GFRPサンドイッチパネル隆起原因の解明

概要

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A sandwich panel with urethane core and GFRP skin plate was developed for the lorry floor. Small spherical bumps were found at a relatively short period in the skin plate along the trail of cart wheels. Fatigue tests were conducted to simulate the wake of the bumps using an apparatus with a wheel pressed onto the surface of sample panels, which were being moved back and forth. After 1, 000 cycles, one or two small bumps were observed along the trail. After fabricating a sandwich panel, spherical bumps were also found in the skin plate at locations where release films were glued on the back surface of the skin plate. The size of bumps increased as the stiffness of the urethane core being high. The mechanism of the bump formation in the skin plate is elucidated as follows: Residual compressive stress exists in the skin plate due to contraction of the core material during consolidation. A crack is initiated in the core closest to the skin plate due to a high moving load by the wheel. Thereafter, the crack grows along the skin plate with an increase of loading cycles. As the delaminated area increases, an out-of-plane deformation of the skin plate occurs due to the residual compressive stress in the skin plate. Finally, a process based on the residual stress relaxation to eliminate such a wake of bumping was proposed.
日本複合材料学会の論文
2004-09-15