Article: JEC Composites
Sensor Film Technology Significantly Reduces Warped and Rejected Composite Parts
Sensor Products Inc. presents Pressurex®, a thin sensor film that carefully maps and measures the amount of interfacial stress exerted on honeycomb cores, composite lay-ups and bonded surfaces within composite structures. By using Pressurex® to see how surface stresses are distributed, an engineer can observe inconsistencies and misregistration in composite parts and thereby greatly reduce the yield defect rate. Other applications for Pressurex® include determination of press planarity in lamination processes, monitoring of vacuum bagging pressures, confirmation of pressure uniformity on wound filaments parts, and calibration of tools and equipment.
Pressurex® comes in the form of a thin plastic sheet or roll that can be cut to required dimensions. When placed between contacting or mating surfaces, the film instantaneously and permanently changes color. This color change is a direct result of the amount of pressure applied. Comparison of color variations to a color correlation chart (conceptually similar to interpreting Litmus paper) can help determine precise pressure magnitude. Pressurex® can detect pressures from 2 to 43,200 PSI (0.14 to 3,037 kg/cm²). Depending on the requirements of the project, Additional evaluation and analysis can be performed with an optical analysis system (Topaq®) available from Sensor Products Inc.
In the aerospace industry, Pressurex® has been used to determine the exact amount of pressure causing cracks in the inner spars of a helicopter’s main rotor blade. A large sheet of Pressurex® was inserted into the bonding tool, bagged up, and pressurized in the autoclave. When the film was removed, the exact amount of pressure causing the crack was determined.