Cure Induced Property Changes and Warpage in Thermoset Resins and Composites

摘要

Theaim of the present work was to investigate the evolution of thermal andmechanical properties during the polymerisation of a thermosetting resin that is typicalthose used as the matrixinadvanced composites. Themechanism of the cure reactionwas studied usingdifferentialscanning calorimetry(DSC) in both dynamic (thermalscanning) andisothermalmodes, and proceduresforcorrelating the two types ofcalorimetricdata weredeveloped. Themodelfinallychosen encapsulates the diffusion-controlled mechanism of reaction byestablishing a one-to-one relationship between thedegree of cure and the glass transition temperature, whichisassumed to bea structuralparameter during the polymerisation. A detailedexperimental investigationof specificheatcapacity, thermalconductivity, secondary transformations (gelationandvitrification), thermal and chemical volume changes and stress relaxation moduli wascarried out to establish a suitabledatabase for the resin.Wherepossible, a closedanalytical model was employed; alternatively, an interpolationprocedure was developedevaluate the changes ina selected propertyduringa more complextemperatureprofile.Experimentalequipment wasdeveloped to perform shrinkage measurements onthe neat resin system; the results obtained werelatercompared with experimentaldatafromstandard liquid dilatometry tests.Asimulation of the curing of a bi-materialcantilever beam ispresented as a test casehighlight the influenceof property changes on the finalcurvature. Sample curvatureduring the experiment was recorded using adigitalcamera and then analysed usinggraphical software.Thecorrelationbetween the observed values of curvature and theresults of afiniteelement based simulation was used to validate the kinetics model andproperty modellingfor the chosen thermosetting resin.