Applied Composite Materials

Colin, David; Bel, Sylvain; Hans, Thorsten; Hartmann, Mathias; Drechsler, Klaus

doi: 10.1007/s10443-020-09819-1pmid: N/A

A numerical description of dry non-crimp fabrics is proposed at the scale of the filaments using a commercially available finite element software package. Deviations in the filament orientation of the fibrous layer is a dominant factor in the occurrence of local defects, which influences the mechanical response of the textile. Therefore, the introduction of variability in the orientation distribution is proposed in this paper. This approach enables to capture the entanglement of the filaments and models all interaction mechanisms. A stepwise generation of the numerical non-crimp fabric is proposed considering the main manufacturing steps to reproduce the local defects in the fibrous mat appropriately. Averaged periodic boundary conditions are developed ensuring an overall periodicity of the model while allowing reorientation at the scale of the filaments. Two various non-crimp fabrics are investigated and modelled. The distribution of the filaments in the simulation results correlate well with measurements of the filament orientation performed on the textiles. Moreover, a detailed comparison of the local defects shows a good agreement with measurements on the specimens. The presented approach can be used to generate geometries for subsequent virtual characterization.

Ajam, Alaa; Tehrani-Bagha, Ali; Mustapha, Samir; Harb, Mohammad

doi: 10.1007/s10443-020-09821-7pmid: N/A

The main objective of this study was to investigate a zero-waste restoration and reprocessing method of carbon/epoxy prepreg. We studied a series of chemical and thermal treatments to reshape and re-strengthen pre-impregnated (prepreg) carbon fiber-reinforced polymer (CFRP) composite rolls that were cured over the shelf, never been used, and would otherwise be discarded. The proposed treatment method is of high interest in minimizing solid waste and reducing the environmental footprint of polymer composites. We used a series of solvents (water, ethanol, N, N- Dimethylformamide (DMF) and Sulfuric Acid) to induce ductility in the scrap already rigid self-cured specimens. The chemical treatments of the scraps using mixtures of DMF-Water or DMF-Ethanol enhanced the ductility of the samples without any negative impact on the mechanical properties. However, the chemical treatment of scarps using a mixture of sulfuric acid with other solvents, could not improve the ductility of the samples. Heat pressing the chemically treated samples further enhanced the ductility of the samples and flattened the scrap composites. The recovered strength and modulus of the recycled prepreg CFRP reached a promising value of over 65% of the original properties, where the samples treated with a mixture of DMF-ethanol preserved their mechanical properties better than other treated samples. The simple, safe, and zero-waste recycling technique presented in this study has proven to be effective for closing the life cycle of a thermoset polymer composite.

Povolo, Marco; Tabucol, Johnnidel; Brugo, Tommaso M.; Zucchelli, Andrea

doi: 10.1007/s10443-020-09818-2pmid: N/A

Hybrid metal-Carbon Fiber Reinforced Polymers (CFRP) core tubes and rollers are becoming progressively important in the automotive, aerospace, and printing industry for the excellent performance/price ratio. The enhanced mechanical properties and favorable tribological performance of these tubes are provided by the coupling of metal with CFRP compared to tubes build from solely CFRP or metal. However, these kinds of tubes are very expensive and only the co-curing technique of metal and CFRP parts guarantees a reduction in production cost and the competitiveness of products. In this work, a simple out-of-autoclave (OOA) electrical resistance co-curing method for hybrid metal-CFRP tubes, based on an analytical model, that exploits the Joule effects, is proposed and verified by experimental test and finite element analysis (FEA). This technique can also be used for other geometries and guarantees considerable energy savings.

Wang, Liwu; Tian, Weiping; Guo, Yunqiang; Li, Geng

doi: 10.1007/s10443-020-09820-8pmid: N/A

An experimental study was conducted to study the effects of chemical vapor deposition (CVD) carbon content on the erosion behavior of 5 direction (5D) carbon-carbon (C/C) composite in a solid rocket motor (SRM). A small SRM, which can compare the erosion performance of two samples under the same working conditions, was designed and tested. The erosion of the carbon-carbon composite ablative morphology at macroscale and microscale was obtained and analyzed. Results show that the average erosion rates of 1# and 2# samples are 0.35 mm/s and 0.45 mm/s, respectively, which means the erosion rate of the sample with high CVD carbon content is 22.2% times lower than the one with low CVD carbon content. During SRM operation, the fibers within fiber bundles and carbon rods are in a dispersive and integral state, respectively, thus carbon rods have a better anti-ablation capability, followed by fiber bundles and matrix in turn. As a result, a carbon rod will be positioned higher than the matrix and fiber bundles around. Furthermore, the ablation of fibers within fiber bundles and carbon rods, although they have significant differences in the ablation process, can both be described as a single fiber ablation. The oxidizing species react with the matrix, then with the CVD carbon and the fiber within a fiber bundle in turn, while they react with the matrix, the CVD carbon and the fiber within a carbon rod simultaneously. This shows that the increase in CVD carbon content will improve the ablation performance of C/C composite by protecting the fibers within the fiber bundles. The present study provides a fundamental understanding of the effect of CVD carbon on the ablation performance of C/C composite, serving as a reference for further design and optimizations of C/C composite.

Islam, Shafiul; Yuan, Songmei; Li, Zhen

doi: 10.1007/s10443-020-09815-5pmid: N/A

Ceramic matrix composites of type C/SiC have great potential because of their excellent properties such as high specific strength, high specific rigidity, high-temperature endurance, and superior wear resistance. However, the machining of C/SiC is still challenging to achieve desired efficiency and quality due to their heterogeneous, anisotropic, and varying thermal properties. Rotary ultrasonic machining (RUM) is considered as a highly feasible technology for advanced materials. Cutting force prediction in RUM can help to optimize input variables and reduce processing defects in composite materials. In this research, a mathematical axial cutting force model has been developed based on the indentation fracture theory of material removal mechanism considering penetration trajectory and energy conservation theorem for rotary ultrasonic face milling (RUFM) of C/SiC composites and validated through designed sets of experiments. Experimental results were found to be in good agreement with theoretically simulated results having less than 15% error. Therefore, this theoretical model can be effectively applied to predict the axial cutting forces during RUFM of C/SiC. The surface roughness of the workpiece materials was investigated after machining. The relationships of axial cutting force and surface roughness with cutting parameters, including spindle speed, feed rate, and cutting depth, were also investigated. In order to identify the influence of cutting parameters on the RUFM process, correlation analysis was applied. In addition, response surface methodology was employed to optimize the cutting parameters.

Hsu, Chun-yen; Zhang, Yuying; Karandikar, Prashant; Deng, Fei; Ni, Chaoying

doi: 10.1007/s10443-020-09825-3pmid: N/A

Reaction bonded SiC/Si (RBSC) composites composed of α-SiC, β-SiC and crystalline-Si phases manufactured at high temperature are widely used in different applications due to their outstanding performances in extreme service conditions. Although the macroscopic mechanical properties of these materials have been extensively explored, there are questions remaining unanswered such as the local material behavior compared to the SiC/Si interface, mechanistic responses in nanoscale and the micro- to nanoscale mechanical properties of major individual components after experiencing the reaction bonding process. In this study, nanoscale specimens were prepared by utilizing Ga focused ion beam (FIB) and an in-situ tensile testing platform was established with a testing stage accommodated inside a field emission scanning electron microscope (FE-SEM). Maximum tensile strength, elastic modulus and Weibull modulus of the nanoscale α-SiC specimens were measured to be 22.9 GPa, 321 GPa and 4.1, respectively. The maximum failure strength was found to be as high as 80% of the theoretical fracture strength. The fracture was found to originate at the side of the specimen surface and appeared to propagate in a brittle manner. The overlap of tensile strength ranges of α-SiC and SiC/Si interface suggests the consistency with an observation of mixed fracture modes in RBSC.