Available at: http://digitalcommons.calpoly.edu/theses/1551
Date of Award
MS in Aerospace Engineering
Impact strength is one of the most important structural properties for a designer to consider, but it is often the most difficult to quantify or measure. A major concern for composite structures in the field is the effect of foreign objects striking composites because the damage is often undetectable by visual inspection. The objective for this study was to determine the effectiveness of using dynamic testing to identify the existence of damage in a small scale composite wing design. Four different impact locations were tested with three specimens per location for a total of 12 wings manufactured. The different impact locations were over the skin, directly over the rib/spar intersection at the mid-span of the wing, directly over the middle rib, and directly over the leading edge spar. The results will be compared to a control group of wings that sustain no damage. The wing design was based on an existing model located in the Cal Poly Aerospace Composites/Structures lab. The airfoil selected was a NACA 2412 airfoil profile with a chord length of 3 inches and a wingspan of just over 8 inches. All parts cured for 7 hours at 148°F and 70 psi. The wings were each tested on a shaker-table in a cantilever position undergoing 1g (ft/s2) acceleration sinusoidal frequency sweep from 10-2000 Hz. The 1st bending mode was excited at 190 Hz and the 2nd bending mode was excited at 900 Hz. After the pre-impact vibrational testing each wing was impacted, excluding the control group. To verify the experimental results, a finite element model of the wing was created in ABAQUS. The frequency and impact numerical results and the experimental results were in good agreement with a percent error for both the 1st and 2nd mode at around 10%.