Effect of Damage on the Creep Response of a Chopped Fiber Composite Material

Damage is often developed in a composite material even if it is under a small fraction of ultimate strength. Such a damage state consequently will introduce a change in mechanical responses. In this paper, the effect of different levels of damage on the creep response of a chopped fiber composite material (SMC-R50) is presented. The damage state of the composite specimens was introduced and stabilized using a mechanical conditioning procedure. The mechanical conditioning procedure is a repeated loading and unloading process at selected stress and temperature levels. A creep experiment was then conducted using the damaged specimens at various stress levels. In general, for the same testing condition, different creep responses were obtained at different damage conditions. Creep strain data was modeled into two components (instantaneous strain and time depen dent strain) using the Findley equation. It was found that at the same stress level, the in stantaneous strain increases while the time dependent strain decreases with an increase in the damage state.