Browsing by Subject "composite"
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Item Open Access Biomimetic Composite Scaffolds for the Functional Tissue Engineering of Articular Cartilage(2009) Moutos, Franklin ThomasArticular cartilage is the connective tissue that lines the ends of long bones in diarthrodial joints, providing a low-friction load-bearing surface that can withstand a lifetime of loading cycles under normal conditions. Despite these unique and advantageous properties, the tissue possesses a limited capacity for self-repair due to its lack of vasculature and innervation. Total joint replacement is a well-established treatment for degenerative joint disease; however, the materials used in these procedures have a limited lifespan in vivo and will likely fail over time, requiring additional - and increasingly complicated - revision surgeries. For younger or more active patients, this risk is unacceptable. Unfortunately, alternative surgical options are not currently available, leaving pain management as the only viable treatment. In seeking to discover a new therapeutic strategy, the goal of this dissertation was to develop a functional tissue-engineered cartilage construct that may be used to resurface an entire diseased or damaged joint.
A three-dimensional (3-D) woven textile structure, produced on a custom-built miniature weaving loom, was utilized as the basis for producing novel composite scaffolds and cartilage tissue constructs that exhibited initial properties similar to those of native articular cartilage. Using polyglycolic acid (PGA) fibers combined with chondrocyte-loaded agarose or fibrin hydrogels, scaffolds were engineered with anisotropic, inhomogeneous, viscoelastic, and nonlinear characteristics prior to cultivation. However, PGA-based constructs showed a rapid loss of mechanical functionality over a 28 day culture period suggesting that the inclusion of other, less degradable, biomaterial fibers could provide more stable properties.
Retaining the original 3-D architecture and fiber/hydrogel composite construction, poly (epsilon-caprolactone) (PCL)-based scaffolds demonstrated initial biomechanical properties similar to those of PGA-based scaffolds. Long-term culture of 3-D PCL/fibrin scaffolds seeded with human adipose-derived stem cells (ASCs) showed that scaffolds maintained their baseline properties as new, collagen-rich tissue accumulated within the constructs.
In an attempt to improve the bioactivity of the PCL scaffold and further induce chondrogenic differentiation of seeded ASCs, we produced a hybrid scaffold system by embedding the 3-D woven structure within a porous matrix derived from native cartilage. We then demonstrated how this multifunctional scaffold could be molded, seeded, and cultured in order to produce an anatomically accurate tissue construct with potential for resurfacing the femoral head of a hip.
In summary, these findings provide valuable insight into a new approach for the functional tissue engineering of articular cartilage. The results of this work will hopefully lead to the discovery of new strategies for the long-term treatment of cartilage pathology.
Item Open Access Correlation of Finite Element Analysis to Impacted Composite Plates(2011) Berry, Jessica LynnThe purpose of this thesis was to examine progressive composite damage models available within LS-DYNA and to correlate the results of these models with drop weight impact testing and with the non-destructive evaluation techniques of shearography, thermography, and ultrasonic testing. The secondary purpose of this study was to assess whether shearography and thermography provide an adequate less expensive replacement to ultrasonic testing. For this investigation, three models were chosen: Chang-Chang, Chang-Chang + Tsai-Wu, and a Faceted Failure Surface
Model. For the experimental impact testing, two sets of specimens were chosen: a 16-ply lay-up and a 32-ply lay-up of carbon fiber pre-preg material. The panel specimens were tested at various impact energies and the displacement and force history of the impactor were recorded. The models showed good correlation for the force history with the experiments. Furthermore, the 16-ply models correlated well with the displacement history. However, due the penalty method implementation, the 32-ply models did not show similar peak displacement output. The damage shown by the models was compared to non-destructive evaluation techniques. The shearography and thermography showed significantly less damage than the ultrasonic scans, and therefore do not provide an adequate replacement to ultrasonic scanning. In looking at correlation between the models and the non-destructive evaluation techniques, the faceted failure surface showed significantly more damage due to its elastic-plastic type formulation.