Maximum Breaking Load Research Articles

Influence of storage conditions on functional properties of multilayer biopolymer films based on chitosan and furcellaran enriched with carp protein hydrolysate

In this paper, the impact of water activity regarding storage environment on mechanical and water properties is presented, as well as the structural and morphological features of triple-layered films. Furcellaran (FUR), chitosan (CHIT) and carp skin gelatin hydrolysates (HGEL) were used for the production of the film. The films were made using a casting method, in which three successive stages were applied. First stage: preparation (pouring onto the mould) of 1st layer – FUR + HGEL, second: 2nd layer preparation (pouring onto 1st layer) – FUR, and third: 3rd layer (pouring onto 1st layer) – CHIT + HGEL. The second and third steps began after gelation of the previously poured layer. The drying process of the film was carried out for 24 h under a fume hood at room temperature. The mechanical properties of control sample was: tensile strength The control sample has tensile strength 7.76 ± 0.35 MPa, elongation at break – 3.69 ± 0.33%, maximum breaking load – 15.86 ± 0.58 N. Water properties of control sample – water absorption a solubility were 25.80 ± 1.14% and 52.91 ± 1.31%, respectively. Reducing the water content in the film increased its tensile strength (from 7.76 ± 0.35 MPa for the control film to 14.36 ± 0.07 MPa) and elongation at break (from 3.69 ± 0.34% for the control film to 8.74 ± 0.69%). Reducing water content in the film also decreased its ability to absorb water, which is crucial in the case of biodegradable films due to their hydrophilic nature. The multimolecular sorption of the films was described using the BET model. Structural and morphological changes observed on the basis of surface and cross-section photographs of the films confirm the negative impact of high water activity on the film and its mechanical parameters.

The use of a two-phase Monte Carlo material model to reflect the dispersion of asphalt concrete fracture parameters

The work covers comprehensive laboratory tests of semi-circular bending (SCB) of asphalt concrete samples. The results of two test series, including four and 32 SCB specimens, indicate a substantial scatter of force–deflection (F-d) histories. The numerical analysis is aimed to reflect the maximum breaking load and fracture energy of the samples, pointing out their random character. The original simulation-based fictitious Monte Carlo material model was introduced. The authors’ algorithm randomly assigns asphalt mortar and coarse aggregate parameters to the finite elements of the numerical model. As a result, sets of random fields are generated to reflect the two-phase material distribution in the samples. The model parameters are numerically adjusted based on laboratory test results of the initial four SCB specimens. In the course of model verification, the 32-sample computations were compared with the laboratory data. The results of FEM simulations are consistent with laboratory test results, including dispersion of fracture parameters. The proposed computational algorithm with a two-phase material model is ready to be implemented in the analysis of actual road pavement constructions and may support the design process.

Effect of Ailanthus species and seasons on yarn parameters of eri silk

Present research entails an in-depth analysis on the effect of two secondary host plants of eri silkworm viz., borpat (Ailanthus grandis Prain) and borkesseru (Ailanthus excels Roxb.) and seasons on yarn parameters of eri silk as quality of silk depends on food quality and rearing season. Seasons had significant effect on all the yarn parameters viz., yarn size, breaking load, tenacity and elongation except twist per inch. Significantly the highest yarn size (10.26s) was observed in autumn season which was at par with the spring season. But the maximum breaking load (0.67 kg) and tenacity (1.40 g/denier) were recorded in spring season and elongation (26.54%) in early summer season. Regardless of the seasons, significantly the higher breaking load (0.64 kg) and tenacity (1.51 g/denier) were recorded on the borkesseru leaves. The interaction effect of seasons and two host plants on eri silk yarn was found to be non-significant. Diversiform effect of both the seasons and the host plants pertaining to yarn characters were witnessed. It can be ensured that all the seasons and host plants are relevant with slight alteration in the yarn quality.

Transportation of chemical fibers and investigation of the process of chemical fiber carding in the unit of the licker-in carding machine

In our contemporary society, the effect of the rotational speed of the licker-in and the clothing overhang and the tooth shape of the clothing on the efficiency on the disconnection of the tufts coming from the manufacturing and transporting machineries are considered. The influence of the shape of the front face of the tooth of the licker-in set on the carding efficiency is also considered. For this reason, this paper discusses the phenomenon that occurs on the verge of one tooth of the serrated set of the licker-in of the flat carding machine to reduce the static charge in the area of the licker-in, a model of fiber movement and recommendations under the conditions of an intensive carding process for processing a cotton-nitrone mixture are presented, and the results of tests of cotton -nitron yarn with different content of components and the optimal composition of the mixture is recommended. Assuming on the findings, we can say that the maximum breaking load of cotton-nitrone yarn is obtained in the range from 10 to 20% of the content of nitron fiber. In this case, unevenness at breaking load has a minimum value of about 17%.

Influence of Methodological Variables on Fracture Strength Tests Results of Premolars with Different Number of Residual Walls. A Systematic Review with Meta-Analysis

The aim of the current meta-analysis was to assess the impact of methodological variables in performing fracture strength tests of upper premolars. Medline (Pubmed), Embase and Google Scholar were screened for studies performing ex vivo fracture strength tests of intact upper premolars or premolars with 0, 1 or 2 walls lost. The outcome variable for each study was the maximum breaking load expressed in Newton (kg × m/s2). Methodological variables (i.e., simulation of the periodontal ligament, load inclination, tip position, tip diameter and thermocycling) were registered to perform subgroup analyses and meta-regression. Overall, 25 studies and 78 study groups were included in the meta-analysis. Intact premolars (17 study groups) were not significantly influenced by any of the methodological variables considered. Subgroup analysis for load inclination (30°/45° vs. 90°/150°) was significant for premolars with 0 (10 study groups), 1 (6 study groups) and 2 (45 study groups) walls lost; thermocycling was significant for premolars with 1 and 2 walls lost. A strong methodological heterogeneity across studies evaluating the fracture strength of upper premolars was highlighted, especially when 0, 1 or 2 walls were lost. Further studies are needed to standardize the methodology used in order to allow for across-studies comparisons.

Reverse cation segregation and crack self-healing of Ba0.3Sr0.7Fe0.9Mo0.1O3-δ perovskite four-channel hollow fiber membrane

The cation segregation in a perovskite-type membrane deleteriously affects the membrane performance and durability. Recovery of segregation is a great challenge because of the complexity of segregation products and severe limitations from the stability of perovskite oxide. This work presents a novel approach for reversing the surface cation segregation by hydrogen-induced annealing which further shows the ability of healing defects and cracks in the oxide bulk. Ba0.3Sr0.7Fe0.9Mo0.1O3-δ (BSFM) four-channel hollow fiber membranes were prepared by one-step thermal processing. A low hydrogen concentration (5 vol %) and a mild temperature (900 °C) were used to anneal the as-prepared BSFM hollow fiber membrane and served to trigger outright reverse segregation of massive complex oxide precipitations at grain boundaries and a self-healing of cracks formed during the sintering stage. The reverse segregation significantly alters the composition and structure which directly affects the performance of BSFM membrane, such as mechanical strength, electrical conductivity, oxygen permeability, and stability. A maximum breaking load of 31.6 N is reached for the hydrogen-induced membrane which is approximately 6 times of the as-prepared BSFM membrane. Hydrogen-induced membranes, having high oxygen permeation flux and low activation energy, can operate stably in partial oxidation of methane catalytic membrane reactor for more than 120 h. Our results demonstrate the feasibility of hydrogen-induced reverse segregation and crack self-healing in the perovskite-type dense membrane, suggesting new directions to design the high-performance materials based on perovskite oxides for application in catalysis, electrocatalysis, and separations in the future.

Viscoelastic properties of the human A2 finger pulley.

Biomechanical evaluation of the viscoelastic properties tissue deformation, stiffness, and maximum breaking load of the human A2 pulley. We hypothesized that the A2 pulleys of index, middle, and ring fingers exhibit no difference regarding the aforementioned biomechanical parameters. Forty-one A2 pulleys of 14 upper extremities (8 body donors) were assessed. Cyclic and load-to-failure testing were performed. The biomechanical parameters tissue deformation during cyclic and load-to-failure testing, stiffness, and maximum breaking load were determined. No significant differences between the fingers could be detected regarding the biomechanical parameters. A significant negative correlation could be detected between stiffness and deformation of the pulley. Significant positive correlations could be identified between stiffness and maximum breaking load and between maximum breaking load and deformation of the pulleys. Assessment of the viscoelastic properties of the A2 finger pulley promotes precise diagnosis of pulley lesions and will help to optimize treatment.

Tensile strength of the pipe material determination according to the ultimate tensile strength

A new calculation method for the strength of concrete pipes, developed, helps to determine the stresses in the walls of concrete pipes under the combined action of an external (compressing pipe) load and internal pressure from the fluid transported under pressure. An analysis of the nature and magnitude of the stresses is necessary to choose the material of the pipe walls, as well as to establish a possible combination of ultimate external. New formulas make it possible to determine the stresses in the pipe walls under the combined action of an external load and internal pressure. Based on the developed formulas, it was found that the main dangerous stresses in the pipes are tensile stresses. Using the obtained equations allows to determine the range of application of pipes made of modified concrete and to select the necessary concrete strength based on operational loads. There are two methods for determining the bearing capacity of pipeline: three-edge bearing method, in which the maximum breaking load (ultimate), and hydro-static loading method to determine the maximum internal pressure. The design of the test bench for pipes was developed in order to determine the maximum internal pressure on the pipe walls.

Yarn degradation during weaving process and its effect on the mechanical behaviours of 3D warp interlock p-aramid fabric for industrial applications

Three dimensional (3D) warp interlock fabric becomes a promising structure due to its good mechanical performances. However, its complex manufacturing process can cause severe yarn damage and affects its overall final performances. The current study addressed the effects weaving process and warp yarn ratios on the multi-filaments yarn degradations and its mechanical performances while 3D warp interlock fabric manufacturing. Four different 3D warp interlock variants having similar fabric architecture, and yarn densities but different warp yarns interchange ratios were manufactured using 930dTex high-performance multi-filament (Twaron® f1000). The multi-filaments yarns at different weaving processes were tested for their tensile properties. The results show that the average tensile strength of twisted yarns show a decrement of 5.68% as compared to the bobbin yarns. Meanwhile, warping process also showed a 16.11% maximum breaking load reduction as compared to the bobbin yarn. Besides, the tensile strength of binding yarn after weaving process for samples 3D-8/0, 3D-8/4, and 3D-8/8 was reduced by 12.79%, 5.22%, and 14.22% respectively as compared to the yarn after warping process. In conclusion, yarn degradation inside the 3D woven structure was affected not only by the various process parameters but also by the type of fabric architecture made with different warp yarn ratios. These phenomena ultimately bring a great influence both on the yarn and overall mechanical performance of the final products. For this, further studies are planned to investigate the multi-filaments yarn degradation effect on the ballistic performances fibrous material as it is directly linked to the yarn performance.

МЕТОД РАСЧЕТА ПРОЧНОСТНЫХ ХАРАКТЕРИСТИК ПОЛИЭТИЛЕНОВЫХ ШНУРОВ

The method for calculating the strength characteristics of a polyethylene cord taking into account the design and based on the study of its destruction processes was described. The calculation method includes determin-ing the actual inner diameter of the braid, which allows identifying the effective layout of the cord braid and to determine the possibility of core and cord joint work, which ensures maximum breaking load of polyeth-ylene cords. To determine the diameter of the core formed by the threads the optimal ratios were used. The formulas for determining the ratio of the braid and core threads length were obtained, which allow to determine the utilization coefficient of braid threads included in the fracture process. The deviation of the results of calculated values due to the proposed method and experimental data do not exceed 3–5%. The proposed method can be used to calculate the strength characteristics of polyethylene cords, in which the joint work of the core and braid threads is structurally possible at break.

Fatigue life of thermoset composite materials

This article deals with the lifetime of laminated materials produced by different production technologies (hand lamination technology, vacuum bagging technology and prepreg technology with curing in the oven) during cyclic repeated bending stress. Like tested materials composite systems were chosen composite systems with epoxy matrix and carbon reinforcement (Kordcarbon CC200T, epoxy resin with trade name L285) and second composite epoxy system with glass reinforcement (Quadra-axial glass fabric, named Saertex Q-E-820, epoxy resin Biresin CR 82 and third prepreg systems (unidirectional prepreg, trade name Deltapreg VV430U-DT860W-39% and prepreg system with glass fabric VV320P_DT806R-37%). Fatigue tests were performed by cyclic bending loads during a three-point arrangement on a universal servo-hydraulic testing machine INSTRON 8871. Experimentally the number of cycles fracture of the material was determined at 90 % and 80 % of the maximum breaking load.

Tensile properties of synthetic, absorbable monofilament suture materials before and after incubation in phosphate-buffered saline.

To compare tensile properties of synthetic, absorbable, monofilament suture material before and after incubation in phosphate-buffered saline (PBS). Two sizes (2-0 and 3-0) of Biosyn, Maxon, Monocryl, PDS II, Securocryl, and Securodox were tested. Ten suture loops per group. Tensile strength, elongation, and modulus of suture loops were measured at baseline and after 7, 14, 21, or 28 days of incubation in PBS. Size, suture material, and size × suture material interaction influenced maximum breaking load, maximum elongation, and modulus of elasticity. At baseline, 2-0 and 3-0 Maxon had the highest breaking loads (111.67 N and 79.71 N, respectively) for their size, and 2-0 PDSII and 3-0 Securodox had the lowest (68.71 N and 48.73 N, respectively). Maxon 2-0 and 3-0 had the greatest elongations (9.68 mm and 8.45 mm, respectively) for their size, and 2-0 Biosyn and 3-0 Securocryl had the least (7.21 mm and 6.58 mm, respectively). Biosyn 2-0 and 3-0 had the highest modulus. With incubation, Maxon (2-0), PDS II (2-0, 3-0), and Securodox (2-0, 3-0) maintained or gained strength over 4 weeks. Strengths of 2-0 and 3-0 Biosyn and 3-0 Maxon were maintained for 2 weeks, while Monocryl and Securocryl lost 20% to 44% of baseline strength within 1 week and 60% to 72% within 2 weeks. Day 7 strengths of 2-0 Biosyn and 2-0 Monocryl were greater than baseline strength of 2-0 PDS II. Strength of 3-0 Biosyn at day 14 was greater than strength of Monocryl at days 7 and 14 and greater than strength of 3-0 PDS II, 3-0 Securodox, and 3-0 Securocryl at baseline and days 7 and 14. Suture tensile properties varied with suture size, composition, and brand. At baseline, Maxon suture had the greatest strength and elongation, and Biosyn had the greatest stiffness. Tensile strength retention, when reported as a percentage of original strength, provides insufficient information for comparison of suture tensile properties.

Improvement in Fatigue Behavior of Dental Implant Fixtures by Changing Internal Connection Design: An In Vitro Pilot Study.

(1) Background: The stability of the dental implant–abutment complex is necessary to minimize mechanical complications. The purpose of this study was to compare the behaviors of two internal connection type fixtures, manufactured by the same company, with different connection designs. (2) Methods: 15 implant–abutment complexes were prepared for each group of Osseospeed® TX (TX) and Osseospeed® EV (EV): 3 for single-load fracture tests and 12 for cyclic-loaded fatigue tests (nominal peak values as 80%, 60%, 50%, and 40% of the maximum breaking load) according to international standards (UNI EN ISO 14801:2013). They were assessed with micro-computed tomography (CT), and failure modes were analyzed by scanning electron microscope (SEM) images. (3) Results: The maximum breaking load [TX: 711 ± 36 N (95% CI; 670–752), EV: 791 ± 58 N (95% CI; 725–857)] and fatigue limit (TX: 285 N, EV: 316 N) were higher in EV than those in TX. There was no statistical difference in the fracture areas (P > 0.99). All specimens with 40% nominal peak value survived 5 × 106 cycles, while 50% specimens failed before 105 cycles. (4) Conclusions: EV has improved mechanical properties compared with TX. A loading regimen with a nominal peak value between 40% and 50% is ideal for future tests of implant cyclic loading.

Experimental study of platelet-rich plasma in treatment of Achilles tendinopathy in rabbits

To explore the effect of platelet-rich plasma (PRP) in treatment of Achilles tendinopathy in rabbits, and provide experimental evidence for the clinical application of PRP in treatment of Achilles tendinopathy. Forty-eight adult New Zealand white rabbits, weighing 2.5-3.0 kg, male or female, were randomly divided into model group (group A), model control group (group B), model+treatment control group (group C), model+treatment group (group D), with 12 in each group. The rabbits were injected with type Ⅰ collagenase to prepare Achilles tendinopathy models in groups A, C, and D, and with an equal dose of normal saline in group B. The blood from the central artery of rabbit ear was taken to preprare PRP by secondary centrifugation in group D. The results of platelet counts showed that PRP platelets reached 3 to 5 times the whole blood. After the model was prepared, the rabbits in groups C and D were injected with physiological saline and autologous PRP at the molding site respectively, once a week, 0.8 mL each time for 4 weeks. At 1 week after PRP injection, the relative hardness (expressed as HRD%) of Achilles tendon was evaluated by ultrasound elastic quantitative imaging detection technique; the maximum breaking load of Achilles tendon was measured by universal electronic tensile testing machine; the contents of collagen type Ⅰ and Ⅲ were determined by ELISA; and the morphology of Achilles tendon collagen fibers was observed by HE and Masson stainings. All animals survived during the experiment. The results of ultrasound elastic quantitative imaging and mechanical tests showed that the HRD% and the maximum breaking load were significantly lower in group A than in group B ( P<0.05) and in group C than in group D ( P<0.05). The results of ELISA showed that the content of collagen type Ⅰ was significantly lower in group A than in group B ( P<0.05) and in group C than in group D ( P<0.05); the content of collagen type Ⅲ was significantly higher in group A than in group B ( P<0.05) and in group D than in group C ( P<0.05). HE and Masson stainings showed that the Achilles tendon collagen fibers were irregularly curled and the structure was severely damaged in group A; the fibers were parallel and ordered, and the structure was complete in group B; the fibers were irregularly curled and structurally disordered in group C; the fibers were slightly curled and the structure was relatively complete in group D. A rabbit model of Achilles tendinopathy can be reconstructed by type Ⅰ collagenase injection. PRP treatment can increase the Achilles tendon hardness and maximum breaking load, up-regulate the expression level of collagen type Ⅰ and Ⅲ, improve the structure of Achilles tendon collagen fiber, and promote the repair in rabbit Achilles tendinopathy model.

Study on Breaking Load of Single Lap Joint Using Hybrid Joining Techniques for Alloy Steel AISI 4140 and Mild Steel: Taguchi and Neural Network Approach

Abstract The present investigation carried out to analyze the breaking load of single lap joint using hybrid joining techniques for alloy steel AISI 4140 and mild steel as base material by experimentally and optimized by Taguchi method and neural network. The six samples of lap joints were prepared namely: bolted joint (BJ); adhesive joint (AJ); welded joint (WJ); bolted-welded joint (BWJ); adhesive-welded joint (AWJ) and adhesivebolted joint (ABJ). The breaking load of the joints in terms of breaking load and elongation were evaluated for each joint. The effect of the adjustment attached to the joint on the breaking load and elongation were evaluated. Taguchi method was applied for given input parameters and L4 design of experiments was used. The breaking load and elongation were taken as output response. The predicted values by Taguchi method were used as target values in neural network fitting curve. Neural network fitting tool was used to check whether the obtained values were near the target value or not. Based on the achieved results, the maximum breaking load and elongation were found for bolted-welded joint.

Influence of relative humidity on the strength of hardwood and softwood pulp fibres and fibre to fibre joints

Cellulosic materials are highly sensitive towards environmental changes such as temperature and especially towards humidity. Besides morphological changes like swelling and/or shrinking, the mechanical properties of pulp fibres and fibre to fibre joints change as well. The current study sets to elucidate the changes and the extent to which elevated or decreased relative humidity (RH) influences the load bearing capacity of individual hardwood and softwood fibres and joints. The device used for the measurements is a micro bond tester with a custom-built humidity chamber in which the humidity can be controlled in a range from 25 to 95% RH. Individual fibres and joints have been tested at 30, 50 and 80% RH after equilibration time of 120 min. The breaking load of individual softwood fibres and joints displayed a maximum breaking load at 50% RH, with the values showing a decreasing trend towards higher or lower RH. In case of hardwoods, no change in the breaking load of either individual fibres or fibre to fibre joints has been observed at different RH.

Characterization of gypsum plasterboard with polyurethane foam waste reinforced with polypropylene fibers

Gypsum plasterboard that incorporates various combinations of polyurethane foam waste and polypropylene fibers in its matrix is studied. The prefabricated material was characterized in a series of standardized tests: bulk density, maximum breaking load under flexion stress, total water absorption, surface hardness, thermal properties, and reaction to fire performance. Polypropylene fibers were added to the polyurethane gypsum composites to improve the mechanical behavior of the plasterboard under loading. The results indicate that increased quantities of polymer waste led to significant reductions in the weight/surface ratio, the mechanical strength and the surface hardness of the gypsum, as well as improving its thermal resistance. The polypropylene fibers showed good adhesion to the polymer and the gypsum matrix, which enhanced the mechanical performance and the absorption capacity of these compounds. The non-combustibility test demonstrated the potential of the new material for use in internal linings.

Long-term Effects of Pre and Postnatal Food Restriction in Mechanical and Structural Properties of Rat Femur

Background: During early phases of life, epigenetic factors interfere with normal growth of the individual and induce morphological and functional alterations. The aim of this study was to analyze the effects of pre and postnatal food restriction in rats, on the microstructure and mechanical properties of the rat femur bone. Methods: Food restricted male rats were from pregnant mothers maintained under daily-restricted diet pre and postnatal periods. After waning, the rats were maintained with access to milk only for 12 h until weaning. The control rats were from normal pregnant mothers feeding with free access to food and water during experimental period. Animals were sacrificed at 6 and 9 weeks of age; with femur bone submitted to 3 point bending mechanical test like indicators of biomechanical properties. After that the samples were morphometrically evaluated at electronic microscope. Results: The restricted diet group showed reductions in the body weight, width and thickness of femur bone. Statistical analysis demonstrated significant (P<0.05) changes in the evaluated parameters, showing different values for the Young modulus, ultimate load at fracture, failure (maximum breaking load), percentage of maximum deformation displacement showed decrement compared with the control rats. The data of structural measure showed that microstructure arrangement was damaged by food scarcity. Findings showed that food restriction contributed to detrimental bone structure, particularly modifying the collagen bundle and consequently inducing bone fragility in adulthood, demonstrated by the flexural diminished values. Conclusion: Nutritional conditions are determinants for the bone structure establishment, with effects persisting for a long-term period, remaining until adult life. Keywords: Bone rat, breaking resistance, development, collagen fibers, food scarcity.

THE STRENGTH OF BONE-METAL BLOCK FOR DIFFERENT TYPES OF IMPLANTS SURFACES UNDER THE CONDITIONS OF NORMAL BONE AND OSTEOPOROSIS IN RATS

Fixing the acetabular component of prosthesis in the conditions of osteoporosis and changes in acetabulum anatomy is an actual problem of modern orthopedics. The goal: to perform a comparative analysis of the strength of bone-metal block for the different type of implant surfaces in the conditions ofnormal bone and in the simulation of osteoporosis in rats. The methods: experimental studies of femur strength were carried in 60 laboratory animals (rats). The animals were divided into two groups of 30 animals each: I — relatively healthy, II — osteoporosis induced by ovariectomy. 6 subgroups were formed in each group of animals. Implants of such differentmaterials as porous titanium, tantalum porous Trabecular Metal (Zimmer), titanium coated with Gription (DePuy), Stiktite (Smith & Nephew), Trabecular Titanium (Lima), Tritanum (Stryker) were used to fill a hole-like defect in distal metaphysis of femur. The animals were taken out of experiment 14 days after implanta­tion and biomechanical investigation was performed to assess the strength of operated and contralateral femurs. Longitudinal axial load using a metal rod was applied to femoral head. Load value gradually increased to complete destruction of anatomical specimen and measured. The results: femurs with implants from porous tantalum Trabecular Metal and Stiktitewith stood the maximum load in the conditions of normal bone density. Specimen of femurs with implanted porous titanium (the most weak) and tantalum Trabecular Metal (the most solid) composed separate subsets in the conditions of simulated osteoporosis. The conclusions: the comparative analysis of biomechanical investigation revealed that bone with implants from porous tantalum withstands the maximum breaking load in the conditions of normal and osteoporotic bone.

A study of fracture toughness of heavy-weight concrete and foam concrete reinforced by polypropylene fibre for road construction

The study explores fracture toughness of heavy-weight concrete and foam concrete solidified by an autoclave-free method and reinforced vs. non-reinforced with polypropylene fibres. The research was conducted by the criteria of fracture mechanics to determine strength and deformation characteristics as well as power and energy features of fracture toughness of the considered concretes. It has been discovered that addition of polypropylene fibreto the composition of heavy-weight concrete and foam concrete mainly affects the supercritical phase of deterioration: the fibre inhibited fracture of the samples once there had appeared a backbone crack (from the moment when the maximum breaking load had already been applied) until its complete defragmentation. The indicator characterizing this effect—the specific energy load used for static destruction, G F —was higher in all series of dispersed concrete reinforcement, which was quite different in the case of non-reinforced concrete and foam concrete. It proved to be the most effective additive in heavy-weight concrete and porous concrete with a density of 700 kg/m 3 (respectively, the indices were 1.5 and 1.8 times higher than in the case of non-reinforced concrete). Besides, adding polypropylene fibre increases, by 22% on average,the tensile strength of concrete while bending it. Hence, formation and development of cracks are inhibited by polypropylene fibres, which can be observed in an increase of all indicators of strength and deformability of the studied concretes as well as of power and energy features of fracture toughness.