GCRIS

Now showing 1 - 2 of 2

Experimental and Numerical Investigation of the Impact Resistance and Impact Damage Tolerance of a Carbon Fiber Reinforced Thermoplastic Polyphenylene Sulfide (pps) Matrix Composite
(01. Izmir Institute of Technology, 2024) Seven, Semih Berk; Taşdemirci, Alper; Güden, Mustafa; Güden, Mustafa; Taşdemirci, Alper; 03.10. Department of Mechanical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
The impact resistance and impact damage tolerance of an aerospace grade high performance 5 Harness Satin woven fabric carbon fiber reinforced/polyphenylene sulfide matrix (CF/PPS) thermoplastic composite were investigated experimentally and numerically. The numerical modeling was performed using the experimentally determined parameters of material model MAT-58 and Hashin failure criteria in LS-DYNA using the single shell and stacked shell models. The numerical models of the low velocity impact (LVI) tests showed good correlations with the experimental tests while the stacked shell model showed nearer results with the experimental tests. The stacked shell model also estimated the LVI test delamination areas, which were comparable with the experimental damage areas. The LVI tested coupons were further subjected to the compression after impact (CAI) tests in order to determine the damage tolerance of CF/PPS composite. The CAI tests were modeled using the single shell model. The numerical models of the CAI tests showed very similar trends with the experimental CAI tests. The trends were shown to be more converging in the specimens tested at 3 m/s and above in the LVI tests. Lastly, three high velocity impact (HVI) tests were performed at around 100 m/s. The failure mode of the HVI tests was shown to be very different from that of the LVI tests. The long longitudinal and transverse cracks were formed in the HVI tests. The delamination damage in the HVI tests determined using the stacked shell model was found to be more comparable with the experimental delamination damage determined by the C-Scan.
Biological Nano Silica Reinforced Polymeric Composites
(01. Izmir Institute of Technology, 2022) Güden, Mustafa; Güden, Mustafa; 03.10. Department of Mechanical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
The present thesis study focused on processing nano-silica powders of varying sizes and crystallinities through heat treatment (900–1200 °C), hydrofluoric acid leaching (1–7 N), and ball milling (1 h, 500 rpm) of natural diatom frustules. As-received frustules was composed of amorphous silica (88%) and quartz. The partially ordered crystalline low-quartz and/or precursor to low-cristobalite started to form at ~900 °C. As the heat treatment temperature increased, the crystallinity of the frustules increased from 9.3% at 25 °C to 46% at 1200 °C. Applying a ball milling reduced the mean particle sizes of the as-received and heat-treated frustules from 15.6–13.7 μm to 7.2-6.7 μm, respectively. Acid leaching of the as-received and heat-treated frustules resulted in a further increase in the crystallinity. Furthermore, ball milling applied after an acid leaching was very effective in reducing the particle size of the as-received and heat-treated frustules. The mean particle size of the acid-leached frustules decreased to 774-547 nm with a crystallinity varying between 12 and 48% after ball milling. A partially dissolved amorphous phase was observed in between crystalline silica grains after acid leaching, which resulted in a rapid fracture/separation of the frustules in ball milling. The prepared nano-silica powders were further used as a filler in an epoxy matrix. The tensile strength, fracture strain, and modulus of epoxy increased with increasing the volume percent of nano-silica up to 2%. The increase in the yield strength and elastic modulus was about 50% and 30% with the addition of 2 vol% frustules, respectively. The rule of mixtures showed a very good agreement with the experimental elastic modulus values and a numerical model of the tensile test in LS-DYNA agreed well with the experimental tensile stress-strain behavior. The microscopic observations showed the presence of nano-silica powder, proving an efficient load transfer from matrix to powders on the fracture surfaces, confirming a strong interface between silica powders and matrix.

Phd Degree / Doktora

Browse

Filters

Settings

Sort By

Results per page

Search Results