Key Engineering Materials Vol. 1058

Abstract: Preface

Abstract: Manufacturing induced defects such as voids and non-uniform fiber distributions significantly affect the mechanical behavior of fiber reinforced polymer composites. However, generating high-fidelity representative volume elements (RVEs) that simultaneously capture fiber randomness and void characteristics remains a key challenge. In this work, we propose a novel adaptive fiber void generation (AFVG) algorithm to construct two-dimensional RVEs incorporating statistically controlled elliptical pores and randomly packed fibers. Based on an improved greedy placement scheme, the method integrates customized scoring functions and constraint checks to ensure realistic void morphology, orientation randomness, and fiber void spatial relationships, while maintaining target fiber volume fraction and porosity. The algorithm’s robustness is verified by spatial randomness metrics, and its effectiveness is demonstrated through finite element homogenization to predict the effective elastic moduli. Results confirm that the proposed method achieves high fiber packing efficiency and incorporates realistic void characteristics, providing a practical and extensible tool for multiscale modeling of composites with manufacturing defects.

Abstract: This study proposed the preliminary development of a new material hardness testing system. It focuses on a simulation analysis while examining the system’s composite materials hardness testing range expander (CHT-RE). A linear funnel-shaped geometric array structure was designed, using the negative Poisson’s ratio as the geometric structure of the CHT-RE. Conducting a simulation analysis of single-layer and multi-layer compression and tension, this study explored the impacts on the variations of the Poisson’s ratio, which was applied to the composite materials hardness testing design. Initial exploration and analysis were performed, testing the indentation depth, material hardness, relevant properties, and load limits of the CHT-RE, the pressure uniformity of composite materials hardness, and analysis of the nine-point stress distribution.

Abstract: When oxide fine particles are impregnated into fibers, the electrostatic potential increases and the half-life of the charged particles increase. An attempt was made to represent this discharge phenomenon using an equivalent circuit model. Fibers containing oxide fine particles were synthesized, and their electrical properties, such as half-life, electrostatic voltage, resistance, and capacitance, were measured to determine the current flowing through the fibers and the electric charge held by the fibers. Furthermore, it was confirmed that an equivalent circuit model composed of resistors and capacitors can represent the discharge phenomenon, and the capacitance and electrical charge retained by the fibers were calculated from this equivalent circuit model. The experimental capacitance and the estimated value from the equivalent circuit model were nearly equal in magnitude, and the electric charge was also nearly equal in magnitude. This suggests that the experimental values and the estimated values obtained by calculation are valid. This research method is effective for the development of fiber materials.

Abstract: The dynamic contact area between tractor tires and rigid surfaces is a key factor influencing traction performance, fuel efficiency, and tire–soil interaction. Traditional experimental techniques used to evaluate this parameter, such as high-speed imaging on transparent platforms and pressure mapping films, are costly, technically demanding, and impractical for large agricultural tires. To address these challenges, this study developed and validated a finite element model of an 8.3-20 tractor tire to investigate its dynamic rolling behavior on a rigid surface at constant velocity. The model accounted for the tire’s composite structural characteristics using specialized techniques in MSC Dytran software and was validated against tire compression tests, achieving an average error of less than 12.66%. The validated model was then used to examine the effects of three inflation pressures (151.68, 206.84, and 262 kPa) on the dynamic contact area, with results showing that at 151.68 kPa the footprint reached approximately 5143.27 cm², compared to 4880.09 cm² at 262 kPa, and further demonstrated that lower inflation pressures produced larger and more stable contact areas compared to higher pressures. These findings highlight the importance of proper inflation management, provide quantitative evidence of its effect on footprint evolution, and establish a robust and scalable framework for evaluating tire–surface interactions and optimizing tractor tire performance.

Abstract: Non-pneumatic tires (NPTs) have been increasingly considered for agricultural machinery due to their puncture resistance, reduced maintenance, and adaptability to varying field conditions. One of the critical components governing their mechanical property is the shear band, which is a composite structure. This study investigated the effects of steel belt layers inside the shear band on the energy loss characteristics of agricultural NPTs. Finite element models were developed to simulate tire deformation under a cyclic load condition. Parametric variations in belt layer numbers and alignment were analyzed to evaluate their contribution to energy dissipation. The results reveal that shear band stiffness played dominant roles in controlling rolling resistance. The results indicated that higher vertical stiffness may not necessarily reduce rolling resistance, highlighting the importance of balancing it with other performance aspects. These findings provide design guidelines for agricultural NPTs that balance durability and energy efficiency, supporting the development of sustainable agriculture.

Abstract: This study presents a finite element analysis (FEA) of an external fixator rod incorporating a carbon fiber-reinforced epoxy resin composites (CFREs) to evaluate its mechanical performance. A detailed three-dimensional CAD model of the rod was developed, and the material properties of each component were defined using composite stacking techniques within the FEA framework. The external fixator rods were subjected to various loading conditions, including axial compression, torsion, and bending. The simulation results demonstrate that 18 mm CFREs rods exhibit superior resistance to compressive, torsional, and bending loads compared to conventional stainless-steel rods. These findings highlight the potential of composite materials to enhance the structural performance of external fixators in orthopedic applications. In addition, four carbon fiber ply orientation cases were investigated to identify the optimal configuration for load-bearing capacity. The [60°, 0°, −60°, 0°] ply orientation was found to provide the best performance under axial compression, offering improved load resistance and reducing deformation between fractured bone segments, thereby minimizing the risk of bone collision.

Abstract: This work investigates the development of residual stress in thick laminates based on measured internal strain and temperature information. Here, FBG and conventional strain gauges are used to investigate the effect of curing on residual stresses in a thick Epoxy-glass composite laminate incorporated. A 14 mm thick EP-FRP laminate is manufactured by embedding strain and temperature sensors to acquire the signals during curing. Later, the EP-FRP composite is cured and the temperature and strain variation at different layers are monitored using embedded strain and temperature sensors. The experimental temperature development is used to predict the degree of cure at different layers. The knowledge of degree of cure in turn helps to estimate the resin shrinkage percentage at different layers. Strain is mainly developed due to the chemical shrinkage of resin during curing and due to the mismatch in CTE of resin and reinforcement material. Both the components of strain are measured by using the embedded strain sensors. It is observed that the middle layers gelled first (Layer 6 and 13), followed by bottom layer (Layer 1), and top layers gelled last (Layer 16,18): the gel times were 28-30 min for middle plies, 34 min for lower plies and 36 min for top layers. The temperature gradient along the thickness is resulted from the heat evolved during exothermic curing reaction. Maximum temperature peak of 99 °C is observed in the middle layer of the laminate. The measured temperature variation can be further related to the variation in cure shrinkage strain and thermal residual strain levels. This work shows embedded strain and temperature sensors are useful to monitor the cure progression as well as residual strain development in a thick composite laminate

Abstract: The aim of this study is to fabricate sustainable hybrid composites using 3D print technology and to evaluate their electrical, mechanical and thermal properties to assess their aptness for thermal and electrical insulation applications. Proper utilization of agricultural waste is crucial for protecting the environment, conserving resources and ensuring a sustainable future. Composite filaments were developed by incorporating rice straw (RS)/ sugar cane bagasse (SCB) in to polylactic acid (PLA) using twin-screw extruder and using these filaments composite samples were prepared by 3D print technology. The results of thermal conductivity (k) showed an enhancement of thermal insulation of hybrid 3D-printed RS/SCB/PLA composites compared to the pure RS/PLA and SCB/PLA composites. All composite materials exhibited good insulating properties, with k values in the range of 0.148 W/mK to 0.194 W/mK. Thermal insulation capacity of hybrid composite was 9.75%, higher than that of PLA control sample. The results also, indicate that the thermal conductivity of composites increased with temperature, even at 60°C, they retain good thermal insulation properties. The electric breakdown voltage of composites is in the range of 19.84 kV to 21.78 kV. The tensile strength of RS/SCB/PLA hybrid composite at 5% fiber loading were 3% and 8.0 % higher than that of RS/PLA and SCB/PLA composites, respectively. The composites studied in this work possess good thermal and electrical insulation properties and are suitable to replace existing synthetic materials in automotive and building industries.

Abstract: Considerable progress has been made in understanding the Wire Arc Additive Manufacturing (WAAM) process, as well as the microstructure and mechanical properties of the fabricated components, because it is feasible to produce large-scale metal components with relatively high deposition rates at an economical cost. A vast array of materials has become associated with WAAM and its applications as it has evolved. Particularly, steels and their alloys are the most common materials used in industrial applications such as aerospace, manufacturing, automotive, and others. This paper reviews the emerging technology of WAAM for steels and their alloys, including the properties of the deposited component, material testing and characterization, and process parameters such as heat input, processing temperature, deposition strategy, and shielding gas. This paper concludes the recent studies on WAAM for steels and their alloys, as well as the advancements in the process to increase productivity and material performance.