Journal of Composite Materials

Control and reduction of microorganism infections in high-risk environments is up to date a challenge. Traditional techniques imply several limitations including development of antibiotics resistance and ecotoxicity. Then, polymers functionalized with photocatalyts arise as a promising solution against a broad spectrum of microorganisms found at, e.g. sanitary, food, and medical environments. Here, we present silicone rubber–TiO₂ composites as novel antibacterial polymers. Four different types of composites with different TiO₂ contents were produced and analyzed under UV irradiation and dark conditions in terms of particle distribution, chemical composition, photocatalytic activity, wettability, and antibacterial efficacy against Escherichia coli. Under UV irradiation, antibacterial sensitivity assay showed a 1000 times reduction of colony forming units after 2 h of light exposure so that the antibacterial ability of silicone–TiO₂ composites was proved. Photocatalytic activity assessment suggested that reactive oxygen species induced by photocatalytic reaction at TiO₂ particles are the main cause of the observed antibacterial effect. Scanning electron microscopy indicated no topographical damage after UV exposure. In addition, chemical analysis through Raman and X-Ray photoelectron spectroscopies demonstrated the stability of the silicone matrix under UV irradiation. Hence, the current work presents silicone–TiO₂ composites as stable nonspecific antibacterial polymers for prevention of infections at multiple high-risk environments.

Carbon compounds have high dielectric losses, which means that these materials are heated efficiently by microwave irradiation. Carbon materials can be used as microwave absorbers in polymeric materials that are transparent to microwave irradiation. In this paper, carbon-reinforced polypropylene composites were exposed to microwave irradiation and then their dynamic mechanical thermal properties, electromagnetic shielding, and surface morphology were investigated. The test results showed that mechanical and physical properties of carbon–polypropylene composites improved following microwave exposure. The dynamic mechanical thermal analysis results showed that their storage and loss modulus were improved following microwave treatment. It is postulated that microwave irradiation heats carbon materials, which is likely to melt neighboring matrix thus improving interfacial adhesion and structural defects.

The cutting edge of the polycrystalline diamond tool easily blunts in high-speed milling of carbon-fiber-reinforced plastic with the tool deterioration. It aggravates the burrs damage due to the change in the tool–material interaction. Therefore, this paper analyzes the tool–material interaction in milling of carbon-fiber-reinforced plastic based on the material-removal mechanism to investigate the tool deterioration mechanism. It reveals that there are two main reasons for the tool deterioration: the extreme crashing and ploughing of the uncut fibers on the tool, and the serious impact of fibers strongly supported on the cutting edge. An indirect measure method is proposed to quantify the tool deterioration including the ploughing-caused wear and impact-caused microchipping. Furthermore, the milling tests are performed to evaluate the tool deterioration under different cutting speeds in the range of 7.33–9.42 m/s. Meanwhile, a modified mathematical model of tool life is proposed based on a strict burr specification in milling of the carbon-fiber-reinforced plastics. Polycrystalline diamond tool has the longest life with the run-in wear and the quasi-steady-state wear for 7.33 m/s cutting speed, and the life rapidly decreases with the increase in the cutting speed in this range. For the cutting speed larger than 8.37 m/s, the wear resistance of polycrystalline diamond tool is very low, because the accelerated state wear occurs instead of the quasi-steady-state wear. Thus, the optimization of the tool geometry and the assisted lubrication should be applied for its improvement.

Chemical functionalization of carboxylated multiwalled carbon nanotubes with vitamin B1 was carried out under ultrasonic irradiation. The functionalized nanotubes were embedded in a chiral and biodegradable poly(ester-imide) to prepare multiwalled carbon nanotubes reinforced polymer nanocomposites. Optically active poly(ester-imide) was synthesized by step-growth polymerization of aromatic diol and amino acid based diacid. The vitamin B1 functionalized multiwalled carbon nanotubes and the resulting nanocomposites were examined using Fourier-transform infrared spectroscopy, thermogravimetric analysis, X-ray diffraction, transmission electron microscopy, and field-emission scanning electron microscopy. Thermogravimetric analysis results indicated that temperature at 10% weight loss was increased from 409℃ for pure PEI to 419℃, 427℃, and 430℃ for nanocomposites containing 5%, 10%, and 15% functionalized multiwalled carbon nanotubes, respectively. The Fourier-transform scanning electron microscopy and transmission electron microscopy images exhibited that the functionalized multiwalled carbon nanotubes were separated individually and enwrapped by polymer chains.

Modern bridge structures need light decks with long durability and promising technical parameters. Glass fiber-reinforced polymer orthotropic bridge deck creates unconventional possibilities in bridge designing. Parallel identification of glass fiber-reinforced polymer deck panel by differential thermal analysis, spectroscopy analysis, scanning and optical microscope monitoring, dynamic mechanical analysis and differential scanning calorimetry analysis, tensile and flexural tests will be presented in the paper. Differential thermal analysis was carried out for estimation of the physical and chemical transformation of glass fiber. The differential scanning calorimetry experiments were performed in the glass fiber-reinforced polymer–bridge deck material for determining the mass variation and the energy changes suffered by the materials, as a function of temperature and time. Dynamic mechanical analysis was allowed to detect thermal effects based on the changes in the modulus or damping behavior. Tensile and flexural tests allowed the observation of the decomposition process and information about the basic stress parameters of glass fiber-reinforced polymer material used in bridge applications was taken. Aforementioned analyses are necessary to examine the durability description of the composite element.

A finite element procedure is developed for the computation of the thermoelastic properties of textile composites with complex and compact two- and three-dimensional woven reinforcement architectures. The purpose of the method is to provide estimates of the properties of the composite with minimum geometrical modeling effort. The software TexGen is used to model simplified representations of complex textiles. This results in severe yarn penetrations, which prevent conventional meshing. A non-conformal meshing strategy is adopted, where the mesh is refined at material interfaces. Penetrations are mitigated by using an original local correction of the material properties of the yarns to account for the true fiber content. The method is compared to more sophisticated textile modeling approaches and successfully assessed towards experimental data selected from the literature.

This paper aims to develop a numerical nonlinear progressive damage model for laminated composite materials considering in-plane and out-of-plane shear stresses in combination with cohesive interface elements to predict the structural response and the failure mechanisms of laminated composite materials. For this purpose, the constitutive models for intralaminar and interlaminar damage modes have been developed as a numerical code by a UMAT subroutine and implemented in commercial finite element software. This model, which is based on the continuum damage mechanics approach, enables to predict the gradual degradation of material properties with five distinct damage parameters for different failure modes; three of these damage factors apply the shear damage contribution as a separate damage mode by a separate damage factor into the model and characterize it by shear damage dissipation energy, and two parameters for fiber and matrix in transverse directions. Also, a series of experiments have been performed to characterize and validate the nonlinear behavior of glass/epoxy laminate. This model is used to predict the behavior and the final strength of open-hole tension specimens. A reasonably good agreement was also achieved between numerical predictions and experimental observations in terms of shapes, orientations and sizes of individual intraply damages induced around the notch and also the final strength of open-hole tension specimen.

Process-induced total spring-in of corner-shaped composite parts manufactured via autoclave-forming technique using unidirectional prepreg is studied both numerically and experimentally. In the numerical study, a three-dimensional finite element model which takes into account the cure shrinkage of the resin, anisotropic material properties of the composite part and the tool-part interaction is developed. The outcome of the numerical model is verified experimentally. For this purpose, U-shaped composite parts are manufactured via autoclave-forming technique. Process-induced total spring-in, due to the combined effect of material anisotropy and tool-part interaction, at different sections of the U-shaped parts are measured with use of the combination of the three-dimensional optical scanning technique and the generative shape design. Total spring-in determined by the numerical model is found to be in good agreement with the average total spring-in measured experimentally. The effect of tool-part interaction mechanism on the total spring-in is studied separately to ascertain its effect on the total spring-in behavior clearly. It is shown that with the proper modeling of the tool-part interaction, numerically determined total spring-in approaches the experimentally determined total spring-in.

Scope of the presented work is a detailed comparison of a macroscopic draping model with real fibre architecture on a complex non-crimp-fabric preform using a new robot-based optical measurement system. By means of a preliminary analytical process design approach, a preforming test centre is set up to manufacture dry non-crimp-fabric preforms. A variable blank holder setup is used to investigate the effect of different process parameters on the fibre architecture. The real fibre architecture of those preforms is captured by the optical measurement system, which generates a three-dimensional model containing information about the fibre orientation along the entire surface of the preform. The measured and calculated fiber orientations are then compared with the simulation results in a three-dimensional overlay file. The results show that the analytical approach is able to predict local hot spots with high shear angles on the preform. Macroscopic simulations show a higher sensitivity towards changes in blank holder pressure than reality and limit the approach to precisely predict fibre architecture parameters on complex geometries.

Rotorcraft drivelines typically utilize a multi-segmented metallic system to transmit power between the engine and tail rotor. The typical arrangement of metal driveshaft segments, hanger bearings, and flexible couplers contribute to a significant logistical footprint, maintenance downtime, and life-cycle costs. Thus, an innovative flexible matrix composite driveshaft design alternative is presented in this paper, intended to simultaneously reduce the number of couplers and bearings, as well as, provide high fatigue strain capacity. Through reduction in number of parts, the maintenance cost and time as well as weight of the system are reduced. Composite driveshafts, representing those used in utility helicopters, were designed using an optimization process that considers: (1) damping-induced self-heating, (2) whirling stability, (3) torsional buckling stability, and (4) lamina strength. The paper provides a ballistic comparison study between a baseline carbon/epoxy composite and flexible carbon/polyurethane composite driveshaft segments. One driveshaft of each material was torsionally loaded to failure without ballistic impact. Additionally, two driveshafts were impacted obliquely at zero torque with 7.62 and 12.7 mm armor piercing/incendiary (API) rounds. After impact, the driveshafts were loaded in torsion to failure. Residual torsional strengths were 17–21% and 13% of un-impacted strengths for the 7.62 mm and 12.7 mm rounds, respectively. For the small sample size, flexible driveshafts had a marginally higher residual strength compared to the carbon/epoxy counterpart. Residual torsional stiffness values were 83–86% and 52–59% for the 7.62 mm and 12.7 mm rounds, respectively.