MAGNUM BONUM · Modelling of human body and protective textiles for estimation of skin sensorial comfort and life risk of fire-fighters working in extreme external conditions

Modelling of human body and protective textiles for estimation of skin sensorial comfort and life risk of fire-fighters working in extreme external conditions

This project concerns modelling of fire-fighter torso’s skin model covered with a composite of three main layers of Protective Textiles (PTs) working under simulated extreme external conditions. The reason why one initiated the work on this subject is the fact that PTs are very important group of textiles that are life savers but the level of comfort when wearing them is low. Thus, improving wearing comfort can support creation of better condition in relation human-outfit-environment. This project revolves around three main aspects: (a) modelling of mechanical and thermal Finite Element Analysis (FEA) of fire-fighter torso’s skin model covered with a composite of three main layers of PTs working under simulated extreme external conditions; (b) verification whether the minor differences in the design of uniforms and their fit can be quantified in terms of their impact on firefighters’ cardiorespiratory parameters and subjective perception of these uniforms; (c) measure a range of motion (ROM) in firefighters to observe whether it can be restricted by wearing stiff and bulky clothing. In order to address some of these aspects FEA of firefighters’ skin and avatars covered by a composite of three main layers of PTs were created. In the current stage of the project, the main focus is on the Finite Element Analysis that concerns human tissue (skin and muscles) and the textile composite in contact with each other as well as a skin compression under the influence of the textile composite. This is a very challenging task as each of the elements (Instances in Abaqus CAE) that were supposed to be modeled must have been presented in a different scale (Figures 1,2,3 & 4). The impact of minor design improvements compared to the existing designs of PPC is still relatively difficult to quantify due to the lack of sensitive devices used in smart measuring methodologies; however, the perception of these slight differences is reported by PPC users. The impact of these design differences in PPC on firefighters was studied via physiological tests based on occupation-related activities in which cardiorespiratory parameters were monitored and three-dimensional (3-D) silhouette scanning was performed on the firefighters. Apart from heart rate (beats/min), none of the other measured physiological parameters, for example, oxygen consumption (VO2, ml/min) demonstrated statistically significant differences when firefighters were testing uniforms: ergonomic (ER), standard (ST), bulky (BU), and reference outfit (RO), the latter being T-shirt and shorts. A statistically significant correlation was found between parameters measured via 3-D body scanning and selected cross-sections of the silhouettes as well as subjective assessments of easiness of specific movement performance during the physiological test and assessment of bulkiness of the uniforms. There is a limited influence of the minor design differences between firefighters’ uniforms on the selected physiological parameters of the subjects wearing them. The outcome of the study can be utilized when performing the test on subjects and improving designs of PPC (Figure 5,6,7 & 8). The ROM, which is unassisted and voluntary motion of joints, is assessed by goniometers or electro-goniometers when subjects are wearing and testing different outfits.The ROM can be restricted by wearing stiff, bulky, and uncomfortable clothing. This is particularly true of firefighter suits that are constructed using fabric layers to provide thermal protection from fire. This study developed an evaluation technique to quantify the loss of mobility associated with wearing firefighters' protective suits that were deliberately selected to represent similar ergonomic design features. The ROM of ten firefighters was measured using electro-goniometers attached to their bodies while they wore uniforms and the RO, and performed specific movements. The most restrictive uniform is the BU suit that contained additional layers of materials in sleeves and on the knees. The ST was more ROM restrictive than ER. The subjective evaluation of suits supported the objective assessments provided by the electro-goniometers. A 3-D body scanning technique was employed to establish a correlation between the bulkiness of firefighter outfits and subject ROM. Practitioner Summary This study presents a methodology for measurements of ROM in firefighters wearing Personal Protective Equipment (PPE). Even small differences in designs of PPE may impact firefighters' ROM, which can be detected by electro-goniometers providing measurements if they are attached along the joint to measure limb angular movement (Figure 9,10).

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