A Comparison of Low-Velocity Impact and Quasi-Static Indentation

The purpose of this investigation is to assess the potential interchangeability of key material response metrics as measured using quasi-static indentation (QSI) and low-velocity impact (LVI). This report compares the response of a S2/SC-15 glass /epoxy composite material subjected these two test methods. Specimens of 102 152 5.5 mm were quasi-statically indented at load rates in the range of 1.2 to 50 mm/min. Differences in material response over this range of loading rate were found to be negligible. The average value of peak input energy calculated from these QSI tests was used as the impact energy for subsequent LVI tests of identical specimens. Material tested using LVI (3.41 m/s velocity) exhibited higher initial stiffness and absorbed energy but with slightly lower maximum force and displacement values compared to material tested with QSI. Thirty QSI and LVI specimens were then evaluated with compression after impact (CAI) testing, and all specimens exhibited equivalent CAI strengths. Lightbox and cross-section analyses showed that material tested under LVI exhibited significantly less delamination and significantly more intralaminar fracture compared to QSI. For these reasons, LVI and QSI data are not interchangeable for this material system.