Use of a simple, inexpensive pressure sensor to measure hydrostatic resin pressure during processing of composite laminates

A simple and cheap method of measuring the resin pressure within a composit e laminate during processing Ys presented. The method consists of using a s mall diameter, long needle filled with inert fluid and connected to an exte rnal pressure sensor, to measure the resin pressure at a point inside a com posite laminate. This method can be used to investigate resin flow, laminat e compaction, the control of voids, and in several composite material proce ssing methods such as autoclave processing, hot press curing and resin tran sfer molding. The sensors are suitable for research and development or trou bleshooting, bur not for production. Sensor assemblies were developed and t ested to show that their response is reproducible, linear and stable with t emperature and time. Resin pressure profiles for two AS4/3501-6 laminates w ere generated and compared. The experimental results were also compared to the resin flow simulation of a general processing model for composites, COM PRO. It is shown that the resin profile in the laminate is influenced by th e presence of the bleeder cloth and the vacuum bag pressure. A significant pressure drop corresponded to the point of minimum viscosity of the resin. Finally, the resin pressure was stabilized when the resin reached gelation.