Compaction Behavior and Part Thickness Variation in Vacuum Infusion Molding Process

Abstract

In vacuum infusion molding process (VIMP), it is difficult to manufacture a composite part with small dimensional tolerance, since the upper mold for the process is flexible. In this study, the static and cyclic compaction responses of five kinds of fabrics were experimentally studied under real VIMP conditions, with the effects of compaction pressure, compaction time, compaction cycle and number of the fabric layers. The static and cyclic compaction responses of the all fabrics follow different power law models and the resulting fiber volume fraction and relaxation factor increase with the number of layers. Although the resulting fiber volume fraction increases with the layer numbers, change of the fiber volume fraction of the composite parts with 10 layers to 100 layers of the all fabrics is less than 2.5%. The thickness of the composite part was monitored and measured using micrometer gauges, and the effects of processing parameters on the final thickness of part was investigated. The part thickness varies as a function of spatial coordinates and time during pre-filling, filling and post-filling stages in VIMP. The variation and the final value of the part thickness would be significantly affected by the processing parameters. Statistical results show that the final part thickness is equivalent to the thickness of the dry preform under the 0.08 MPa vacuum compaction pressure in VIMP. The difference between the fiber volume fraction of the final part and that of the dry preform is 2% ~ 5.7%.