Pull-out testing of multiscale structured metallic z-reinforcements for CFRP laminates

Effect of Selective Z-Pinning on the Static and Fatigue Strength of Step Joints between Composite Adherends

“…The performances of lap joints reinforced using a different hybrid technology, wherein a thin metal sheet with protruding spiked pins is inserted between the two prepreg ad-herends before consolidation, were examined in a series of studies [31][32][33][34][35][36]. As an example, the effect of metal inserts featuring three distinct patterns of steel pins (with pins uniformly distributed over the overlap region, concentrated near the overlap edges, or clustered at the overlap corners) on the strength of single-lap carbon/epoxy adherends was investigated in [35].…”

“…Post-mortem analyses revealed a transition in the failure mode of the joints, which changed from pin shear rupture when the pins were uniformly distributed over the bond region to being controlled by pin pull-out when they were clustered at the overlap corners. The static strength properties of carbon/epoxy lap joints reinforced by metal sheets with spiked pins arranged in various patterns and densities were also examined in [32]. The load-carrying capacity of the joints was increased by 11% to 55% depending on the pinning pattern and content.…”

“…Very few experimental investigations have been specifically carried out on the fatigue response of lap joints reinforced by z-pins [14,19,20] or through spiked inserts [31,[33][34][35][36]. The results of the test reported in [14], conducted on lap joints reinforced with 0.28 mm carbon pins at areal densities of 0.5%, 2%, or 4%, show that the crack-bridging mechanisms applied by the pins significantly extend the fatigue life of the joints.…”

“…The results of fatigue testing on single-lap joints reinforced with spiked metal sheets are reported in [31,33,34]. Despite significant variability, preliminary testing on joints with spiked inserts positioned at the edges of the overlap [31] revealed longer fatigue lives for reinforced joints compared to their unreinforced counterparts.…”

Load transfer mechanism and reinforcement effect of segmentally yieldable anchorage in weakly consolidated soft rock

“…The hyperbolic model 7,8 proposes that the displacement and the shear stress between the anchoring agent and the interface decay with depth, following a hyperbolic function. Experimental results of pull-out tests [9][10][11][12][13] show that the shear stress of a full-length anchorage agent does not reach its peak value at the end of the anchor. This is evidenced by the solution to the elastic equation governing the shear stress distribution concerning the surface anchorage (full-length anchorage) and the internal anchor cable in the anchoring section established by You.…”