Riassunto analitico
The thesis focuses on the analysis of cracking behaviour in inserts made of carbon fiber-reinforced plastic (CFRP) for motorsport applications, particularly in racing vehicles. Thanks to the use of composite materials, these inserts offer advantages in terms of strength and lightness compared to traditional materials, but they are prone to cracking, especially under high mechanical stress. This thesis explores the possible causes of these cracks through experimental tests and FEM (Finite Element Method) models to better understand the behaviour of the inserts during the thermal cycles they undergo during production. The inserts, made through CNC machining of carbon plates and subsequently laminated, undergo several thermal curing cycles that can lead to interlaminar cracks, a critical factor for safety and performance in racing. Quality control techniques such as Computed Tomography (CT) and Multi Phased Array technology are used to detect internal defects in the inserts. In addition to non-destructive inspections, an experimental test campaign was conducted on various material configurations and curing cycles to replicate the cracking phenomenon in simplified geometries. Dynamic Mechanical Analysis (DMA) was used to characterize the viscoelastic properties of CFRP materials, allowing the measurement of the glass transition temperature (Tg) and storage modulus (E'). Interlaminar Shear Strength (ILSS) tests evaluated the shear strength between the layers of the composite, demonstrating that thermal cycles significantly affect the material's mechanical properties. The final part of the thesis focuses on the development of a reliable FEM model to simulate the cracking behaviour in the inserts. This model replicates the complex interactions between the CFRP layers and the thermal stresses induced by curing and cooling phases. The FEM analysis was crucial in identifying the regions most prone to cracking, particularly at the interface between the insert and the outer skins. In summary, the thesis proposes an experimental, modeling, and testing approach to understand the causes of cracking in CFRP inserts and evaluates possible solutions to prevent these defects, with the aim of improving the quality and safety of components used in motorsport.
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