Vakum destekli reçine transfer kalıplama yönteminde parça boyutunun ve fiber yoğunluğunun gözlemlenmesi

Vacuum Assisted Resin Transfer Molding (also known as Vacuum Bag Infusion) process is used to manufacture large composite parts within a single-sided mold. The upper side of the mold is made of a nylon vacuum bag which compacts the fabric preform underneath it to the lower mold part due to the vacuum applied. The initial thickness of the dry fabric preform is dependent on the static vacuum pressure; however at a level of vacuum pressure, the thickness varies with time as fiber nesting occurs for longer than 30 minutes as observed in our characterization experiments. As resin flows through the fabric preform, the resin pressure inside the mold increases (and hence compaction pressure decreases). Because of the non-rigid upper mold (nylon vacuum bag), the decrease in the compaction pressure will increase the thickness distribution of the part. In this study, it is aimed to construct general guidelines and a database so that the user can automate the VARTM process and predict the part thickness before the infusion starts. The thickness of the composite part and resin pressure in the system are monitored by using an on-line data acquisition system. The thickness of the preform is measured by using digital dial gages. To observe the effect of resin pressure on the thickness variation, multiple pressure sensors are placed at the same longitudinal location of the dial gages. The experimental results are compared with results of thickness and flow model which is developed by Correia et al. [13]. To model the process accurately, two databases are constructed based on the process parameters: (i) compaction of fabric in dry and dry/wet form, and (ii) permeability of the preform at different compaction pressures. The results indicate that random fabric and woven fabrics? compaction characteristics are very much different: (i) random fibers are further compacted upon being wetted when resin reaches there; (ii) this further nesting was not observed in woven fabrics significantly.