Analysis of the interface between a thermoplastic fiber and a thermosetting matrix using photoelasticity

The photoelastic images of the isochromatic fringes for a pull-out specimen were used to measure and to analyze the maximum interfacial shear strength for a thermoplastic–thermoset interface (PET/Epoxy). The photoelastic technique allows the loading process to be followed in-situ, as well as the determination of the shear stress distribution on a tested sample. A description of the stress transfer process and the measurement of the shear stress level along the embedded fiber were done. The maximum shear strength was located along the fiber surface at a distance of 2.5 times the diameter from the specimen border. The maximum shear stress values obtained from the photoelastic analysis were corrected to include the tri-dimensional axisymmetric distribution of the shear stress around the fiber. The corrected shear stress measured τcMax ranged from 0.27 to 1.17 MPa.