Influence of time-dependent damage on creep of multidirectional polymer composite laminates

An experimental study (Birur et al., 2006 [1]) on time-dependent evolution of various damage modes under constant load was extended; specifically, time-dependent evolution and influence of transverse cracks, in +/- 45 degrees and +/- 90 degrees plies, on the creep of [+/- 45/90(2)](S) multidirectional laminate of a polymer composite (Hexcel F263-7/Toho G30-500) was studied and modeled. The damage evolved with time in both ply groups sequentially and/or simultaneously depending on the test conditions. For the latter case, the two ply groups influenced each other's damage evolution. The creep of the laminate was due to both the viscoelasticity of the plies and the time-dependent damage. A damaged ply was modeled using an equivalent undamaged ply with an apparent compliance, which was determined as a function of time-dependent transverse crack density. This was used along with a model frame work, based on lamination theory, to predict the creep compliance of the [+/- 45/90(2)](S) laminate. The model predictions compared well with experimental results. (c) 2010 Elsevier Ltd. All rights reserved.