Mechanics of formation of wrinkles during the processing of thermoplastic composites
Abstract
A lamination theory incorporating the effect of interply slip is developed to model the deformation behavior of polymer matrix composite at processing conditions. The model includes the interlaminar slip in the form of a new variable 'gross rotation' of the cross-section. 'Gross rotation' of the cross-section is defined as the slope of line joining the center of the cross-section of every layer. Individual layers follow Kirchhoff's assumption; the laminate itself, however, shows behavior identical to Mindlin plate theory. Effect of processing rate and interface stiffness on the stress development is studied. The deformation model is used for finding the stress history and distribution in the individual layers. The stresses are then used to study amount of spring back as well as magnitude and distribution of residual stresses in the post processed component. The history and distribution of the stresses are also used as initial stress for performing the analysis of wrinkle formation during the processing of thermoplastic composites. Two different approaches: (1) layer-by-layer analysis, and (2) single-layer-curved plate approach is used for analysis. The effect of interface strength, dissipation, initial curvature, etc., on the critical load and the wrinkle length is studied. Both approaches are tested for their applicability.
Degree
Ph.D.
Advisors
Sun, Purdue University.
Subject Area
Mechanics|Aerospace materials|Mechanical engineering|Materials science
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