BS in Materials Engineering
Materials Engineering Department
Thermoplastic matrix composites containing carbon fibers and 4 different resins (TP 1-TP 4) were tested in tension with the fibers at 90 degree to the longitudinal axis following ASTM D 3039-00. The tensile strengths varied from 5.07-13.87 ksi with TP 1 as the strongest, and TP 4 as the weakest. SEM images were taken of the fracture surface of the samples to explore the fiber-matrix interaction. The SEM images showed significantly more wetting of the fibers in the higher strength materials. The SEM images of the two stronger materials showed resin coating the fibers even after fracture while the two weaker materials showed a clean interface between the fibers and resin. As the second portion of the project, 3 and 4 point bend tests were conducted on the same 4 composite materials with a support span width of 1.4 inches according to ASTM D 790-03 and ASTM D 6272-02. The fibers were oriented 90 degrees to the long axis of the samples. The 3 point bend test flexural strength values ranged from 8.30-21.73 ksi and the 4 point values ranged from 6.26-19.25 ksi. The only discrepancy with the data points was TP 1 was not consistently stronger than TP 2. Data analysis was run using the STAT17 program to confirm that the TP 1 and TP 2 strength values were comparable and thus the inconsistency was not relevant. The flexural strength values were graphed versus the tensile strength values and showed a strong correlation. The 3 point binding strength versus tensile strength graph had an R2 value of 0.9894 and the corresponding 4 point binding versus tensile graph had an R2 value of 0.9979.