In situ characterization of in-plane chemical shrinkage of thermoset laminated composites using a simple setup

Abstract

Cure shrinkage in the thermoset matrix is the major source of cure-induced defects in composite parts for industrial applications. Thus, its correct determination is very important to optimize the composite fabrication process. In general, volume chemical shrinkage of resin is tested and assuming it is isotropic, rule of mixture or a homogenization technique is used to model the linear chemical shrinkage of composite. Some studies are also found in the literature on the measurement of linear chemical shrinkage of very small composite samples under atmospheric pressure. In the present article, a new setup is presented for the measurement of evolution of in-plane chemical shrinkage of thermoset laminated composite during curing. Using this setup, characterization of mass scale samples was done under pressure and heating ramp conditions. Degree of cure of composite during the test was determined using differential scanning calorimeter. Results show that chemical shrinkage in the composite appears from gel point and its evolution with the degree of cure is nonlinear. Experimental results also led to conclusion that most of the chemical shrinkage occur along the thickness direction.