Glass fiber-reinforced plastics are an important composite material in the marine, automotive, and military industries due to their excellent mechanical properties, such as high strength, corrosion resistance and lightweight. This study aims to determine the effect of the number of glass fiber layers on the hardness of glass fiber/polyester composite materials. Random chopped strand mat glass fibers with a mass per unit area of ​​450 g/m² were used to prepare samples using the hand layup technique. The number of layers varied between 3 to 6 layers. The thickness of all samples is 3 mm. The Vickers microhardness device is used to measure the hardness, with a load of 50 g applied for a dwell time of 15 s. The results indicated that when increasing the number of glass fiber layers decreases the hardness values. The sample of three-layer listed the highest hardness value of 14.34 HV, while the values ​​for the four-layer sample decreased to 11.42 HV, the five-layer sample to 9.72 HV, and the six-layer sample had the lowest value of 7.7 HV. This decrease in hardness is attributed to the increased number of interfaces between layers, which may lead to the appearance of weak points or air voids that affect the mechanical properties of the composite material.

Glass fiber/polyester composites are increasingly used in naval, aerospace, and automotive industries due to their excellent strength-to-weight ratio and corrosion resistance. However, drilling-induced delamination remains a major concern that compromises hole quality and structural performance. In this study, the drilling behavior of randomly oriented chopped strand mat GFRP/polyester laminates (3 mm thickness, 5 layers, 450 g/m² areal density) was experimentally investigated under varying spindle speeds (1000–2000 RPM), feed rates (100–300 mm/min), and drill diameters (5, 8, and 10 mm). Hole quality was evaluated using AutoCAD-based measurement of the delamination factor. The results show that delamination factor increases with feed rate, while higher spindle speeds reduce it, in agreement with previous studies that attribute this behavior to reduced thrust forces. Among the tested conditions, the lowest delamination factor (≈1.09) was obtained at 1500 RPM and 100 mm/min feed rate, whereas the highest (≈1.54) occurred at 1000 RPM and 300 mm/min. The contribution of this work lies in focusing on the underexplored chopped strand mat GFRP/polyester composites and employing AutoCAD-based quantitative assessment, providing new insights and a practical baseline for improving drilling performance in these materials.

This paper introduces a compact wideband Reconfigurable Intelligent Surface (RIS) leveraging Schiffman phase shifters to overcome the traditional narrowband limitations of RIS technology. The proposed design achieves ±15° phase balance across a broad frequency range of 7.5–13 GHz, addressing a key challenge in RIS design. The proposed RIS features a compact unit cell, with dimensions of (0.25λ×0.25λ) at 10.25 GHz, integrating a single PIN diode and a tailored internal geometry to enable efficient phase control and scalable implementation. Experimental validation is carried out in two phases: initially, the unit cell is characterized using a waveguide setup; subsequently, a 30 cm×30 cm RIS panel is fabricated and tested under horn antenna excitation. The measured data exhibit strong agreement with simulations, demonstrating the accuracy and robustness of the proposed design. The full RIS surface is further evaluated for its reconfigurability and ability to generate Orbital Angular Momentum (OAM) beam scanning. These findings highlight the design’s potential for enabling key 6G communication features, offering a compact and wideband RIS solution through the integration of Schiffman phase shifters and contributing to advancements in next-generation wireless systems.

This paper introduces an innovative design and analysis of a magneto-electric dipole antenna exhibiting high-gain, ultra-wideband operation, and stable radiation characteristics in the 60-GHz mm-wave band. Furthermore, the trapped printed gap waveguide (TPGW) technology is presented as a low-cost, minimal-loss, and low-dispersion guiding structure to feed the proposed antenna. The antenna covers a relative matching bandwidth of over 33.33% from 50 to 70 GHz with a maximum gain up to 8 dBi. In addition, the antenna is integrated with a perforated dielectric substrate layer lens on the antenna’s broadside location, enhancing the gain by an average of 3 dB along its entire operational bandwidth. Moreover, an efficient approach for designing a large ME dipole antenna array and its corporate feeding network is presented. Both ME-dipole sub-arrays and the out-of-phase power divider with WR-15 standard interface are designed and studied separately, where a systematic design procedure is presented to obtain initial design parameters. A 2 × 2 planar antenna array is designed and implemented, featuring proper integration between the radiating elements and a differentially fed wide-bandwidth TPGW power divider. Then, the operation of the individual components has been assessed using simulation and measurements. Furthermore, an in-depth mathematical analysis is presented to investigate the potential resonance conditions arising from disparities in complementary components. Consequently, a proposed solution is provided to break the resonance loop and shield the two opposing sub-arrays. The 2 × 2 array of ME-dipoles has overall dimensions of 1.6 1.4 and demonstrates an impedance bandwidth (– 10 dB) exceeding 33.33 at 60 GHz, with a peak gain of over 18 dBi.