In the realm of engineering simulations, the ability to accurately predict the behavior of materials under various conditions is paramount. This is where the Cohesive Section Property option in Abaqus and the structural simulation roles on the 3DEXPERIENCE platform offer a robust solution for engineers trying to realistically simulate models with components or surfaces that are connected via adhesives.
Applications of cohesive properties are vast and varied. They are essential in industries where structural integrity and material failure are critical concerns, such as aerospace, automotive, and civil engineering. For instance, in the design of aircraft, cohesive properties can be used to simulate the behavior of composite materials under stress, predicting potential delamination or failure points.
Cohesive section property is particularly useful for simulating the behavior of adhesive joints, interfaces in composites, and even limited modeling of gaskets, rock fractures, or small adhesive patches, where the integrity and strength of interfaces are of interest. Cohesive Property can be assigned via the Properties tab of the action bar as shown in the image below.
The entities for support can be solid geometry, geometry from an ordered geometric set, or even gasket section or meshed components including solid elements. Materials can be defined as necessary. Cohesive elements are used in modeling the sections that have cohesive properties assigned. The constitutive response of these elements depends on the specific application and is based on certain assumptions about the deformation and stress states that are appropriate for each application area.
As a best practice, it is recommended to mesh cohesive sections with a single layer of elements, such as those created by extruding surface elements. There are three options when it comes to defining the mechanical behavior of the cohesive section properties.
Traction-Separation-Based Modeling
This type of behavior can be used to model the delamination at interfaces in composites directly in terms of traction versus separation. The modeling of bonded interfaces in composite materials often involves situations where the intermediate glue material is extremely thin. In this case, the macroscopic material properties are not relevant directly. The cohesive elements model the initial loading, the initiation of damage, and the propagation of damage leading to eventual failure at the bonded interface. The behavior of the interface prior to initiation of damage is often described as linear elastic. The stiffness would degrade under tensile or shear loading but is unaffected by pure compression. Because of the ability to model this kind of behavior, cohesive elements can be used in areas of the model where cracks are expected to develop.
The property allows for the detailed representation of cohesive zones, which can be discretized with a single layer of cohesive elements through the thickness [1]. The image below shows the results of a simulation where Cohesive property with Traction separation behavior was used.
Continuum-Based Modeling
This option can be used to model adhesives with finite thickness, connecting two bodies together. The macroscopic properties, such as stiffness and strength, if available, can be for modeling purposes. (*insert image Coh_05)
This type of behavior assumes adhesive material is more compliant than the surrounding material [1]. The cohesive elements model the initial loading, the initiation of damage, and the propagation of damage leading to eventual failure in the material.
Gasket
This option can be used to model adhesive patches accounting for the uniaxial stress state. It also provides limited capabilities for modeling gaskets. With this kind of cohesive behavior, elements can model nonlinear states with finite strains and rotation as well as include mass for dynamic analyses.
A cohesive element can be thought of as being composed of two faces separated by a small thickness. The relative motion of the bottom and top faces measured along the thickness direction represents the opening or closing of the interface. The relative change in position of the bottom and top faces measured in the plane orthogonal to the thickness direction quantifies the transverse shear behavior of the cohesive element. Stretching and shearing of the midsurface of the element are associated with membrane strains in the cohesive element [1].
Spatial Representation of a 3D Cohesive Element
The availability of the Cohesive Section Property in the structural simulation app on the 3DEXPERIENCE platform offers engineers yet another realistic modeling capability. These tools allow design engineers to quickly innovate, validate designs, and make informed decisions.
