The goal of a failure analysis is to discern the mechanism and cause of the component failure – essentially to identify how and why the part broke. Fractography plays critical role in this, particularly in identifying the failure mode. Cracking occurs as a result of the exertion of stresses, both external and internal, on a component. Cracking is simply a stress relief mechanism in which the material is attempting to reach a lower energy state. Plastics fail through a disentanglement mechanism in which polymer chains slide past each other.
The features on the fracture surface are created based upon a number of parameters:
Much of the information regarding the failure mechanism can be gleaned by interpreting the features found on the fracture surface. The examination and interpretation of the fracture surface is known as fractography. This presentation will explore some common plastics failure mechanisms and the associated telltale features.