کلیدواژهها
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Glass/epoxy, laminates, low-velocity impacts, cyclic
indentation, damage, delamination, critical energy level
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چکیده
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Barely visible impact damage (BVID) occurs in composite laminates
subjected to low-velocity impact. They can then exhibit significant effect on
mechanical performance of laminates. Previously, it is shown, analytically
and experimentally, that BVID occurs at a critical energy level and below
this energy level there is no induced damage. However, repeated impact
may cause BVID even below the critical energy level. This paper is a novel
investigation that deals with the cyclic behaviour of quasi-isotropic
glass/epoxy laminated composites under indentation, which is a quasistatic
version of low-velocity impact. In particular, this study aims to
investigate the ply thickness effect on matrix crack-induced delamination
damage in the case of laminated composites under cyclic quasi static
indentation loadings. The effect of different parameters, such as load level
and ply thickness, on the damage evolution were here investigated. Tests
were performed according to the ASTM 7136 standard. Since the glass
layer was translucent, it was also possible to visually inspect the matrix
delamination during the tests. The laminates were subjected to load levels
lower than the critical load level, while there was no evidence of damages
when samples were indented just once. However, by increasing the number
of cycles, matrix crack-induced delamination appeared in the samples. In
brief, it was observed that the ply thickness and energy level have
significant effects on the intensity of the induced damage.
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