Laboratory Testing Program Research Articles

Bulk adhesion of ice to concrete–strength

This paper presents the results of a laboratory test program designed to investigate the adhesive effects of large-scale (bulk) ice on concrete. Medium-strength concrete cylinders were sawn into discs, and attached to a sample table. Freshwater ice samples, frozen using smaller, standard-sized concrete cylinders, were adhered to the concrete with both varying bond times and added weight during bonding. Shear strength tests were conducted at a set displacement rate, under a number of temperatures. The effect of these variables on the adhesive strength of ice to concrete was examined, as well as whether there was any noticeable removal of concrete cement paste or aggregate during testing. The tests indicate that the adhesive strength is negligible when the method of adhesion is “dry” (no liquid layer at the onset of adhesion). Tests with “wet” adhesion indicated a significantly higher strength. The nominal versus the apparent contact area had significant implications for the determination of the adhesive strength of the bond between the ice and the concrete. Removal of cement paste was evident in a number of tests, however the amount was not significant. The results have relevance for design of structures in a marine environment, such as revetement dams or rubblemound breakwaters, as well as for the standardization of adhesion tests with ice and concrete.

Prediction of resilient modulus with pre-post experimental data of undisturbed subgrade soils using machine learning algorithms

The resilient modulus (MR) of subgrade, which shows relationship between stress and unit deformation of a pavement systems under traffic loads, is a design parameter of the pavement structure. Although a cyclic triaxial test apparatus can be used to directly determine the MR of the subgrade in the laboratory, utilizing prediction models based on easily obtainable soil parameters, is a more efficient method when taking time and cost considerations into account. A comprehensive laboratory testing program is designed to create MR prediction models using machine learning (ML) algorithms. 70 undisturbed soil samples are subjected to MR tests, as well as physical and engineering soil properties tests (water content, field density, specific gravity, gradation, consistency limits, unconfined compressive strength, swell pressure, swell percentage). Soil samples are drilled from a highway that has been in operation for over five years.First, a linear model like MLR is used in the study. Next, nonlinear regression models like RF, GBM, LightGBM, CatBoost, and XGBoost algorithms are used. Research findings showed that nonlinear regression models outperformed linear regression models in predicting the MR (R2 > 0.85), with the XGBoost algorithm yielding the best accuracy (R2 = 0.90). Apart from the primary effects such as confining pressure (σ3) and deviatoric stress (σd), it was found that unconfined compressive strength (qu), natural water content (wn), and swelling percentage (SR) are significant parameters in the prediction of MR among all parameters.

Evaluation of the energy saving potential in electric motors applying a load-based voltage control method

This paper studies the viability of energy savings in electric motors by adjusting the voltage according to load in motors that operate under significant load variations during their work cycles. The laboratory test program used a 1.1 kW electric motor to compare its measured efficiency operating without voltage control with the load-based voltage control method results. A neural network was developed, and a time series generator was used to model the motor and estimate the results of applying the method in its useful life in the load behavior of three operating regimes. The results show an energy saving potential of 2 %–5.2 % using the load-based voltage control method in motors operating with a load factor of less than 40 % during the simulated motor life cycle for the three operating regimes. Also, the economic feasibility of implementing the load-based voltage control method was evaluated on three industrial electric motors. Results indicated potential annual savings between $1227 and USD 1,549, with a projected investment payback period of less than three and a half years.

Improving the performance of CFRP-reinforced concrete cylinders in sulfate-laden environment through nanoclay modification of epoxy resin

The durability of epoxy-concrete interface is a crucial factor for practical application of externally bonded fiber-reinforced polymer (FRP) retrofit systems, particularly when the strengthened structure is subjected to severe environmental conditions. Given the demonstrated potential of nanoclays in enhancing engineering performance of polymers, this work assesses the beneficial effect of organic montmorillonite (OMMT) nano-modification of epoxy resin on the axial compressive properties of FRP-reinforced concrete under a 10 wt% sodium sulfate wet/dry (W/D) cycling environment. Three types of concrete samples were fabricated and tested: plain concrete cylinders, CFRP-reinforced concrete cylinders using unmodified vs. OMMT-modified epoxy resin as the adhesive, respectively. The optimal dosage of OMMT was determined to be 2 wt% through tensile and lap shear tests, as well as microscopic characterization of the fractured cross-section of the molded resin samples. This optimal dosage of OMMT allows the epoxy adhesive to achieve the highest values in the tensile strength (90.4 MPa), lap shear strength (80.0 MPa), Tg (280.5°C) and water contact angle (115.1°). In the fracture section of epoxy resin with a 2 wt% OMMT, multiple microcracks developed and the OMMT nanoplatelets were well dispersed in the epoxy matrix. The laboratory testing program explored various W/D cycle periods. The experimental results indicate that the OMMT-modified epoxy resin significantly improved the mechanical properties and deformation resistance, altered the failure mode, and effectively delayed the strength degradation of the protected concrete. After 150 W/D cycling days, the OMMT-modified CFRP-confined concrete samples maintained their ductility coefficient and axial compressive strength at 3.58 and 123.5 MPa, respectively, 12.6 % and 9.1 % better than the common CFRP-confined samples. Combining these results with the residual axial compressive strength ratio, we propose an improved design model for calculating the axial compressive strength of CFRP-retrofitted concrete structures in sulfate-laden environments. This study demonstrates the beneficial role of OMMT in enhancing the epoxy adhesive and provides insights into the reinforcement of concrete structures by externally bonded CFRP in sulfate-rich environments.

A Comparison of Ukrainian Hospital Services and Functions Before and During the Russia-Ukraine War

Since the full-scale Russian invasion, hospitals in Ukraine have been compelled to close or operate at reduced capacity due to inadequate supplies, damage, or destruction caused by war. To analyze hospital services in Ukraine during the period before and after the Russian invasion. Of the 450 hospitals currently functioning in Ukraine, a cross-sectional survey was carried out with the participation of 74 hospitals from 12 oblasts. Hospital administrators responded to an online survey with questions on the use of hospital services. Data were abstracted from hospital databases for the prewar period (before February 23, 2022) and during the war (February 23, 2022, to May 30, 2023). Hospital services (including emergency services, preventive services, screenings, laboratory tests, obstetrics, telehealth, pharmacy, and rehabilitation services) were compared during the prewar and war periods. Of 450 Ukrainian hospitals in operation, 74 hospitals (16.0%) across 12 oblasts provided data for the current analyses. During the war, daily emergency admissions increased to 2830, compared with 2773 before the war. At the same time, hospitals reported reduced laboratory testing (72 [97%] vs 63 [85%]), tobacco education (52 [70%] vs 36 [49%]), cancer screening (49 [66%] vs 37 [50%]), gynecological services (43 [58%] vs 32 [43%]), rehabilitation services (37 [50%] vs 27 [36%]), pharmacy services (36 [49%] vs 27 [36%]), and telehealth programs (33 [45%] vs 21 [28%]). Hospitals reported additional difficulties during the war, including disruptions in the supply chain for essential equipment and pharmaceuticals, shortages of laboratory test kits, delays in the delivery of crucial medications, and problems around appropriate medication storage due to power outages. The ongoing war has inflicted profound devastation on Ukraine's hospitals. The findings of this cross-sectional survey offer valuable insights into the formidable challenges that hospitals confront in war-affected regions and underscore the pressing necessity for bolstering support to sustain and enhance hospital services during wartime.

Predictive abilities of constitutive models for clay under monotonic and cyclic loading: element tests and centrifuge experiments

A critical investigation of three constitutive models for clay by means of analyses of a sophisticated laboratory testing program and of centrifuge tests on monopiles in clay subjected to (cyclic) lateral loading is presented. Constitutive models of varying complexity, namely the basic Modified Cam Clay model, the hypoplastic model with Intergranular Strain (known as Clay hypoplasticity model) and the more recently proposed anisotropic visco-ISA model, are considered. From the simulations of the centrifuge tests with monotonic loading it is concluded that all three constitutive models give satisfactory results if a proper calibration of constitutive model parameters and proper initialisation of state variables is ensured. In the case of cyclic loading, the AVISA model is found to perform superior to the hypoplastic model with Intergranular Strain.

Ground Tire Rubber as a Sustainable Additive: Transforming Desert Sand Behavior

Managing waste tires presents a significant challenge globally, particularly in regions experiencing high temperatures and shortage of landfill sites. This issue is affecting countries like Kuwait, where the abundance of waste tires is a major source of environmental and safety risks, particularly during the intensely hot summer months. This extreme heat has sparked numerous fires, leading to substantial air pollution due to thick black smoke. Given the limited disposal options, recycling waste tires and finding practical applications for ground tire rubber (GTR) is essential. To address the challenge, a comprehensive laboratory testing program was conducted, using locally produced rubber aggregates as an additive to Kuwait's local surface sands. Two new variables were examined namely the size and gradation of the GTR, and the density of the compacted mixes. For this purpose, two different sizes of rubber aggregates, fine and coarse produced locally, were utilized, and the impact of relative compaction on the strength and compressibility of the mixtures was investigated by testing samples compacted to the maximum density and to 95% of the maximum density. The results suggest that combining local surface sands with rubber tire additives results in a lighter, more permeable, and compressible material, contributing significantly to sustainable waste management. With 20% rubber additive the maximum dry density decreased by nearly 20%, and the permeability increased by 1.74–3.11 times and the compression index increased by 6.15 and 3.8 times with fine and coarse rubber respectively. The angle of friction remained unchanged at 36° with the addition of coarse rubber and decreased by 3°–4° with fine rubber. The change in behavior although not an increase in the strength and stiffness, offers a range of suitable practical applications in civil engineering and environmental management, including use as a drainage layer, embankment construction on soft ground, earth fill around retaining walls, an additive in asphalt mixes, and in manufacturing compressible tiles for sports facilities.

Experimental determination of hypoplastic parameters and cyclic numerical analysis for railway bridge backfills

AbstractLong integral bridges experience an enhanced cyclic soil structure interaction with their granular backfills, especially due to seasonal thermal loading. For numerical modelling of this interaction behaviour under cyclic loading, it is important to employ a suitable constitutive model and calibrate it thoroughly. However, up to the present, experimental data and calibrated soil models for this purpose with focus on typical well-graded coarse-grained bridge backfill materials are rarely available in the literature. Therefore, one aim of this paper is to present results of a comprehensive cyclic laboratory testing programme on highly compacted gravel backfill material. Based on this, a hypoplastic constitutive model with intergranular strain extension for small strain and cyclic behaviour is calibrated and evaluated against the experimental test data. The soil model’s abilities and limitations are discussed at element test level. In addition, cyclic FE analyses of an integral bridge are conducted with several hypoplastic parameter sets from the literature and compared to the calibrated gravel backfill material. The investigation highlights that poorly-graded sands show significantly smaller cyclic earth pressures compared to well-graded gravels intended for the backfilling of a bridge. The soil structure interaction behaviour is clearly governed by the general soil model stiffness, including the small strain stiffness.

Life cycle assessment and pavement performance of recycled aggregates in road construction

Integrating environmental goals in the construction of infrastructure has attracted great attention over the past two decades. The use of construction and demolished waste materials (C&D) as a base layer for pavement structures gained popularity as a sustainable alternative to virgin aggregates (VA). An experimental testing program was designed to investigate several recycled materials as a potential replacement to VA in flexible pavements base layer. The testing program included routine tests, matric suction, static, and repeated load triaxial tests to measure the general engineering properties and evaluate the material performance under static and cyclic loading. The results of the laboratory testing program were employed to predict the pavement performance utilizing different combinations of C&D waste as a base layer for flexible pavement structures using the AASHTOWare Pavement ME Design at different climate conditions. The sustainability of using C&D material as a partial or full replacement of VA base material in pavement construction was evaluated by using the life cycle assessment (LCA) approach. The results showed that all the C&D materials yielded a much thinner base layer compared to the natural VA achieving the same pavement performance. Moreover, the reduction in the thickness is more significant in cold and wet climatic conditions rather than the hot and dry climatic conditions. LCA results revealed that the VA base layer had the highest environmental impact on all tested categories. VA materials, used as a base layer, show 65% higher global warming potential compared to C&D materials as a base layer in all climatic conditions.

Soil liquefaction sites following the February 6, 2023, Kahramanmaraş-Türkiye earthquake sequence

AbstractSeismically induced soil liquefaction was listed as one of the major causes of damage observed in the natural and built environment during the 2023 Türkiye-Kahramanmaraş earthquake sequence. Reconnaissance field investigations were performed to collect perishable data and document the extent of damage immediately after the events. The sites with surface manifestations of seismic soil liquefaction in the form of soil ejecta, excessive foundation and ground deformations were identified and documented. The deformations were mapped, and samples from ejecta were retrieved. The ejecta samples were predominantly classified as sands with varying degrees of fines. Laboratory test results performed on liquefied soil ejecta revealed that the fines-containing liquefied ejecta samples are mostly classified as low plasticity clays (CL). Most of CL soil type ejecta were retrieved from Gölbaşı–Adıyaman region. The liquid limits of these samples varied in between 32 and 38%, their plasticity index values were estimated in the range of 16–23%. Surprisingly, two ejecta samples with plasticity indices higher than 30% were retrieved from Hatay airport, one of which was classified as high plasticity clay (CH). The majority of the fine-grained ejecta samples fall either on “Zone B: Testing Recommended” region of the Seed et al. (Keynote presentation, 26th Annual ASCE Los Angeles Geotechnical Spring Seminar, Long Beach, CA, 2003) susceptibility chart. Moreover, 12 out of 74 samples fall outside the susceptible limits defined by Seed et. These preliminary results suggest that clayey soils can produce liquefied ejecta when subjected to cyclic loading. Detailed site investigation and laboratory testing programs are ongoing to further investigate this rather unexpected response. Until their findings become available, the liquefaction susceptibility of silty-clayey soils’ mixtures is recommended to be assessed conservatively with caution.

Small Strain Shear Modulus of the Ljubljana Marsh Soil Measured with Resonant Column and Bender Elements under Isotropic and Anisotropic Stress Conditions

The increasing use of finite element analysis in modern infrastructure design emphasizes the importance of determining soil stiffness at small strains. This is usually represented by the normalized shear modulus degradation curve, which is crucial for accurate design. In the absence of specific measurements on the local soil, engineers often rely on empirical correlations and assume comparable behavior of soils with similar intrinsic properties. However, the application of this approach leads to uncertainties, especially for unique geological formations such as the soft cohesive soils of the Ljubljana Marsh. The main objective of this study was to determine the small strain shear modulus of Ljubljana Marsh soil with a plasticity index between 11 and 35%. Isotropic and anisotropic stress conditions were investigated as part of an extensive laboratory test program that included 45 bender element and 89 resonant column tests on 20 soil samples. By emphasizing the importance of measuring soil stiffness at small strains, this study not only provides reliable data for the development of the built environment in the Ljubljana Marsh and similar areas, but also underlines its necessity.

A Sustainable Option to Reuse Scaly Clays as Geomaterial for Earthworks

Scaly clays are structurally complex clay formations found throughout the world. Their typical fissured structure, the low shear strength and the high swelling potential often make them unsuitable for earthworks in road and railway infrastructure. This research has attempted to extend the possibilities of using this geomaterial in this field after appropriate lime treatment. A laboratory test programme was carried out to evaluate the response of the treated geomaterial to typical loads acting on road infrastructures. Unconfined and confined compression tests as well as cyclic triaxial tests, in undrained conditions, were carried out to investigate the static and dynamic mechanical behaviour. The results show that lime treatment induces significant improvements in the geomechanical properties and limits the swelling behaviour upon saturation of the geomaterial. Dynamic tests showed that, after only 28 days of curing, the treated scaly clay became insensitive to the damaging cyclic loading caused by vehicular traffic. The collected results show that the scaly clay can be properly used as a subgrade and embankment layer in road and railway construction with limited economic and environmental costs, after accurate treatment with lime. These results are significant for researchers and practitioners to increase sustainability in the construction of linear infrastructures involving excavations in scaly clays and to avoid landfill, which in some cases represented the only option.

Determination of hypoplastic parameters for a typical gravel backfill material of railway bridges

Laboratory test programs on gravel are rare due to the maximum grain size of the material. In this paper an experimental program with triaxial tests under cyclic loading and oedometric tests on highly compacted gravel specimens, representative for bridge backfills materials, is summarized. It is used to calibrate a hypoplastic constitutive model, which includes an extension for intergranular strain to account for the cyclic loading behaviour. So far calibrated parameter sets of this soil model are scarce in literature, especially for coarse grained materials. The calibrated parameter set can be used in numerical studies, e. g. on the cyclic soil structure interaction of integral railway bridges.

Effect of stud dimension and material properties on predicted and tested sound insulation

A common wall design is gypsum wall board (GWB) cladding on each side of a row of steel studs, which may or may not include insulation. Steel studs are available in a range of metal thicknesses, dimensions, and structural properties. Most published laboratory testing on these walls uses a small subset of the available stud types, and the acoustical effect of changes to stud parameters has not been completely studied or documented. As a result, theoretical models of stud walls have not been evaluated over the full set of stud parameters. This work is a continuation of previous laboratory testing programs to systematically investigate the acoustical effects of stud properties. This paper analyzes the effects of stud depth and structural properties on third-octave transmission loss values and single-number ratings and investigates the capability of existing models for wall transmission loss to predict performance of walls with an expanded set of stud parameters. Our findings indicate that the parameters currently used to describe stud walls in acoustical test report are not sufficient to characterize the assembly.

Effect of using Oil Shale Ash on geotechnical properties of cement-stabilized expansive soil for pavement applications

Expansive soil is considered an engineering problem that may cause cracks and distresses in structures and roads. Due to its swelling potential and low unconfined strength, expansive soil causes failures in structures and leads to financial losses. Oil Shale Ash “OSA” is the byproduct of the combustion of the oil shale rock to produce electricity. Instead of dumping OSA materials into landfills, which has several negative environmental implications and cost burdens, utilizing these materials as building materials might alleviate the environmental concerns caused by their disposal. This research investigates the possibility of experimentally using the by-products Oil Shale Ash (OSA) and Portland Cement (PC) to enhance the geotechnical properties of problematic expansive soil. OSA and cement have been added to the soil, where OSA is used in four percentages by dry weight of soil (10%, 20%, 25%, 30%), and cement is used in three percentages (2%, 4%, 6%). A laboratory test program was implemented, including Atterberg limits, compaction test, unconfined compressive strength test (UCS), swell test, linear shrinkage test, and California Bearing Ratio (CBR) test. The results showed that OSA and cement have reduced the expansive natural soil's swelling potential, plasticity index, and linear shrinkage. Also, the UCS and CBR values of treated soil have improved significantly. Pavement analyses demonstrated that OSA-cement-stabilized soil could be a suitable stabilization agent for the subgrade and base layers in constructing pavements.

The Mechanical Characterization of Pyroclastic Deposits for Landslide Early Warning Systems

Broad mountainous areas in the western Campania (southern Italy), where young pyroclastic deposits extensively outcrop, frequently experience rainfall-induced slope movements of different degrees of mobility, causing heavy damage and fatalities. Such landslides cannot be easily mitigated, and the implementation of physically based early warning systems is still not able to predict the post-failure evolution of slope movements and the exposed areas at risk. This paper is devoted to overcoming this limit. To this end, the mechanical characterization of pyroclastic soil, carried out through an extensive laboratory testing program, is presented and compared with those of two other ashy soils of different depositional mechanisms. The results show that the depositional mode influences soil properties; to begin with, it affects the unsaturated shear strength, whose intercept of cohesion is up to 5 kPa higher in ashes of flow deposition than in airfall ash deposits. The saturated undrained soil response allowed for the identification of different levels of susceptibility to the liquefaction of pyroclastic deposits, which is one of the main factors governing the post-failure evolution of landslides. Gathering all the acquired information, including saturated and unsaturated soil shear strength, permeability function, and water retention curves, into a soil database, it was possible to present all data under a unitary framework. Finally, the implementation of the proposed flowchart for a simplified assessment of post-failure evolution to be employed in regional early warning systems can enhance our knowledge of the areas at risk.

Determination of the stress-strain demand curve of the sprayed waterproofing membrane interface in composite SCL tunnels

Understanding the evolution of the stress-strain states of the sprayed waterproofing membrane within composite sprayed concrete lined (SCL) tunnels from the short-term dry condition to the long-term wet condition is critical to ensure the integrity of the composite SCL tunnels. This paper presents a conceptual framework describing the evolution of the states and demonstrates a methodology that enables the designer to determine the states using a demand curve that bounds all possible stress-strain states of the membrane interface.It firstly presents a conceptual framework for the evolution of the state stress and strain of the membrane interface in typical composite SCL tunnels from short to long term and from ‘dry’ to ‘wet’ membrane saturation. A numerical method to simulate this evolution is presented. A numerical analysis of a full composite SCL tunnel in typical over-consolidated ground was carried out for the range of possible locations of groundwater pressure application in the lining, and the results used to demonstrate the process of obtaining a set of stress-strain demand curves for the tunnel.The research shows that the membrane interface in a composite SCL tunnel is in a state of combined normal and shear stress and strain but that these stresses and strains remain finite and do not become unbounded, due to the statically indeterminate nature of the structure. It is however an interaction problem so that the normal and shear stress and strain need to be checked together. Some insights are given as to the nature of a laboratory testing programme that could be carried out on the membrane interface to obtain capacity envelopes to compare with the demand curves for design.

Geometric imperfection measurement on welded hybrid steel box‐section girders

AbstractHigh‐strength steel materials (steel grades of S500 ‐ S960) gaining prominence in civil engineering, especially for large‐span bridges. In the case of bridges, the application of hybrid girders combining low‐ and high‐strength steel materials is an effective and economical solution. The hybrid girders generally consist of webs comprised of low‐strength steel and flanges made of high‐strength steel. In Europe, apart from some minor practical applications and research results in Sweden, these structure types are completely new solutions in bridges, and the theoretical background of their stability design is missing from the current European standardized design provisions. To determine the theoretical background of this girder type and to develop the design theories for application purposes it is essential to execute experimental laboratory test programs. Analyzing the local buckling and plastic behavior of hybrid steel plate girders through experiments is essential to have an approopriate knowledge on the geometrical and structural imperfections of the hybrid girders. Therefore, in the present paper the measurement of geometric imperfection on 14 welded hybrid steel box‐section girders with varying geometry is presented and their results are evaluated and discussed. The flanges of the examined hybrid girders are made of S700 or S500, the web of the specimens consists of S355 steel grade. The measured imperfection values are evaluated based on the steel grade and geometric parameters such as plate width or thickness. Using the measured imperfection, a numerical model will be developed to predict the bending and shear resistance of the specimens.

Characterization and environmental sustainability of open pit coal mine overburden waste rock as pavement geomaterial

As the global economy grows and living standards increase, the use of gravel and sand is expected to nearly quadruple by 2060, putting twice as much strain on the environment as it does now. Local solutions to the global problem are always more sustainable and resilient. In recent times, coal mine overburden (OB) is an unprocessed, highly heterogenous waste of coal mining industries. However, it has proved to be a sound potential alterative of natural aggregate. The associated engineering properties are very site specific and are highly influenced by geology and exposed climate. A comprehensive laboratory testing program oriented at determining the geotechnical and geoenvironmental properties is implemented to investigate the suitability of the OB as pavement material. The load-deformation performance as pavement material is evaluated using 3D finite element modelling and environmental sustainability is assessed through streamlined Life cycle assessment (LCA). This inert geomaterial is acceptable as a pavement material for base and subbase layers with impact value of 28 %, and abrasion value 34 %. The California bearing ratio (CBR) of 76 at unsoaked and 61 at soaked conditions also affirm its choice as an excellent subgrade material. The critical state parameters of the fine aggregate defined the long-term serviceability as a subgrade material. The load-deformation behavior of overburden was found to be similar to the natural aggregate as a pavement material with comparable maximum deflection of 1.20 mm for OB and 1.25 mm for natural aggregate. The LCA revealed that OB are more environmentally sustainable than natural aggregates as base and subbase material. The study highlights the importance of proper characterization and testing of OB to ensure its safe and effective use in construction applications, providing robust local solutions to global problems.

FLEXURAL STRENGTH OF KEVLAR EPOXY COMPOSITES ON DIFFERENT FIBER ORIENTATIONS

Nowadays, polymer fiber composites are very popular due to its weight-strength ratio in various industries. There are different types of natural and artificial fibers used for different purposes, according to the strength requirements. Uni-directional and bi-directional woven fabrics are very common for commercial purposes. Here this paper is focused on the behavior of different orientations of bi-directional woven reinforced composites to improve the efficiency of the ability of composites to resist bending deflection when energy is applied to the structure, it determines the resistance to flexing or stiffness of a material. In the present research, the theoretical and practical method was used to calculate the flexural strength of composite material consisting of epoxy resin LY 556 (50%) with different fiber orientations of woven Kevlar fibers. Ansys 2020R version was used to study the effect on different shapes of Kevlar-epoxy composite material. The standard ASTM D790 was used for the laboratory test and Ansys program. the result analysis focused on the stress-strain variation with the orientation and shapes