This work reports the preparation of carbon fiber reinforced thermoplastic composites via the in situ anionic ring opening polymerization of ε-caprolactam. Vacuum assisted resin transfer molding was used to fabricate polyamide-6/carbon fiber composites at different molding temperatures. As a result, the higher polymerization of ε-caprolactam was observed with the condition at 140 °C for satisfactory impregnation. Regarding molding temperature, the physical properties of polyamide-6/carbon fiber were observed that the bending and impact strengths at 140 °C were higher than those to at other molding temperatures. The polymerization kinetics of polyamide-6 was analyzed using differential scanning calorimetry by experimentally acquiring kinetic parameters according to model fitting approaches. Polymerization and crystallization, which occur simultaneously throughout the whole process, were separated using Gaussian and Maxwell–Boltzmann distributions to study polymerization kinetics. The result of the developed model was in good agreement with the experimental data for the presented first order autocatalytic reaction model.

In this study, a carbon nanotube (CNT) buckypaper was interleaved in a carbon-fiber-reinforced polymer (CFRP) composite to improve the interlaminar fracture toughness. Interleaving the film of a laminate-type composite poses the risk of deteriorating the in-plane mechanical properties. Therefore, the in-plane shear modulus and shear strength were measured prior to estimating the interlaminar fracture toughness. To evaluate the effect of the buckypaper on the interlaminar fracture toughness of the CFRP, double cantilever beam (DCB) and end notch flexure (ENF) tests were conducted for mode I and mode II delamination, respectively. No significant change was observed for the in-plane shear modulus due to the buckypaper interleaving and the shear strength decreased by 4%. However, the interlaminar fracture toughness of the CFRP increased significantly. Moreover, the mode II interlaminar fracture toughness of the CFRP increased by 45.9%. Optical micrographs of the cross-section of the CFRPs were obtained to compare the microstructures of the specimens with and without buckypaper interleaving. The fracture surfaces obtained after the DCB and ENF tests were examined using a scanning electron microscope to identify the toughening mechanism of the buckypaper-interleaved CFRP.

In this paper, an epoxy resin-based carbon fiber reinforced composite (CFRP) bar pultrusion system using a closed impregnation device which has various advantages in process compared to traditional open bath type pultrusion system was developed, and the fiber impregnation system was improved through the analysis of resin properties for the high-speed production of CFRP bars used to support the mother glass in the display transfer cassettes. To improve the fiber feeder system, fiber guides were switched from perforated plates to roller guides for spreading fibers, which allowed the input fibers to be widened and flattened while reducing the fiber thickness. Additionally, the correlation between resin viscosity and impregnation speed were analyzed to evaluate the resulting mechanical properties at different pultrusion speeds and temperatures. A CFRP bar was produced with resin injection at room temperature and a pultrusion rate of 400 mm/min and compared to a CFRP bar produced with fiber spreading, a resin injection temperature of 40 °C, and a pultrusion rate of 600 mm/min; the latter with a 50% improved production rate showed improvements in mechanical properties, including the cross-sectional void by 98.7%, surface roughness by 75.5%, deflection by 34.9%, and bending strength by 70%.

Polymer microlens manufacturing using thermal reflow was simulated and optimized by a numerical approach. Microlenses are used in various industrial fields, such as optical, semiconductor, and observation experiment equipment. Therefore, polymer microlens fabrication using an economical thermal reflow process is important for mass production and cost reduction. The feasibility of a thermal reflow process for microlens fabrication was analyzed in this paper by numerical methods. First, we refer to the previous studies and papers for the theoretical shape of the microlens. Second, for numerical simulation of the process above Tg (Glass Transition Temperature), we studied the multiphase flow simulation using a VOF method and adopted a Cross-WLF model to consider the rheological characteristics of PMMA. Finally, several parametric studies were carried out to compare the simulation profile and the theoretical lens shape in order to optimize the thermal reflow process. The numerical approach presented in this paper would enable a more efficient analysis and provide better understanding of reflow behavior to obtain the optimal process.

In this study, numerical modeling through the cohesive zone theory was performed to simulate the end notch flexure (ENF) test with same conditions of the experimental results of previous study that investigated the effect of a carbon nanotube (CNT)/epoxy film in carbon fiber reinforced polymer (CFRP) composite through the mode II interlaminar fracture toughness of a non-interleaved, epoxy film interleaved, CNT/epoxy film interleaved CFRP laminate specimen. The effect of the presence of CNT/epoxy film interleave on a composite laminate was modeled. The influence of the interleave cohesive parameters was studied to link the parameters to the material strength and energy release rate. Cohesive parameter identification was performed by matching the initial loading and the damage evolution phase by dividing the cohesive zones into cohesive front and remaining cohesive zones. This is because, when modeling with a single cohesive zone, the critical load point that causes delamination or the curve after load drop do not match the experimental values. Results showed that the divided cohesive zone model is in good agreement with the experimental results and that there is a clear relationship between the cohesive energy of the interface and CNT/epoxy film parameters.