The influence of different joining processes on mechanical performance of carbon fiber/polyamide (CF/PA6) composites

تستخدم المواد المركبة المصنوعة من مادة البولي أميد (PA6) المقوى بألياف الكربون (CF) على نطاق واسع كمواد هيكلية في صناعات السيارات والفضاء نظرًا لخصائصها المتميزة. ومع ذلك ، نظرًا لمتطلبات السلامة الهيكلية للمواد المركبة ، لا تزال هناك محدودية فيما يتعلق بالإنتاج الفعلي للمواد المركبة المكونة من (CF/ PA6). الروابط القوية لصفائح CF/PA6 مطلوبة بشدة  لعمل تصميم خفيف الوزن يستخدم في العديد من المجالات. بهدف إجراء مقارنات ، تم تدراسة مختلف طرق المعالجة مثل الربط بمواد لاصقة والربط الحراري لتشكيل روابط اللإلفة بين صفحتين مركبتين من (CF/PA6). كما تم دراسة تأثير الطرق المختلفة ومتغيرات المعالجة  المختلفة على مقاومة القص للروابط. أظهرت النتائج أنه من السهل جدًا التعامل مع الروابط اللاصقة التقليدية وقد تتشكل روابط  أقوى إلى حد ما. يمكن استخدام الروابط الحرارية القائمة على التوصيل الكهربائي عن طريق CF لتشكيل توصيلات متلدنة بالحرارة مع المرونة في التصميم. يمكن أن تزيد الروابط الحرارية عن طريق الضغط الساخن من قوة الاتصال؛ عندما تتشكل بالضغط الساخن في ظروف مثالية في درحة حرارة تبلغ 250 درجة مئوية وضغط 2.5 ميجا باسكال ، فإن قوة القص للمفصل 138.85 ميجا باسكال. وبالتالي تم التأكيد على أنه يمكن الحصول على روابط قوية لأجزاء الصفائح للمادة المركبة CF/PA6  عن طريق الالتصاق الحراري عبرعملية الضغط  الساخن.Carbon fiber (CF) reinforced polyamide (PA6) composite materials are broadly used as structural materials in the automotive and aerospace industries due to their distinguished properties. However, due to requirements for the structural integrity of composite materials, there are still limitations in connection of the actual production of CF/PA6 composite. Strong joints of CF/PA6 laminates are highly required for the lightweight design in many fields. Aiming at making comparisons, different processing methods such as adhesive bonding and thermal jointing to form single lap joints between the two CF/PA6 composite laminates are studied. The influences of different processing methods and parameters on the shear strength of joints were also studied. Results showed that conventional adhesive bonding is quite easy to handle and may form rather stronger connections. Thermal joining based on electrical conductors of CF can be used to form a thermoplastic flexible joint design. Thermal joints by hot pressing can further increase the connection strength; when formed by hot pressing under optimum conditions of 250 °C and 2.5MPa, the joint has a shearing strength of 138.85 MPa. It is consequently confirmed that a strong joint of CF/PA6 composite parts could be obtained by thermal joints via the hot pressing process

The performance of heteroatom-doped carbon nanotubes synthesized via a hydrothermal method on the oxygen reduction reaction and specific capacitance

Due to the increasing demand for electrochemical energy storage, various novel electrode and catalysis materials for supercapacitors and rechargeable batteries have developed over the last decade. The structure and characteristics of these catalyst materials have a major effect on the device's performance. In order to lower the costs associated with electrochemical systems, electrochemical systems, metal-free catalysis materials can be employed. In this study, metal-free catalysts composed of nitrogen (N) and sulfur (S) dual-doped multi-walled carbon nanotubes  were synthesized using a straightforward and cost-effective single-step hydrothermal method. Carbon nanotubes served as the carbon source, while l-cysteine amino acid and thiourea acted as doping elements. As a result of the physicochemical characterization, many defects and a porous structure were noted, along with the successful insertion of nitrogen and sulfur into the carbon nanotube was confirmed. According to the cyclic voltammetry tests for the dual-doped samples in alkaline conditions, the D-CNT2 catalyst exhibited onset potentials of -0.30 V higher than the -0.37 V observed for the D-CNT3 catalyst. This indicates enhanced oxygen–reduction reaction due to the synergistic effects of the heteroatoms in the structure and the presence of chemically active sites. Moreover, the outstanding specific capacitance of the D-CNT2 catalyst (214.12 F g-1 at scanning rates of 1 mV s-1) reflects the effective porosity of the proposed catalyst. These findings highlight the potential of N/S dual–doped carbon nanotubes for electrocatalytic applications, contributing to efficient energy conversion

Surface Modification of Carbon Fibers by Grafting PEEK-NH2 for Improving Interfacial Adhesion with Polyetheretherketone

Due to the non-polar nature and low wettability of carbon fibers (CFs), the interfacial adhesion between CFs and the polyetheretherketone (PEEK) matrix is poor, and this has negative effects on the mechanical properties of CF/PEEK composites. In this work, we established a modification method to improve the interface between CFs and PEEK based chemical grafting of aminated polyetheretherketone (PEEK-NH2) on CFs to create an interfacial layer which has competency with the PEEK matrix. The changed chemical composition, surface morphology, surface energy, and interlaminar shear strength were investigated. After grafting, the interlaminar shear strength (ILSS) was improved by 33.4% due to the covalent bonds in the interface region, as well as having good compatibility between the interface modifier and PEEK. Finally, Dynamic Mechanical Analysis (DMA) and Scanning Electron Microscopy (SEM) observation also confirmed that the properties of the modified CF/PEEK composites interface were enhanced. This work is, therefore, a beneficial approach towards enhancing the mechanical properties of thermoplastic composites by controlling the interface between CFs and the PEEK matrix

Non-isothermal crystallization kinetics and its effect on the mechanical properties of carbon fiber/polyphenylene sulfide composites

The degree of crystallization of semi-crystalline thermoplastics is an important factor in determining the final properties of the structure of composite materials. This article studied the non-isothermal crystallization kinetics of carbon fiber (CF) reinforced polyphenylene sulfide (PPS) composites by differential scanning calorimetry (DSC) with various cooling rates from 10 k/min to 70 k/min. The MoZhiShen method was applied to the analysis of the nonisothermal crystallization of the composites. Moreover, the effects of the crystallization behavior of CF/PPS composites on their mechanical properties were also investigated. It was found that the MoZhiShen method can effectively be applied to study the nonisothermal crystallization kinetics of CF/PPS composites. The result indicated that the crystallization peak gradually became strengthened in intensity, and crystallization decreased with increasing the cooling rate. Moreover, the increase in the cooling rate during composite fabrication was found to decrease the flexural properties of the composite, but the energy absorption and the impact strength were significantly increased by 15.1%

The role of high-performance microwave absorbing materials in electromagnetic interference shielding: a review of the advanced internal design of polymer-based nano-composites

Electromagnetic interference (EMI) shielding refers to the ability of a material to block the EM waves generated by electronic systems. In the past few decades, there has been sustained research in the use of conductive metal and conductive polymer-based shielding approaches, but these have shown difficulties with high density and processability. In recent years, other strategies have been developed to obtain more practical shielding materials. A summary of lightweight polymer-based nanocomposites with EM absorption characteristics for EMI shielding is provided. The advantages, disadvantages, and EMI shielding mechanisms of various types of nanocomposites are discussed. This article focused on understanding the approaches related to different types of fillers, which include carbon materials as well as metal particles and microwires which are used separately and in the form of hybrids designed to achieve highly effective shielding capabilities. This review focuses on structure configurations such as multilayer structures, coating, and advanced three-dimensional (3D) structures, which may be used to encourage the development of more environmentally responsible EMI shielding materials. In summary, it can be said that the thickness, dielectric, magnetic characteristics, and filler concentration, can be adjusted to obtain the desired combination of higher shielding performance and EM absorption properties