Search results for " Toughness"
showing 10 items of 83 documents
Mental Toughness Moderates Social Loafing in Cycle Time-Trial Performance
2016
The purpose of this study was to determine if mental toughness moderated the occurrence of social loafing in cycle time-trial performance.Twenty-seven men (Mage = 17.7 years, SD = 0.6) completed the Sport Mental Toughness Questionnaire prior to completing a 1-min cycling trial under 2 conditions: once with individual performance identified, and once in a group with individual performance not identified. Using a median split of the mental toughness index, participants were divided into high and low mental toughness groups. Cycling distance was compared using a 2 (trial) × 2 (high-low mental toughness) analysis of variance. We hypothesized that mentally tough participants would perform equall…
Age, training, and previous experience predict race performance in long-distance inline skaters, not anthropometry
2012
Knechtle, Beat | Knechtle, Patrizia | Ruest, Christoph Alexander | Rosemann, Thomas | Lepers, Romuald; International audience; ''The association of characteristics of anthropometry, training, and previous experience with race time in 84 recreational, long-distance, inline skaters at the longest inline marathon in Europe (111 km), the Inline One-eleven in Switzerland, was investigated to identify predictor variables for performance. Age, duration per training unit, and personal best time were the only three variables related to race time in a multiple regression, while none of the 16 anthropometric variables were related. Anthropometric characteristics seem to be of no importance for a fast …
Infrared Thermography assisted evaluation of static and fatigue Mode II fracture toughness in FRP composites
2019
Abstract The work proposes the combined use of a Modified Transverse Crack Tension (MTCT) test coupon and Infrared Thermography, to evaluate the static and fatigue behaviour of Fibre Reinforced Polymer composites under Mode II delamination. Artificial delaminations starters are added to the TCT coupon, whose effects on the Strain Energy Release Rate are discussed. Infrared Thermography and Thermoelastic Stress Analysis are implemented to investigate stresses and delaminations growths on two FRP materials: a pre-preg IM7/8552 carbon fibre-epoxy and a glass-fibre reinforced epoxy laminates. The thermographic, thermoelastic and second harmonic signals have been obtained and used to monitor the…
Thermoelastic Stress Analysis of modified Transverse Cut Tensile composite specimens under pure Mode II fatigue delamination
2018
The present work investigates the behaviour of a Transvers Crack Tensile (TCT) specimen undergoing fatigue loading, by means of a Thermoelastic Stress Analysis (TSA) experimental setup. The TCT is a tensile composite specimen where a number of internal layers are cut through the beam width. The presence of such transverse notch favours the formation of interlaminar Mode II delaminations, starting from the notch tips and propagating between the cut and continuous plies. In this work, a modification is adopted to the classic TCT specimen, where insert films, mimicking artificial delaminations, are laid across the notch tips. This is done with the purpose to favour a pure Mode II and a symmetr…
Fracture toughness of synthesised high-performance epoxies subject to accelerated water aging
2018
Abstract The effects of water uptake on the fracture toughness of epoxy systems with high glass-transition temperatures (Tg above 170 °C) are investigated. Aging conditioning has been conducted in hot water, followed by a desorption conditioning in a room temperature dry-airborne. Water aging determines plasticisation effects and crosslink-density modifications, revealed by reductions of the Tg. It is less known how such modifications influence the material fracture toughness. In this study, Single Edge Notched Bending samples have been tested according to standards, to evaluate the KIC fracture toughness at different stages of water absorption-desorption. The characterisation has been supp…
Moisture Absorption Effects on the Resistance to Interlaminar Fracture of Woven Glass/Epoxy Composite Laminates
2012
The influence of moisture absorption on the interlaminar fracture behaviour of 8/8 harness satin weave glass/epoxy composite was investigated. Two series of specimens with 0°/0° and 90°/90° predominant interfaces immersed in water for different duration were tested under double cantilever beam (DCB mode I), single leg bending (SLB mode I + II) and end notched flexural (ENF mode II) loadings. In general, the apparent flexural modulus: E, and the fracture toughness: G C, decrease with increasing moisture content. This effect is more remarkable if mode II participation is bigger. The value of G C measured on 90°/90° specimens reveals higher than that on 0°/0° ones, but the variation in G C is …
Mechanical properties of steel fibre reinforced lightweight concrete with pumice stone or expanded clay aggregates
2001
This paper presents basic information on the mechanical properties of steel fibre-reinforced light-weight concrete, manufactured using pumice stone or expanded clay aggregates. Results are presented for standard compressive tests and indirect tensile tests (splitting tests on cylinder specimens and flexure tests on prismatic beams using a three-point loading arrangement) under monotonically increasing or cyclically varying loads. The influence of steel fibres and aggregate types on modulus of elasticity, compressive and tensile strength and post-peak behaviour is evaluated. Test results show that compressive strength does not change for pumice stone aggregates, while an increase is observed…
Induced Modification of Flexural Toughness of Natural Hydraulic Lime Based Mortars by Addition of Giant Reed Fibers
2020
Abstract Nowadays, there is a growing need to reduce the environmental impact generated by the use of inorganic materials for building applications. The aim of this work is to investigate the bio-lime based mortar flexural toughness improvement due to the addition of common reed fibers (Arundo donax L.) in order to evaluate their possible application as ductile eco-compatible prefabricated bricks or laying and joint mortars for masonry. Different sets of specimens were tested by varying the fiber weight content and the fiber length. Moreover, chemical treatments with Linseed Oil and Polyethylene glycol (PEG) were performed to improve the physical and mechanical properties of the fibers as w…
A three-dimensional cohesive-frictional grain-boundary micromechanical model for intergranular degradation and failure in polycrystalline materials
2013
Abstract In this study, a novel three-dimensional micro-mechanical crystal-level model for the analysis of intergranular degradation and failure in polycrystalline materials is presented. The polycrystalline microstructures are generated as Voronoi tessellations, that are able to retain the main statistical features of polycrystalline aggregates. The formulation is based on a grain-boundary integral representation of the elastic problem for the aggregate crystals, that are modeled as three-dimensional anisotropic elastic domains with random orientation in the three-dimensional space. The boundary integral representation involves only intergranular variables, namely interface displacement di…
Prediction of crack onset strain in composite laminates at mixed mode cracking
2009
Failure process of continuous fiber reinforced composite laminates in tension usually starts with appearance of intralaminar cracks. In composite laminates with complex lay-ups and/or under combined loading, intralaminar cracks may develop in plies with different reinforcement directions. A necessary part of mixed mode cracking models is the criterion of failure. For propagation-controlled fracture it is usually formulated in terms of energy release rates and their critical values of the particular composite material. Intralaminar fracture toughness of unidirectionally reinforced glass/epoxy composite was experimentally determined at several mode I and mode II ratios. It is found that the c…