Characterization and Analysis of Manufacturing Processes Induced Defects in Composite Structures for the AFP (Automated Fiber Placement) Process

Abstract

Automated Fiber Placement (AFP) is a widely used advanced process of manufacturing composite layups. The placement head in an AFP machine automatically lays down individual tows of composites to produce a composite layup. Because of the nature of this process, composite layups produced by this process have inherent defects. Although these defects can not be totally eliminated, the manufacturer has the knowledge of defect geometry as these defects are characteristic of the AFP machine and ply boundary settings. The AFP process facilitates manufacturer to have control over the placement of defects as to where these defects should appear in the layup. The main objective of this work is to develop a computational tool that will allow user to model composite layup with user defined defect configuration and then evaluate the effective properties and ultimate strength of the composite layup in fairly short time, so that the user can model and test different defect configurations and select an optimum one for the best performance. The computational tool is completely developed in python programming language and Abaqus scripting interface which is an extension of the python programming language. The tool allows the user to model straight gaps and curvilinear gaps at a desired location in a composite layup. It implements displacement periodic boundary conditions which are a precursor to implementation of classical homogenization theory in this work. The effective properties are evaluated by effective stress/strain formulations defined by the classical theory of homogenization. The tool is also capable of determining the ultimate strength of a layup by carrying out finite element strength analysis. In the end, the ability of the tool to evaluate effective properties and strength with precision was tested by comparing the results with experimental and analytical data from a similar work found in literature carried out for two dimensional case.