Quality Control of Composite Part Preforms

INVENTION: The invention tests individual preforms used in composite parts. The invention has these advantages over currently available methods:

It does not rely upon visual inspection It avoids scrap by testing preform defects before a composite part is formed It can utilize low cost test fixtures It can test preform defects with a high degree of reliability The invention injects low-pressure gas into the preform, and uses statistics to characterize preform quality. Because only low-pressure gas is used, in-line production testing can be run on a low cost fixture capable of sustaining only low mechanical stress. The savings potential for certain applications can be great. For some applications, early detection of a preform defect can prevent hours of wasted machine cycle time to mold and cure a single defective part. When a production order is for a set of parts, one defective part may delay the entire order. Furthermore, a single preform part can cost thousands of dollars for some applications. Early detection can enable some preforms to be repaired before they are processed into composite parts (at which point the part needs to be scrapped or reworked).

The invention can handle a variety of preforms, ranging from fabric to semi-rigid to rigid. There are three variations of this invention (See patent links below for two such variations). Each variation of the invention injects gas through the preform, then takes pressure readings to identify the location of preform defects before resin is injected into the mold. A software tool has been used to statistically evaluate pressure readings and to characterize the severity, location and nature of a preform defect. A “normal” part is identified from a base of data generated for parts identified as normal. The differences between actual and normal pressures form a basis for quality control criteria. The software employs statistical methods to classify preforms into normal or defective groups, and to answer four basic questions:

1. Is there a defect? 2. How severe is the defect? 3. Where is the defect?
4. What is the nature of the defect?

Stage of Development:Blind validations of the invention (second variation) have shown greater than a 99% success rate to identify the existence, severity, location and type of quality defects. Extensive experimentation was done on a large commercial industrial component, covering a wide-range of variables.

Northwestern invites prospective licensees of this invention to participate in blind tests of the invention, and is prepared to work with a licensing partner to develop and deliver a system to the market place.

U.S. Patent number 6,853,925 and U.S. Patent Number U.S. 6,907,357

Patents:
US 6,853,925
US 6,907,357

Inventor(s): Isaac M. Daniel, Sun Kyoung Kim, Jeremy G. Opperer

Type of Offer: Licensing



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