Papers by Keyword: Tensile

Abstract: Polymethylmetharylate (PMMA) has been widely used for aircraft canopies and transparent structural components, and processed into various parts through vacuum forming. In this study, the effects of forming speed and deformation characteristics on thickness uniformity during high-temperature vacuum forming of PMMA were analyzed. First, creep tests and high-temperature tensile tests were conducted at the specimen level to quantitatively distinguish between creep deformation and plastic deformation. Creep tests were performed under constant temperature and load conditions, and strain was measured through Digital Image Correlation. For plastic deformation analysis, tensile tests at room temperature and elevated temperatures were carried out to compare yield strength and elongation changes. To analyze thickness uniformity during the forming process, rectangular-shaped parts were fabricated using vacuum forming under various conditions where temperature and forming speed are key variables. After forming, thickness uniformity and surface transparency of the products were measured. Additionally, internal structural changes according to forming speed and temperature conditions were analyzed, and a comprehensive evaluation of material stability was performed.

Abstract: This study explores the potential of self-healing concrete with bacteria encapsulated in calcium lactate and expanded clay (LECA) to enhance the durability and strength of concrete structures. The effect of encapsulating Lysinibacillus sphaericus bacteria in LECA on the mechanical properties of concrete was investigated, including compressive and tensile strength. Calcium lactate acts as a precursor and nutrient source for the biomineralization process through Microbially Induced Calcium Carbonate Precipitation (MICP). Experimental results demonstrate that concrete with bacteria encapsulated in LECA exhibits a significant increase in compressive strength compared to conventional concrete and concrete containing non-encapsulated bacteria. This increase is attributed to the protection provided by LECA to the bacteria and calcium lactate, promoting their self-healing activity and improving the concrete's ability to withstand loads. An increase in compressive load was observed for design DR-5 compared to DR-0 (control), with increments of 3.40%, 0.21%, and 6.92% on days 7, 14, and 28, respectively. However, challenges were identified regarding tensile strength, as design DR-5 was initially lower than design DR-0 by 24.25% and 19.51% on days 7 and 14, respectively. Nonetheless, on day 28, design DR-5 surpassed the control design by 1.45%. This study concludes that the encapsulation of bacteria in LECA, along with calcium lactate as a nutrient source, is a promising strategy for enhancing the performance of self-healing concrete, opening new avenues for research and applications in sustainable construction.

Abstract: This research improves the mechanical properties of laminates in ship hulls made of glass fiber reinforced plastics (GFRP) with the design of auxetic sheets, to take advantage of the property in their geometry to reduce the damage energy due to surface impacts absorbed by the laminate. 3D printing of second generation auxetic components to produce modified specimens. Laboratory reproductions of mechanical damage were compared with those of specimens extracted from a ship under construction. The mechanical properties of the bending and tensile tests demonstrated that the insertion of the core in the laminate protected the matrix from damaged energy, prolonging its useful life. Comparative results are presented, which will allow GFRP hull designers to insert auxetic sheet cores into their design. Mechanical tests allowed us to compare the progress of delamination.

Abstract: Composite fibers are a significant aspect in changing the mechanical properties through the direction of the fiber. The proposed composite fiber organized by the direction of 90º-45º-90º, 45º-90º-45º, and 90º-90º-90º can add to the substitution of composite fiber that enhances stiffness and impact strength. Thus, the Acrylonitrile-butadiene-styrene ABS arrangement has a place with amorphous polymers that can expand the effect and increase the impact and the mechanical properties, for example, woven ramie utilizing different direction orientations. The outcomes show that the elasticity direction of 45º-90º-45º is 56wt%, 90º-45º-90º is 83wt%, and further increments while utilizing 90º-90º-90º is 94%. The analyses incorporate tensile tests to obtain tensile stress, tensile strain, and elastic modulus, which are performed on the ASTM D3039 utilizing the General Testing Machine Zwick Roell Z020. Findings demonstrated that specimens with various directions demonstrated mechanical characteristics that produce different mechanical properties through stress-strain analysis. The toughness of various directions can endure influence stacking without a fracture with 90º-45º-90º, and toughness for 45º-90º-45º and 90º-90º-90º show the stored energy without having permanent deformation ASTM D256 utilizing Zwick Roell Effect Analyzer HIT 2P. Furthermore, SEM images were also obtained to see the morphological changes on the composite polymer surface due to the tensile test. Overall, the utilization of the tensile test shows the maximum stress that the structure can maintain. Assuming fibers are oriented parallel to the main loading direction 0° and 90° will provide greater strength in that direction, while fibres diagonal 45º more absorb energy. By observing the SEM results, there is no reduction in strength and toughness through the 90º-45º-90º orientation of the layers using the hand laid-up technique.

Abstract: Hybrid Fibre Metal Laminates (HFMLs) are composite materials made of alternating layers of metal and fibre-reinforced polymers. The paper discusses the development of HFMLs and their applicability in aerospace applications when compared to conventional FMLs. Experimental (Mechanical and vibrational) studies are conducted to assess the strength and vibrational properties of these materials. Mechanical and vibrational characteristics of the proposed materials are explored and presented. Aluminium 2024 T3 sheets as metal layer and hybrid (glass, carbon) polymer fibre reinforcements are used for developing hybrid lightweight laminates. SEM (scanning electron microscope), and stereomicroscopy are used for microscopic characterization studies and a universal testing machine (UTM) is employed to perform mechanical characterization. The impact behaviour of these materials is also disclosed using the Charpy impact test. An improvement in the strength and vibrational properties are clearly observed in the FMLs after fibre hybridization, which may be due to improved bonding compatibility in carbon prepregs. The outcome of the research contributes to the advancement of lightweight materials for next-generation aerospace structures.

Abstract: Steel has been one of the most widely used materials in land and sea construction due to its advantageous properties, especially carbon steel. This study focuses on molecular dynamics simulation to demonstrate carbon steel’s mechanical behavior. A uniaxial tensile test was conducted for body-centered cubic (bcc) structured carbon steel and pure iron to learn the effect of carbon presence. Both simulation cells were simulated under temperature variation to reveal its effects. It was found that carbon steel is stronger than pure iron based on their value on yield and tensile strength, namely up to 2.434 GPa and 1.368 GPa respectively, which are stronger at room temperature. This study also revealed that carbon steel exhibits better elastic properties with a Young’s modulus of 285.749 GPa, compared to that of pure iron 230.117 GPa. Additionally, this molecular dynamic study also identified another phenomenon, such as brittle-to-ductile temperature of carbon steel at 340 K. Structural explanation is provided in the form of bcc structure fraction during the strain progression and under temperature variation. These findings provide a comprehensive molecular perspective to unveil mechanical properties of carbon steel.

Abstract: This study examines the impact of Al₂O₃ particles on composites made of sisal and epoxy. A unique combination of hand lay-up and compression molding procedures are used to fabricate the Sisal/Al₂O₃/epoxy hybrid composites, with different weight percentages of Al₂O₃ particles of 0%, 1%, 2%, and 3%. The produced sisal/Al₂O₃/epoxy hybrid composites' flexural, tensile, and compressive properties are then correlated with water absorption studies. The sisal/epoxy composites have undoubtedly been affected by the Al₂O₃ particles, which have improved their mechanical and physical properties. Compared to other composite samples, the sisal/2wt.%Al₂O₃/epoxy hybrid composites show superior flexural, tensile, compressive, and water absorption resistances. Therefore, the optimal combination of hybrid sisal/Al₂O₃/epoxy composites can prominently improve the properties, making them a viable alternative for a variety of industrial applications.

Abstract: Post weld heat treatment is heating objects in the furnace to certain temperatures and times after the object has been welded. PWHT is expected to reduce residual stress on objects due to the welding process. In this case, we warm up annealing (holding in a furnace) at a temperature of 750 °C with a heating time of 40 minutes. We use MIG welding (metal inert gas) and a metal filler FS 705-6 with a diameter of 0.8 mm, with a total of 3 layers. First, the object will be formed according to the standard and welded in three layers with MIG welding. Then, the object will be cut and formed according to the tensile test standards, after which the tensile test and hardness test will test it to determine the mechanical characteristics of the object. From the testing that has been carried out, it is known that objects without PWHT have a higher stress and hardness value than objects with PWHT, with a stress value of 346.57 MPa and the highest hardness value of 93.5 HRB at the 3rd welding point. However, objects with PWHT have higher elasticity and strain values, with an elasticity value of 3.32 MPa, and the strain value of objects with PWHT is 13.1.

Abstract: Fracture mechanics has been a crucial aspect in the field of engineering science as technologies are rapidly growing nowadays. Various numerical methods have been developed to analyze fracture behaviour in different types of materials used in industries. Meanwhile, the application of polymers garners attention worldwide due to outstanding characteristics such as good strength, lightweight, and high temperature resistance, exemplified by polymers like polycarbonate (PC) and polypropylene (PP). Hence, failure aspects of such materials must be taken into consideration when conditions arise that may lead to failure, such as high-load impact, fatigue, and extreme temperatures. In this study, a bond-based Peridynamic model (PD) for the tensile behaviour, including fracture, of polymers has been developed. The PD model is constructed using the Centos software and encompasses both brittle and ductile fracture behaviours. Numerical results, including crack propagation, damage zone, and force-extension curves of notched specimens, are validated by comparison with experimental results of PC and PP. Through the validation process, PC specimens exhibit a difference percentage range for maximum load and rupture extension of 2.9% to 18.8% and 2.4% to 4.6%, respectively. PP specimens show a difference percentage range for maximum load and rupture extension of 31.2% to 43.5% and 0.9% to 30%, respectively. Consequently, the validation results indicate that the PD model for brittle specimens aligns more closely with experimental data compared to the PD model for ductile specimens.

Abstract: The objective of this work is to carry out a comparison of different materials in the form of a bidirectional carbon fabric and hybrid Kevlar and glass as reinforcements in an epoxy matrix with a loading rate of 30wt%. Two experimental tests have been carried out in order to determine the mechanical properties, such as tensile and Brinell hardness tests. In the case of tensile and Brinell hardness tests, the characterization was performed on two types of composite plates reinforced with Woven Carbon Fiber and Hybrid Woven Kevlar and E-Glass with Epoxy (WCF-HWKG/EPOXY) and Hybrid Woven Kevlar and E-Glass with Epoxy (HWKG/EPOXY). Consequently, it has been observed that the tensile and hardness properties of the hybrid composite material (HWKG/EPOXY) are respectively 36% and 46.43% lower compared to (WCF-HWKG/EPOXY). Based on these findings, the studied materials demonstrate potential applications across various fields, including aeronautics, aerospace, and high-performance automotive sectors.