ETD

• analytical model
• cohesive law
• composites
• dcb
• delamination
• fibre-bridging
• mode I

The thesis addresses the large-scale bridging phenomena occurring in the delamination failure of some types of fibre-reinforced polymer composites. After a brief Introduction about the underlying physical phenomena, Chapter 2 presents a concise literature survey on the available theoretical models and the related analytical and numerical solution methods. The thesis focuses on the cohesive zone model (CZM), which describes the interaction between the separating crack faces by suitable traction-separation laws. Chapters 3 presents the development of an analytical model of the double cantilever beam (DCB) test based on a bi-linear cohesive traction-separation law. This model is suitable for describing the experimental response if no bridging phenomena occur. Chapter 4 extends the previous analytical model by adopting a tri-linear cohesive traction-separation law. In this way, large-scale bridging phenomena can be addressed. All of the analytical solutions derived have been implemented into MATLAB codes. The predictions of the developed models are compared to experimental and numerical results obtained elsewhere. Thus, the consistency of the proposed approaches is evaluated. In particular, a comparison between models based on the Bernoulli and Timoshenko Beam Theories was crucial to understand how the effects of shear deformability cannot be generally disregarded in order to accurately capture the mechanical response of DCB specimens.