Three dimensional (3D) glass fiber epoxy composites reinforced with nano-SiO2 particles at ratios of 0.5 wt.%, 1 wt.%, 2 wt.% and 3 wt.%, were manufactured using the vacuum infusion method to improve the mechanical properties. Differential scanning calorimetry, thermo-gravimetric analysis, particle dispersion detection by color measurement, scanning electron microscopy, energy dispersive X-ray spectroscopy mapping, three point bending and tensile testing were performed to characterize the nano-particle-reinforced 3D composites. Mapping and color measurement revealed good dispersion of the nano-particles. The mechanical tests showed improvement rates of 52 % and 64 % respectively on warp and weft directions compared with the non-reinforced 3D composite. The tensile strength of the nano-SiO2 reinforced 3D woven composites also increased to 6 % and 10 % according to the warp and weft directions compared with the non-reinforced 3D composite.

This study reports an optimization of finish turning of hardened AISI D6 (60 HRC) cold work tool steel with ceramic and cubic boron nitride cutting tools using grey relational analysis. Optimization of the process parameters was performed using quality characteristics, i.e. tool wear, surface roughness, machining force and specific cutting force. Analysis of variance was used for observing the most influencing machining parameters on the quality characteristics. Evaluation of tool wear type and wear mechanism was done by tool makers' microscope and scanning electron microscope analysis. The optimal process parameters were calculated using grey relation grade and confirmation test was performed. Based on analysis of variance results, the feed rate is the most significant controllable machining factor for the finish hard turning of AISI D6 according to the quality characteristics. Flank and crater wears were the prominent wear types on the ceramic and cubic boron nitride inserts. Grey relational analysis was successfully applied on optimization of high-speed finish hard turning of hardened AISI D6 using multi-performance characteristics.

Three-dimensional polymer composites offer various features and design options due to their hollow structure and lightweight. However, to exploit their advantages, it is a must to improve their structural features and mechanical performances including out-plane direction. Although introducing thermoplastic fillers between the plies or multilayered design addresses on this critical issue, the benefits offered by the nanoparticles with superior mechanical properties come a step forward as an another engineering solution. Based on this motivation, the goal of this study is to investigate the impact of multiwalled carbon nanotubes on the mechanical and thermomechanical performances of three-dimensional woven glass/epoxy spacer composites. Therefore, multiwalled carbon nanotubes at various content were introduced into epoxy matrix, and the multiwalled carbon nanotubes–epoxy mixture was infused to three-dimensional woven fabric with the vacuum-assisted resin transfer method. The obtained results indicated that the three-point bending strength and modulus were enhanced up to 25 and 80% for warp direction and enhanced up to 44 and 85% for weft direction with carbon nanotube addition, respectively. Tensile strength developed in the warp direction by 7%, while the strength value in the weft direction did not change. The tensile strain values for warp and weft directions enhanced up to 19 and 12% with carbon nanotube addition, respectively. In addition, thermomechanical analysis has revealed that the glass transition temperature and storage modulus were also improved. Particle dispersion detection with color measurement and scanning electron microscopy analyses revealed the effectiveness of the ultrasonic mixing on the dispersion of carbon nanotubes in the epoxy matrix. The consequences of carbon nanotube addition on microscale morphology were discussed based on the fracture morphologies to nanoscale and microscale toughening mechanisms in the existence of carbon nanotube reinforcement.

The development of structural fiber reinforced polymer composites with various additional functionalities is becoming a hot research area to achieve the application of multi‐functional composites in the aerospace and automotive industries. An innovative material solution is 3D spacer composites with distinctive anisotropic structural characteristics. Herein, we report the manufacturing of multi‐walled carbon nanotubes (MWCNTs) grafted of 3D spacer glass/epoxy multi‐scale composites and their electromagnetic interference shielding efficiencies (EMSE). To manufacture multi‐scale composites, we utilized dip coating, vacuum filtering, and vacuum infusion methods to introduce MWCNTs of the woven fabric, while we also modified the epoxy resin with MWCNTs to increase electrical conductivity of intrinsic insulator epoxy resin. Owing to the rectangular‐shaped channel structure, which is beneficial for multiple reflection and scattering between top and bottom face sheets, the resultant 3D spacer multi‐scale composite represented a good EMSE performance of −18.3 dB in the frequency range of 8.2–12.4 GHz with an increase of 107% comparing the corresponding neat composite counterpart. Moreover, we measured the in‐plane conductivity as 1.89E‐2 S/m after MWCNTs grafting, while the out‐of‐plane conductivity remained three times lower than the in‐plane conductivity. Dynamic mechanical analysis revealed that the storage modulus increased almost three times with the MWCNTs grafting, while glass transition temperature shifted to higher temperatures (from 77.5 to 89.7°C). Therefore, we anticipate that our study will expand the use of 3D spacer composites in the aviation and automotive industries.

Fiber-reinforced polymer composites serving in harsh conditions must maintain their performance during their entire service. The cryogenic impact is one of the most unpredictable loading types, leading to catastrophic failures of composite structures. This study aims to examine the low-velocity impact (LVI) performance of 3D woven spacer glass-epoxy composite experimentally under cryogenic temperatures. LVI tests were conducted under various temperatures ranging from room temperature (RT) to −196°C. Experimental results reveal that the 3D composites gradually absorbed higher impact energies with decreasing temperature. Besides, the effect of multi-walled carbon nanotube and SiO2 nanofiller reinforcements of the matrix on the impact performance and the damage characteristics were further assessed. Nanofiller modification enhanced the impact resistance up to 30%, especially at RT. However, the nanofiller efficiency declined with decreasing temperature. The apparent damages were visually examined by scanning electron microscopy to address the damage formation. Significant outcomes have been achieved with the nanofiller modification regarding the new usage areas of 3D woven composites.