Time–temperature viscoelastic behavior of an interlaminar‐toughened epoxy composite

Viscoelastic deformation of an interlaminar‐toughened laminated composite was investigated, and effects of the interlaminar heterogeneity were examined. Dynamic mechanical experiments were performed on the laminates and neat matrix resins of the laminated composite in the temperature range of 82–210°C to probe linear time‐temperature behavior. The reason for using torsional shear deformation for probing was that it usually is more dominated by the matrix. In the relatively low‐temperature regime, time‐temperature superposition was applicable, and the effect of the interlaminar heterogeneity was found to be not pronounced. A methodology based on the Arrhenius activation energy approach was proposed for predictions of long‐term viscoelasticity of the heterogeneous‐phase composite. The effects of the interlaminar toughening phase became more significant at temperatures greater than the T_g of the toughening phase and presented some limitations for accurate predictions of time‐dependent behavior. © 1993 John Wiley & Sons, Inc.