Quasi-static Tension Research Articles

Microstructural image based convolutional neural networks for efficient prediction of full-field stress maps in short fiber polymer composites

The increased demand for superior materials has highlighted the need of investigating the mechanical properties of composites to achieve enhanced constitutive relationships. Fiber-reinforced polymer composites have emerged as an integral part of materials development with tailored mechanical properties. However, the complexity and heterogeneity of such composites make it considerably more challenging to have precise quantification of properties and attain an optimal design of structures through experimental and computational approaches. In order to avoid the complex, cumbersome, and labor-intensive experimental and numerical modeling approaches, a machine learning (ML) model is proposed here such that it takes the microstructural image as input with a different range of Young's modulus of carbon fibers and neat epoxy, and obtains output as visualization of the stress component S11 (principal stress in the x-direction). For obtaining the training data of the ML model, a short carbon fiber-filled specimen under quasi-static tension is modeled based on 2D Representative Area Element (RAE) using finite element analysis. The composite is inclusive of short carbon fibers with an aspect ratio of 7.5 that are infilled in the epoxy systems at various random orientations and positions generated using the Simple Sequential Inhibition (SSI) process. The study reveals that the pix2pix deep learning Convolutional Neural Network (CNN) model is robust enough to predict the stress fields in the composite for a given arrangement of short fibers filled in epoxy over the specified range of Young's modulus with high accuracy. The CNN model achieves a correlation score of about 0.999 and L2 norm of less than 0.005 for a majority of the samples in the design spectrum, indicating excellent prediction capability. In this paper, we have focused on the stage-wise chronological development of the CNN model with optimized performance for predicting the full-field stress maps of the fiber-reinforced composite specimens. The development of such a robust and efficient algorithm would significantly reduce the amount of time and cost required to study and design new composite materials through the elimination of numerical inputs by direct microstructural images.

Hierarchical multiscale crystal plasticity framework for plasticity and strain hardening of multi-principal element alloys

The multi-principal element alloys (MPEAs) exhibit the unprecedented combinations of the excellent mechanical properties, especially high strength and good ductility. However, the accurate and reasonable models for describing the mechanical behavior of MPEAs are still scarce due to their distinctive serious lattice distortion effects, which limit the performance prediction. Here, we develop a new general framework by combining the atomic simulation, discrete dislocation dynamics, and crystal plasticity finite element method, to study the strain-hardening behavior for MPEAs, which achieves the influence of the complex cross-scale factors, including the lattice distortion at the nanoscale and the dislocation hardening at the microscale, on the plastic deformation. Compared with the classic crystal plasticity finite element, the bottom-up hierarchical multiscale model could couple the underlying physical mechanisms from the nano-micron-meso scales and captures the inhomogeneous strain field induced by the serious lattice distortion, thus showing the high accuracy and ubiquitous availability for MPEAs. The result shows that the prediction of the strain-stress curve in the polycrystal MPEAs agrees well with the experimental result at the quasi-static tension, which verifies the accuracy of the proposed method. In addition to the dislocation evolution, the heterogeneous strain distribution combined with the significant change from the orientation of some grains could be an important reason for the enhanced strength at the micron scale. The present work not only gives an insight into the relationship between the multiscale microstructure and strain hardening considering the mechanistic linkages of the lattice distortion, dislocation behavior, and grain structure, but also provides a general approach to physically predict the mesoscopic mechanical response in MPEAs.

A 3D metamaterial with negative stiffness for six-directional energy absorption and cushioning

To attenuate the impact acceleration under multidirectional loads, a mechanical metamaterial with six-directional cushioning and energy-absorbing properties is urgently needed. The study proposes a 3D negative stiffness (NS) metamaterial (NS-MM), which exhibits a bidirectional NS effect and cushion capacity under compressive and tensile loading in three principal directions. The unit cell of NS-MMs contains three pairs of parallel cross-curved beams mounted in a cubical frame, and the NS effect is obtained by controlled elastic buckling of the cross-curved beams. The mechanical analysis of one unit cell is conducted toward predicting the static response. The static performance of the NS-MMs composed of 1×1×1 and 2×2×2 unit cells in three principal directions is investigated by numerical calculations and experiments with quasi-static tension–compression conditions. Comprehensive results indicate the proposed structure has the characteristics of shape recovery, bidirectional NS property, and good energy absorption under tension and compressive loads in one principal direction and has the same mechanical properties in three principal directions. Transient dynamic analysis is exploited to investigate the cushioning performance. The obtained response acceleration (RA) is effectively attenuated in both directions and limited to a certain threshold.

Mechanical Properties, Constitutive Behaviors and Failure Criteria of Al-PTFE-W Reactive Materials with Broad Density.

Quasi-static tension tests, quasi-static compression tests and dynamic compression tests were conducted to investigate the mechanical properties, constitutive behaviors and failure criteria of aluminum-polytetrafluoroethylene-tungsten (Al-PTFE-W) reactive materials with W content from 20% to 80%. The analysis of the quasi-static test results indicated that the strength of the materials may be independent of the stress state and W content. However, the compression plasticity of the materials is significantly superior to its tension plasticity. W content has no obvious influence on the compression plasticity, while tension plasticity is extremely sensitive to W content. Dynamic compression test results demonstrated the strain rate strengthening effect and the thermal softening effect of the materials, yet the dynamic compression strengths and the strain rate sensitivities of the materials with different W content show no obvious difference. Based on the experimental results and numerical iteration, the Johnson–Cook constitutive (A, B, n, C and m) and failure parameters (D1~D5) were well determined. The research results will be useful for the numerical studies, design and application of reactive materials.

Tensile-Mechanical Degradation-Properties and J-C Constitutive Model of Studs after Strong-Acid Corrosion

This paper presents an investigation on strong-acid relations between corrosion rate and corrosion time in 30 studs, dipped into 36% industrial hydrochloric acid through 0.5 h, 1 h, 2 h, 4 h, 8 h, 12 h, 24 h, 48 h, and 72 h, respectively. These corroded studs are performed tensile tests to study failure mode and stress-strain curves in studs with different corrosion time. Thereafter, a 3-D finite element is established through computer program to validate test results, and then analyze mechanical properties along with failure mode of studs exposed to strong-acid corrosion. The analysis results show that the failure mode gradually changes from ductile-damage state to brittle-damage state. The corrosion rates present a non-linear elevation with an increase of strong-acid-corrosion time. The nominal yield strength, the nominal ultimate strength, and the elongation in the corroded studs exhibit a fast-downward trend when increasing corrosion time. However, the degradation of elastic modulus turn into a slow step and the yield strength ratio in studs tends to be steady. The J-C model (Johnson-Cook Constitutive) with updated coefficients can be applied to reflect the constitutive relations in studs after strong-acid corrosion under quasi-static tension conditions. Further, this model can simulate stress flows within studs after strong-acid corrosion. This research results can provide a guide for long-lifetime construction and safe maintenance in steel structural bridge.

Viscoplastic Self-Consistent (VPSC) Modeling for Predicting the Deformation Behavior of Commercial EN AW-7075-T651 Aluminum Alloy

Viscoplastic self-consistent (VPSC) modeling was used for investigating the deformation behavior of commercial EN AW-7075-T651 aluminum alloy at room temperature under quasi-static tension and compression (i) parallel, (ii) diagonal and (iii) transverse to the rolling direction. Textures of the as-received plate and of the samples after tensile and compression testing were determined using electron backscatter diffraction (EBSD). Euler angles and area fractions of the grains were used as input for calculating direction-dependent flow curves and pole figures of the deformed material. The coefficients of the integrated Voce strain hardening law were adjusted in order to fit the calculated flow curves to flow curves obtained from tensile and compression testing. Pole figures calculated with the VPSC modeling method were validated with pole figures obtained from EBSD analysis of deformed samples. VPSC modeling was successfully applied for predicting the general deformation behavior of EN AW-7075-T651 under both tension and compression. However, texture evolution during tensile testing was negligible, whereas notable texture evolution during compression testing occurred beyond a critical strain value.

Tensile behavior of the titanium-steel explosive welded interface under quasi-static and high-strain rate loading

Explosive welding is well known for its capability to join a wide variety of both similar and dissimilar metals. The strengths of the welded composite plates are largely influenced by the bonding strengths of the welding interfaces, which generally exhibit a periodic wavy shape. The measurement of the tensile properties of the bonding interface is challenging due to the difficulties in preparing conventional direct tensile specimens arising from the millimeter-sized thickness of the flyer plate. In this paper, a novel small-sized (15 mm × 14 mm × 8 mm) double-T-shaped specimen was designed to study the tensile properties and failure mechanisms of the titanium/steel bonding interface, in which a clamping apparatus was used to apply compressional load on the specimen to generate tensile stress. The quasi-static (∼0.001/s) tension was conducted using the Instron MTS and the high strain rate (2000–5000/s) tension was performed using the split Hopkinson pressure Bar apparatus. Further, the microstructure of interfacial zone was characterized by optical microscopy, scanning electron microscopy and energy dispersive spectrometer. The experimental results indicated that the interface strength increased with increasing strain rate, showing an obvious positive strain rate effect. The fluctuation in tensile strengths and failure strain of the titanium/steel bonding interface were due to the presence of non-uniform defects, (e g. cavities, cracks and brittle intermetallic etc.) formed on the bonding interface. Those defects as discontinuities and stress concentration points would result in degraded mechanical properties. The fracture morphology mainly reveals brittle fracture under quasi-static, while ductile fracture existed in some zone at high strain rate. Failure mainly occurred in the bonding interface near the steel side from the interface, which showed microcracks, cleavage plane, tearing ridges, dimples, fragmentation of brittle intermetallic compounds. Meanwhile, the double-T-shaped specimen has proven to be effective to measure the tensile mechanical properties of the interface of materials with small thickness.

Crystal plasticity modeling of strain-induced martensitic transformations to predict strain rate and temperature sensitive behavior of 304 L steels: Applications to tension, compression, torsion, and impact

This paper advances crystallographically-based Olson-Cohen (direct γ → α’) and deformation mechanism (indirect γ→ε→α’) phase transformation models for predicting strain-induced austenite to martensite transformation. The advanced transformation models enable predictions of not only strain-path sensitive, but also of strain-rate and temperature sensitive deformation of polycrystalline stainless steels (SSs). The deformation of constituent grains in SSs is modeled as a combination of anisotropic elasticity, crystallographic slip, and phase transformation, while the hardening is based on the evolution of dislocation density and explicit shifts in phase fractions. Such grain-scale deformation is implemented within the meso‑scale elasto-plastic self-consistent (EPSC) homogenization model, which is coupled with the implicit finite element (FE) method to provide a constitutive response at each FE integration point for solving boundary value problems at the macro-scale. Parameters pertaining to the hardening and transformation models within FE-EPSC are calibrated and validated on a suite of data including flow curves and phase fractions for monotonic compression, tension, and torsion as a function of strain-rate and temperature for wrought and additively manufactured (AM) SS304L. To illustrate the potential and accuracy of the integrated multi-level FE-EPSC simulation framework, geometry, mechanical response, phase fractions, and texture evolution are simulated during gas-gun impact deformation of a cylinder and quasi-static tension of a notched specimen made of AM SS304L. Details of the simulation framework, comparison between experimental and simulation results, and insights from the results are presented and discussed.

Data-Driven Construction Method of Material Mechanical Behavior Model

To obtain the mechanical behavior response of the material under loading, a data-driven construction method of material mechanical behavior model is proposed, which is universal for predicting the mechanical behavior of any material under different loads. Based on the framework of artificial intelligence and finite element simulation, the method uses Python script to drive an Abaqus loop calculation to obtain data sets and performs artificial intelligence training on data sets to realize model construction. In this paper, taking the quasi-static tension of 9310 steel as an example, a material mechanical behavior model is constructed, and the accuracy of the prediction model is verified based on the experimental data. The results show that the simulation results are in good agreement with the experimental data. The error between the simulation results and the experimental results is within 2%, indicating that the model constructed by this method can effectively predict the mechanical properties of materials.

Practical Considerations For The Application Of A Survival Probability Model For Rockfall

Rockfall fragmentation is a common and very complex phenomenon that is still inadequately understood and rarely modelled. When falling rock blocks break upon impact, their shape and size change and the kinetic energy is distributed amongst fragments. To efficiently design mitigation measures, it is necessary to adequately account for fragmentation when modelling rockfall trajectories. To do so, a better understanding of the fragmentation process, its occurrence and its likely outcomes is needed. The authors have recently proposed a novel model which can predict the survival probability (SP) of brittle spheres upon impact from the statistical distribution of material parameters, obtained by standard quasi- static tests (Brazilian tests and unconfined compression tests). The model predicts two Weibull parameters (shape parameter -m- and scale parameter – critical kinetic energy) that are used to define the SP. The model is based on theoretically-derived (from Hertzian contact theory) conversion factors used to transform the critical work required to fail disc samples in quasi-static indirect tension into the critical kinetic energy to cause failure of spheres at impact in vertical drop tests. The objective of this paper is to provide some practical insights into this model in relation of the analysis of the Brazilian test results and the number of Brazilian tests required to achieve an acceptable prediction. A first analysis highlights the importance of distribution of forces required to break the specimens in Brazilian tests and a common statistical based outlier removal methodology was applied to reduce the experimental error associated with the operator. After eliminating the outlier data, the quality of prediction is improved and, in particular, the influence of the specimen diameter used in Brazilian compressions to derive the model input parameter is significantly reduced. This latter point implies that the size effect is adequately captured. The second analysis reveals the highest variability for batches with low number of tests and a progressive reduction as the number of sampled test increases. Based on these results, it is suggested to use at least 30 Brazilian tests and remove outliers using the simple statistical approach presented in the paper.

Hygrothermal effect on mechanical behaviours and failure mechanisms of single-lap countersunk-screwed CFRPI-metal joint

This paper seeks to probe experimentally and numerically hygrothermal effect on mechanical behaviors and failure mechanisms of single-lap countersunk-screwed CFRPI (carbon fiber reinforced polyimide composite)-metal joints. Accelerated moisture absorption tests were conducted on CCF300/AC721 plate until effective moisture equilibrium, and quasi-static tension tests were performed on single-lap countersunk-screwed CCF300/AC721-30CrMnSiA joints in RD (room temperature and dry), RW (room temperature and wet) and EW (elevated temperature +55 °C and wet) environments, respectively. From the experiment results, moisture and temperature impacts were analyzed and discussed. By considering hygrothermal-mechanical interaction, non-linear shear constitutive relationship and complicated failure modes, an improved PDM (progressive damage model) was devised to simulate mechanical behaviors and failure mechanisms of single-lap countersunk-screwed CCF300/AC721-30CrMnSiA joints. Predictions agree well with the experimental results, demonstrating the effective use of new PDM. It is shown from experimental and numerical results that delamination around screw hole is likely the primary reason for final failure of joint, and the negative hygrothermal effect on joint performance mainly contributes to the decrease in inter-laminar properties of composite laminate with the increase in moisture and temperature. HIGHLIGHTS Accelerated moisture absorption tests were conducted on CCF300/AC721 plate, followed by quasi-static tension tests on single-lap countersunk-screwed CCF300/AC721-30CrMnSiA joints in the RD, RW and EW environments. An improved PDM was devised to simulate mechanical behaviours and failure mechanisms of single-lap countersunk-screwed CCF300/AC721-30CrMnSiA joints, and the predictions agree well with the experimental results. Research results demonstrate that hygrothermal effect likely contributes to the decrease in inter-laminar properties of composite laminate with moisture and temperature, ultimately deteriorating joint performance.

Temperature-induced enhancement of tensile strength of perforated Ti–6Al–4V sheet revealed through mechanical-thermal coupling quasi-static tension

In order to investigate the effect of temperature on the tensile strength of perforated Ti–6Al–4V (TC4) alloy, the tensile mechanical properties of TC4 alloy with various micro-hole array distributions were obtained at a temperature in a range from 20 °C to 500 °C by using a novel mechanical-thermal coupling tensile test instrument developed by ourselves. The experimental results showed that the tensile strength of all types of TC4 alloy specimens decreased with the increase in temperature, and the elastic modulus of most types of TC4 alloy specimens decreased with the increase in temperature. The tensile strength of the perforated specimen iii was 14.8% lower than that of the solid specimen and the elastic modulus of perforated specimen ii was 5.5% lower than that of the solid specimen at room temperature (RT), and all types of the perforated specimens continued to exhibit relatively lower tensile strengths and elastic modulus at 180 °C and 340 °C. Abnormally, the tensile strength of the perforated specimen iii was 2.1% higher than that of the solid specimen and the elastic modulus of perforated specimen ii was 23% higher than that of the solid specimen at 500 °C. With the increase of temperature from 20 °C to 500 °C, the fracture mode of the solid specimen gradually changed from equiaxed dimple to shear dimple. Regarding the perforated specimens, the cracks and dimples adjacent to the holes gradually decreased as a function of temperature. The existence of prefabricated holes in the specimens dissipated part of the thermal stress, maintained the integrity of the micro-hole structure, and made the nearby section relatively flat, which induced a relatively higher tensile strength and structural stiffness at an elevated temperature. The relatively lower stress in the gauge section of the perforated specimens obtained through finite element analysis also indicated the temperature-induced enhancement of tensile strength.

Tensile Behavior and Statistical Analysis of Washingtonia Filifera Fibers as Potential Reinforcement for Industrial Polymer Biocomposites

ABSTRACT Natural fibers continue to attract the attention of researchers because of their use in reinforced polymer composites. They allow industrial designers to find solutions to aging infrastructure problems more than 50 years after their use in aerospace, automotive, construction, consumer products, etc. These fibers are economical and low density. In fact, in addition to their specific properties, such as non-abrasiveness and biodegradability, they are an ecological material with low environmental impact. Washingtonia Filifera (WF) fiber, among others, is attracting more and more researchers to replace certain fibers such as synthetic or glass fibers, being widely used in the world. This study aims to determine the mechanical parameters of WF fibers with a gauge length (GL = 50 mm) in quasi-static tension. Tensile tests were carried out on 150 fibers in five-test series to determine the influence of their variability on the tensile stress, strain at break and Young’s modulus of plant fibers. Due to the dispersion of the results of the mechanical tensile properties of WF fibers, which is a characteristic of natural fibers, a statistical study is necessary. Thus, statistical tools such as the two and three-parameter Weibull distribution at 95% confidence level (CI) and the one-way analysis of variance ANOVA were carried out to study this dispersion.

Less damage accumulation of aluminum alloy sheet during electromagnetic forming based on Gurson-Tvergaard-Needleman model

The formability of aluminum alloy sheet is usually improved during electromagnetic forming (EMF). Here, the ductility enhancement mechanism was investigated on the basis of Gurson-Tvergaard-Needleman (GTN) model. The parameters of GTN models under quasi-static tension and EMF conditions were respectively determined by inverse identification. For AA2024-O aluminum alloy sheet under quasi-static tension, the initial void volume fraction is identified as 0.006, the critical void volume fraction where voids begin to aggregate is 0.075, the void volume fraction of nucleating particles is 0.131 and the mean nucleation strain is 0.44. With the similar initial void volume fraction, the other parameters under EMF condition are determined as 0.045, 0.055 and 0.58. The evolution curve of void volume fraction with strain were compared under EMF condition and quasi-static tension. The results show that the total growth of void volume fraction is less under EMF condition than that under quasi-static tension. A box part with inclined flange was preliminary achieved by electromagnetic forming process. The GTN model was finally verified by comparing the numerical and experimental results.

Mechanical characterization of the stress-strain behavior of the polydimethylsiloxane (PDMS) substate of wearable strain sensors under uniaxial loading conditions

Polydimethylsiloxane (PDMS), one type of silicone elastomers, has been widely used in the fabrication and prototyping of microfluidic and micro-engineering devices due to its high transparency, nontoxicity, and high chemical inertness. Considering its applications in precisely controlled conditions, e.g., wearable strain sensors, the mechanical properties of PDMS can critically influence the sensor performance. However, due to its viscoelastic properties and flexibility, the mechanical behavior of PDMS is generally difficult to measure accurately. In this study, the digital image correlation (DIC) technique has been adopted to accurately measure full-field strains generated in various quasi-static tension tests, including the cyclic tension test, the uniaxial tension test, and stress relaxation test, and critical material properties of PDMS (Sylgard 184), which are directly related to the performance of wearable strain sensors, were accurately measured. Experimental results indicate that the PDMS (Sylgard 184) elastomer exhibits very consistent and stable mechanical properties under quasi-static loading conditions, which is beneficial to the application of wearable strain sensors. However, the Poisson’s ratio, as a function of stain, needs to be carefully considered into this application.

Influence of metal texture and loading rate on heat release under quasi-static tension

This paper presents a study of the influence of the initial structure of metal materials obtained from plastic deformation methods on the processes of heat generation under quasi-static tension and low cyclic tests. Experimental data on the dependence of changes in the fraction of latent energy during deformation on the anisotropy of the initial structure of polycrystalline specimens of copper M1, duralumin D16, titanium VT6, as well as the grain size of copper M1 and magnesium alloy AZ31B are presented. It is shown that the thermodynamics of the plastic deformation process significantly depends on the anisotropy of the initial structure of the materials, brought about by the material processing used, as well as on the features of the lattice and the development of a meso-defect structure.

Spall Fracture of High-Strength Steel during Quasi-Static Tension

Spall Fracture of High-Strength Steel during Quasi-Static Tension

Design characteristics of the strength of VKS-9M and 300M steels

The mechanical properties of square section (up to 350 mm) forgings made of domestic steel VKS-9M (obtained by the duplex process of vacuum induction melting plus vacuum arc remelting) are studied. The mechanical properties of steel VKS-9M and American high-strength structural steel 300M are compared in terms of the calculated characteristics of materials. We extend the concept of «design characteristics of materials» to all the mechanical properties of materials used in determination of the strength and durability of structures. The design characteristics of materials include the strength characteristics under quasi-static tension, compression, crushing and shearing, as well as the strength under variable loads and the crack resistance of the material. The correctness of comparing the calculated values of the static strength of steels VKS-9M and 300M is based on the identity of test methods and the equivalence of processing and presentation of test results. The determination of the strength characteristics was carried out according to domestic standards, which are basically harmonized with the American standards. A difficult situation arises when determining the strength indicators of a newly developed material. Nowel material, as a rule, is developed in laboratory conditions, produced on experimental equipment in small volumes, and, therefore, the statistical assessment of the general population at the development stage is unreliable. In conditions of the full-scale manufacture of industrial semi-finished products, a statistical assessment of their strength characteristics becomes necessary. In the aviation industry, a statistical assessment of the calculated values of the strength characteristics of the material is prescribed by the law. The airworthiness standards set the levels of the calculated values of strength characteristics with a certain probability of non-destruction. For parts, the destruction of which can lead to an accident, the calculated values of the strength characteristics of materials should be selected in such a way that the strength of the material is to be ensured with a probability of 99% — with a 95% confidence interval (basis «A»). Statistical evaluation of the static strength characteristics of two heats of VKS-9M steel on the basis of «A» revealed their insignificant excess in comparison with steel 300M. The data obtained allow us to believe that the calculated values of the static strength characteristics of VKS-9M steel will not be lower than the calculated values for 300M steel. Large-scale fatigue tests of VKS-9M steel were carried out, which proved that the fatigue characteristics of VKS-9M and 300M steels practically coincide, as well as the arrays of their determinations. The equivalence of the strength characteristics of the VKS-9M and 300M steels allows replacement of the American 300M steel by the domestic VKS-9M steel.

Temperature effect on mechanical performances and failure mechanisms of single-lap countersunk-screwed CFRPI-metal joint

This paper seeks to experimentally and numerically probe temperature effects on mechanical performances and failure mechanisms of single-lap countersunk-screwed CFRPI-metal joints. Quasi-static tension tests were performed on single-lap countersunk-screwed CCF300/AC721-30CrMnSiA joints at −40 °C, −25 °C, RT (room temperature), +250 °C and +350 °C, and temperature impact was analyzed and discussed from experimental results. By considering thermal–mechanical interaction, non-linear shear constitutive relationship and complicated failure modes, an improved PDM (progressive damage model) was devised to simulate mechanical performances and failure mechanisms of single-lap countersunk-screwed CCF300/AC721-30CrMnSiA joints, and the predictions agree well with the experimental results. Based on numerical results, it is demonstrated that temperature effect on joint performances arises from the changes in clamping and friction forces and in interlaminar properties of material with temperature, and delamination around screw hole is likely the primary reason for final failure of joint.

Investigating relative density effects on quasi-static response of high-density Rigid Polyurethane Foam (RPUF)

This study aims at characterisation of various densities of Rigid Polyurethane Foam (RPUF) under quasi-static tension and compression. The density of foam is key parameter in selection of suitability for structural applications. Various densities of RPUF are synthesised using commercial grade Polyols and Methylene diphenyl isocyanate (MDI). The ratio of mixing both constituents was maintained at 1:1.15 for polyol and MDI respectively. Free rise density of the foam was achieved at 234 kg/m3 and is considered the baseline density for comparison. The higher than baseline densities were achieved by blowing the mixture into a mould with variable pouring times and three densities in the range of 252 kg/m3, 303 kg/m3 and 353 kg/m3 were achieved. The tensile and compression specimens were prepared from the manufactured blocks. SEM images were taken from the blocks of various densities and uniform cell patterns were observed for all densities. The specimens were then tested under compressive and tensile loads. It was found that the specimen exhibit consistency in results and the density affects the mechanical properties directly. Optimum density of foam for energy absorption capability of RPUF based on specific work done is also estimated. A phenomenological model based on relative density of foam was developed to assess material behaviour which can reduce the requirement of test specimens for obtaining a set of particular material properties.