Anne-Sophie Caro-Bretelle

While perineal tears continues to occur in 90% of births worldwide, the PELVITRACK project aims at characterising perineum damages in order to predict them and thus to adapt obstetrical process and to improve perineal rehabilitation. With images and videos, that can be easily collected, predictive analysis based on texture descriptors could help perineal tears prevention. Fractal-based method have proved to be efficient at highlighting time series differences in terms of rugosity or complexity at different time scales. Among fractal methods, the Detrended Fluctuation Analysis (DFA) has mainly been applied to time series but some works have proposed extensions to images and videos. In this paper, 2D-DFA is performed on experimental perineal image sequence with the objective of perineal damage characterisation. At the global and local levels the preliminary results are encouraging and illustrate the suitability of 2D-DFA for movement analysis on images.

This paper deals with the mechanical behavior of soft living tissues under load-unload and relaxation cyclic strains. It proposes a thermodynamic model formulated within the Generalized Standard Materials framework that incorporates both Mullins' effect and viscoelasticity, integrating the history dependent behavior of the material under finite strain. A key innovation lies in the use of a common softening function to modulate both the hyperelastic and viscous components, capturing history-dependent behavior more accurately. Viscous parameters are adjusted based on the loading history via the maximum strain invariant. Numerical implementation is validated against uniaxial tensile tests on porcine perineal tissues and a global Sobol sensitivity analysis confirms that elastic, viscous, and Mullins-related parameters are identifiable from different phases of the loading protocol. This model provides a unified, thermodynamical consistent tool for simulating soft tissue mechanics.

Les troubles au niveau du périnée sont trop souvent décelés après apparition des premiers symptômes. Des outils sont développés pour mieux prédire leur survenue et améliorer ainsi la prise en charge.

Three layers film shaped by thermocompression of acrylonitrile butadiene styrene copolymer and polycarbonate have been analyzed in dynamic mechanical thermal analysis in tensile mode. They present two peaks as the film is loaded perpendicularly to the layers and three peaks as the film is loaded in parallel to the layers. Numerical computations confirm that the origin of this peak is not related to a mechanical issue such as the transmission of the imposed deformation from one layer to the other. Using this method, it is demonstrated that this third peak can only be obtained assuming a material transition with its own behavior between layers. Tan δ measurements provide a simple and useful experimental tool to understand more about the interfacial zone in polymer blends.

The detection of inclusions in soft material is of great interest, especially in the medical field. Traditionally, a biopsy exam is performed after palpation, when necessary. In the present work, a potentially quantitative method, via monitored indentation, is used to mimic palpation. This method consists in investigating the relaxation and stress‐free relaxation responses to an indentation test performed on a silicone block with an inclusion. The aim of the study is to evaluate how a difference in position, size and adhesion of the inclusion can influence the response of the samples to monitored indentation. A finite element model is constructed to conduct comparative studies. The hyper‐viscoelastic parameters of the silicone have been identified experimentally. Results from the simulations showed that the indicators measured during monitored indentation, especially during the stress‐free relaxation phase, are sensitive to adhesive inclusions, while they provide little information regarding their non‐adhesive counterparts. Depths and sizes for which adhesive inclusions are more likely to be detected have been identified. These results are encouraging but are conducted on polymer material and a rigid inclusion; nevertheless, they suggest that the non‐destructive measure of the stress‐free relaxation response of a tissue may help practicians to quantitatively characterize the nature of a nodule.

Recycling of plastics is hindered by their important variety and strong incompatibility. However, sorting technologies bear costs and meet limits. Very high purities (<2 wt%) are difficult to reach. Yet, such rates may be detrimental to functional properties. In this work, an ABS matrix (major plastic in Waste of Electrical and Electronic Equipments) was filled with 4 wt% of PP to mimic impurities in ABS after recycling. PP-g-MA was introduced in the blend to improve the compatibility. A finite element model was developed from the mechanical behavior of each component. ABS and PP were individually characterized from tensile tests instrumented with photomechanics and their behaviors were modelled through a set of numerical parameters (elasto-visco-plasticity with a Gurson’s criterion behavior). Comparison between the determinist model results and the experimental data (strength, volumetric variation) shows that this type of modelling could be a predictive tool in order to anticipate composite mechanical properties and to understand micromechanisms of deformation (damage, cavitation). The main result is that PP introduced at 4 wt% into ABS does not alter the static mechanical properties despite polymers incompatibility. The addition of PP-g-MA modifies the local properties and possibly conduct to a premature breakage of the polymer blend.

With the development of dark polymers for industrial sorting technologies, economically profitable recycling of plastics from Waste Electrical and Electronical Equipment (WEEE) can be envisaged even in the presence of residual impurities. In ABS extracted from WEEE, PP is expected to be the more detrimental because of its important lack of compatibility. Hence, PP was incorporated to ABS at different rates (2 to 8 wt%) with a twin-screw extruder. PP was shown to exhibit a nodular morphology with an average diameter around 1–2 µm. Tensile properties were importantly diminished beyond 4 wt% but impact resistance was decreased even at 2 wt%. Both properties were strongly reduced as function of the contamination rate. Various potential compatibilizers for the ABS + 4 wt% PP system were evaluated: PPH-g-MA, PPC-g-MA, ABS-g-MA, TPE-g-MA, SEBS and PP-g-SAN. SEBS was found the most promising, leading to diminution of nodule sizes and also acting as an impact modifier. Finally, a Design Of Experiments using the Response Surface Methodology (DOE-RSM) was applied to visualize the impacts and interactions of extrusion temperature and screw speed on impact resistance of compatibilized and uncompatibilized ABS + 4 wt% PP systems. Resilience improvements were obtained for the uncompatibilized system and interactions between extrusion parameters and compatibilizers were noticed.

The authors wish to make the following corrections to this paper