Fracture Cross-section Research Articles

Pengaruh Penambahan Serat Pohon Bambu Ampel (Bambusa Vulgaris) pada Komposit Hybrid untuk Material Bumper Kendaraan Bermotor

Technological developments continue to increase in line with the times, producing various innovations that provide benefits to society, especially in the material sector. The use of a mixture of natural and synthetic fibers in composites (hybrid) has produced a stronger material, which can function as an alternative material for car bumpers. This research was carried out with the aim of determining the values ​​of impact toughness, tensile strength, and failure patterns that occur in the fracture cross section of the specimen through macro photographs. In this research, a hybrid composite was formed by combining ampelous bamboo fiber, fiberglass, and polyester resin. Variations in volume fraction applied include: 5%:25%:70%, 10%:25%:65%, and 15%:25%:60%. The specimens were formed according to ASTM E23 standards for impact tests and ASTM D638 for tensile tests. The results of the impact and tensile tests showed that the lowest value of impact toughness was 0.0744 J/mm² and tensile stress was 120.29 MPa. Meanwhile, the highest value for impact toughness was 0.0986 J/mm² and the tensile stress value was 147.65 MPa. Macro photo analysis of the fracture cross section is categorized as splitting in multiple areas and the fracture cross section also shows debonding and fiber pull out after the fracture occurred.

Sifat Mekanik Komposit Serat Pelepah Kelapa Sawit sebagai Penguat Komposit Terhadap Kekuatan Tarik dan Impak

Palm fronds are solid waste from oil palm plantations that contain a lot of natural fibers. One of the utilization efforts that can be done is to optimize palm frond fiber waste into composite materials. The use of natural fiber mixtures in composites has produced stronger materials, which can serve as alternative materials for car bumpers. This research was conducted with the aim of knowing the value of impact toughness, tensile strength, and the type of failure that occurs in the fracture cross section. In this study, composites were made using palm frond fibers and polyester resin. The volume fraction variation applied is 30% fiber and 70% matrix with fiber lengths of 20 mm, 40 mm, and 60 mm. Impact toughness testing refers to ASTM E23 standard and tensile strength testing refers to ASTM D638 standard. The impact toughness value obtained in the 20 mm variation was 0.0065 J/mm², 40 mm was 0.0108 J/mm², and the 60 mm variation had the highest value of 0.0164 J/mm². The tensile strength value obtained in the 20 mm variation is 6.18 MPa, the 40 mm variation is 8.26 MPa, and the 60 mm variation has the highest value of 16.45 MPa. Analysis of the fracture cross section is categorized as a splitting fracture in multiple areas and the fracture cross section also shows the occurrence of fiber pull out after the fracture.

Investigation of shaft and segment failure in co-rotating twin-screw extruder

This research is focused on identifying the reasons behind the failure of the shaft and screw segment associated with the ABS plastic material co-rotating twin-screw extruder. These steel parts failed during production and after only 12 days of operation. To understand the failure causes, their chemical composition was examined initially. The results showed that the chemical composition of the analyzed parts meets the design and standard of BS EN 4957 (2018). Subsequently, a detailed study of the fracture cross-section of both pieces was conducted, along with microscopic and mechanical tests, to gather comprehensive information on the failure reasons. The findings indicate that the initiation of the cracks is linked to the presence of coarse carbide deposits, leading to micro-cracks on the surface of the shaft. Under torsional-bending cyclic loading, these cracks expanded as low-cycle fatigue fractures. When the fatigue crack reached its critical extent, rapid and abrupt crack propagation and failure ensued. Furthermore, defects like holes and coarse sediments within the segment also contributed to the conditions conducive to rapid crack growth and failure. In conclusion, to prevent future accidents and issues with comparable equipment, various safety measures and recommendations were introduced.

The effect of Polyolefin elastomer on the 3D printing properties of Acrylonitrile butadiene styrene, Polyethylene, and Polypropylene

This study investigates the influence of incorporating 30 wt.% polyolefin elastomer (POE) on the physical, mechanical, and microstructural properties of 3D printed three widely used thermoplastic: acrylonitrile butadiene styrene (ABS), low density polyethylene (LDPE), and polypropylene (PP). Three ABS-POE, LDPE-POE, and PP-POE blends were prepared by melt mixing method and printed by direct granule-based material extrusion, and finally the printability, microstructure, thermal, and mechanical properties aiming for potential usage in various applications were investigated. Dynamic Mechanical Thermal Analysis (DMTA) results revealed a notable shift in the glass to rubber phase to a higher temperature range and an increase in the glass transition temperature due to the presence of POE elastomers. Mechanical properties of the 3D printed samples were meticulously examined and compared with prior research. All blend samples containing 30 wt.% POE exhibited significantly enhanced ductility, attributed to aligned polymer chain reactions. ABS-POE samples demonstrated superior mechanical properties compared to PP-POE and LDPE-POE samples, likely attributed to fewer potential failure points, as evidenced by Scanning Electron Microscope (SEM) analysis of fractured cross-sections of 3D-printed samples immersed in liquid nitrogen. Additionally, 3D-printed samples with combined infill orientations (0° and 90°) were generated and subjected to tensile strength testing. Furthermore, samples 3D-printed specimens by honeycomb filling pattern for compression tests were included in the study. Microstructure analyses identified common 3D printing defects responsible for failure modes in the printed samples.

Effect of N2 to total pressure ratio on the structure, mechanical and tribological properties of magnetron-sputtered Ti-Al-Ta-Si-N coatings

Ti-Al-Ta-Si-N coatings produced by reactive DC magnetron sputtering at the nitrogen to total pressure ratio (pN2/pt) varying from 0.1 to 0.4 are studied. Using energy dispersive X-ray spectroscopy it is shown that pN2/pt has a pronounced effect on the elemental composition of the coatings. Ti and Al contents vary most significantly that causes the Al/Ti ratio to change from 0.68 to 1.20 within a pN2/pt range of 0.1 to 0.17, which is followed by its decrease down to 0.85 at pN2/pt = 0.4. X-ray diffraction measurements reveal that (200) texture of the face-centered cubic structure evolves with increasing the pN2/pt ratio. It is found that while the coating obtained at pN2/pt = 0.1 has featureless fracture cross-section morphology, the sample deposited at pN2/pt = 0.17 exhibits pronounced columnar morphology. In contrast the coatings produced at pN2/pt ≥ 0.23 are characterized by denser microstructure with no obvious columnar grains. The evolution of the structure and chemical composition results in variations of the hardness, the reduced Young's modulus, adhesion and wear resistance of the Ti-Al-Ta-Si-N coatings. The coating deposited at pN2/pt = 0.23 is found to be characterized by an optimal combination of the reasonably high mechanical characteristics along with improved adhesion and wear resistance. Due to the dense fine-grained microstructure, its wear rate is almost four times lower than that of the coating obtained at pN2/pt = 0.1.

Improving the performance of CFRP-reinforced concrete cylinders in sulfate-laden environment through nanoclay modification of epoxy resin

The durability of epoxy-concrete interface is a crucial factor for practical application of externally bonded fiber-reinforced polymer (FRP) retrofit systems, particularly when the strengthened structure is subjected to severe environmental conditions. Given the demonstrated potential of nanoclays in enhancing engineering performance of polymers, this work assesses the beneficial effect of organic montmorillonite (OMMT) nano-modification of epoxy resin on the axial compressive properties of FRP-reinforced concrete under a 10 wt% sodium sulfate wet/dry (W/D) cycling environment. Three types of concrete samples were fabricated and tested: plain concrete cylinders, CFRP-reinforced concrete cylinders using unmodified vs. OMMT-modified epoxy resin as the adhesive, respectively. The optimal dosage of OMMT was determined to be 2 wt% through tensile and lap shear tests, as well as microscopic characterization of the fractured cross-section of the molded resin samples. This optimal dosage of OMMT allows the epoxy adhesive to achieve the highest values in the tensile strength (90.4 MPa), lap shear strength (80.0 MPa), Tg (280.5°C) and water contact angle (115.1°). In the fracture section of epoxy resin with a 2 wt% OMMT, multiple microcracks developed and the OMMT nanoplatelets were well dispersed in the epoxy matrix. The laboratory testing program explored various W/D cycle periods. The experimental results indicate that the OMMT-modified epoxy resin significantly improved the mechanical properties and deformation resistance, altered the failure mode, and effectively delayed the strength degradation of the protected concrete. After 150 W/D cycling days, the OMMT-modified CFRP-confined concrete samples maintained their ductility coefficient and axial compressive strength at 3.58 and 123.5 MPa, respectively, 12.6 % and 9.1 % better than the common CFRP-confined samples. Combining these results with the residual axial compressive strength ratio, we propose an improved design model for calculating the axial compressive strength of CFRP-retrofitted concrete structures in sulfate-laden environments. This study demonstrates the beneficial role of OMMT in enhancing the epoxy adhesive and provides insights into the reinforcement of concrete structures by externally bonded CFRP in sulfate-rich environments.

The Influence of Centerline Segregation on Impact Toughness in Welding Heat-Affected Zone of X70 Pipeline Steel

The influence of centerline segregation on the low-temperature impact toughness of the heat-affected zone (HAZ) of welded joints was studied by welding experiments on X70 steel plates rolled from continuous casting slabs with segregation grades of class 2 and class 3. The experimental results show that the impact toughness at HAZ from class 2 slab steel plate is more stable and has excellent low-temperature toughness than that of class 3 slab steel plate. The impact toughness of the HAZ of the class 3 slab steel plate is low to 100 J at −40 °C and has a severe fluctuation range (~150 J), and the delamination phenomenon is also observed in the fracture cross-section. The reason for this phenomenon is due to the enrichment of C and Mn elements in the centerline segregation zone. The formation of abnormal microstructure (martensite/bainite) in the segregation zone leads to stress concentration, which easily weakens the low-temperature toughness of the joint.

Effect of stable-structural 3D woven preform on tensile and flexural properties of carbon fiber/epoxy composites

The geometry of yarns effect the structural stability of 3D woven preform, which influence the mechanical properties of carbon fiber/epoxy composites. To investigate the effect of stable-structural preform on the elastic properties of 3D woven composites, the factors that caused the unstable structure of preform were discussed, and comparative study was conducted. The geometric models of yarn cross-section and preform were established to discuss the stability. The results showed that increasing the opening angle of warp yarns and the elongation of yarn outer contour can improve the stability of preform. The tensile and bending tests of 3DLAC and 3DBAC with stable and unstable structural preform were conducted. The results showed that the tensile and flexural elastic moduli were inversely proportional to the curvature of load-bearing yarns, and the elastic modulus of composites with stable-structural preform can increase by 9%–13%. The redistribution of internal stress in composites was macroscopically manifested as stable changes in experimental process. 3D woven composites with stable-structural preform showed the regular fracture cross-section, and fiber fracture and interface adhesion effect were the main failure mode in tensile tests, and fiber fracture on the compression surface and matrix cracking were the main failure modes in bending tests.

A comparison of the mechanical properties of 3D-printed, milled, and conventional denture base resin materials.

This study investigated the mechanical properties of three denture base resin materials produced by three-dimensional (3D) printing (Group P), computer-aided design/computer-aided manufacturing milling (Group M), and conventional (Group C) methods. Three-point flexural tests were performed before and after thermocycling treatment to evaluate the mechanical properties. Additionally, nanoindentation and dynamic mechanical analysis (DMA) were used to analyze the behavior of the materials. After flexural strength tests, scanning electron microscopy (SEM) was performed to evaluate the fracture cross-section. The results consistently showed that Group P exhibited significantly higher flexural strength and modulus regardless of thermocycling than Groups C and M (p<0.05), along with a higher storage modulus in DMA and greater resistance and resilience to nanoindentation deformation. SEM analysis showed that Group C had a relatively smooth cross-section, whereas Groups M and P had torn cross-sections. This study suggests that the 3D-printed material has suitable mechanical properties for hard dental prosthesis applications.

Non-Covalent Functionalization of Graphene Oxide with POSS to Improve the Mechanical Properties of Epoxy Composites.

Phenyl polyhedral oligomeric silsesquioxane (POSS) is modified onto the GO surface by using the strong π-π coupling between a large number of benzene rings at the end of the phenyl POSS structure and the graphite structure in the GO sheet, realizing the non-covalent functionalization of GO (POSS-GO). The POSS-GO-reinforced EP (POSS-GO/EP) composite material is prepared using the casting molding process. The surface morphology of GO before and after modification and its peel dispersion in EP are examined. Furthermore, the mechanical properties, cross-sectional morphology, and reinforcement mechanism of POSS-GO/EP are thoroughly examined. The results show that the cage-like skeleton structure of POSS is embedded between the GO layers, increasing the spacing between the GO layers and leading to a steric hindrance effect, which effectively prevents their stacking and aggregation and improves the dispersion performance of GO. In particular, the 0.4 phr POSS-GO/EP sample shows the best mechanical properties. This is because, on the one hand, POSS-GO is uniformly dispersed in the EP matrix, which can more efficiently induce crack deflection and bifurcation and can also cause certain plastic deformations in the EP matrix. On the other hand, the POSS-GO/EP fracture cross-section with a stepped morphology of interlaced "canine teeth" shape is rougher and more uneven, leading to more complex crack propagation paths and greater energy consumption. Moreover, the mechanical meshing effect between the rough POSS-GO surface and the EP matrix is stronger, which is conducive to the transfer of interfacial stress and the strengthening and toughening effects of POSS-GO.

Fatigue fracture cross-sections after cyclic tests with a combination of cyclic bending and torsion of samples made of aluminum alloy 6060

The paper presents the results of fatigue tests of the 6060 aluminum alloy. The test material was taken from the profiles used for production of side windows and external doors of the passenger trains by the RAWAG company. The tests were carried out for cyclic loads with pure bending, pure torsion, and two combinations of bending and torsion. Fatigue tests were performed at zero mean values. Using scanning electron microscopy, a fractographic analysis was made, which is a supplementary basis for considerations about the mechanism of initiation and development of fatigue cracks. Based on the appearance of individual zones and the characteristics of cracks, a picture of the behavior of the material under specific conditions was obtained. Finally, the plastic property of fatigue cracks was indicated. The work demonstrates the influence of aluminum alloy processing on the fatigue properties of this alloy during operation in order to obtain maximum reliability and safety of railway transport.

Residual stress effect on fatigue behavior of steel welded: A review

A manufacturing process that can be used to join two or more steels by welding. This process involves an uneven distribution of heat which causes residual stresses to occur. Residual stresses in the material, even though the external forces acting have been removed in the local heat distribution area in plastic deformation. Residual stress has a significant relationship with material exhaustion. Tensile residual stress (TRS) can reduce fatigue life, while compressive residual stress (CRS) will increase fatigue life. CRS makes the stress received by the material lower, resulting in a more expansive Fatigue Crack Propagation (FCP) area and a much smaller final fracture cross-section. Materials with CRS have a higher fatigue life than materials without CRS. Fatigue resistance can be increased by reducing the residual stress in tension. Currently one method that is widely used to increase fatigue resistance is shot peening. Shot peening provides CRS on the surface so that crack initiation originates below the surface of the material causing an increase in fatigue resistance.

Construction of a high-performance anti-corrosion epoxy coating in the presence of poly(aniline-co-pyrrole) nanospheres

Since corrosion with its direct and indirect negative effects is a global issue, coatings are commonly used as a structural corrosion protection strategy. The reinforcement effects of Poly (aniline-co-pyrrole) (PACP) nanospheres on corrosion resistance of solvent-based epoxy coatings are investigated in this study. The corrosion behavior of mild steel substrates coated with epoxy containing different weight percents (0.25, 0.5, 0.75, and 1.0 wt%) of PACP nanospheres is investigated using electrochemical impedance spectroscopy (EIS) in a 3.5 wt% NaCl solution, while the fracture cross-section is studied by field emission scanning electron microscopy (FE-SEM). The incorporation of the PACP nanospheres in the polymer coatings considerably improves the protective performance of the epoxy coatings. The results of the EIS test shows that the highest corrosion resistance is for the EP-PACP- 0.75 wt% sample. In the first day of immersion, |Z|100kHz is equal to 5.2 × 1012 Ω.cm2, which is much more than the pure epoxy sample (105 Ω.cm2). After two months of immersion, the resistance reduction for the optimum sample is negligible and the amount of water uptake into the coating is the lowest. These findings demonstrate that the epoxy/PACP nanocomposite is superior when compared to the pure epoxy coating.

Alteration of Cu3Sn growth and retention of multi-orientation Cu6Sn5 during thermal aging in Cu-xNi-yZn/Sn3.5Ag/Cu transient liquid-phase bonding

With the development of the artificial intelligence (AI) industries, electronic packaging is developing in the direction of high-density, high efficiency and multi-functionality. To realize the high density and tiny scale interconnection, application of microbumps is inevitable. Thus, the mechanical and thermal properties of intermetallic compounds (IMCs) become quite important as the proportion of IMC in the bump is greatly increased. In this study, three types of full IMCs bump, Cu/Sn-3.5Ag(SA)/Cu, Cu18Ni/SA/Cu and Cu18Ni18Zn/SA/Cu, were fabricated through transient liquid phase (TLP) bonding. The evolution of orientation and the sizes of the Cu6Sn5 grain before and after long-term thermal aging were analyzed and compared. After long-term thermal aging, the full IMCs bump with Ni and Zn added into Cu substrate simultaneously maintained consistent structure. In addition, the unusual growth of network-like Cu3Sn was observed in Cu18Ni/SA/Cu. Furthermore, the mechanical test and fracture cross-section analysis were conducted to discuss the crack paths. The study focused on establish the correlation between microstructure and mechanical performance. Network-like Cu3Sn was considered to enhance the strength of interfaces. Finally, the full IMCs bump which demonstrated the extraordinary thermal stability provided a reliable microstructure for application.

Improving fatigue performance of Cr-coated zirconium alloy cladding by ultrasonic shot-peening proces

In this paper, Cr-coated zirconium fuel claddings were treated with ultrasonic shot-peening process (USPP). The mechanism of improving fatigue performance of Cr-coated zirconium fuel cladding was investigated by low cycle fatigue experiment. It was shown that USPP effectively improved fatigue life of Cr-coated zirconium fuel cladding under different temperatures. The enhancement mechanism is that USPP treatment changes the surface topography, increases in residual compressive stress and decreases surface roughness of the Cr coating. The fracture cross-section of tested specimens show that the Cr coating has little plastic deformation, showing brittle fracture characteristics. In addition, compared to the large amount of cracking inside the original Cr coating, the integrity of the USPP-Cr coating is better. The USPP-Cr coating has fewer cracks penetrating into the substrate, indicating that the Cr coating with USPP treatment has excellent fatigue crack resistance.

Mechanical and morphological analysis of laser transmission welded dissimilar plastics using metal absorber

This study aims to investigate the laser transmission welding (LTW) of polystyrene and polycarbonate using an electrolytic iron powder absorber. For this purpose, the experiments are performed to explore the effect of laser power and scan speed on the weld strength and bond morphology. The lap shear tests are conducted to obtain the breaking force and ductility of the welded joints. The fractured surface and cross-sections are analyzed by scanning electron and optical microscopy to investigate the bond morphology and bonding mechanism of the weldments. The results show that laser power and scan speed significantly affect the weld strength and ductility of the joints. The optical and scanning electron micrographs clarify that mechanical anchoring of iron particles, polymeric interdiffusion, and small bubbles enhance the bond strength but thermal degradation, burning, and large bubbles negatively affect the bonding.

Tensile properties of transversely isotropic closed-cell PVC foam under quasi-static and dynamic loadings

The uniaxial tensile mechanical properties of PVC foam considering the effects of strain rate ([Formula: see text]) and anisotropy ([Formula: see text]) have been investigated by quasi-static and dynamic (Split Hopkinson Tensile Bar, SHTB) tests. Combined high-speed camera system and Digital Image Correlation (DIC) technique, the real-time surface strain field of the specimen during the whole tensile process was obtained. On this basis, the macroscopic response and failure mode of PVC foam were investigated. The failure mechanism of PVC foam under tensile loading was revealed through Scanning Electron Microscope (SEM) images on fracture cross-section of loaded specimen. Finally, based on experimental data, a prediction equation on tensile strength of PVC foam considering the effects of strain rate and loading angle (anisotropy) is proposed. Furthermore, a nonlinear constitutive model is developed to describe the uniaxial tensile mechanical properties of PVC foam.

Metal ion-assisted fabrication of aramid nanofilm with high strength and toughness for the dye separation

Herein, Fe3+, Co2+, and Ni2+ were respectively introduced into the splitting of aramid fibers, and then the metal hydroxide nanoparticles (NPs) were formed on the aramid nanofibers (ANFs). The nanofilm assembled from NP-grafted ANFs shows high stress, toughness, and dielectric breakdown strength. The results indicate that the ANF nanofilm contained 5 wt% Fe3+ presents the highest enhancing capacity to the mechanical properties of ANF film, with a strength of 312 MPa and a toughness of 61.9 MJ m−3, increased by 73.3% and 215.8%, respectively. The NPs increase the ANF film's dielectric breakdown strength by 40.8%–60.2%. Different from the previous studies, we have not observed the densification of the nanofilm, and the enhanced mechanical properties may be caused by the strong electrostatic and coordinate interactions between NPs and ANFs, evidenced by the large numbers of fiber pull-out on fracture cross-sections. Because of the hydrophilicity of the NPs and the un-densified structures, the composite films show both high flux and rejection to methylene blue (MLB).

M3+/NaTiO3/PVA–chitosan nanocomposites (M = Ga, Ce, Nd or Er): novel solid polymer electrolytes for supercapacitors

Designing flexible and thermally stable solid polymer-electrolyte (SPE) -based green materials for energy storage devices is an interesting approach from environmental and technological points of view. In this paper, NaTiO3 (ST) nanofibers of diameters in the range of 4.88–9.48 nm were hydrothermally prepared and loaded into the poly(vinyl alcohol)–chitosan (PVA–Ch) bio-blend via solution casting. Additionally, the obtained nanocomposite solution was mixed with Ga3+ and rare Earths (Ce3+, Nd3+, or Er3+) for preparing novel solid polymer electrolyte films. XRD results indicated the semicrystalline nature of all samples, and the degree of crystallinity decreased after loading these additives. FE-SEM and EDS were used to investigate the surface morphology, fracture cross-section and the elemental chemical composition. FTIR analysis confirmed the complexation and complete dissociation of the salts inside the blend. UV–vis spectroscopy showed that the optical band gap of the films was reduced from 4.4 eV to 3.5 eV, and the refractive index is in the range of 2.376–2.648. The thermo-gravimetric analysis (TGA) revealed that the samples are thermally stable until 200 °C, and the maximum decomposition occurs in the temperature range 255–300 °C. In addition, four endothermic peaks were detected in the differential scanning calorimetry thermograms. Dielectric properties were measured in the fRequency range of 100 Hz–8.0 MHz and at temperatures in the range of 30–120 °C. The dielectric constant and ac conductivity were greatly improved due to doping with ST and mixing the salts. The small dielectric loss associated with the improvements in the dielectric constant and ac conductivity suggest the use of the ST/blend and salts/ST/blend films for energy storage devices and related applications.

An experimental investigation of screw-based material extrusion 3D printing of metallic parts

With the introduction of additive manufacturing (AM) methods, processes with the capability of 3D printing of metal materials were noticed. In general, AM processes with the ability to 3D print metals are more complex and costly in terms of equipment than processes that 3D print other materials (polymers and ceramics). Therefore, the use of 3D printing devices with less complexity and cost, such as extrusion-based 3D printers, for metal printing has attracted the attention of researchers. In this research, an extrusion-based 3D printer, equipped with a direct granule extruder system, was used for 3D printing of the feedstock of the metal powder injection molding (MPIM) process (with 93.7 % by weight of 440 C stainless steel metal powder). The optimal parameters of printing including linear speed (10 mm/s), temperature at the beginning (140 ℃) and end of the barrel (180 ℃), chamber's temperature (60 ℃), and nozzle diameter (0.5 mm) were determined experimentally. The debinding and sintering process was performed on 3D-printed samples. The samples are brittle after the sintering process, in such a way that the failure of the samples occurs by applying a small amount of force to them. According to the scanning electron microscope (SEM) micrograph of the fracture cross-section of the sintered samples, the number of cavities and defects in the samples was negligible and the presence of residual carbon can be seen in the sintered samples. According to the results of X-ray diffraction (XRD) and energy dispersive X-ray spectroscopy (EDAX), the oxidation of iron and chromium elements as well as the presence of residual carbon (7.8 %), are the main factors for the incomplete sintering of the 3D printed samples.