Numerical Characterization of Pretensioning of a Hybrid Joint Under Longitudinal Load

Most mechanical structures are composed of several components of different shape, size and material. In order to guarantee the connections among such parts is often necessary to adopt different connection mechanisms. The joints represent the structure possible weak points, can be easily site of damage and rupture so their careful design plays a decisive role. In recent years, the use of polymeric composite materials has become widespread, both in the automotive, aerospace and nautical fields. They allow advantages not only in terms of durability in aggressive environments, such as sea water or chemical industry, but also in terms of effective strength-weight ratio. In particular, the latter translates into fuel savings and a consequent reduction in costs and pollution. It is stated a weight reduction of just 1 kg, on a mid-range routing aircraft, can save up to 3000 L of fuel per year. The scientific community is making great efforts to develop high-performance and reliable connections. Among the types of composite joint, the one of interest for this study is called hybrid, as it combines two connection mechanisms: bolting and bonding. Numerous studies and experimental researches, conducted on both the two separate variants and their hybrid version, the comparison of the analyses shows the hybrid one offers better results in terms of strength and fatigue life. In this paper, virtual models are built to simulate traction tests; the results are compared to experimental ones in order to validate the numerical model. In particular, the study focuses on the pretensioning influence on the joint structural behavior