• Composites Research
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• v.36 no.5
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• pp.321-328
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• 2023

This study developed the in-situ stamp-forming process using the multi-axis robotic arm to fabricate thermal composite parts. Optimal fabrication parameters with the multi-axis robotic arm were determined using finite element analysis and these parameters were further refined through the practical manufacturing process. A comparison between the manufactured parts and finite element analysis results was conducted regarding thickness uniformity and wrinkle distribution to confirm the validity of the finite element analysis. Additionally, to evaluate the formability of the manufactured composite parts, measurements of crystallinity and porosity were taken. Consequently, this study establishes the feasibility of the In-situ stamp-forming consolidation using a robotic arm and verifies the potential for producing composite parts through this process.

• Composites Research
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• v.34 no.5
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• pp.296-304
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• 2021

This study presented the evaluation of the stamp forming process for L-shape CF/PEKK thermoplastic composite using the finite element model. The formability of three different trimming allowances has been examined for representative product geometry. The results showed that those manufactured by high trimming allowance showed more excellent formability in those areas. Moreover, the effects of the trimming allowances on the stress, thickness, wrinkle distributions of thermoplastic composites fabricated with the stamp forming process were evaluated. The comparison of the simulation and experimental results for the thickness and wrinkle distributions proved the accuracy of the stamp forming model. The crystallinity of the composite was performed by differential scanning calorimetry (DSC). The void content of the composite was evaluated by matrix digestion. Then, the fabricated structure was characterized and achieved high quality in crystallinity and void content. Consequently, the presented FEM modeling shows excellent potential for application in the aircraft product design process. This pragmatic approach could efficiently offer a valuable solution for the thermoplastic composite manufacturing field.

• Composites Research
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• v.35 no.2
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• pp.93-97
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• 2022

The application of infrared heating in the hot press forming of the thermoplastic composites is conducive to productivity with high-speed heating. However, high energy, high forming temperature, and high-speed heating derived from infrared heating can cause material degradation and deteriorate properties such as re-melting performance. Therefore, this study was conducted to optimize the process conditions of the hot press forming suitable for carbon fiber reinforced polyetherketoneketone(CF/PEKK) composites that are actively researched and developed as high-performance aviation materials. Specifically, the degradation mechanisms and properties that may occur in infrared high-speed heating were evaluated through morphological and thermal characteristics analysis and mechanical performance tests. The degradation mechanism was analyzed through morphological investigation of the crystal structure of PEKK. As a result, the size of the spherulite decreased as the degradation progressed, and finally, the spherulite disappeared. In thermal characteristics, the melting temperature, crystallization temperature and heat of crystallization tend to decrease as degradation progresses, and the crystal structure disappeared under long-term exposure at 460℃. In addition, the low bonding strength was observed on the degraded surface, and the bonding surfaces of PEKK did not melt intermittently. In conclusion, it was confirmed that the CF/PEKK composite material degraded at 420℃ in the infrared high-speed heating. Furthermore, the spherulite experienced morphological changes and the re-melting properties of thermoplastic materials were degraded.

• Polymer(Korea)
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• v.38 no.3
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• pp.320-326
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• 2014

The effects of high shear rate processing on the thermal properties of PC/ABS blends were studied. It was executed by the high shear processing machine (NHSS2-28) at the varied conditions of screw speeds and loaded duration. After the samples were processed with NHSS2-28, the $T_gs$ were shifted from 143 to $133^{\circ}C$, and the behavior of degradation determined by TGA showed two distinct steps before high shear rate processing, while it showed a straight line after the processing. In order to provide the reasons of the properties, it was showen by SEM and UTM that the droplet sizes morphologically decreased after the processing, and the elongations decreased slightly until 1000 rpm of screw speed and then sharply decreased, according to the conditions of high shear rate processing. Therefore, it can be confirmed that $T_g,s$ of PC/ABS blends were considerably shifted under an appropriate high shear rate condition, and rapidly dropped, so that blends degraded above the condition, due to stress-induced degradation.