We study the effect of inter-fiber adhesion on the mechanical behavior of cross-linked ran- dom fiber networks in two dimensions. To this end, we consider networks with connectiv- ity number, z , below, at, and above the isostaticity limit of the structure without adhesion, z c . Fibers store energy in the axial and bending deformation mode and the cross-links are of freely rotating type. Adhesive forces lead to fiber bundling and to a reduction of the total volume of the network. The degree of shrinkage is determined as a function of the strength of adhesion and network parameters. The mechanical response of these struc- tures is further studied in uniaxial tension and compression. The stress-strain curves of networks without inter-fiber adhesion exhibit an initial linear regime, followed by strain stiffening in tension and strain softening and strain localization in compression. In pres- ence of adhesion, the response becomes more complex. The initial linear regime persists, with the effective modulus decreasing and increasing with increasing adhesion in cases with z > z c and z < z c , respectively. The strain range of the linear regime increases signif- icantly with increasing adhesion. Networks with z > z c subjected to tension strain-stiffen at rates that depend on the adhesion strength, but eventually enter a large strain/stress regime in which the response is independent of this parameter. Networks with z < z c are stabilized by adhesion in the unloaded state. Beyond the initial linear regime their tangent modulus gradually decreases, only to increase again at large strains. Adhesive interactions lead to similar effects in compression. Specifically, in the z > z c case, increasing the adhe- sion strength reduces the linear elastic modulus and significantly increases the range of the linear regime, delaying strain localization. This first investigation of the mechanics of cross-linked random networks with inter-fiber adhesion opens the door to the design of soft materials with novel properties.
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Effect of Network Architecture on the Mechanical Behavior of Random Fiber Networks
Fiber-based materials are prevalent around us. While microscopically these systems
resemble a discrete assembly of randomly interconnected fibers, the network architecture
varies from one system to another. To identify the role of the network architecture, we
study here cellular and fibrous random networks in tension and compression, and in the
context of large strain elasticity. We observe that, compared to cellular networks of same
global parameter set, fibrous networks exhibit in tension reduced strain stiffening,
reduced fiber alignment, and reduced Poisson’s contraction in uniaxial tension. These
effects are due to the larger number of kinematic constraints in the form of cross-links
per fiber in the fibrous case. The dependence of the small strain modulus on network density
is cubic in the fibrous case and quadratic in the cellular case. This difference persists
when the number of cross-links per fiber in the fibrous case is rendered equal to that of
the cellular case, which indicates that the different scaling is due to the higher structural
disorder of the fibrous networks. The behavior of the two network types in compression is
similar, although softening induced by fiber buckling and strain localization is less pronounced
in the fibrous case. The contribution of transient interfiber contacts is weak in
tension and important in compression
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- Award ID(s):
- 1634328
- NSF-PAR ID:
- 10059668
- Date Published:
- Journal Name:
- Journal of applied mechanics
- ISSN:
- 0021-8936
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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