Malaysian Journal on Composites Science and Manufacturing

Experimental and Simulated Investigation of S-parameters and Power Loss Characteristics of PTFE/Glass Composites at X-band Frequency

Ibrahim Abubakar Alhaji — 2024-11-22

Polytetrafluoroethylene (PTFE)-based substrates are in high demand for high-frequency (microwave) applications because of their low relative permittivity, enabling efficient signal transfer. In this work, PTFE composites have been prepared with different content (5 wt.% - 25 wt.%) of soda lime silica glass (SLSG) for substrate application. The composites were characterized by their complex permittivity and S-parameters through the rectangular waveguide (RWG) measurement method over x-band frequency (8.2 GHz – 12.4 GHz). The RWG set-up was connected to a vector network analyser for the characterization. Power loss of the composites due to material absorption was calculated using the measured S-parameters. As the content of the SLSG increased from 5 - 25 wt.%, complex permittivity rose from 2.18-j0.0035 to 2.56-j0.0047 in the frequency range considered. In addition, |S11| reduced from 0.623 and 0.700 to 0.418 and 0.441, whereas |S21| varied from 0.780 and 0.713 to 0.906 and 0.895 for 5 wt.% and 25 wt.% SLSG contents at 8.2 GHz and 12.4 GHz, respectively. The calculated power loss increased from 2.94 dB to 3.29 dB and 4.01 dB to 4.88 dB for the same filler contents and frequency. Furthermore, the S-parameters were simulated using the finite element method (FEM) via COMSOL software and compared with the measured values. The comparison revealed a mean relative error of < 0.1, denoting the accuracy of the RWG method. Also, the electric field distribution across the waveguide length was visualized. Thus, the optimal performance of the composite was found at 5 wt.% SLSG filler content for microwave substrate application.

The Influence of Process Parameters on Tensile Features of Vetiver Fiber Reinforced Polymer Matrix Composites

Haydar Zaman — 2024-11-22

Due to their outstanding specific strength and modulus, fiber-reinforced polymer composites have long been influential in a range of applications. Composites made of thermoplastic and vetiver fiber (VF) offer an alternative to synthetic polymers that cause environmental contamination. The advantages of natural fibers (like banana, sisal, coir, jute, vetiver, flax, hemp, kenaf, etc.) over conventional reinforcing fibers (glass and carbon fiber) are their ease of procurement, renewability, non-corrosive nature, light density, biodegradability, high specific energy (strength of density ratio), and low cost. In place of costly chemical treatment of VF in polymer composites, VF length management has been offered as a low-cost and ecologically friendly alternative. In the current study, VF-reinforced low-density polyethylene (LDPE) composites were altered using the film process stacking method with the hot press compression molding technique using a variety of process parameters, including VF condition (untreated and sodium dodecyl sulfate (SDS) treatment), VF sizes (short VF < 3 cm and long VF > 3 cm), and VF percent (5, 10, and 15 wt%). The tensile modulus and modulus efficiency factor of the LDPE composite were studied in relation to the impacts of VF size, VF content, and SDS treatment. The results showed that a specific amount of tensile modulus and modulus efficiency factor was boosted by VF content up to 10 wt%, processing temperature up to 160oC, and SDS treatment during processing up to 5 hours due to an increase in load bearing and interfacial adhesion. The improvement in tensile modulus and its efficiency factor because of efficient load transfer is evidently attributable to long VF load transfers, which have had a favourable impact. The brittle nature of the fibers caused a loss in ductility.

Physico-Mechanical Behaviors of Chemically Treated Natural Fibers Reinforced Hybrid Polypropylene Composites

Haydar Zaman — 2024-11-22

The goal of current research is to replace synthetic materials with natural, biodegradable, and renewable ones. Natural fiber composites are extensively studied due to their unique properties and environmental benefits. These fibers are easily available, easy to handle, and biodegradable. Reinforcing polymers with natural fibers enhances mechanical properties, potentially balancing stiffness, strength, and ductility in hybrid composites. This study assessed the mechanical characteristics of polypropylene reinforced with chopped banana fiber and coconut husk. Investigations were also conducted into the effects of fiber chemical treatment, content, and ratio on mechanical properties. In Bangladesh, two fibers that are commonly available are coconut husk and banana. Raw coconut husk and banana fiber were chemically treated with 5% sodium lauryl sulfate to improve their adhesion with polypropylene. Hot pressing was employed to manufacture the composite using fibers that had been treated with sodium lauryl sulfate (SLS) as well as untreated fibers. The fiber loading was adjusted to be 5, 10, 15, and 20 wt%, while the ratios of coconut husk to banana fibers were modified to be 15/5, 10/10, and 5/15. After that, tests for tensile, flexural, hardness, and water absorption were performed on the created composites. All mechanical parameters increased with increased fiber loading, except for tensile strength. The characteristics of the generated composites were found to be better than those of the polypropylene matrix. The mechanical properties of composites including coconut husk and banana fiber at the 5/15 ratio were superior to those of composites comprising those fibers at the 10/10 or 15/5 ratios. Specifically, the 5/15 ratio composites improved tensile strength, tensile modulus, flexural strength, flexural modulus, and hardness by 11%, 6%, 12%, 24%, and 2%, respectively, compared to the 10/10 ratio composites. Treated fiber composites using SLS-treated coconut husk and banana fiber at the 5/15 ratio showed enhanced mechanical properties compared to untreated composites. These treated composites improved tensile strength, tensile modulus, flexural strength, flexural modulus, and hardness by 17%, 5%, 4%, 1%, and 2%, respectively, over untreated composites. Thus, SLS-treated fiber-reinforced hybrid composites exhibited superior characteristics compared to their untreated counterparts.