Available at: http://digitalcommons.calpoly.edu/theses/402
Date of Award
MS in Aerospace Engineering
This thesis presents a parametric study on the effects of how damage arrestment devices application interacts with a fastener in a composite sandwich panel. The primary objective of the damage arrestment device was to prevent the failure of the composite face sheet, such as crack propagation, around the hole/fastener joint. The damage arrestment devices are made of composite strips that are inserted under the face sheet to increase the overall structural strength of the panel and to prevent the propagation of failure along the hole. This was supposed to be a quicker and stronger alternative to potted inserts for composite sandwich panels for designer. The manufacturing curing cycle of the composite sandwich specimens has been carried out by using a Tetrahedron Composite Air Press. The press has been used to fabricate composite sandwich panels by applying constant pressure and variable heat to create panels with dimensions of 5” x 2” x .552”. The panels were stacked using a polyurethane foam, Last-A-Foam FR-6710 with two layers of a carbon-fiber/epoxy weave, LTM45, on both sides of the foam. The specimens were loaded under a compressive strain of 0.5 mm/min. The damage arrestment devices’ thickness was varied and tested under both monotonic and fatigue loading. The experimental results indicate that as the thickness of the device increased the overall strength of the part increased at a parabolic curve with it topping at a thickness of 0.065” and a strength increase of 109%. Under fatigue loading, a control group test case and damage arrestment device configuration case was tested. The experimental results indicate that both cases have similar fatigue trends but shows that the damage arrestment specimens are stronger due to the increase of structural strength. The experimental results were compared with numerical results or Finite Element Model. The results showed that numerical results can capture the linear or elastic portion of the experimental results having identical Elastic Modulus values. The models do differ in the maximum displacement of the specimen and the failure mode around the hole of the composite sandwich panel. The discrepancy in displacement and the failure mode was attributed to inaccurate loading on the hole of the composite sandwich panel and non-linear modeling of the solution. The correlation between the FEM and the experimental data was good enough in predicting the trends of the composite sandwich panels.