Tension failure assessment of composite bolted joints under bearing-bypass load interaction using analytical means

Abstract

Bolted joints are often used in thin parts such as plates or shell-like components in lightweight structures, e.g. air- and spacecraft. This is also motivated by an inexpensive manufacturing and the ability to disassemble. To make these joints, holes need to be drilled and stress concentrations arise. Leading to the instantaneous destruction of the connection, attention should be drawn to fatal tension failure. The efficient and precise prediction of the corresponding failure stresses using analytical methods is the focus of this paper. Usually, rows of bolts are placed. Then, the load is partly introduced into one bolt while the rest stays in the plate. This setting is also referred to as bolted joint under combined bearing-bypass load, which shall be idealised as a linear 2D plate problem. The corresponding characteristic stresses are discussed for orthotropic laminates showing good agreement to Finite Element values. Then, failure analysis is conducted using Finite Fracture Mechanics. This part is dedicated to quasi-isotropic laminates. The size effect and in this context the failure stress reduction with increasing bolt diameter is analysed. Primary physical effects due to finite dimensions and the ratio of bearing and total load are identified. The higher this ratio and the larger the bolt diameter, the lower the sustained failure stress. Failure envelopes for the graphical determination of the critical bearing and bypass stresses are provided. All in all, a comprehensive and efficient framework for tension failure assessment of composite bolted joints under bearing-bypass load interaction is developed.