Applications for carbon fiber reinforced composites in the aerospace industry are ever increasing due to their attractive strength-to-weight ratio and high stiffness. A majority of current fiber reinforcement is two-dimensional, resulting in an inherent interlaminar weakness that may lead to delamination and brittle failure. The next generation of fiber reinforcement is being developed based on a three-dimensional fiber architecture and preforming, offering enhanced through-the-thickness performance. One of the leading companies in three-dimensional weaving technology for aerospace applications has identified the need to characterize the response of these materials in fastened joints.
The exploration of three-dimensional woven composites within this dissertation is focused on three major areas: experimental baseline characterization, experimental bolted evaluation and numerical simulation. The research work presented begins with an investigation into the mechanical properties and behavior of various three-dimensional woven composite materials. Two ply to ply woven and one orthogonal architecture are evaluated under tensile, compressive and shear loading and compared with a traditional two-dimensional woven material.
Joints are analyzed experimentally in single bolt, single-shear and single-bolt, double-shear configurations, representing typical composite-to-composite connections in aerospace structures. To evaluate the effectiveness of three-dimensional reinforcement in bearing, both three-dimensional and two-dimensional reinforced composites were analyzed. Three-dimensional woven samples showed a non-linear, quasi-ductile bearing response which suggests superior damage tolerance of three-dimensional woven composites over two-dimensional at high bearing strain. Additionally, three-dimensional woven composites were able to maintain bearing strength in off-axis loading conditions.
A non-linear three-dimensional progressive damage model was developed and applied to the unique as-molded morphology of three-dimensional woven composites using Hashin failure criteria and the Matzenmiller-Lubliner-Taylor damage model. This mechanics-based mesoscale finite element analysis, representing the unique as-molded geometry of three-dimensional woven ply to ply reinforcement, was implemented to predict the onset and initial propagation of damage within single-bolt, double-shear joints. The combination of experimental results and micro-CT scans were used to validate the progressive damage model performance.
|Advisor:||Lopez-Anido, Roberto A.|
|School:||The University of Maine|
|School Location:||United States -- Maine|
|Source:||DAI-B 78/04(E), Dissertation Abstracts International|
|Subjects:||Aerospace engineering, Mechanical engineering|
|Keywords:||Bolted Joints, Mechanical Behavior, Mechanics Modeling, Polymer Marix Composites, Three-Dimensional Reinforcement|
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