Experimental characterization of Mode II fatigue delamination growth onset in composite Joints

Abstract

In this article, the structural behavior of co-cured composite joint (CC), co-bonded composite joint (CB), and secondary-bonded composite joint (SB) under Mode II fatigue loading was evaluated. Fatigue performance was evaluated in sub-critical strain energy release rate (SERR) associated with Mode II fatigue induced delamination growth onset. Fatigue tests were carried out using the three-point bending End Notched Flexure test setup for different energy ratios. The experimental results are presented in terms of SERR versus number of cycles, and the SERR threshold for no growth is determined (Gth). Fractographic analyses were performed in order to identify the main failure mechanisms related to each joining technology under Mode II. The results indicated an initial cohesive failure followed by an adhesive failure promoted by crack propagation at the interface between the adhesive and the composite adherend on SB and CB samples, through the coalescence of microcracks that promote the adhesive failure process, leading to fiber pull-out from the matrix and cusps formation in the fracture surface. These results explain the low performance behavior observed on SB and CB bonded techniques. It is worth mentioning that the results and behavior observed in this work are valid only for the laminates, adhesives, surface treatment, and environmental conditions tested herein.

Numerical Simulation Study on Relationship between the Fracture Mechanisms and Residual Membrane Stresses of Metallic Material

“…The projectile continued to progress in the x-axial to counter the through-thickness wave in the opposite direction [ 25 ], resulting in a transverse shear force. This force continued to form a wave to counter the projectile progression, resulting in the growth in-plane delamination wave [ 42 ]. This phenomenon especially occurred at the first few predefined interfaces or the refined zone of the cart brass target plate which was elucidated by selecting the simulation cycles of 10,415 and 21,664 (as shown in Figure 9 ).…”

Delamination onset in composite materials due to fatigue loading

“…González Ramirez et al 21 and Garpelli et al 22 performed an experimental activity on DCB and ENF specimens to assess the fatigue delamination resistance of co-cured (CC), co-bonded (CB) and secondary bonded (SB) joints; T800/3900–2 carbon/epoxy specimens were manufactured similarly to the joints and 5% compliance increase curves were obtained. A no-growth criterion based on 10 6 cycles without propagation was established and a better behaviour of the two solutions containing an epoxy adhesive interleaf (CB and SB) was observed, both statically and in fatigue, for mode I tests while the mode II tests showed for CB and SB specimens a lower performance, that was associated with a change of the failure mechanism from initially cohesive to adhesive.…”

Adhesion Analysis of Adhesive Mortar Joints in Ceramic Tiles under Static Loading

“…In [6], the ENF (shear) propagation test was carried out to evaluate the quality of an epoxy resin joint used in the manufacture of parts in the aeronautics sector. The analysis of the quality of the material was carried out based on the assessment of its fracture toughness, where lower toughness values indicated lower adhesion capacity.…”