GAS FLOW METHOD FOR DETECTION OF LOCALPREFORM DEFECTS BASED ON STATISTICAL ANALYSIS

摘要

An in-situ method employing gas flow has been developed to determine the quality offibrous preforms in the resin transfer molding (RTM) process prior to resin injection. Defectsresulting from fiber preform misplacement, accidental inclusions, preform surface density variation,etc., are quantified. Permeability variations, caused by local defects, affect the pressure profilesgenerated during steady state gas flow. By checking the deviations of measured pressures from theexpected reference value at various locations in the mold, anomalies can be detected. Furthermore, amultivariate statistical approach is applied to compare measured quantities from a test preform toquantities obtained from known groups in order to determine the location and severity of a specificflaw. A specially designed mold, with multiple ports for gas injection and pressure measurement, wasused to test various cases with and without defects.