Key Engineering Materials Vol. 1031

Abstract: This study examines the performance of hybrid steel-GFRP pipes compared to steel pipes, with a focus on bonding properties and the occurrence of internal corrosion. Some pipes were worn screw-shaped to mimic the effects of corrosion. The hybrid material was manufactured from two steel pipes reinforced with GFRP, bonded with polyester resin and 10% styrene to reduce viscosity and prevent bubble formation. Distortion problems during the manufacture of the specimens are addressed. Results indicate greater deformation in the worn pipes than in the steel-only specimens, whereas the hybrid material showed no significant difference between the two types. The hybrid material supported higher loads in some probes, but only two hybrid probes failed. Strain gauges measured the deformations, and the composite material's behavior was examined under a microscope. The hybrid material presented a lower flexural modulus and greater compliance to cracking. Despite the performance of the proposed hybrid material not being able to stand up to steel’s superior mechanical properties, the study offers useful insights and recommendations for future research, backed by stress-strain graphs.

Abstract: Woven glass fibre-reinforced polymer composite materials are widely used in different sectors, replacing traditional construction materials with their advantages in lightweight construction, high strength-to-weight ratio, etc., and especially their ability to impart transverse stiffness to the structure. The objective of the current investigation is to introduce a side edge notch to the laminate and study the failure pattern. The effect of crack length on the failure pattern and strength of the laminate is also studied here using the extended Finite Element Method (XFEM). Maximum stress criteria based on bilinear traction separation law are utilised for crack initiation, and critical energy release criteria are used for crack opening and propagation. The results show the effectiveness of XFEM in capturing failure patterns in the laminate for all the considered cases.

Abstract: A reliable hybrid modeling and simulation methodology is developed to predict the progressive damage evolution and ultimate strength in multidirectional fiber-reinforced polymer (FRP) composite laminates. The integrated modeling approach combines continuum damage modeling (CDM), the extended finite element method (X-FEM), and the cohesive zone modeling (CZM) technique, to capture fiber breakage, polymer matrix major cracking, composite ply interlaminar delamination, and the interactions of these failure modes. The Schapery theory is incorporated into the finite element model to accurately simulate the pre-peak nonlinearity of the load-bearing response caused by matrix micro-cracking. Multidirectional composite laminates with open-hole tension (OHT), open-hole compression (OHC), filled-hole tension (FHT), and filled-hole compression (FHC) configurations are examined as case studies. It is demonstrated that this hybrid modeling framework and methodology can effectively and efficiently capture the complex composite damage progression and properly predict the residual strengths of damaged composite laminates.

Abstract: This study investigates the effectiveness of a commercially available two-part fiberglass patching kit for repairing steel plates with cracks of varying sizes. The kit, produced by DuraPower Product Inc., includes a fiberglass patch, resin, and an activator, which serve as the adhesive for the repair. Four steel plates were tested: one without a crack and three with small (5 mm), medium (13 mm), and large (20 mm) cracks machined at the center. The repair process involved applying a fiberglass patch to each plate, and Non-Destructive Evaluation (NDE) using PZT-SLDV Lamb waves employed to assess the repaired specimens. The NDE results showed that the patching material significantly influenced wave energy transmission, with wave energy being more confined within the patch on the repaired surfaces. The study demonstrated that the repair process was effective in restoring the structural integrity of plates with varying crack sizes, successfully addressing defects of different lengths, and achieving good adhesion with minimal air bubble formation. This research provides valuable insights into the real-world applicability of the patching kit for repairing cracked steel surfaces.

Abstract: Due to their ability to impart transverse stiffness, glass fibre-reinforced polymer (GFRP) composite materials have increasingly been used in different sectors, especially the woven type. The assembly of such materials in many configurations requires drilling a hole, thus creating a material discontinuity in that component. The failure strength and mode of failure significantly depend on the shape of such notches. The analysis of the effect of notch shapes and sizes is of utmost importance from a design point of view. In this investigation, the numerical model of woven GFRP laminates with various shaped notches is developed and subjected to a displacement-controlled quasi-static tensile test. The size of the notches is also varied to study its effect on the laminate's Bearing Strength (BS). The effect of three shapes, constituting a circle, a square, and a diamond, is evaluated for different ply orientation angles on their failure pattern is identified.

Abstract: This study investigates the cause of in-service failure in a sprinkler system pipe, focusing on the material condition and the presence of perforated areas. The research involves a comprehensive analysis of the pipe material, including its: chemical composition analysis, macroscopical and microstructural examinations, tensile and HV10 hardness testing. The study case also examines the characteristics of the perforated areas, such as their size, shape, and distribution. Through a combination of material characterization techniques and failure analysis methods, the research aims to identify the root cause of the pipe failure, including potential contributing factors such as corrosion, stress cracking or manufacturing defects. The findings provide valuable insights into the mechanisms of failure in sprinkler systems and contribute to the development of strategies for preventing similar incidents in the future. From the analysis of the materials/sections received from the beneficiary, it follows that there is both a difference in nominal wall thickness between the material from the old system and that from the new system, put into operation in 2020, of approximately 1 mm, a difference in metallographic structure in longitudinal and transverse direction, as well as difference in mechanical characteristics.

Abstract: This research examines the friction and wear characteristics, as well as the mechanical properties, of EPDM (ethylene propylene diene monomer) rubber filled with oleamide. The friction measurements are done in contact with PA66GF30. The goal is to determine the suitability of this material combination for usage in dynamic sealing applications on the cathodic side of PEMFC (Proton Exchange Membrane Fuel Cell) systems. The EPDM rubber, specifically designed for reduced friction, underwent aging procedures such as heat aging and water-glycol soaking to assess its long-term performance. The pin-on-disk tests demonstrated a rapid initial rise in the coefficient of friction (CoF) and notable wear, but the hot water extraction experiments showed inadequate chemical stability with substantial ion leaching. The tensile tests demonstrated a significant decrease in mechanical characteristics during the aging process. The findings indicate that the EPDM containing oleamide has promise for dynamic sealing. However, its performance is greatly affected by aging and exposure to the environment, which highlights the need for more material optimization.

Abstract: Protective foils for buttons fabricated using 3D printing with TPU (Thermoplastic Polyurethane) material offer innovative solutions for enhancing durability, functionality, and user experience in various applications. TPU, known for its elasticity, abrasion resistance, and transparency, is ideal for creating thin, flexible foils that shield buttons from wear, moisture, and contaminants while maintaining tactile feedback. The 3D printing process allows for precise customization, enabling the production of foils that fit specific button designs with high accuracy. This approach is particularly beneficial in sectors like consumer electronics, automotive, and industrial equipment, where buttons are subject to frequent use and harsh conditions. Moreover, TPU's resilience ensures long-lasting protection without compromising the aesthetic or ergonomic qualities of the buttons. The integration of 3D printing technology facilitates rapid prototyping and production, allowing for quick iterations and tailored solutions to meet diverse protective needs. Overall, the use of TPU in 3D-printed protective foils represents a significant advancement in the design and manufacture of durable, high-performance button covers.

Abstract: The current work investigates the high cycle fatigue behaviour of two aluminium alloys (5754-H22, 6082-T4) under a tensile shear-loading condition joined by clinching methods. Clinching is a rapidly growing technology in the automotive, electronics, and household appliances industries. Several industrial sectors apply this technology to join lightweight materials due to their cost-effective and environmentally friendly characteristics that involve interlocking two (or more) sheets of materials without the need for additional fasteners or adhesives. Clinched joint specimens were prepared using a standard clinching process, ensuring consistent joint geometry and interfacial contact. The joined sheets have been produced in three levels: a similar pair of 5754, a similar pair of 6082, and a combined of 5754-6082, with a bottom thickness of 0.5 mm and a base TOX tool dimension. Subsequently, the high cycle fatigue behaviour of the clinched joints was assessed through cyclic loading tests. The ΔL-N curves were constructed to illustrate the relationship between the number of cycles to failure and the applied load range levels. Both the fatigue and the previous tensile strength tests were conducted with an MTS-type electro-hydraulic materials testing equipment. During the constant load amplitude investigations, the stress ratio was constant (0.1). Furthermore, a sinusoidal loading waveform with a frequency of 30 Hz were applied for the entire test series. Additionally, all tests were carried out at room temperature and in laboratory air. The results from the tests indicated that both the tensile shear and the high cycle fatigue resistance, in other words, both the static and cyclic behaviour of clinched joints were appropriate. In conclusion, this investigation provides valuable insights into the mechanical performance of aluminium alloy clinched joints under both loading conditions. The findings emphasize the importance of joint design optimization for improving durability and reliability in structural applications Results, show that the high cycle fatigue strength of the clinched joints represents competitive fatigue resistance than traditional welding joints.