Progressive damage analysis of pinned joints of composite plates
Arboleda Gonzalez, Gerardo I.
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A composite payload attach fitting (PAF) is being designed and fabricated at NASA MSFC for the Block 1B heavy-lift Space Launch System (SLS).Functioning as the primary structural interface, the PAF is connected to the payload by metal clevis fittings via pin connections.The overall goal of this study was to develop a reliable FE based methodology to analyze the pinned joints of composite honeycomb panels and determine their load-carrying capacities.This goal has been achieved by the following: (1) development of two-dimensional progressive damage models of composite panels for various failure modes, (2) experimental determination of the necessary parameters for the progressive failure models, (3) incorporation of the developed composite failure models into an FE-based algorithm to analyze the damage progression of composite laminates under pin bearing loading conditions and to determine the load carrying capacity of pinned joints of composite honeycomb sandwich panels, and (4) validation of the developed failure models via experiments. Carbon/epoxy unidirectional tape and eight-harness fabric were used for this investigation. At the coupon-level tests, the basic mechanical properties and the material degradation parameters were obtained. Multi-axial loaded tests served as a validation exercise for the damage models.The finite element analyses were conducted using a commercial FE software package Abaqus in conjunction with a user material subroutine written in Fortran. The pin-bearing specimens tested at WSU as well as test data provided by MSFC were used for the final validation of the developed material model. From the results comparison, the FE model with the developed material model was able to predict the maximum pin-bearing capacity of composite panels, and the in-plane deformations showed satisfactory correlation between the FE models and the experiments.
Thesis (M.S.)-- Wichita State University, College of Engineering, Dept. of Aerospace Engineering