Effect of strain rate on the compressive properties of graphite/epoxy composite in a submarine environment

The present study examines the effects of the strain rate on the compressive properties of carbon fiber-reinforced composite in a submarine environment. The material system used was graphite/epoxy prepreg tapes, where the volume fraction of fiber was 64%. Compressive tests have been performed in three steps of the strain rate using fully seawater-absorbed graphite/epoxy composite specimens under atmospheric and hydrostatic pressure environments. The strain rates applied were 0.05, 0.25, and 0.55%/s. Compressive elastic modulus, strength, and strain were determined as a function of applied strain rate for each pressure environment. The results showed that compressive elastic modulus increases with increasing strain rate increases, irrespective of environmental pressure. The increased rate of modulus in hydrostatic pressure condition was higher than that in atmospheric pressure condition. The compressive strength was less affected by the strain rate under both atmospheric pressure condition and hydrostatic pressure condition. However, the compressive strain decreases as the strain rate increases for both atmospheric and hydrostatic pressure environments. The decrease of compressive strain with increasing strain rate occurs because epoxy becomes more brittle as there is not sufficient time for the stress to be relieved.