# Mimicking stress-strain behavior of Human Abdominal Wall muscles by fiber reinforced elastomer composites

Zakaria Fadil, Baptiste Pierrat, Anicet Le Ruyet, Guillaume Passot, Aline Bel-Brunon

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Zakaria Fadil, Baptiste Pierrat, Anicet Le Ruyet, Guillaume Passot, Aline Bel-Brunon. Mimicking stress-strain behavior of Human Abdominal Wall muscles by fiber reinforced elastomer composites. Multidisciplinary Biomechanics Journal, 2025, 50th congress of the.., 10.46298/mbj.16186 . hal-05191738v2

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Submitted on 23 Oct 2025

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# Mimicking stress-strain behavior of Human Abdominal Wall muscles by fiber reinforced elastomer composites

Zakaria Fadil<sup>a, b, c, e*</sup>, Baptiste Pierrat<sup>b</sup>, Anicet Le Ruyet<sup>a</sup>, Guillaume Passot<sup>c, d</sup>, Aline Bel-Brunon<sup>e</sup>

<sup>a</sup> Medtronic, Surgical Operating Unit, General Surgical Technologies, BioTex, Trévoux, France

<sup>b</sup> Mines Saint-Etienne, Univ Jean Monnet, INSERM, U1059 Sainbioe, Centre CIS, F-42023, Saint-Etienne, France

<sup>c</sup> Centre pour l'Innovation en Cancérologie de Lyon, Université Lyon 1, France

<sup>d</sup> Hospices Civils de Lyon, Service de chirurgie viscérale et oncologique, Hôpital Lyon Sud, Pierre Bénite, France

<sup>e</sup> Univ Lyon, Univ Gustave Eiffel, Univ Claude Bernard Lyon 1, LBMC, UMR_T9406, Lyon, France

* Corresponding author: zakaria.fadil@medtronic.com

Received date: 04/04/2025

Accepted date: 27/06/2025

Publication date: 27/10/2025

**Keywords:** biomechanics, abdominal wall, fiber-reinforced membrane, tensile tests

© 2025 The Authors

Licence CC-BY 4.0

Published by Société de Biomécanique

## 1. Introduction

The abdominal wall (AW) is a complex anatomical structure that defines the boundaries of the abdominal cavity. Its anterior and lateral periphery consists of a flexible wall and a complex mechanical multi-layered structure composed of muscular and fibrous tissues (Deeken et al. 2014). Within these layers, the distribution of all components exhibits varying fiber composition and architecture. These histological characteristics give abdominal tissues a nonlinear, anisotropic, and predominantly hyperelastic mechanical behavior (Astruc et al. 2018).

In the last decades, biological tissues from animals and human cadavers have been the primary resources used to study the interactions between hernia implants and the AW. This research has helped establish safety margins and improve the characterization of medical devices. However, experiments on human or animal abdominal walls raise major ethical concerns, are complex to conduct, time-consuming, and have low reproducibility due to the high interindividual variability of biological tissues. For this reason, physical models have been developed to mimic the AW behavior: Kroese et al. used a single layer of isotropic elastomer, but it was unable to replicate the J-shaped hyperelastic, anisotropic nature of the AW (Kroese et al. 2017). To improve fidelity, certain synthetic materials have been developed.

These materials often use composites, combining a hyperelastic silicone matrix with collagen fibers, carbon fibers, or textiles to replicate the mechanical complexity of AW tissues (Xu et al. 2023).

Therefore, the objective of this work is to design and develop new artificial materials capable of mimicking the macroscopic properties of AW tissues and their J-shaped mechanical response. These materials could help develop a more realistic AW model that better captures its complexity.

## 2. Methods

To replicate the behavior of the muscles of the AW, three silicones were used: Ecoflex 00-10, Dragon Skin 10, and 30 (Smooth On, Inc., United States). One knitted textile from the Medtronic product range were also used in this study due to their anisotropy and relatively low stiffness (Polyethylene terephthalate, 45-g m²), with tangent moduli of 1.4 MPa in warp and 2.2 MPa in weft. Silicone samples measuring 150×25×10-mm were fabricated, while textile sample measured 150×25×0.8 mm. Each sample was characterized through uniaxial tensile tests at a constant strain rate of 50-mm/min (Instron 5965).

Textile-reinforced elastomer composites were prepared in a two-layer configuration using a vertical casting method. Ecoflex 00-10 was selected as the matrix material for all composites in this study, due to
its tangent modulus of 0.02 MPa. The elastomer was prepared by mixing its two components (a base and a curing agent) in a 1:1 ratio, and vacuum degassed to remove air bubbles. A 3D-printed mold was designed for fabricating silicone samples and composite samples (Stratasys 370). These bipartite molds allowed the textile to be held in place at mid-height by securing it between two plates. The elastomer was poured vertically to fully encapsulate the textile. Scanning electron microscopy then analyzed the composite microstructure (Hitachi, TM4000).

All samples were subjected to uniaxial tensile testing, with an effective length of 100 mm and a constant strain rate of 0.5/min. The resulting stress-strain curves were compared with experimental human AW stress-strain curves extracted from (Cardoso 2012).

## 3. Results and discussion

The microscopic evaluation of the interaction between the silicone matrix and the textile reinforcement showed that the silicone successfully penetrated and filled the pores of the textile, ensuring good adhesion between the components.

Mechanical tensile tests were compared in terms of tension, i.e. force divided by initial sample width, as this is the metric of interest for our application.

Tensile testing revealed that the silicone exhibits a hyperelastic concave mechanical behavior with a tension of 0.025 N/mm at 30% strain, while the textile shows significantly higher stiffness, adopting a convex J-shaped curve with tension of 0.1 N/mm at 30% strain. Additionally, the incorporation of textile into the silicone matrix further stiffens the composite structure, giving it a convex behavior similar to that of biological tissues. It was observed that the composite under uniaxial tension did not fully align with the predictions based on the sum of forces from the individual components. Indeed, the silicone penetrates the pores of the textile, limiting the mobility of the fibers and thereby stiffening the composite further compared to the theoretical model.

Finally, compared to the uniaxial tensile data on human cadavers, it is observed that the composite exhibits a mechanical behavior comparable to that of the rectus abdominis muscle in the AW, notably its J-shape.

<figure><img src="image_2.png" /><figcaption>**Figure 1.** (a) Tension-strain curves of samples (b) Stress-strain comparison with experimental data from the Rectus Abdominis.</figcaption></figure>

## 4. Conclusions

This study demonstrates the benefit of integrating fibers into a silicone matrix to replicate the mechanical behavior of biological tissues. The next step is to examine the composite's behavior under biaxial tension to understand deformation coupling and anisotropy, which can vary with the textiles used. Ultimately, the goal is to create phantoms for each AW component to develop a realistic model replicating the region's complex physiological behaviors.

## Conflict of Interest Statement

The authors declare no conflict of interest.

## References

Astruc, L., De Meulaere, M., Witz, J.-F., Nováček, V., Turquier, F., Hoc, T., & Brieu, M. (2018). Characterization of the anisotropic mechanical
behavior of human abdominal wall connective tissues. *Journal of the Mechanical Behavior of Biomedical Materials*, 82, 45–50. https://doi.org/10.1016/j.jmbbm.2018.03.012

Cardoso, M. H. S. (2012). *Experimental study of the human anterolateral abdominal wall* (Master’s thesis, Integrated Master in Bioengineering – Biomedical Engineering, Faculty of Engineering, University of Porto). Retrieved from http://hdl.handle.net/10216/65576

Deeken, C. R., Thompson, D. M., Castile, R. M., & Spencer, P. L. (2014). Biaxial analysis of synthetic scaffolds for hernia repair demonstrates variability in mechanical anisotropy, non-linearity and hysteresis. *Journal of the Mechanical Behavior of Biomedical Materials*, 38, 6–16. https://doi.org/10.1016/j.jmbbm.2014.06.001

Kroese, L. F., Harlaar, J. J., Ordrenneau, C., Verhelst, J., Guérin, G., Turquier, F., Goossens, R. H. M., Kleinrensink, G. J., Jeekel, J., & Lange, J. F. (2017). The ‘AbdoMAN’: An artificial abdominal wall simulator for biomechanical studies on laparotomy closure techniques. *Hernia* 21(5), 783–791. https://doi.org/10.1007/s10029-017-1615-x

Xu, X., Wang, G., Yan, H., & Yao, X. (2023). Constitutive relationship of fabric rubber composites and its application. *Composite Structures*, 304. https://doi.org/10.1016/j.compstruct.2022.116302