Dynamic thermomechanical behavior of fiber reinforced composites

Dynamic thermomechanical behavior of a carbon-epoxy composite material as well as its matrix material is investigated in the present study. Tension and compression Split Hopkinson Bars coupled with a high-speed infrared detector array were used to measure in real time the variation of stress, strain and temperature in a fiber composite under a range of strain rates. Significant temperature rise was observed in both compression and tension tests. Combined results from temperature measurements and stress-strain curves indicate that this temperature rise is mainly due to damage of the material. The rate of temperature rise in all cases was seen to be almost linearly proportional to applied loading rate. Substantial differences were seen between the temperature generation during the compression and the tension experiments. The difference in the thermomechanical response was explained by different mechanisms being active in the compression and tension loading cases. The dependence of these results on strain rate indicates that there exists the concept of `damage rate sensitivity', which might be useful when establishing damage models that account for the energy absorbed during impact of fiber reinforced composite materials.