Embedding Viscoelastic Damping Materials in Low-Cost VARTM Composite Structures

摘要

It has been well established that using viscoelastic damping materials in structural applications can greatly reduce the dynamic response and thus improve structural fatigue life. Previously these materials have been used to solve vibration problems in metallic structures, where the damping material is attached to the structure and then a stiff outer layer is attached to promote shear deformation in the damping material. More recently, these materials have been used successfully in expensive aerospace composite structures, where the damping material is embedded between plies of prepreg graphite/epoxy prior to being cured in a high-temperature, high-pressure autoclave. The current research involves embedding these damping layers into low-cost composite structures fabricated using the Vacuum Assisted Resin Transfer Molding (VARTM) process. The damping layers are perforated with a series of small holes to allow the resin to flow through the damping layer and completely wet-out the structure. Experimental fabrication, vibration testing, and stiffness testing investigate the effect of hole diameter versus hole spacing. Results show that the damping and stiffness can be very sensitive to perforation spacing and size. It is shown that for closely spaced perforations (95% damping area) that damping increases by only a factor of 2.2 over the undamped plate. However, for greater perforation spacing (99.7% damping area) the damping is increased by a factor of 14.3. Experimental results as well as practical design considerations for fabricating damped composite structures using the VARTM process are presented.