BS in Materials Engineering
Materials Engineering Department
Composite sandwich panels were constructed with 4-ply plain weave carbon-fiber/epoxy face sheets in the 0o/45o/0o/45o orientation and 1/8th inch Nomex honeycomb core. The panels were cut into 5-inch square test plates for mechanical testing. All testing was done on a fixture designed and fabricated by Pratt & Miller Engineering and installed on an Instron testing system at Cal Poly. The twist test was performed by supporting diagonal corners of the plate while simultaneously loading the opposite two corners at a crosshead rate of .06 in/min (ASTM 3044-94R11). Out of 10 panels tested, six were tested longitudinally, with the L direction of the honeycomb parallel to the front of the test plate, and four were tested in the transverse orientation, with the L direction of the honeycomb perpendicular to the front of the plate. The average compliance for the longitudinal loading was 1.303 mil/lb, and the transverse loading was 1.394 mil/lb. The panels failed with a combination core shear failure and face-to-core debonding. The anisotropic nature of the honeycomb core supports the difference in the compliance of the panels; however the complex loading of the twist test results the difference being not statistically significant. The biaxial bending tests involved supporting the composite plate on each corner and loading it in the center. In 5 tested plates, the measured average compliance was .4363 mil/lb with face-to-core debonding being the primary failure mode. The results of these tests will be used to improve existing FEA models for the performance of racing vehicle composite panels.