The application of composite laminates to fan blade of turbofan engine is demanded in order to reduce the fuel cost and the noise of aircrafts. Bird strike is one of the most important problems in the engineering application of fan blades. However, the soft-body impact damage on the composite laminates under high-velocity impact has not been clarified sufficiently due to their complexity. Therefore, it is necessary to understand the damage process of the composite materials under the soft-body impact. The current work presented the numerical simulation for soft-body impact using the SPH method to address the large deformation problem, and discussed the change of the failure mode of the composite laminates as a function of impact velocity. Especially, in order to simulate the realistic damage process in composite laminates, a novel approach for the separation of particles was introduced to the model. We confirmed that the numerical simulation was applicable in the soft-body impact problem by the agreement of contact pressure with the experimental results. Moreover, it was shown that the catastrophic failure of the composite laminates by the soft-body impact could be also predicted using this numerical simulation.

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This paper experimentally investigates damage mechanisms which is closely related with the bearing failure in bolted joints of CFRP laminates and proposes a finite element model to reproduce those damage mechanisms. First, the damage was observed in the bearing failure of bolted joints, and the main factor of the large stiffness degradation in bearing failure is the fiber kinking damage. In addition, the fiber kinking is suppressed by the bolt clamping, which increases the bearing strength of bolted joints. Then, three-dimensional finite element model was developed for addressing the bearing failure in bolted joints based on the experimental observation. In this model, the initiation and the propagation of the fiber kinking damage which plays an important role in the bearing failure of bolted joints were reproduced and the stress failure criteria were investigated. The variation of the load at the kinking onset due to the bolt clamping was simulated and consequently the load history during the evolution of the fiber kinking damage was simulated.

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The effect of molding conditions on the mechanical properties of glass fiber reinforced in situ polymerizable polyamide6 matrix (I-GFRTP) were investigated by the use of differential scanning calorimeter (DSC), three-point bending tests and Izod impact tests for various types of the composites which were molded at temperatures of 140, 160, 180 and 200°C respectively. The three-point bending test at 160°C revealed the highest strength within all the specimens tested. For Izod impact tests, no correlation between the molding temperatures and Izod impact strength was observed. Furthermore, it was shown that although I-GFRTP has a higher crystallinity than GFRTP of which matrix is PA6 that has already polymerized, impact strength of I-GFRTP is on a level with that of GFRTP.

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