  This article studies the fundamental problem of separating two adhesive
elastic fibers based on numerical simulation employing a recently developed
finite element model for molecular interactions between curved slender fibers.
Specifically, it covers the two-sided peeling and pull-off process starting
from fibers contacting along its entire length to fully separated fibers
including all intermediate configurations and the well-known physical
instability of snapping into contact and snapping free. We analyze the
resulting force-displacement curve showing a rich and highly nonlinear system
behavior arising from the interplay of adhesion, mechanical contact interaction
and structural resistance against (axial, shear and bending) deformation. While
similar to one-sided peeling studies from the literature, a distinct initiation
and peeling phase can be observed, the two-sided peeling setup considered in
the present work reveals the extended final pull-off stage as third
characteristic phase. Moreover, the influence of different material and
interaction parameters such as Young's modulus as well as type (electrostatic
or van der Waals) and strength of adhesion is critically studied. Most
importantly, it is found that the maximum force occurs in the pull-off phase
for electrostatic attraction, but in the initiation phase for van der Waals
adhesion. In addition to the physical system behavior, the most important
numerical aspects required to simulate this challenging computational problem
in a robust and accurate manner are discussed. Thus, besides the insights
gained into the considered two-fiber system, this study provides a proof of
concept facilitating the application of the employed model to larger and
increasingly complex systems of slender fibers.
