IMPACT OF STRAND LENGTH AND THICKNESS ON MOLD EDGE AND WELD LINES IN COMPRESSION MOLDING OF CFRTP-SMC
Topic(s) : Special Sessions
Co-authors :
Zihao ZHAO (JAPAN), Yi WAN , Jun TAKAHASHI (JAPAN)Abstract :
Carbon Fiber Reinforced Thermoplastic Sheet Molding Compound (CFRTP-SMC) materials have been extensively researched and used in practical applications, particularly in the automotive industry. However, there is limited understanding of the effects of certain defects that can occur during their manufacturing and molding processes. Weld lines (WL) are known as one of the most detrimental defects affecting polymer composites, including CFRTP-SMC [1]. At the same time, anomalous mechanical properties have often been observed in mold edge parts. The purpose of this study is to investigate the effect of strand variations, which have been shown to significantly affect the performance of CFRTP-SMC [2], on the defects or features on the WL and mold edge area that are commonly formed during compression molding.
Experimental molding was performed using CFRTP-SMC with varying fiber strand lengths (10mm, 20mm 30mm) and thicknesses (44μm, 88μm), which were cut into various sizes to fit the mold. Two types of experiments were designed: The initial experiment concentrated on WL and utilized different strand types in opposing flow, adjacent flow, and hybrid flow. The second experiment aimed to investigate the flow of mold edges at various flow levels, determined by charge ratios, as shown in Figure 1. Other molding conditions were held constant. After molding, three-point bending tests and tensile tests were performed to evaluate the modulus and strength of the molded plates. A comparative analysis of different strand types and plate areas was performed. The specimens were subjected to CT scans to observe and compare damage in different specimens. The 3D model's fiber orientation distribution was analyzed with ease thanks to the reconstructed 3-dimensional structure of the images. The results showed that weld lines will affect the mechanical performance regardless of stand type, with significant reductions in modulus and strength compared to flawless molding plates. The mold edge exhibited a distinct performance from the reference area. The structure analysis reveals a reorientation of fibers in both WL and mold edge, as shown in Figure 2, which means the defect only exists in a certain direction.
This study provides insight into the correlation between CFRTP-SMC strand length, thickness, and their effects on fiber performance during forming, shedding light on the multifaceted interplay between material dimensions and manufacturing techniques
Experimental molding was performed using CFRTP-SMC with varying fiber strand lengths (10mm, 20mm 30mm) and thicknesses (44μm, 88μm), which were cut into various sizes to fit the mold. Two types of experiments were designed: The initial experiment concentrated on WL and utilized different strand types in opposing flow, adjacent flow, and hybrid flow. The second experiment aimed to investigate the flow of mold edges at various flow levels, determined by charge ratios, as shown in Figure 1. Other molding conditions were held constant. After molding, three-point bending tests and tensile tests were performed to evaluate the modulus and strength of the molded plates. A comparative analysis of different strand types and plate areas was performed. The specimens were subjected to CT scans to observe and compare damage in different specimens. The 3D model's fiber orientation distribution was analyzed with ease thanks to the reconstructed 3-dimensional structure of the images. The results showed that weld lines will affect the mechanical performance regardless of stand type, with significant reductions in modulus and strength compared to flawless molding plates. The mold edge exhibited a distinct performance from the reference area. The structure analysis reveals a reorientation of fibers in both WL and mold edge, as shown in Figure 2, which means the defect only exists in a certain direction.
This study provides insight into the correlation between CFRTP-SMC strand length, thickness, and their effects on fiber performance during forming, shedding light on the multifaceted interplay between material dimensions and manufacturing techniques