Pressurex®, a thin Mylar-based sensor film that maps and measures the amount of interfacial stress exerted on honeycomb cores, composite lay-ups and bonded surfaces within composite structures has been introduced by Sensor Products Inc. 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 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.
The film is available in sheets or rolls. 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. It can detect pressures from 2 to 43,200 PSI (.14 to 3,037 kg/cm2). Depending on the requirements of the project, additional graphical and statistical data can be retrieved from the film through Topaq®, an optical analysis system that can be bought or leased from Sensor Products Inc. or used by their staff.
It has been used in the aerospace industry 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.