Investigation of Failure Modes in Glass/Polyester Composites by Means of Acoustic Emission

The non-destructive Acoustic Emission (AE) techniques acquire and analyze the signals emitted from the deformation or fracture of materials under external loading. In this study, the AE techniques with statistical analysis were used to study the damage process of composite laminate under buckling loads. Different damage mechanisms are activated within the composite laminate during loading scenario. These ‘‘damage entities’’ are acting in different space and time scales within the service life of the structure and may be interdependent. It has been argued that different damage mechanisms attribute distinct acoustic behaviour to the composite system. Loading of composite laminates in particular leads to the accumulation of distinct damage mechanisms, such as matrix cracking, delamination between successive plies and fiber rupture at the final stage of loading. Buckling is consisted of two main stages including delamination and fracture. The complex failure mechanisms that are commonly considered as the distinctive characteristic of composites are being amenable to nondestructive test advance. The tested of glass/polyester composite specimens include three lay-up patterns: [00/900]6s, and [00]6s . Each specimen includes 12 layers, and the thickness of each layer is about 0.416 mm. Moreover, the microscopic properties of different composite specimens after fracture are watched and analyzed by scanning electron microscope (SEM). Based on the SEM conception, the controlling failure mechanisms of composites including the splitting matrix cracking, fiber/matrix interface debonding, fiber pull-out and breakage as well as delamination are identified.