Study on damage equivalence of composite laminates subjected to low-velocity impact and quasi-static indentation

Through the comparison of low-velocity impact testing and quasi-static indentation and testing, three kinds of relationship are obtained between the impact energy (or the quasi-static indentation force) damage area and dent depth. An analysis of these relationships indicates clearly that the damage area and dent depth can be chosen as the damage parameters to set up the damage relationship between drop-weight impact and quasi-static indentation. When impact energy or quasi-static indentation force is reached at the some value, then, the knee point appears in the three kinds of relationship curves, and the knee-points of the two tests are very close and the variation tendency is identical, which indicates that quasi-static indentation tests may replace low-velocity impact tests. Under the lower impact energy (before knee point), quasi-static indentation force approximately is equal to the maximum force caused by impact process of corresponding impact energy. By analyzing the process of the two tests, the delamination onset load in the quasi-static indentation is lower than that in the low-velocity impact, but the tendency of the load variation is similar, which further indicates the damage equivalence of composite laminates subjected to low-velocity impact and quasi-static indentation tests.