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Fibre metal laminates (FML) are the modern hybrid materials with potential wide range of applications in aerospace technology due to their excellent mechanical properties (particularly fatigue strength, resistance to impacts) and also excellent corrosion resistance. The study describes the resistance to low velocity impacts in Ti/CFRP laminates. Tested laminates were produced in autoclave process. The laminates were characterized in terms of their response to impacts in specified energy range (5J, 10J, 20J). The tests were performed in accordance with ASTM D7137 standard. The laminates were subjected to impacts by means of hemispherical impactor with diameter of 12,7 mm. The following values have been determined: impact force vs. time, maximum force and the force at which the material destruction process commences (Pi). It has been found that fibre titanium laminates are characterized by high resistance to impacts. This feature is associated with elasto-plastic properties of metal and high rigidity of epoxy - fibre composite. It has been observed that Ti/CFRP laminates are characterized by more instable force during impact in stage of stabilization of impactor-laminate system and stage of force growth that glass fibre laminates. It has been observed more stable force decrease in stage of stress relaxation and withdrawal of the impactor. In energy range under test, the laminates based on titanium with glass and carbon fibres reinforcement demonstrate similar and high resistance to low-velocity impact, measured by means of failure initiation force and impact maximum force. [ABSTRACT FROM AUTHOR]

Post-impact strength and damage tolerance of composite structures stands as a paramount design consideration in the aeronautical industry. In the event of a low velocity impact, a set of damage manifestations within laminated structures are induced, including matrix cracking, delamination and fiber breakage. Despite the critical importance of discerning the influence of each damage type on post-impact compression strength, only a limited number of studies have endeavored to quantify these effects comprehensively. In response to this research gap, we have developed a novel methodology capable of mimicking damage extension and shape caused by a low-velocity impact, while preserving fiber integrity. This innovation is achieved through the application of induced electrical currents, thereby facilitating controlled damage simulation without compromising fiber structural integrity. Our investigation compares the residual stiffness and strength of AS4/PEEK laminates subjected to low velocity impacts and induction currents, under conditions of equivalent damage. Our findings reveal that fiber breakage significantly influences the loss of stiffness in the laminate, but not its strength. Moreover, our results confirm the role of delamination as the primary determinant of strength degradation in the damaged material. [ABSTRACT FROM AUTHOR]

Abstract The effect of impact load with low velocity in thin-walled plates and profiles has been investigated. The paper deals with the relation between damage propagation, size and shape as a function of boundary conditions, layer arrangements and impact energy. The structures under consideration were made of eight-layer Glass Fiber Reinforced Polymer (GFRP) laminate with a quasi-isotropic, quasi-orthotropic and angle ply arrangement of layers. The standardised plates predefined to CAI tests and channel section profiles have been subjected to impact load. Based on the performed tests, the impact characteristics have been obtained and compared with the theoretical model (one degree of freedom mass-spring system). Further, despite it not being mentioned in the ASTM 7136 standard, characteristic curves were identified. It was noted that the impacts introducing matrix damages and the partial fracture of the fibres significantly change the course of the Force-Time histories, particularly after the maximum impact force is reached. [ABSTRACT FROM AUTHOR]