Various types of composites are known to have excellent and superior mechanical properties. The extremely high strength to weight ratio and the high resistance to corrosion as favorable mechanical properties, converts the composites to multifunctional structures in various applications. This thesis focuses on details of experimental investigations of fracture mechanics on two different composite materials: a sandwich composite T-joint and an ultra-high performance concrete (UHPC).
The utilization of sandwich composites in aviation industry is significantly increased. In this respect, the aim of the current research is to identify the damage mechanism of sandwich composite T-joints and to obtain accurate material behavior under various loading and environmental conditions. For investigation of the sandwich composite Tjoints, series of experimental tests have been carried out in quasi-static and dynamic loading conditions and failure mechanisms are investigated. Moreover, effects of working conditions during the flight on the behavior of the sandwich composite are studied. To this end, the natural environment is simulated experimentally which influences the strength of the T-joints. This effect is determined by accelerated ageing of the honeycomb
Developments of material science as one pillar of modern technology, leads to substitute metallic materials with cementitious composites which can be counted a milestone in human living standards. Although a huge potential in application of UHPC material is given, technical information about the dynamic behavior of this material is still limited. In this dissertation, in order to study the UHPC response to the dynamic loading, series of spalling tests and dynamic Brazilian experiments have been conducted. In this regard, a linear elastic fracture mechanics-based approach is used to study the dynamic fracture and determine material properties under a high rate of loading. Parallel to the experiments, the performed tests on both mentioned composites, are numerically simulated in commercial finite element software.
By the obtained results from experiments on the sandwich composite T-joints, reliable technical information about the fracture behavior of this type of joint is provided. The achieved results prepare not only new data for the designers, but can also be used for future computational models of adhesively bonded composite T-joints. The outcomes of the experiments at high rate of loading on UHPC material, presents data regarding to response of this material to dynamic loading regime. The data extracted from the experiments can speed up the robust design and it is beneficial for future material developments and load carrying capabilities of this cementitious composite materials.