Kejing Yu

Modification of the Interfacial Interaction between Carbon Fiber and Epoxy with Carbon Hybrid Materials

The mechanical properties of the hybrid materials and epoxy and carbon fiber (CF) composites were improved significantly as compared to the CF composites made from unmodified epoxy. The reasons could be attributed to the strong interfacial interaction between the CF and the epoxy composites for the existence of carbon nanomaterials. The microstructure and dispersion of carbon nanomaterials were characterized by transmission electron microscopy (TEM) and optical microscopy (OM). The results showed that the dispersion of the hybrid materials in the polymer was superior to other carbon nanomaterials. The high viscosity and shear stress characterized by a rheometer and the high interfacial friction and damping behavior characterized by dynamic mechanical analysis (DMA) indicated that the strong interfacial interaction was greatly improved between fibers and epoxy composites. Remarkably, the tensile tests presented that the CF composites with hybrid materials and epoxy composites have a better reinforcing and toughening effect on CF, which further verified the strong interfacial interaction between epoxy and CF for special structural hybrid materials.

The synergy effect of Graphene/SiO2 hybrid materials on reinforcing and toughening epoxy resin

Based on the situ preparation of silica nanoparticles (SiO2) on the surface of Graphene nanoplatelets (GNPs) in the previous work, these unique three dimensional (3D) materials were introduced into epoxy resin to study the reinforcing and toughening synergy effect on the composites. Firstly, the tensile tests showed that Graphene/SiO2 hybrid materials attached with different size of SiO2 particles exhibited different reinforcing and toughening effect on the composites. With the increasing of the diameter of SiO2 particles, the toughness and strength properties of the composites firstly improved and then decreased, and when the average diameter was 0.14 μm, the elongation reached the max.. Meanwhile, the fractured surfaces presented on SEM images were consistent with the results of the tensile tests, which further explained the hybrid materials increased the interfacial adhesion between the fillers and matrix, leading to significant improvement in mechanical properties. Moreover, the DSC curves demonstrated that Graphene/SiO2 hybrid materials accelerated the curing process of epoxy resin due to the cross-link structure between fillers and matrix. Lastly, the crack propagation modes were built to clarify the synergy effect mechanism of reinforcing and toughening on nanoparticles/epoxy resin composites.

Stress field distribution of warp-reinforced 2.5D woven composites using an idealized meso-scale voxel-based model

The evaluation of the stress field distribution of warp-reinforced 2.5D woven composites using meso-scale voxel-based model is described. The idealized geometry model is established by using measured parameters from the CT image. Comparison between voxel-based finite element method and experimental measurements is included. The results show that the proposed meso-scale voxel-based method is capable of accurately predicting the mechanical properties of warp-reinforced 2.5D woven composites, validated by the comparison of the initial modulus, max stress as well as the failure modes. Also, the numbers of representative volume element have an important effect on mechanical behaviors of warp-reinforced 2.5D woven composites.

In Situ Synthesis of Carbon Nanotubes/Graphene Nanoplatelets Hybrid Materials with Excellent Mechanical Performance

A two-step method for the preparation of hybrid materials consisting of multi-walled carbon nanotubes (MWCNTs) attached to graphene nanoplatelets (GNPs) was proposed. Firstly, poly (acryloyl chloride) was grafted in situ onto the surface of MWCNTs. Secondly, the obtained MWCNTs (MWCNTs-PACl) were reacted with acid-treated GNPs to form a nanotube–polymer–graphene hybrid. Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, transmission electron microscopy (TEM) and thermal gravimetric analysis (TGA) were used to investigate the forming of the hybrid materials. FTIR results showed that MWCNTs/PACl and GNPs were successfully bridged by chemical bonds like O–C = O and C–O–C. Raman spectroscopy furthermore revealed that acryloyl chloride can be used to connect the MWCNTs and GNPs due to the defects of MWCNTs, and consequently the defects of the hybrid materials were limited. Meanwhile, TEM observation demonstrated the nanostructure clearly in which the MWCNTs with a polymer layer were attached s...

Experimental and theoretical analysis of failure mechanism of UHMWPE Yarn under transverse cut loading

Abstract This paper is concerned with transverse cut resistant properties of UHMWPE yarns by the methods of experimental and theoretical analysis. Rheological theory of fabric was applied to evaluate relation of stress and strain of UHMWPE yarn, when the UHMWPE yarn is subjected to external cut force. The dynamic response of yarn and the contact volume of yarn and blade in the cutting have been identified to interpret cut failure mechanism of yarn. The experimental results show that yarn structure, blade edge, and test parameters have great influence on cut resistant property of UHMWPE yarn, and which are consistent with the theoretical analysis. It provides a theoretical basis for quantifying the cutting resistance of fabrics.

Cut resistant property of weft knitting structure: a review

Abstract Application fields of cut resistant textile are very wide, such as, workplace, sports, transportation, and military. With the requirement of lightweight and comfortable cut-proof clothes, the knitted fabric has the advantages of its structure, which is more and more widely used. The common four forms of yarn in the knitting structure is held loop, tuck loop, float loop, and free yarn. The cut resistant mechanism of fabric is much more complex, due to their fiber and yarn intrinsic properties and fabric structure. So, cut test of fiber, yarn, and fabric is necessary, while no established standard for the cut testing of fiber or yarns exists, there are three standards used to evaluate the cut resistance of knitted or woven fabrics used in protective clothing: BS EN 388, ASTMF1790, ISO13997. Now, there are simple models on cut resistance of fabric, consisting of forces in the cutting process and contact area. There are still a lot of work to continue to get a thorough understanding of mechanism of fabric’s cut resistance.

Effects of graphene surface energy on the structure and mechanical properties of phenolic foams

Abstract Graphene nanoplates (GNPs) and graphene oxide (GO) were used to investigate the effects of surface free energy (SFE) of nanoparticles on the cellular structure and mechanical properties of phenolic nanocomposite foams. The results showed that the SFE of nanoparticles is a key parameter in determining the interfacial action between fillers and matrix before foaming, which in turn determines the energy barrier of bubble nucleation during foaming process. It indicated that the higher interfacial energy of GO brought out the lower Gibbs free energy and smaller driving force for heterogeneous nucleation, leading to smaller cell size with more uniform distribution. According to the effect of SFE in foaming process, different mass fractions of GNPs and GO were used in phenolic foams to investigate the effects of heterogeneous nucleating agent on cell nucleation. As a result, phenolic foam with 0.6 wt% graphene oxide (GO-0.6/PF) exhibited the optimized mechanical properties and cell microstructure.

Morphologies and compression performance of graphene oxide/SiO2 modified phenolic foam

In this study, the graphene oxide/SiO2 hybrid materials with different sizes (GO/SiO2-80, GO/SiO2-170, GO/SiO2-250) were prepared via in situ preparation. Different sizes and weight fraction of GO/SiO2 were added into phenolic resin to prepare phenolic foam composites. The cell properties, morphologies, and mechanism of GO/SiO2 reinforced PF composites were studied. The results showed that the GO/SiO2-80 can improve the cell structure and compressive property obviously than other size nanoparticles. The PF modified with 1 wt% GO/SiO2-80 exhibited most uniform cell structure, and it showed a mean cell size of 117 µm and narrow cell size distribution from 50 µm to 225 µm. The obtained PF/(1 wt% GO/SiO2-80) also showed an excellent compressive strength and modulus of 0.18 and 3.22 MPa, which has increased by 80% and 61%, respectively, compared to the pure PF. This method may make it possible for using GO/SiO2 hybrid materials to enhance the cell structure and compression performance of the phenolic foam composites with broader applications.

Preparation and characterization of phenolic foam reinforced with expandable graphite and expanded graphite

In this paper, two kinds of phenolic foams modified with expandable graphite and expanded graphite were prepared and the effect of particles on the mechanical properties and structure of the foams has been discussed. The mechanical properties, density and morphology of reinforced phenolic foams were studied. The images of scanning electron microscope showed that the size of the modified phenolic foams was smaller and more complete. The mean diameter of the expanded graphite-reinforced phenolic foams was smaller than that of the expandable graphite-reinforced phenolic foams due to the specific surface area of the expanded graphite. The compressive test results showed that the expandable graphite and expanded graphite could enhance the mechanical properties of the foams obviously. And the smaller cell size of the expanded graphite-reinforced foams provided them better mechanical properties. When the addition of the reinforcement reached to 0.8 wt%, the reinforced phenolic foams showed the best compression performance. The compressive strength and modulus with the 0.8 wt% expandable graphite were increased by 70% and 48% and that with the 0.8 wt% expanded graphite were increased by 80% and 69%.