Yüksek kaliteli kompozit plakaların imalatı için basınçlı VARTM imal usulünün geliştirilmesi

Although vacuum-assisted transfer molding (VARTM) is preferred for manufacturing medium to large composite parts due to its simple tooling and low operational cost, part quality dictated by dimensional tolerances, void content and mechanical properties is usually low due to inherent limitations of the process. In this study, the conventional VARTM process was modified and an alternative process for manufacturing of high quality composite laminates was developed by (i) heating a mold to enable the utilization of a high temperature resin system (EPON 862), and (ii) external pressurization of the mold to increase fiber volume fraction and improve mechanical properties. During post-filling stage, various levels of pressure were applied in a pressure chamber mounted on top of the mold and effect of external pressurization on laminates made of various number of plies was investigated. It was observed that pressurized and heated VARTM led to laminates with less than 1% void content in all laminates manufactured under various external pressure levels. In addition, up to 25% and 13% increase in fiber volume fraction and flexural strength were achieved, respectively. Microstructural analyses, dry and wet compaction characterization of 8-harness satin woven fabric were carried out to understand the void morphology and compaction characteristics of the fabric. Moreover, the applicability of pressurized VARTM was studied by using another resin type (PRO-SET INF 114) which was processed at low temperatures. It was observed that fiber volume fraction increased similarly to that of EPON laminates and void content of laminates was below 1%. This epoxy resin system had high viscosity which yielded to long mold filling times in conventional VARTM. The pressure chamber was vacuumed at a certain pressure to relax the fabric and increase its permeability which significantly enhanced the resin flow and shortened the mold filling time by 48%. It was concluded that pressurized VARTM could also be implemented to low temperature resins with high viscosity to (i) enhance resin flow, (ii) increase fiber volume fraction, (iii) achieve low void content, and (iv) assure uniform thickness distribution.