Single-layer woven carbon fibers improved the thermal and mechanical properties of epoxy resin

To improve the thermal and mechanical properties of epoxy resins, epoxy-functionalized POSS (E-POSS) and glass fiber (GF) were used to reinforce epoxy resin (E51) composites. The tensile, thermo-mechanical, fractured, and thermal tests were carried out to characterize these hybrid materials. The results show that E-POSS and GF could significantly improve the mechanical and thermal properties of epoxy resins due to high crosslink density of resin matrix and synergistic interaction between the epoxy resin, E-POSS, and GF. Compared with the pure E51 resin, the tensile strength of the E51 + E-POSS (10%) + GF (16%) sample increased by 257.6%, and the thermal decomposition temperature (Td5%) of the E51 + E-POSS (10%) + GF (16%) sample increased by 32 °C to 378 °C.

The effect of fiber length and structure on joint strength in bonded joints with fiber-reinforced composite adhesive

Multiwalled carbon nanotube (MWCNT) filaments were grown by catalytic chemical vapor deposition on 2-D weave carbon fiber (CF) cloth substrates. Two different sets of experiments were carried out to understand the growth mechanism of these filaments. In the first set of experiments where CF cloths were coated with the catalysts particles, CNT filaments having long length (>200 μm) and large diameter (15–25 μm) were obtained. In another set of experiment, where CF cloths without catalyst particles were used, only MWCNTs without any filament formation were obtained. On the basis of the results, a growth mechanism has been proposed. These MWCNT filaments can be used for preparing CNTs reinforced polymer composites having very good structural properties, which are being sought after.

The nanofiller improve the properties of the pristine polymer resins to the great extent. In present findings, the preparation of nanocomposites (epoxy/PNCC/LDHs) was done by the ‘Slurry-compounding method’. Precipitated nano-calcium carbonate (PNCC) were mixed with Layer double hydroxides (LDHs) in varying ratio and added to epoxy resin with constant stirring at room temperature. The degree of distribution of the nanofiller and the kind of polymeric nanocomposites formed was observed by Wide-angle X-ray Diffraction, and Scanning Electron Microscopy. The thermal and mechanical properties of epoxy nanocomposites were characterised by Thermogravimetric analysis and Universal Testing Machine, respectively. However, harmonisation and coactive influence of PNCC with LDHs showed a better effect on the mechanical and thermal properties of epoxy resin and offers superior mechanical and thermal properties as compared to pristine epoxy resin and two-component ( Epoxy/PNCC) nanocomposites.

This research explores the effect of the cell size, cross-linking ratio, and the force fields used in the molecular dynamic simulation for determining the mechanical and thermal properties of cross-linked epoxy formed with a heuristic cross-linking procedure. The effects of the abovementioned variables on density, Young’s modulus, shear modulus, bulk modulus, and glass transition temperature values by molecular dynamics (MD) simulation were evaluated. Epoxy resin diglycidyl ether of bisphenol A and hardener diethyl toluene diamine were used in modeling the epoxy. A Heuristic method for reactive molecular dynamics (REACTER) protocol was used as the cross-linking procedure. Firstly, six structure cells were prepared in different cell sizes with a crosslinking ratio of 75%, and a mechanical analysis of all cells was performed. Then, the largest cell was prepared for three different crosslink ratios and its mechanical and thermal properties were calculated. Finally, the mechanical properties of the largest cell were calculated using the three different force fields namely the COMPASS, DREIDING, and UNIVERSAL. The results were also compared with the molecular dynamic simulation results performed using the other crosslinking procedures, and experimental results available in the literature. In comparison, it was observed that the results obtained with MD simulations coincided with the experimental data. It has been concluded that using the largest cell gives closer results to the experimental data but the processing time is also increasing rapidly. Moreover, it was also observed that the increase in the crosslinking ratio caused an increase in the mechanical properties of the epoxy and a significant increase in the glass transition temperature. Finally, compared to other force fields, it is seen that the mechanical analysis results obtained with the COMPASS force field comply more with the experimental data.

Graphene-related materials (GRM) show great potential as reinforcement in polymeric matrices, offering enhanced physicochemical and mechanical properties. In the aerospace sector, reinforced composites are increasingly used for their superior mechanical attributes and design flexibility. Incorporating graphene nanoplatelets (GNP) into epoxy resin (ER) is a promising approach to enhance the resin’s fracture toughness. The effectiveness of these nanocomposites depends heavily on the dispersion of nanoparticles within the matrix. Therefore, this work aimed to produce nanocomposites based on ER and GNP by evaluating different mixing processes and assessing the influence of GNP content on the resin´s properties, to determine the optimal conditions for the incorporation GNP-ER as matrix to produce hybrid laminated composites with carbon fiber fabric. Characterization of GNP powder revealed its organization in regular nanoplatelet stacking patterns, exhibiting multilayers with few defects. The characterization of nanocomposites showed that ultrasonication dispersion improved the dispersion of GNP in the resin, reducing agglomerates and increasing homogeneity. Tensile tests demonstrated that ultrasonication led to an increase of approximately 14% in the ultimate tensile strength (UTS) and up to 46% in the deformation at the break of the nanocomposites. Carbon fibers/GNP-ER composites were produced by the hand lay-up process and exhibited a decrease in UTS with the addition of GNP, suggesting that GNP may have acted as stress concentrators or even modified the viscosity of the matrix, which may have hindered the matrix´s ability to penetrate the carbon fabric, thereby reducing the mechanical properties.

Graphene aerogel modified carbon fiber reinforced composite structural supercapacitors

Carbon fiber reinforced polyimine (CF/PI) composites had promising applications due to their flame retardancy and ease of recyclability. However, the mechanical properties of CF/PI are generally insufficient, and optimizing the interface between carbon fiber (CF) fabrics and polyimine (PI) matrix could effectively solve this problem. The interfacial bonding between CF fabrics and the PI matrix was enhanced by a combination of CF fabrics pre‐treatment and grafting with the silane coupling agent (APTMS). CF/PI laminates were prepared by the “pre‐fabrication‐lamination” method to optimize the production cycle. Interlaminar delamination failure of CF/PI laminates was analyzed using the cohesive element method. The experimental results showed that the combination of pre‐treatment and grafted APTMS treatment increased the impact strength, flexural strength, and interlaminar shear strength (ILSS) of CF/PI laminates by 227.5%, 158.2%, and 259.8%, respectively. The simulation results showed excellent agreement with the experimental results. The scanning electron microscopy morphology of the fracture surface showed that delamination was the primary damage mechanism, which was consistent with the cohesive element simulation delamination. In this paper, a strategy for the optimization of the interface between CF fabrics and the PI matrix was proposed for the first time, and reliable numerical simulation results were provided. Highlights CF/PI laminates were produced by “pre‐fabrication‐lamination”. Enhanced CF/PI interface by CF fabrics pre‐treatment and APTMS grafting. CF/PI laminates showed significant improvements in impact strength, flexural strength, and ILSS. Cohesive element method accurately predicts interlaminar delamination. The error between experimental and numerical simulation results was less than 5%.

Layer-by-layer macroassembly of inorganic CNTs and MXenes with organic PVA for enhancing the interfacial properties of carbon fiber/epoxy composites

In this study, microcrystalline cellulose fibers (MCFs) derived from sisal were treated with a hyperbranched aromatic polyamide (HBAP). The modified sisal fibers were used to produce composites with epoxy resins. Firstly the MCFs were treated with a silane coupling agent, then a HBAP was grown on the modified surface. The HBAP-MCFs were used to reinforce epoxy resins. The HBAP-MCF/epoxy composites were studied by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), thermal gravimetric analysis (TGA), dynamic mechanical analysis (DMA), and mechanical properties analysis. The results show that the HBAP-MCFs enhanced the thermal and mechanical properties of the epoxy resin. For instance, the impact strength, tensile strength, Young's modulus and toughness of the HBAP-MCF/epoxy composites with 2.0 wt% HBAP-MCFs were 32.1 kJ m−2, 59.4 MPa, 695 MPa, and 4.37 MJ m−3. These values represent improvements of 83.4%, 34.7%, 25%, and 178.3%, respectively, compared to a neat epoxy resin. Moreover, the addition of HBAP-MCFs produced composites with higher thermal degradation temperatures and glass transition temperatures. The HBAP-MCF swere effective in improving the thermal and mechanical properties due to a strong affinity between the fillers and the matrix.

A new method with extremely large friction force by broad interface of carbon fiber (CF:6µm-diameter) cloth coated by nickel (Ni) to control Al4C3 formation rate and to enhance the ability of fiber rapping by molten Al have been suggested for a joint (Al/cloth/ABS-CFRP) of carbon fiber reinforced ABS polymer (ABS-CFRP) and aluminum (Al). The new joint part was strengthened by impregnated nickel-coated carbon fiber cloth. The Al/cloth/ABS-CFRP joint exhibited the high values of the initial and maximum elasticity ((d·/d¾)i and (d·/d¾)m), as well as the tensile strength (·b )o f Al/cloth/ABS-CFRP (8.38MPa), which was 5.3 and 16.1 times higher than that of Al/Glue/ABS and Al/ ABS, respectively. Based on the XRD analysis and EPMA observation, aluminum carbide could not be detected. Consequently, the new joint method by using carbon fiber cloth remarkably enhanced the safety level with lightweight and high resistance to fracture of airplane. [doi:10.2320/matertrans.M2013424]

Nanoporous composites have been extensively applied in aerospace applications for their outstanding thermal insulation and ablation resistance. A ceramizable polysilazane (PSZ)‐modified phenolic resin (PSZ‐PR)/carbon fiber fabric (PSZ‐PR/CF) aerogel composite was synthesized through ambient pressure drying (APD). The homogeneous nanopore structure and improved thermal stability of the PSZ‐PR aerogel matrix provided the composites with good performance (thermal conductivity as low as 0.126 W/(m·K)). The PSZ‐PR/CF composites achieved high compressive strength (up to 43.75 MPa), tensile strength (59.22–124.75 MPa), and bending strength (23.35–97.94 MPa). Furthermore, the generation of ceramization products during the oxyacetylene flame ablation process, specifically SiC and Si 3 N 4 , enhanced the ablation resistance of PSZ‐PR/CF composites: the linear ablation rates are as low as 0.112 and 0.018 mm/s at 4.18 MW/m 2 (20 s) and 1.20 MW/m 2 (120 s) of oxyacetylene heat flow, respectively. The corresponding maximum back temperatures are only 51.0°C and 60.3°C. Notably, the carbon/ceramic network is still present in the ablation layer to protect the carbon fibers from oxidation. This ceramizable PSZ‐PR/CF composite has good potential for application in the field of thermal protection. Highlights PSZ improves thermal stability and ablation properties of PSZ‐PR/CF. The PSZ‐PR/CF composites exhibit excellent mechanical and ablation properties. The ceramic products improve the scouring resistance of aerogel matrixes. The ceramizable PSZ‐PR/CF was prepared by low‐cost ambient pressure drying.

Aluminum matrix composites reinforced with carbon fiber have been manufactured for the first time by infiltrating an A413 aluminum alloy in carbon fiber woven using high-pressure die casting (HPDC). Composites were manufactured with unidirectional carbon fibers and with 2 × 2 twill carbon wovens. The HPDC allowed full wetting of the carbon fibers and the infiltration of the aluminum alloy in the fibers meshes using aluminum at 680 °C. There was no discontinuity at the carbon fiber-matrix interface, and porosity was kept below 0.1%. There was no degradation of the carbon fibers by their reaction with molten aluminum, and a refinement of the microstructure in the vicinity of the carbon fibers was observed due to the heat dissipation effect of the carbon fiber during manufacturing. The mechanical properties of the composite materials showed a 10% increase in Young’s modulus, a 10% increase in yield strength, and a 25% increase in tensile strength, which are caused by the load transfer from the alloy to the carbon fibers. There was also a 70% increase in elongation for the unidirectionally reinforced samples because of the finer microstructure and the load transfer to the fibers, allowing the formation of larger voids in the matrix before breaking. The comparison with different mechanical models proves that there was an effective load transference from the matrix to the fibers.

Three types of carbon nanoscale reinforcements (CNRs) including the shortened electrospun carbon nanofibers (ECNFs, with diameters and lengths of ∼200 nm and ∼15 µm, respectively), carbon nanofibers (CNFs), and graphite nanofibers (GNFs) were electrophoretically deposited on carbon fiber (CF) fabrics for the fabrication of hybrid multi‐scale epoxy composites. The results indicated that the electrophoretic deposition (EPD) of CNRs onto CF fabrics led to substantial improvements on mechanical properties of hybrid multi‐scale epoxy composites; in particular, the hybrid multi‐scale epoxy composite containing surface‐functionalized ECNFs (with amino groups) exhibited the highest mechanical properties. The study also indicated that some agglomerates of CNRs (particularly GNFs) could form during the EPD process, which would decrease mechanical properties of the resulting composites. Additionally, the reinforcement mechanisms were investigated, and the results suggested that continuous (or long) ECNFs would outperform short ECNFs on the reinforcement of resin‐rich interlaminar regions in the composites. POLYM. COMPOS., 35:1229–1237, 2014. © 2013 Society of Plastics Engineers

Today, due to the frequent use of composite materials used in the aerospace and automotive industries, an intensive study is carried out on the joining methods of these materials. One method of joining composite or aluminum alloy materials is adhesive bonding. Studies on the development of the strengths of adhesively bonded joints focused on adhesive type, the bonding method, and hybrid joints. In the present study, a different method was used to increase joint strength. This study experimentally and numerically investigated the mechanical properties of single-lap joints bonded by a composite adhesive – obtained by adding fiber fabric to the adhesive. Adhesively bonded single-lap joints were produced using DP460 toughened adhesive type as the adhesives; AA2024-T3 aluminum alloy was used as the adherend, and carbon fiber and glass fiber fabric were used as the added fiber. In addition, for the numerical analysis of the presented study, the bulk properties of the composite adhesives were obtained. As a result, the use of fiber-reinforced adhesive in bonding joints significantly increases the failure load of the joint, as it prevents the progression of cracks formed in the joint. However, the increase rate in the failure load changes depending on the adhesive thickness and the type of fiber fabric. As follows, the failure loads of the fiber-reinforced joints increase between 5% and 41% compared to the non-fiber-reinforced joints. In addition, it was observed that the results obtained from the numerical analysis and the results obtained from the experiments were consistent with each other.