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In this study, shear-induced crystallization of short carbon fiber (SCF)-reinforced isotactic polypropylene (iPP) composite was investigated using polarized optical microscopy (POM) and rheometry. Although the SCF exhibited no nucleation ability to iPP in the quiescent melt under the chosen conditions, different interfacial morphologies were observed after shear was applied. The POM results revealed that the crystallite morphologies along the SCF strongly depended on the shear rate ([??]) and shear duration. A nucleation kinetics model was proposed to determine how shear affects the fraction of SCF covered with transcrystalline. The nucleation rate on the SCF was proportional to [[??].sup.n]. The dependence of the nucleation rate corresponded well with the change in the shear-induced free energy of the melt, indicating that the interactions between SCF and iPP were insignificant. The rheological results demonstrated that conformational ordering directly affected the nucleation rate. The helical content near the SCF increased rapidly owing to the enhancement of shear. Therefore, the nucleation kinetics on the SCF surface accelerated significantly. KEYWORDS composites, crystallization kinetics, nucleation, shear-induced crystallization, short carbon fiber, 1 | INTRODUCTION Carbon fiber-reinforced polymer (CFRP) composite materials have been widely applied in automobiles and other industries owing to their excellent properties. [1,2] To improve the interfacial interaction between [...]

This study investigates the vibration transmission in coupled metal and composite plates with curvilinear fibers from the power flow viewpoint. The time-averaged power flow variables are obtained using a substructure method to assess the levels of vibration transmission of coupled structures with various configurations and fiber angles. It is demonstrated that by adopting tailored curvilinear fiber designs, the vibration transmission through the coupling edge of the plates can be effectively suppressed. Variable fiber angle designs are shown to exert significant effects on the dominant-excited mode and can be exploited to achieve desirable energy transmission paths for low-vibration transmission and effective suppression. [ABSTRACT FROM AUTHOR]

A combined model is presented to simulate the crystallization behavior of short carbon fiber-reinforced polymer (SCFRP) composites in this work. The combined model accounts for two morphologies in SCFRP: transcrystalline and spherulite. Transcrystalline is affected by complicated processing conditions and fibers and significantly affects the performance of composites. The quantitative modeling of crystallization kinetics of transcrystalline is thus important in predicting the mechanical properties of the composites. Therefore, this work proposes a novel analytical crystallization kinetics model of transcrystalline for SCFRP. In the combined model, the crystallization kinetics of spherulites is calculated using a classic Kolmogorov model. The combined model for SCFRP is first validated using a pixel coloring method in a two-dimensional (2D) simulation experiment and is then compared with the results of a differential scanning calorimeter (DSC) experiment. The results of the model and experiments (using pixel coloring method and DSC) were found to be in agreement, which proves the rationality of the combined model. The modeling results also show that transcrystalline can accelerate the crystallization rate of composites, and the acceleration effect is more remarkable at high temperature. The proposed crystallization kinetics model has good potential for modelling the crystallization behavior of SCFRP under complex processing conditions., INTRODUCTION Carbon fiber-reinforced polymer (CFRP) materials have been applied widely in automobiles and other industries owing to their excellent properties. Strong interfacial interaction between fibers and matrix plays a crucial [...]

Simulations are performed for the polymer melt injection molding filling flow using an improved SPH (smoothed particle hydrodynamics) method. For improving the numerical stability of the high‐pressure and high‐viscosity injection molding filling simulation, a modified low‐dissipation Riemann solver is proposed, and the Tait equation of state and several improvements are adopted in the improved SPH method. Simulations with three cavities are performed for verification of the SPH method, including a simple long rectangular cavity and two relatively complex cavities for study of injection flow balancing. For each cavity, the pressure and velocity results of the injection molding filling simulation are demonstrated, discussed, and compared with the results of the corresponding Moldflow simulation. Furthermore, results of particle motion tracking are also analyzed for an insight into the fountain flow effect. The SPH simulation results indicate that the improved SPH method can well weaken the non‐physical pressure oscillation with reasonable pressure results and controlled melt compressibility, and the SPH results are in good agreement with the Moldflow results. [ABSTRACT FROM AUTHOR]

At present, the main frictional components of artificial hip joint (AHJ) are mainly the combinations of hard materials (metal, ceramic) and soft materials (polymer), such as, metal‐on‐metal (MoM), ceramic‐on‐ceramic (CoC), metal‐on‐polymer (MoP), and ceramic‐on‐polymer (CoP). As a new type of AHJ, the polymer‐on‐polymer (PoP) combination has gradually begun to be explored and studied. In this paper, PoP AHJ of CF/PEEK composite are studied, and elastohydrodynamic lubrication analysis based on the solution of the Reynolds equation is performed, and the results are compared with the MoM and MoP AHJs. The comparison shows that under the same steady‐state condition, the PoP AHJ has better lubrication performance. The influence of the key structural parameters of the CF/PEEK PoP AHJ is also analyzed in this paper, and the results show that the femoral head size and radial clearance have great influence on the thickness and pressure distribution of the lubricating film. The research results in this paper further confirm the application potential of the PoP AHJ, and are helpful to its practical application and structural design. [ABSTRACT FROM AUTHOR]

This work presents a facile method to produce low-density PET foams using pristine semi-crystalline resin by moisture-induced controlled-hydrolysis in a tight processing window (moisture content ∼ 0.12 wt.%). We investigated the effect of moisture and moisture containing activated carbon (AC) on the foam expansion ratio, cell morphology, and PET resin degradation and crystallization properties. Controlled-hydrolysis increased the melt-flow rate of PET resin (intrinsic viscosity: 0.52 to 0.54 dL/g) without losing crystallinity, and thus the PET foams possess better tensile properties (∼2 MPa stress and ∼100% strain) and higher thermal stability (>200°C) than chemically modified PET foams. The foam density could be made as low as ∼ 0.15 g/cm3 using a lab scale twin-screw extruder. A strand array die was also designed to produce plate-shaped foam samples. AC allowed easier control of the moisture content and delayed resin degradation in extrusion. Both AC and micrographite (mGr) could stabilize the PET foam morphology in extrusion and serve as good infrared attenuation agents (IAAs) in a simulated housing thermal insulation experiment. [ABSTRACT FROM AUTHOR]

A carbon fiber/epoxy composite modified by electrospun coaxial dicyclopentadiene/poly(phthalazinone ether sulfone ketone) (DCPD/PPESK) nanofibers was successfully fabricated, and the addition of DCPD/PPESK fibrous membranes made the composite have remarkable self‐healing ability, and meanwhile effectively improve its mechanical properties. Results of polarization microscope observation and thermogravimetric analysis confirmed liquid DCPD as the healing agent was encapsulated into the PPESK coaxial nanofiber. Three‐point bending test was utilized to evaluate the mechanical properties and self‐healing effect of the composite. Experimental results indicated that the embedded nanofibers significantly improved the toughness of the composite, and maintained good mechanical properties even at low resin content. Most importantly, the flexural strength of the composite recovered to close to 90% observed 2 h after the bending failure. [ABSTRACT FROM AUTHOR]

Short carbon fiber reinforced poly‐ether‐ether‐ketone (SCF/PEEK) composites have attracted great attention in automobile and aerospace industries for their excellent thermal and mechanical properties. To investigate the anisotropy and temperature effects on mechanical properties of SCF/PEEK composites, tensile tests were conducted in various mold flow directions at 23, 80, 140, and 200°C. Results show that the tensile behavior of SCF/PEEK is highly influenced by temperature and fiber orientation. Both tensile strength and elastic modulus decrease with the increasing of temperature, and fracture strain increases with the increasing of temperature. Scanning electron microscopy was conducted to investigate the effects of anisotropy and temperature on fracture mechanism by scanning the tensile fracture surfaces. A shell‐core‐shell structure across the sample thickness was observed. Fibers are mainly aligned in mold flow direction in shell layers and perpendicular to the mold flow direction in core layers. The anisotropy of SCF/PEEK composites is fiber orientation dominated, and the temperature‐dependence of SCF/PEEK is matrix‐dominated. The variations of elastic modulus and tensile strength with temperature were mathematically represented. Constitutive model was established to predict the stress‐strain curves over a wide range of temperatures. Overall, the constitutive model could predict the temperature dependent stress‐strain relationships well. [ABSTRACT FROM AUTHOR]