Development of B-staged Polymer Thin Films and Integration of Randomly Aligned Carbon Nanotubes in Carbon Fiber Epoxy Composite Plates
Open Access
- Author:
- Mu, Grace
- Area of Honors:
- Aerospace Engineering
- Degree:
- Bachelor of Science
- Document Type:
- Thesis
- Thesis Supervisors:
- Namiko Yamamoto, Thesis Supervisor
Namiko Yamamoto, Thesis Honors Advisor
Charles E Bakis, Faculty Reader - Keywords:
- CFRPs
CNTs
OOA VBO
infiltration - Abstract:
- Carbon fiber-reinforced polymers (CFRPs) have widespread uses in the aerospace industry due to their high strength-to-weight ratio and corrosion resistance when compared with aluminum. However, CFRPs have brittle and crack-prone matrices, making them susceptible to delamination. Carbon nanotubes (CNTs) are being introduced into CFRPs to reinforce their out-of-plane properties through the bridging of cracks. In this work, the out-of-autoclave (OOA) vacuum bag only (VBO) process was used for CNT-CFRP fabrication. Partially cured films can infiltrate layers of dry carbon fiber (CF) without forming undesired interlaminar layers. Three research tasks were established. First, methods to prepare thin polymer films were studied in a literature review: pressing, rolling, and calendering. Based on the literature review and some trials with pressing, I chose to use a simple mold to fabricate thin partially cured CNT-epoxy layers. In this method, the epoxy was heated to decrease its viscosity and the mold was tilted until the epoxy formed a thin film at the bottom. The second task was to improve the thin film fabrication. The films exhibited more uniform thicknesses (~400 μm) than in the pressing method, but the process was sensitive to the uniformity of release spray application, the cleanliness of the mold, the temperature of the epoxy (~50°C), and the CNT volume fraction (up to 0.5 vol%). The third task was to infiltrate the CNT-epoxy layers into dry CF preforms through the OOA process. Three CNT-CFRP plates were fabricated: an epoxy-only reference plate, a 0.1 vol% CNT plate, and a 0.5 vol% CNT plate. The plates were inspected using optical microscopy for void fractions (Vv) and fiber fractions (Vf); Vv was kept relatively low (1.07% for 0.1 vol% CNTs, and 1.61% for 0.5 vol% CNTs). When the first CF-CF boundary and the midplane of the composites were inspected by scanning electron microscopy (SEM), CNTs were observed in the midplane location in the 0.1 vol% CNT plate, but in neither in the 0.5 vol% CNT plate, indicating that volume fraction of CNTs can limit their infiltration between CFs. Future work includes the preparation of even thinner partially cured CNT-epoxy films, CNT organization before and during the OOA process, and an improved image analysis method to calculate Vf and Vv.