Experimental and Numerical Study of Low-Velocity Impact and Tensile after Impact for CFRP Laminates Single-Lap Joints Adhesively Bonded Structure

Abstract

To investigate the mechanical behavior of the single-lap joints (SLJs) adhesively bonded structure of carbon fiber reinforced polymer (CFRP) laminates under the low-velocity impact (LVI) and tensile-after impact (TAI), tests and simulations were carried out. A finite element model (FEM) was established based on the cohesive zone model (CZM) and Hashin criterion to predict the damage evolution process of adhesive film, intra- and inter-laminar of the SLJs of CFRP laminates, and its effectiveness was verified by experiments. Moreover, three different overlap lengths (20 mm, 30 mm, and 40 mm) and four different impact energies (Intact joint, 10 J, 20 J, and 30 J) are considered in the present study. Finally, the effects of different impact energies and overlap lengths on the residual strength of SLJs after impact were discussed. The results divulged that numerical results of impact and TAI processes of SLJs were in good agreement with experiment results. During the impact process, the damage of the laminates was primarily fiber and matrix tensile damage, whereas the adhesive film was damaged cohesively; the areas of damage increased with the increase of impact energy, and the normal stress of the adhesive film expanded from the edge to the middle region with the increase of impact force. The influence of LVI on SLJs adhesively bonded structures was very significant, and it is not effective to obtain a higher impact resistance by increasing the overlap length. For the tensile process, the failure mode of TAI of the SLJs was interface failure, the surplus strength of the SLJs gradually decreased with the increase of the impact energy because of the smaller overlap length, the overlap length more than 30 mm, and the low energy impact has almost no effect on the residual strength of the SLJs.

A Model of Damage for Brittle and Ductile Adhesives in Glued Butt Joints

“…The damage parameter ρ evolves via the kinetic Equation (13). By substituting (2), ( 5)-( 7), (14), and ( 18) into ( 13) and simplifying, we obtain the following evolution problem for the damage parameter ρ = ρ(t) :…”

“…The classic strategy used for modeling damage in adhesivebonded joints is based on cohesive zone models (CZMs) [6], which are described by a traction-separation (TS) law across the cohesive surface. Several TS laws of different shapes (i.e., bilateral, trapezoidal, polynomial) have been proposed (see [12,13] and the references therein), and they adequately describe the global response of adhesive-bonded joints [14][15][16][17]. However, a crucial drawback of CZMs is that they adopt a phenomenological approach, and thus, the model parameters describing the damage/failure behavior of adhesives are not based on their physical properties (e.g., material properties, geometry).…”

Bondline Thickness Effects on Damage Tolerance of Adhesive Joints Subjected to Localized Impact Damages: Application to Leading Edge of Wind Turbine Blades

“…Overall, the impact loads did not modify the failure modes for the joints tested under tensile lap shear testing. Another important finding was that for all the cases, the impact loads did not significantly reduce the failure load of joints compared to their intact values as reported in [58] for Carbon-fiber-reinforced polymers (CFRP) based adhesive joints (see Figure 22a-c). Interestingly, for some of the cases, the failure load seems to have increased by 20% compared to the intact values (see Figure 22a,b).…”

“…Hence, this test setup enables a consistent comparison of localized impact-induced effects on adhesive joints between different bondline thicknesses. The test setup has also been explored in the literature [56][57][58] for impact testing on adhesive joint, and was judged as the most suitable configuration for the present study.…”

A novel methodology to research the residual compressive mechanical properties of composite stiffened panel after low velocity impact based on quantification damage simulation

“…Carbon fiber reinforced polymer (CFRP) composites have been widely utilized in the field of the aviation industry as a consequence of their outstanding mechanical behaviors such as high strength/stiffness to weight ratio, high specific modulus and excellent fatigue resistance, and they are gradually replacing the conventional metallic materials like aluminum alloy to achieve the light-weight of the structure and enhance the maneuverability of the aircraft. [1][2][3][4][5] The composite stiffened panel, which is made up of the skin panel and the stiffener with a certain stacking sequence of the composite prepreg, [6,7] is one of the most common used structural components in the manufacturing process of the airplane, and it is going to sustain complicated loading conditions like axial compression during the process of the service, [8][9][10][11][12] which may directly trigger the emergence of the buckling. [13,14] However, these structural components are very vulnerable to the low velocity impact (LVI) loading while the airplane is flying.…”