Date of Award

Fall 2023

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Mechanical & Aerospace Engineering

Program/Concentration

Mechanical Engineering

Committee Director

Oleksandr Kravchenko

Committee Member

Gene Hou

Committee Member

Krishnanand Kaipa

Abstract

Post-cure through thickness reinforcement is a method used to increase the mechanical properties of composite laminates in the transverse direction. This study conducted a test on skin-stringer structures bonded together in three configurations using an epoxy or thermoplastic adhesive at the interface with reinforcing pins inserted through the laminate thickness located at the edge of the stringer at differing angles between -30º and 30º. The fabrication of these samples in configurations B and C consisted of the use of carbon fiber prepeg laminate at a ply orientation of [02902]2s for the skin and [0 90]2s for the stringer. Adhesive bonding between the skin and stringer was completed with an epoxy resin and thermoplastic bonded using the autoclave and heat press, respectively. Drilling of 0.75 mm holes was done using a Dremel, and carbon fiber rods at 0.5 mm diameter were inserted and cured in the samples using an INF- 211/INF-114 epoxy resin. The samples were then tested using a three-point bending apparatus at 2 mm/min. In configuration C, the presence of pins significantly enhanced both the maximum force and displacement of the skin-stringers on average by 78.60% and 109.64%. However, between angles there was no significant effect in either maximum force or displacement. Using a finite elements model in Abaqus, loadings on the O-ATTR at different angles directly prior to failure were analyzed. -30º O-ATTR took the greatest load in both the fiber and transverse directions, at 57.91 N and 188.83 N, respectively. The minimum load taken in the fiber direction was by a 25º reinforcement, 92.08 N, but further simulation is needed to enhance these results. Using O-ATTR in repair increased the maximum load and displacements in the samples by an average of 45.45% and 152.17%, respectively, but decreased the initial stiffness by 45.45%. Further, the configuration type of reinforced samples influenced the initial stiffness of the skin-stringers, and in configuration B the addition of reinforcement significantly decreased the maximum loads and displacements taken by 21.20% and 23.54% respectively. The addition of O-ATTR caused a different mode of failure which was described by the delamination of the skin element.

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DOI

10.25777/4erb-ch24

ISBN

9798381446753

ORCID

0009-0005-4847-3207

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