Prediction of chemical and thermal shrinkage in thermosetting composite
The effects of cure shrinkages were investigated on the residual stresses, dimensional stability and interlaminar fracture toughness of thermosetting composites. The chemical shrinkage due to the cure reaction of the resin was considered. The evolution of resin mechanical properties was determined with dynamic mechanical analysis. A new experimental procedure utilizing digital image correlation was used to measure chemical and thermal shrinkages. A constitutive composite material model, which included mechanical and thermo-chemical shrinkages was developed using self-consistent field micromechanical approach. The composite material model was validated with the newly proposed bi-lamina strip experiment, which used the linear elastic formulation and included large deformation analysis. The excellent agreement was found between the model and the experiment, including the strip end deflection as well as deflected profiles. Using the validated model, the residual stresses were estimated on different scales of the composite, including local lamina stresses, homogenized ply stresses and stresses in the 90-degree ply of the quasi-isotropic laminate. The cure history dependent response was analyzed using bi-lamina strip experiment. The mechanism responsible for reducing the residual deformation was described, based on the strain dependent Young’s modulus of the resin near the glass transition temperature. Finally, a double cantilever beam configuration with 90-degree fiber orientation was proposed to study the effects of the residual cooling stresses on the instability of the crack propagation direction.
Pipes, Purdue University.
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