Accelerated Viscoelastic Characterization of T3OO/5208 Graphite-Epoxy Laminates.
Abstract
The viscoelastic response of polymer-based composite laminates, which may take years to develop in service, must be anticipated and accommodated at the design stage. Accelerated testing is therefore required to allow long-term compliance predictions for composite laminates of arbitrary layup, based solely upon short-term tests. In this study, an accelerated viscoelastic characterization scheme is applied to T3OO/52O8 graphite-epoxy laminates. The viscoelastic response of unidirectional specimens is modeled using the theory developed by Schapery. The transient component of the viscoelastic creep compliance is assumed to follow a power law approximation. A recursive relationship is developed, based upon the Schapery single-integral equation, which allows approximation of a continuous time-varying uniaxialload using discrete steps in stress. The viscoelastic response of T3OO/S2O8 graphite-epoxy at 1490 to transverse normal and shear stresses is determined using 90-deg and lO-deg off-axis tensile specimens, respectively. In each case the seven viscoelastic material parameters required in the analysis are determined experimentally, using a short-term creep/creep recovery testing cycle. A sensitivity analysis is used to select the appropriate short-term test cycle. It is shown that an accurate measure of the power law exponent is crucial for accurate long-term predictions, and that the calculated value of the power law exponent is very sensitive to slight experimental error in recovery data. (MM)
Document Details
- Document Type
- Technical Report
- Publication Date
- Mar 01, 1985
- Accession Number
- ADA302327
Entities
People
- H. F. Brinson
- M. E. Tuttle
Organizations
- Virginia Tech