MECHANISM OF DAMAGE AND FAILURE IN AN ORTHOTROPIC GLASS POLYPROPYLENE COMPOSITE

The mechanism of damage accumulation and failure in thin sheets of an orthotropic long discontinued glass fiber reinforced polypropylene composite was studied using optical and electron microscopy coupled with acoustic emission (AE) monitoring. The effect of strain rate (0.1 to 100 percent) was investigated, and a close correspondence was established between AE response and microscopic observations. Furthermore, simultaneous AE monitoring and optical microscopy performed during sample deformation substantiated the assignment of certain AE amplitude ranges with specific failure events in the composite. Specifically, the failure process was found to be very inhomogeneous in nature, and could be divided into three main stages of damage accumulation. Finally, cumulative AE energy curves were found to follow an interesting power-law behavior. Results based on the coupling of AE methods with optical and electron microscopy were found to be self consistent and in agreement with previous reports on thicker-section composites manufactured from the same materials.