Response of the adhesive interlayer under dynamic loading
Date
2011
Authors
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Publisher
University of Delaware
Abstract
Thick section composites consisting of ceramic tiles and a composite backing plate are effective in stopping high velocity projectiles. The adhesive interlayer, which is used to bond the tiles to the composite, is an important component but little is known about its role when the structure is impacted. Finite element modeling is employed to develop a test method that could be used to observe the interlayer’s dynamic response during impact. The finite element models are based upon basic plate and beam test set-ups. It is determined that a beam set-up under low velocity impact is best suited to subject the interlayer to a high strain and strain rate while allowing visual observation of the response. The FE models are further utilized to optimize the beam test and establish geometric parameters. The low velocity beam set up is fabricated for use with a gas gun. In this test a projectile is fired from the gas gun. This projectile impacts a punch which rests on a composite backing plate through a cavity in the tiles. As the punch loads the backing plate, the interlayer is dynamically deformed. A high speed camera captures this deformation and the images are used to analyze the interlayer’s response. A polyurethane interlayer, VPS 2.2, is studied using the low velocity beam test. Tests are performed with an initial punch velocity of 20.5 m/s, 30 m/s, 5.5 m/s, 12.2 m/s, and 14.7 m/s to achieve strain rates up to 23270 s-1 . The traction-separation relationships for these tests are back-fit into the finite element model so that the model results match the experimental results. Quasi-static tests are also performed and the maximum strain at failure is measured for comparison to the dynamic results.