Experimental design of the bearing performances of flax fiber reinforced epoxy composites by a failure map

Pinned Hybrid Glass-Flax Composite Laminates Aged in Salt-Fog Environment: Mechanical Durability

“…For edge distances higher than 10 mm (i.e., E/D > 2.5), a plateau is reached and the bearing stress becomes constant (region II). In this region, the pinned composite joint fails mainly through bearing failure mode [32]. However, after 1 month of aging exposition, glass-flax laminates (i.e., batches B and C) highlighted a combined net-tension and bearing fracture mode with the former dominating on the latter one.…”

“…In fact, kink bands develop due to plastic micro-buckling phenomena in the compression area and favour large local deformations at the fibre-matrix interface, inducing the triggering of premature secondary failure mechanisms [31]. Therefore, a progressive process of damage accumulation is activated by coupling different damage modes, such as fibre kink bands and shear cracks at the layers interface that evolve to large-scale delamination phenomena, resulting in a reduction in the mechanical stability of the joint [32]. The fracture image of GFA-4-12-15 unaged sample (Figure 3a), fails through bearing mode, as can be evidenced by the large compression collapse area on the pin/hole contact surface area.…”

An Aging Evaluation of the Bearing Performances of Glass Fiber Composite Laminate in Salt Spray Fog Environment

“…Afterward, for edge distance higher than 6-8 mm (i.e., E/D > 1.5-2.0) the bearing stress reaches a plateau (region II). In this region, the prevailing failure mechanism is bearing mode [10] and, for this reason, the stress value reached is indicated as bearing stress at failure. As can be seen from the horizontal trend of the curve of the region II, the bearing stress is also independent by E and remains almost constant at increasing the edge distance.…”

“…Furthermore, the kink bands induce local deformations at the fiber-matrix interface thus activating secondary failure premature modes [26]. As a consequence, a mixed damage process due to fiber plies kink bands, shear cracks and layers interface delamination evolve to large-scale delamination phenomena, reducing the joint's mechanical stability [10]. The softening of the epoxy matrix due to the water absorption, favors the formation of a large compression collapse area on the pin/hole contact surface area without the occurrence of shear cracks.…”

“…In this context, the kind of failure mechanism (i.e., bearing, net-tension, shear out and cleavage), and consequently, the capability of pinned laminates to support a load was investigated as a function of their geometrical parameters [9][10][11][12][13]. In particular, in our recent paper [14], pinned, glass-reinforced laminates were tested with varying hole diameter D, laminate width W and hole center distance from the free edge of laminate, E; thus, highlighting that the pin-loaded composite configuration has a relevant influence on the mechanical stability and on the joint-failure mechanism.…”