Benny Malengier

ODES : a high level interface to ODE and DAE solvers

ODES offers a high level object oriented API to Differential Equation solving in Python. The backbone of ODES is the SUNDIALS package (Hindmarsh et al. 2005), which offers ODE and DAE solvers with root finding, preconditioning, error control and more. ODES can be used in Python 2.7 or 3.3-3.6, while for speed purposes the integrator can be a Cython function instead of a pure Python function. Comparison between different methods for a test problem is given in following graph:

3D Printing on Textiles: Testing of Adhesion

3D printing on textiles is a possible future application for mass customization of textile products. In this paper nwe investigate three test methods to quantify the adhesion of 3D printed PLA parts to a textile substrate. The first nproposed test method is a perpendicular tensile test, the second is a shear test, and the third is a peel test. These nthree tests are used to characterise the adhesion of a 3D printed shape on six different textile substrates. The test nmethods are compared and it is shown how they can help in standardizing the research of 3D printing on textiles.

Practical considerations of the FTT device for fabric comfort evaluation

The Fabric Touch Tester (FTT) is a device used to measure fabric handle properties. Since the device is considerably new in the market, no standard is available for now and the only reference for users is the brief guidelines by the manufacturer. Having done the experiments for more than 100 types of samples on FTT, the gathered experiences are reported in this paper including the handling of the device, possible analysis to be performed with the FTT data and other possible tests on fabric comfort related matters. We found that extensive care is needed to verify the accuracy of the device sensors, reference samples must be acquired, and a different test setup is required. The default comfort models also must be controlled using panel testing when testing new types of fabrics, and replaced with own models if needed. Apart from these, the FTT is a very useful addition towards fast and reliable comfort testing.

Experimental and numerical analysis of the tendon repair process using tubular braided fabrics

Abstract This paper presents the experimental and numerical analysis of the potential of a braided fabric for flexor tendon repair. Numerical models of tubular braided fabrics were generated using a python script interface and imported into ABAQUS® while Flexor tendon models were represented as silicone rubber rods. Experimental tests and Finite Element Modelling (FEM) of the flexor tendon repair was undertaken by deploying two tendon ends from opposite sides of a tubular braided fabric. This was done such that the tendon ends meet at the midpoint within the fabric. The tendons were tightly held to emulate a realistic repaired tendon. A displacement driven uniaxial loading was induced on the tendon-fabric assembly sufficient to cause a 2mm gap between the tendon ends. Numerical analysis of the repair potential of a braided fabric in tendon repair was done by analyzing selected fabric parameters that were crucial in tendon repair applications. The results show that changing the parameters of the braided fabrics significantly affected the potential of the fabrics during tendon repair.

Evaluating the Effect of Fines on Hydraulic Properties of Rammed Earth Using a Bench Scale Centrifuge

Unstabilized Rammed Earth (RE) has been historically used to form earth walls or blocks. Recently RE has resurfaced as a sustainable building material with little attention given to it in building codes and manuals. The percentage of the fine-grained fraction in RE is one of the most important factors affecting its behavior. Such percentage has been selected in practice based on experience and rules of thumb, not on a scientific rationale. This research examines the influence of the amount and type of fine particles on the hydraulic conductivity and water retention characteristics of compacted soils using a bench scale centrifuge. A Durner curve (1994) was applied to describe the water retention curve as it allows portraying a bimodal pore structure. In an attempt to understand the basis on which fines contribute to the strength of RE, two different types of fine grained soils were used in the mixtures, plastic fines (PF) and non-plastic fines (NPF). Each type was divided further into different mixtures, each with different percentages of fines. The influence of the fines’ percentage was tested using different methods and by using saturated and unsaturated samples of the soil mixtures. Larger suction developed in samples with PF in comparison to those with NPF. Suction increased as the percentage of fines in the mixture increased. Such effect is more pronounced in samples with PF.

FTT comfort indices of ring-spun and air-jet knitted fabrics with post-treatments

The Fabric Touch Tester (FTT) is a relatively new instrument that simultaneously measures several fabric indices and subsequently compute from them primary and global comfort indices (fabric total touch and total feel). The main aim of this research was to investigate the ability of the FTT to discriminate between primary comfort indices of fabrics differentiated by yarn type (i.e. ring-spun yarns and air-jet yarns) and finishing treatments. Polyester-cotton knitted fabrics were produced and their FTT-predicted primary comfort indices (i.e. smoothness, softness and warmth) were compared with those of the finished knits (i.e. dyed and dyed with softening treatments). For the considered fabrics, it was fond that the type of yarn did not lead to statistically significant different comfort indices. Nevertheless, significant differences were found between the comfort indices of the untreated fabrics and the fabrics dyed and treated with a softener regardless the type of yarn. The findings are in line with similar findings from literature where other instruments were used. These first results suggest that FTT is a promising tool that is able to distinguish between samples with small differences induced by finishing treatments.

A new physical method to assess handle properties of fabrics made from wood-based fibers

In this work, the handfeel of fabrics made of wood-based fibers such as viscose, modal and Lyocell was investigated in relation to cotton fabrics applying the Tissue Softness Analyzer (TSA) method in comparison to other classical methods. Two different construction groups of textile were investigated. The validity of TSA in assessing textile softness of these constructions was tested. TSA results were compared to human hand evaluation as well as to classical physical measurements like drape coefficient, ring pull-through and Handle-o-meter, as well as a newer device, the Fabric Touch Tester (FTT). Physical methods as well as human hand assessments mostly agreed on the softest and smoothest range, but showed different rankings in the harder/rougher side fabrics. TSA ranking of softness and smoothness corresponded to the rankings by other physical methods as well as with human hand feel for the basic textile constructions.