability assessment of short reclaimed carbon fiber (rCF) for additive technologies via commonly used analytical methods. Acrylonitrile butadiene styrene (ABS) based plastics reinforced with virgin or recycled CF samples were received, their mechanical properties and morphology of tensile fractured surface were determined by SEM (Scanning Electron Microscopy) and tensile strength test. As long as operating characteristics of CFRP are affected by single fiber strength as well as adhesion (interfacial interaction) between matrix and CF, this research also includes investigation of fiber surface with Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy and X-ray diffraction (XRD). Correlation between suggested complex parameters of investigated CF and strength of plastics (CFRP) samples was shown. It was also established that contribution of each investigated parameter is additive.

A Novel Automatic Image Intensity Analysis Using Machine Learning Algorithms and Characterization of Tensile Fracture Surface of AA8011-B4C Nano-composite

A Novel Automatic Image Intensity Analysis Using Machine Learning Algorithms and Characterization of Tensile Fracture Surface of AA8011-B4C Nano-composite

Mechanism of improvement in the strength of para-aramid paper by polyphenylene sulfide pulp

Aramid paper has been widely applied in aerospace, rail transit, and other fields because of its outstanding mechanical properties, high-temperature resistance, and excellent insulation. We prepared para-aramid chopped fibers/polyphenylene sulfide (ACFs/PPS) composite paper, which has superior mechanical strength compared with other aramid papers. However, the mechanism of PPS pulp improving para-aramid paper is still unclear. Herein, the structure change and interface behavior of composite paper during hot pressing were studied. The surface of ACFs was modified by PPS pulp in-situ melting and self-wetting at high temperatures, which made the surface of ACFs rough and viscous. ACFs were staggered in three-dimensional space, and countless network nodes were formed at the staggered parts. With the node as the vertex and the ACF as the side length, countless stable triangular structures were formed. Under this structure, the tensile fracture surface of the composite paper showed the splitting of the bulk structure of aramid fiber, indicating that the paper had strong interfacial strength. More importantly, PPS pulp breaks the limitation of weak interfacial strength between ACFs and resin matrix. We can predict that PPS pulp can be made into advanced paper-based materials with other high-performance inert fibers.

Tessellated dimple geometry of high entropy alloy

This article focuses on the characterization and analysis of dimple geometry on the published tensile fracture surfaces of a HfNbTaTiZr refractory high entropy alloy of different matrix microstructures, generated through cold deformation and systematic annealing treatments. Changes in different microstructural states which led to different tessellated fracture complexions have been quantified, compared and correlated with the corresponding tensile responses of the alloy. This interpretation allows the use of fracture surface morphology and image texture in a quantitative way.

Investigation on the effect of stacking order and hybridization on mechanical and water absorption properties of woven flax/bamboo composites

AbstractIn virtue of the performance of natural fiber reinforced composites, hybridization and stacking order play a crucial role in defining the behavior of engineering components. Furthermore, no studies have been reported on the mechanical and water absorption properties of woven flax/bamboo hybrid composites with different stackings. The present study investigates the influence of stacking sequences and hybridization of flax (F)/bamboo (B) epoxy composites on its mechanical and water absorption properties. The stacking sequence is varied as follows: B/F/F/B, F/B/B/F, F/B/F/B, F/F/B/B. A numerical model for interlaminar shear strength (ILSS) is developed and validated using ANSYS composite repost, which can predict the critical stresses and damage in each ply, as it is not possible through experimental studies. The tensile fractured surfaces are examined by scanning electron microscopy. Results indicate that the mechanical and water absorption of hybrid composite laminates are influenced by the stacking sequence. The optimum stacking order with maximum performance is obtained for B/F/F/B. The increase in tensile, flexural, impact, and ILSS values is observed as 8.3%, 25%, 4.4%, and 14.6%, respectively. The water diffusion coefficient is reduced by 34.75% by the addition of the bamboo layer to the skin. The computational analysis predicted the different modes of critical stresses and failures acting on each ply during the ILSS test.

Processability and Physical Properties of Compatibilized Recycled HDPE/Rice Husk Biocomposites

The circular economy promotes plastic recycling, waste minimization, and sustainable materials. Hence, the use of agricultural waste and recycled plastics is an eco-friendly and economic outlook for developing eco-designed products. Moreover, new alternatives to reinforce recycled polyolefins and add value to agroindustrial byproducts are emerging to develop processable materials with reliable performance for industrial applications. In this study, post-consumer recycled high-density polyethylene (rHDPE) and ground rice husk (RH) of 20% w/w were blended in a torque rheometer with or without the following coupling agents: (i) maleic anhydride grafted polymer (MAEO) 5% w/w, (ii) neoalkoxy titanate (NAT) 1.5% w/w, and (iii) ethylene–glycidyl methacrylate copolymer (EGMA) 5% w/w. In terms of processability, the addition of RH decreased the specific energy consumption in the torque experiments with or without additives compared to neat rHDPE. Furthermore, the time to reach thermal stability in the extrusion process was improved with EGMA and MAEO compatibilizers. Tensile and impact test results showed that using coupling agents enhanced the properties of the RH composites. On the other hand, thermal properties analyzed through differential scanning calorimetry and thermogravimetric analysis showed no significant variation for all composites. The morphology of the tensile fracture surfaces was observed via scanning electron microscopy. The results show that these recycled composites are feasible for manufacturing products when an appropriate compatibilizer is used.

The effect of transverse low-velocity pre-impact on the residual strength of Al/PEEK/CFRTP adhesive joints

Due to their excellent impact resistance, high toughness, short forming time, and recyclability, carbon fiber-reinforced thermoplastic (CFRTP) composite materials can be blended and bonded with aluminum alloys (Al) to produce lighter structures with better impact resistance. In this study, the effects of impact energy (5, 10, 15, 20 J) and impact surface (CFRTP and Al) on Al/PEEK/CFRTP joints with different relative bond lengths (20/L, 25/L, 35/L, 45/L, where L is the length of the adherend) were explored through a combination of joint impact damage modes, energy absorption rates, residual strengths, and tensile fracture surfaces. The results showed that when the relative bond lengths were 20/L and 25/L, using CFRTP as the impact surface significantly reduced the residual strength loss of the joint. When the relative bond lengths were 35/L and 45/L, the influence of the impact surface on the joint was significantly reduced. A relative bond length of 35/L was the ideal choice for structural safety and cost savings.

Effect of microwave on mechanical properties of laser-sintered carbon nanotube polymer composites

ABSTRACT In this work, carbon nanotubes (CNT)/polyethersulfone (PES) polymer composites were prepared by selective laser sintering, and the effects of microwave treatment on mechanical properties and tensile fracture surfaces of the composites were investigated. The experimental results indicated that tensile strength and bending strength of the composites upon microwave treatment for 5–25 s were improved by 4–20.4% and by 4.5–47.7%, respectively. The tensile fracture surface morphology of the composites depended on the time length of microwave treatment. Upon microwave treatment, the fracture surface showed fewer pores and better interfacial bonding between adjacent polymer particles. The fracture mechanisms for the microwave-treated carbon nanotube/polymer composites prepared by selective laser sintering were discussed.

Improvement of mechanical and microstructural properties of AA 5052-H32 TIG weldment using friction stir processing approach

The effect of Friction Stir Process (FSP) on the weld bead of Tungsten Inert Gas (TIG) welded 5052-H32 Aluminium alloy is investigated in this work in terms of mechanical and microstructural characterization. A comparison study was conducted on the FSP treated and unprocessed TIG-welded Aluminium alloy joints. Optical and scanning electron microscopes were used to study the microstructure of the welded joints. Electron backscattered diffraction (EBSD) analysis was performed to analyze the grain size and orientation. The mechanical properties of the weldment were investigated using tensile strength and hardness measurements. The yield strength of unprocessed TIG welded joints was 79.5 MPa, but following friction stir processing, it improved to 129.5 MPa. The tensile strength of TIG-welded joints was 176.5 MPa. However, after post friction stir processing, it was increased to 201 MPa. On friction stir treated TIG welded joints, the elongation values improved from 8.5 percent in TIG welds to 20.75 percent. The refinement of fine grain structure is noticed in the stir zone due to the influence of high stirring action, intense plastic deformation, and frictional heat by Friction stir processing, which improves the mechanical characteristics of the weldment and decreases weld flaws. The tensile fractured surface of the joints was examined using SEM analysis. Brittle failure was seen in the TIG weld joints, and ductile failure with dimples was found in FSPed TIG junctions. The results show that the friction stir processed weldment has better mechanical properties than unprocessed TIG welded joints.

Performance comparison of carbon fiber reinforced polyaryletherketone and epoxy composites: Mechanical properties, failure modes, cryo‐thermal behavior, and finite element analysis

AbstractHigh‐performance thermoplastic composites are gaining attention as potential replacement for thermoset composites in high‐end structural applications owing to their superior fracture toughness and recyclability. In this study, polyaryletherketone (PAEK) and carbon fabric (CF) reinforced PAEK are compared with epoxy and epoxy‐CF composites. PAEK‐CF composites are prepared by film stacking method followed by compression molding while hand lay‐up technique was used for epoxy‐CF composites. PAEK and PAEK‐CF composites possess superior tensile properties, flexural strength and fracture toughness compared to those prepared from epoxy. The incorporation of CF improved the wear resistance in both PAEK and epoxy and PAEK‐CF exhibited the lowest wear rate. The investigation of interlaminar shear strength of the composites was conducted and the highest value observed for PAEK‐CF composite. Wear and fracture surface analysis suggested ductile failure for PAEK and PAEK‐CF composites and brittle failure in epoxy composites, as indicated by interfacial bonding/debonding and fiber pullout, at the fracture surface. Cryo‐thermal cycling effects on the tensile properties, fracture toughness and fracture surface morphology of the composites are studied. The failure behavior obtained from experimental studies was corroborated with finite element method‐based simulation models of fracture toughness response in single edge notch bend test using Abaqus/Explicit.

Tensile fracture characteristics of carbon fibers collected from the outer and inner parts of a CFRP laminate by thermal decomposition

Thermal decomposition treatment (TDT) is a typical recycling method for CFRP. However, the recovered CFs (rCFs) tend to show a decrease in performance owing to the thermo-oxidation during this process. In particular, the thermo-oxidation rates of the outer and inner parts of CFRP are different during TDT; thus, the amount of damage is different between the rCFs collected from the outer (oCFs) and inner (iCFs) parts of CFRP. This study investigated the tensile fracture characteristics of the oCFs and iCFs of the CFRP laminates subjected to TDT, through the single-fiber tensile test and fracture surface observations. The tensile strength of the iCFs was higher and presented a narrower variation than that of the oCFs because the fracture of iCFs occurred from the largest pit formed on the skin whereas that of oCFs occurred from the largest defect in the core. Finally, the strength distribution of the rCFs collected randomly from the TDT treated CFRP was estimated using a mixture distribution model with the aid of the experimental data. The model fitted the strength distribution well. The results indicated that the strength of the rCFs varied more widely with an increase in the number of rCFs undergoing the core fracture.

Fabrication and investigation of the physico-mechanical properties of Jute-PALF reinforced LLDPE hybrid composites: Effect of gamma irradiation

The hybridization effect of agro-waste pineapple leaf fibre (PALF) and jute fibre as reinforcement in linear low-density polyethylene (LLDPE) composites was investigated in this work. The samples were fabricated by using the heat press compression moulding. The effect of gamma irradiation on composite physico-mechanical properties was also investigated in order to determine the best gamma dose among 2.50, 5.00, 7.50, and 10.00 kGy. The composite sample containing 40% PALF and 60% jute (with a total weight of 50% fibres) demonstrated the most feasible tensile strength (33.36 ± 0.59 MPa), tensile modulus (1494.41 ± 10.94 MPa), elongation at break (50.92 ± 0.77%), bending strength (82.58 ± 0.49 MPa), bending modulus (4932.46 ± 96.12 MPa), and impact strength (34.38 ± 0.42 kJ/m2) at 7.50 kGy irradiation. Thermogravimetric analysis (TGA) determined the thermal performance of the samples. Scanning electron microscopy (SEM) images at the tensile fracture surfaces of composites revealed the interfacial interaction between reinforcement fibres and matrix.