Bi-material free edge joint
O1. A better understanding of the failure mechanisms in composite materials with the focus on the interface reliability.
Task 1 (T1: Months 1 - 3). Identification the variety of fracture modes in composite materials and the role of interface cracks.
O2. Describing the asymptotic stress field around interface cracks and bonded – joints interfaces as an initial stage of crack initiation, and to study the effect of the interface on the fracture parameters (stress intensity factors, energy release rate).
Task 2 (T2: Months 4 - 9). Evaluation the capabilities of available finite element software to model the asymptotic stress field, for elastic and elasto-plastic material behaviour.
Task 3 (T3: Months 9 - 12). Development of analytical solutions based on asymptotic analysis for describing the stress field for a bi-material interface and for cracks approaching the interface.
Task 4 (T4: Months 13 - 18). Linear-elastic finite element analysis for a variety of interface cracks: determination of the singular order, asymptotic fields, crack tip parameters: Energy Release Rate, Stress Intensity Factors and T – Stress.
Task 5 (T5: Months 18 - 22). Elasto-plastic analyses: determination of singular orders s, produce FE asymptotic model with boundary conditions given by displacements from analytical solution, determine characteristic plastic-zone dimension rp, determine interfacial load-phase angle zp, determine mathematical composition of inelastic upper region in terms of sectors (centred fans, constant state, elastic regions).
O3. Investigating the influence of the material properties (considering elastic and elastic—plastic materials) on the stress field and crack path for the interface cracks and cracks approaching an interface.
Task 6 (T6: Months 20 - 24). Comparison between numerical and experimental results for different material combinations on crack propagation path near interface.
Experimental fatigue crack paths after 17177 fatigue cycles Comparison numerical-experimental paths