Dry Spot Formation and Changes in Liquid Composite Molding: I—Experimental.

Dry spot formation and changes in liquid composite molding (LCM) were investigated by flow visualization experiments. The dry spot size can be reduced by three mechanisms: (1) it can be compressed by the hydrostatic pressure from the surrounding saturated region; (2) it can be reduced by bleeding trapped air into the surrounding saturated region if there is a pressure gradient in the saturated region; and (3) it may gradually disappear by the wicking flow due to the capillary pressure difference between the saturated region and the dry fiber region. Experiments of packing and bleeding, a technique used in industry to eliminate dry spots, were also carried out and the results are explained based on the three types of dry spot changes. [ABSTRACT FROM PUBLISHER]