Experimental evaluation of the vibration behavior of flat and curved sandwich composite beams with face/core debond

A systematic experimental study to determine the effect of curvatures and debond on the flexural stiffness and strength of composite sandwich beam structures made from fiber-glass/epoxy laminate skins and polyurethane foam core has been carried out. Flat and curved sandwich beams (with 15°, 30°, 45° and 60° open angle) with debond located at the top (upper) and bottom (lower) face/core interface were manufactured. Flexural stiffness and strength were determined from impulse frequency response technique and four-point bending. Vibration test results indicate that the natural frequencies and apparent stiffness are less affected by the presence of curvature and debond, whereas, the loss factors are significantly affected. Four-point test results indicate a reduction in stiffness due the presence of debonds and curvature, but more predominantly, the results show that the peak load reduces sharply with the presence of upper debond.