Effect of Compression Process on Void Behavior in Structural Resin Transfer Molding

In order to realize low void content molded parts, we proposed a new structural resin transfer molding (SRTM) with compression process. Resin was injected with gap height between upper and lower halves of matched metal dies and then moved the upper die, so that mold filling was performed by squeezing motion. The usefulness of the compression process was examined by contrast to a conventional SRTM method. Void distribution and bending properties of the moldings were compared between both processes. SRTM method with the compression process could improve driving out of the voids compared with conventional SRTM method. Effect of gap closure rate during mold closing on the void distribution was examined. When the gap closure rate was high, the voids were expelled towards the end of cavity, whereas voids remained on the top surface of the molded parts in the case of small gap closure rate. The difference of void formation by the gap closure rate was examined by using finite element flow analysis and it was confirmed that a balance of the permeability between in-plane and out-of-plane directions was important.