Experimental Investigation of Fastener Pull-out Response in Composite Joints under Static and Dynamic Loading Rates

Abstract

A novel device is adopted in order to experimentally investigate the effect of various loading rates on the pull-out response of a fastened composite joint configuration. The joint coupons comprise a composite plate made of the carbon/epoxy AS4/8552 material system and a centrally located titanium lockbolt. Tensile-type (pull) loading was applied to the specimens in a velocity range from quasi-static to 2.1 m/s. Both quasi-static and dynamic tests were conducted using the same specimen geometry and boundary conditions, which conform to international and industrial standards. The experim ental work expands the limited literature and understanding of the mechanical response of composite pull-out joints under the action of dynamic loading. The main experimental observations revealed an increase of 15% regarding maximum load values when loading rate shifts from the static to the impact regime, while the failure patterns derived from static and dynamic tests were similar, although the latter presented a more intense damage zone.

Measuring the Effect of Strain Rate on Deformation and Damage in Fibre-Reinforced Composites: A Review

“…Heimbs et al's study suggested that while single-lap shear with one bolt showed little to no rate dependence [230], a single lap shear with two bolts did show increased strength and energy absorption at 10m/s due to a change in failure mode from net tension to "extensive bearing and pull-through failure". Another study also noted a change in damage mode between quasistatic and 2m/s loading [231], but while they found that the failure stress increased, the absorbed energy decreased (presumably due to rate-dependent stiffening).…”