**Conflict of interest**

*Composite and Nanocomposite Materials - From Knowledge to Industrial Applications*

The power of numerical procedures allows to expand the analysis and consider exact three-dimensional models. Evidently, the parameters of the interface will have to defined in the three-dimensional system. For example, the damage onset will require a fracture criterion, and the fracture toughness will have to be applied

For aramid fiber composites, an FE analysis was reported by Kanerva et al. [18] with a full 3D representation (see **Figure 2**). For the DLC-coated aramid fibers,

It is clear that the current numerical modeling techniques and computational capacities can offer efficient tools to study fiber-matrix interactions in composites with aramid fibers. However, the multiplicity of parameters currently leads to overlapping fitting procedures. Thus, the solutions are not typically unitary to the simulation case in question. There is an urgent need to improve the microtest methods in order to gain more experimental output and data to validate the numerical models. There are very recent works in the current literature that target to improvements in the test systems to enhance statistical significance, data rate, and accurate

In future, it will be possible to accurately account for plastic deformation, residual stresses, and a multistage fracture process in the simulations of fibermatrix interfaces. This will be an important step toward analyses of fatigue and

Aramid fibers have been modified and optimized for various applications ever since they were established. Around three decades, academic researchers have focused on trial-and-error type experiments to improve the surface characteristics in the sense that feedback based on laminate testing was behind burdensome and expensive testing efforts. After millennia, the microlength scale testing of fibermatrix interfaces has improved, and more information about the interfacial performance is available. Meanwhile, the numerical analysis of interfaces has gained increasing amounts of attention. Efficient and valid numerical simulations could save time and resources in the optimization of surface treatments of aramid fibers for specific applications. However, there are still challenges in the validation of numerical models because the experimental output does not provide for necessary

environmental effects on interfaces in composites with aramid fibers.

were determined for the case-specific critical trac-

via an interaction function.

**Figure 2.**

values of 22.2 MPa and 500 J/m2

output from the microtests [34, 35].

parameters and statistical certainty.

**6. Conclusions**

tion and interfacial fracture toughness, respectively.

*An example of a 3D model simulating the microdroplet testing.*

**46**

The author confirms no conflicts of interest.
