Drop Weight Research Articles

Effect of fibre hybridization and stacking sequence on the low velocity impact response of flax/basalt/aluminum composite-metal joints

A lot of composite materials with better impact resistance and better strength and stiffness can be manufactured these days. Many researchers have been using different materials to form new composites to understand their impact performance. This paper discusses such an attempt to make new composites by utilizing the concept of hybridization and then proposes which among them has better strength and performance under low-velocity impact (LVI) loading. In this work, circular patches of composites made up of a combination of basalt and flax fibers were used while being bonded with aluminum plate Al 2024-T3 of 3 mm thickness. The three different configurations which include asymmetric, symmetric, and sandwich were prepared using vacuum assisted bagging process and their impact performances were investigated using the Drop Weight Impact test. The results obtained were analyzed and they concluded that the asymmetric configuration of basalt/flax composite has better impact resistance, and strength and is better to use in structural components of automobiles, and the defense industry as compared to the other two.

Behaviour of glued-laminated timber beams under impact loading

Short duration loads, such as impact loading, have the potential to generate catastrophic effects on infrastructure and loss of life. Although design provisions for engineered wood products are included in Canada’s blast design standard, CSA S850, how these structural materials respond to blast and impact loads across a wide range of high strain rates has not been well documented. An experimental program was carried out using a newly established Drop Weight Impact Testing Facility to investigate the flexural behaviour of glued-laminated timber beams subjected to impact loading. High strain rates were generated, whereby the dynamic specimens were found to differ quantitatively and qualitatively from their quasi-static counterparts. Dynamic increase factors of 1.13 and 1.20 were observed on the peak resistance and initial stiffness, respectively. A single-degree-of-freedom model was developed and validated against the experimental test results, where it was found to accurately predict the displacement–time histories of the specimens until failure.

Bayesian optimization-based prediction of the thermal properties from fatigue test IR imaging of composite coupons

The prediction of the prevailing self-heat transfer parameters of a glass/epoxy composite coupon during fatigue testing in general and the distinction between viscoelastic- and frictional crack growth-related energy dissipation in particular, are not trivial problems. This work investigates the feasibility of predicting the convective film coefficient, the total work loss as well as the ratio between viscoelastic and fracture-induced damping from thermal images using Bayesian optimization in conjunction with 3D FE thermal analysis. To this end, glass fiber/epoxy biax coupons are pre-damaged by means of a drop weight impact machine and subsequently tested under uniaxial tension-tension high cycle fatigue conditions. IR images are taken of the self-heating thermal profile at steady-state conditions. Synthetic surface thermal images are generated by numerical thermal analysis of the damage distribution obtained by μ-CT scanning prior to testing. Bayesian optimization of the aforementioned parameters is conducted by minimizing the loss function between the as-measured and the synthetic IR image. The predicted work-loss is consequently validated against the measured hysteretic response, from which a very good agreement is found.

"Cohesiveness of Hyaluronic Acid Fillers": Evaluation Using Multiple Cohesion Tests.

Background Hyaluronic acid fillers can be manufactured using various processes. They have multiple properties, including their concentration, degree of modification, and rheological data. Cohesion is one such property to evaluate gel integrity; however, there is no standardized method for calculating this parameter. This study aimed to evaluate different tests for calculating hyaluronic acid cohesion and discuss the importance of hyaluronic acid cohesion as a consideration when selecting fillers. Methods The cohesion levels of five different hyaluronic acid fillers with different rheological properties were evaluated and compared using the drop weight, compression, tack, and dispersion time tests. Results The cohesion tests yielded different results in the samples. Samples 2 and 4 showed approximately two times the number of droplets when compared with Sample 5 in drop weight test. Samples 1, 2, 3, and 4 were superior to Sample 5 in tack test. Samples 1, 2, and 3 showed cohesive appearances at 95 seconds in most cases in dispersion test. Rheological test results did not reflect the measures of cohesion. Conclusion Although there are no definite standardized tests to evaluate the cohesion of hyaluronic acid fillers, our proposed tests showed similar results for different hyaluronic acid filler products. Further studies are needed to evaluate the cohesion of hyaluronic acid fillers and determine the clinical use of this distinguishing characteristic for clinicians selecting the product of choice. Level of evidence statement: These data are Level IV evidence.

Low-velocity impact behavior of warp-knitted spacer fabric reinforced with spiderweb shaped stitch

Warp-knitted spacer fabrics are a widely considerable material owing to its unique sandwich structure and superior performance, employed across diverse fields such as military, transportation, construction, and personal protection. However, they are inevitably subjected to impacts in practical applications. This work investigated the influence of surface layer structure on the impact resistance property of fabrics by drop weight tests. The damage tolerance of warp-knitted spacer fabrics was also studied through repeated impact experiments. To further improve the impact resistance property of the fabric, a simple sewing method was proposed in this work. Inspired by the spiderweb structure, a spiderweb shape was sewn on the fabric. The results demonstrated that hexagonal mesh as the impact surface provided better impact resistance for the fabric. As the number of impacts increases, the deformation of the fabric gradually intensifies, and the fabric is completely damaged during the fourth impact. The stitch can enhance its impact resistance, and the shape of the stitch had a significant influence on the impact resistance performance.

Calibration of tensile tests in drop-weight impact machine and implementation in simulation of Charpy impact tests

Material modeling and simulation of deformation under very high loading rate in the dynamic/impact range are applied in crash resistance, ballistic impact analysis, and other time-sensitive phenomena. Servo-hydraulic UTM tensile test data from medium to higher strain rate > (500 s-1) is reliable but expensive and complexity in experiment. Tensile testing at very high strain rate (upto 1500 s-1) can be done in a drop-weight impact testing machine with a special fixture and the impactor velocity controls strain rate. In INSTRON CEAST 9350 drop weight impact testing machine tensile tests are conducted at four velocities for amour steel. A 5MHz data acquisition system (DAQ) measures strain in specimen gauge length mounted with high-elongation strain gauge. An extensometer is used to calibrate the strain gauge in a quasi-static 10-4 s-1 tensile test. Tensile test data from impact machine is compared with stress-strain data from the INSTRON servo-hydraulic testing machine with DIC for different strain rates. Close matching in elastic modulus, yield strength, tensile strength, and elongation are observed. Material parameters of a strain rate-dependent material model (modified J-C model) are extracted from drop weight impact testing machine data clubbed with other tensile test data, used in FE simulation of very high strain rate tensile tests, and validated with experimental results. Later, the same material model and material parameters are used to simulate Charpy impact tests at various velocities and compared with experimental results which also show close matching.

Impact Performance Improvement of Multiscale Hybrid Fiber Reinforced Polymer Composites with CNT

Improving the interface properties of carbon nanotubes increases the mechanical performance of fiber-reinforced polymer matrix composites. Studies on different fiber types and different polymer matrix materials present promising results in literature. The effect of carbon nanotube (CNT) additives on impact performance of fiber reinforced polymer matrix composites produced by vacuum infusion method and drop weight impact test applied. Glass and carbon 1 m2 fiber fabrics were divided into 9 equal square pieces and placed on top of each other to make them multi-layered structure. Fiber reinforcements were produced using vacuum infusion method with epoxy resin. 0.5% of the total composite weight was added to CNT with same production parameters and intraply hybrid composite containing glass, carbon and aramid fibers was also produced. Samples were produced from the composite plates and the drop weight impact test was performed with 50 J impact energy in accordance with ASTM D7136 standard. While this increase could be observed in glass fiber and carbon fiber reinforced composites, the impact energy absorption performance in carbon fiber reinforced composite increased more than 100%. CNT increased the impact performance of multi-layer fiber reinforced polymer matrix composites.

Dynamic and Residual Static Behavior of Axially Loaded RC Columns Subjected to Low-Elevation Impact Loading

Columns can suffer heavy damage due to dynamic impact effects, which are ignored during their design. The impact effect could be a vehicle crash to columns of streetside buildings, parking garages or bridges. However, the effect of impact loading on the behavior of reinforced concrete columns has not been sufficiently studied. In this study, an experimental and numerical investigation is carried out on the impact behavior of axially loaded reinforced concrete columns. Dynamic experiments were carried out by dropping a mass from different heights to apply low-elevation impact on axially loaded, full-scale (30 × 30 × 320 cm) columns. After evaluating the performance of the columns under varied impact loadings, the residual load carrying capacities of the columns were also obtained by static loading. Additionally, a three-dimensional finite element model was developed and validated by using drop weight experimental results. The effect of increasing the impact energy on the behavior of RC columns was also examined numerically. As a result of the research, it has been observed that, as the applied impact energy increases, the dynamic damage/failure mode changes from flexure to shear. When a column was impacted by 75.8% of its total impact energy capacity, a decrease of 38.1% in its stiffness and a decrease of 49.7% in its load carrying capacity were determined compared to its previous unimpacted state. Additionally, the static energy dissipation capacity loss of the column was reached, up to 81.7% of its preloading state. The developed finite element model can also be utilized to determine the dynamic performance and the damage modes of columns under vehicle collision-type low-elevation impacts, which can be a guide for structural engineers in the design of such vulnerable columns and will contribute to safer structural designs.

Investigation on impact properties of basalt and glass fiber reinforced polyester composites filled with nano silica

The relevance of granite waste is growing alongside the global demand for granite. This waste comprises various forms, including large granite pieces, tiny fragments, dust, and other debris. This research aimed to create a novel composite by incorporating nano silica from granite powder as a filler, combining it with basalt and glass fibres as the matrix, and using polyester as the resin. The fabrication involved Fiber Reinforced Composite (FRP) production through hand lay-up and vacuum silicon moulding to eliminate trapped air during lamination. After fabrication, tests were conducted for hardness, density, and Low-Velocity Impact under dropping weight. The results indicated that introducing nano silica as a filler in polyester resin positively impacted Basalt Fiber Reinforced Polyester Composite (BFRPC) and Glass Fiber Reinforced Polyester Composite (GFRPC). Analysis showed that as the nano-silica content increased, so did energy absorbed, impact strength and ductility index, up to a 1wt% nano-silica concentration. Beyond this point, agglomeration occurred, causing a decrease in these values. The 1 Nano silica Basalt Fiber Reinforced Polyester Composite (1NSBFRPC) material exhibited the highest energy absorption at 103.21J, indicating strong impact strength at 21.27kJ/m2. Conversely, the 1NSGFRPC material demonstrated the highest ductility index at 4.13. In comparison, Carbon Tech Global's (CTG) energy absorption, initially 25.56J, experienced a significant increase of 303.79%, reaching 103.21J. The impact strength also showed a notable shift, escalating by 396.96% from 4.28 KJ/m2 to an impressive 21.27kJ/m2. This shift in impact strength represented a remarkable 128.2% surge, highlighting the significant influence of integrating nano-silica. This new composite suits truck body carriers and offers environmental benefits. Furthermore, utilising nano silica in this context not only aids in waste reduction within the granite sector but also contributes to sustainable resources.

Research on the lightweight design and multilevel optimization method of B‐pillar of hybrid material based on side‐impact safety and multicriteria decision‐making

AbstractThis paper designs and optimizes a new structure hybrid material B‐pillar assembly. Establish a finite element analysis model for the side impact test of an electric vehicle to verify the model's accuracy. Construct a finite element model of the hybrid material B‐pillar assembly. Combined with the static performance analysis of the B‐pillar, the laminate design of the carbon fiber composite B‐pillar reinforcement plate and optimization. For the outer and inner panels of the B‐pillar, the surrogate model method and the multiobjective optimization method are combined to set 11 design variables and 13 responses. The optimal Latin hypercube design method was used to randomly sample each design variable and fit the radial basis function (RBF) approximate model. The modified second‐generation non‐dominated sorting genetic algorithm (MNSGA‐II) was used to carry out multiobjective optimization of the mixed material B‐pillar assembly, and the multicriteria decision‐making method was used to obtain the optimal solution for the Pareto solution set. A drop weight impact test was performed on the hybrid material B‐pillar assembly. The results showed that the peak collision force of the hybrid material B‐pillar was reduced by 43.7% compared with the original steel B‐pillar, the specific energy absorption was increased by 17.5%, and the side impact safety performance was better. After optimization, the weight of the mixed material B‐column was reduced by 26.44%. The improvement rates of the intrusion amount at P2 and the intrusion speed at P1 were 23.99% and 0.63%, respectively, and the lightweight effect and side impact safety were significantly improved.Highlights The finite element analysis parameters of carbon fiber composite materials were constructed through experiments, and the basis for simulation analysis under various working conditions of the B‐pillar based on performance‐driven optimization was established. A hybrid material B‐pillar design method is proposed, which consists of a variable‐thickness high‐strength steel B‐pillar outer plate, a variable‐thickness high‐strength steel B‐pillar inner plate, and a carbon fiber composite B‐pillar reinforcement plate. The super layer of the carbon fiber composite B‐pillar reinforcement plate was optimized and the laying plan of the carbon fiber composite B‐pillar reinforcement plate was determined. Performance‐driven optimization is adopted to realize the collaboration of multilevel design and optimization methods such as B‐pillar conceptual design, detailed design, and multiobjective optimization. A modified NSGA‐II algorithm was proposed and combined with the multicriteria decision‐making method and the entropy‐weighted gray relation analysis method to determine the Pareto optimal solution and the optimal design scheme for the mixed material B‐pillar.

Improved mechanical properties of carbon fiber/epoxy composites via fiber surface grafting of rigid-flexible chain structure

The surface topography and interface characteristics play a significant role in determining the mechanical properties of carbon fiber reinforced polymer (CFRP) composites. These features are primarily influenced by the surface chemical structures and their interactions with the matrix resin. Here, we developed a rigid-flexible coating consisting of polyetheramine (PEA) and polydopamine (PDA) on the fiber surface to control the interface and improve the mechanical properties of CFRPs. X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectrum (FT-IR) results validated the successful introduction of polymeric chains and fiber surface characteristics including rough surfaces, slim polymer layers and uniform dots were examined by scanning electron microscope (SEM) and transmission electron microscopy (TEM). Contact angle tests indicate that the functionalized coating noticeably enhances the interaction force between carbon fibers, promoting improved wettability by the matrix resin. The bending and interlaminar shear strength of CFRP prepared by functional carbon fiber are increased by 45.76 % and 47.63 %, respectively. The drop weight impact (DWI) test confirms the positive effect of improved interfacial properties on the out-of-plane impact resistance of CFRPs.

The longitudinal biochemical profiling of TBI in a drop weight model of TBI

Traumatic brain injury (TBI) is a major cause of mortality and disability worldwide, particularly among individuals under the age of 45. It is a complex, and heterogeneous disease with a multifaceted pathophysiology that remains to be elucidated. Metabolomics has the potential to identify metabolic pathways and unique biochemical profiles associated with TBI. Herein, we employed a longitudinal metabolomics approach to study TBI in a weight drop mouse model to reveal metabolic changes associated with TBI pathogenesis, severity, and secondary injury. Using proton nuclear magnetic resonance (1H NMR) spectroscopy, we biochemically profiled post-mortem brain from mice that suffered mild TBI (N = 25; 13 male and 12 female), severe TBI (N = 24; 11 male and 13 female) and sham controls (N = 16; 11 male and 5 female) at baseline, day 1 and day 7 following the injury. 1H NMR-based metabolomics, in combination with bioinformatic analyses, highlights a few significant metabolites associated with TBI severity and perturbed metabolism related to the injury. We report that the concentrations of taurine, creatinine, adenine, dimethylamine, histidine, N-Acetyl aspartate, and glucose 1-phosphate are all associated with TBI severity. Longitudinal metabolic observation of brain tissue revealed that mild TBI and severe TBI lead distinct metabolic profile changes. A multi-class model was able to classify the severity of injury as well as time after TBI with estimated 86% accuracy. Further, we identified a high degree of correlation between respective hemisphere metabolic profiles (r > 0.84, p < 0.05, Pearson correlation). This study highlights the metabolic changes associated with underlying TBI severity and secondary injury. While comprehensive, future studies should investigate whether: (a) the biochemical pathways highlighted here are recapitulated in the brain of TBI sufferers and (b) if the panel of biomarkers are also as effective in less invasively harvested biomatrices, for objective and rapid identification of TBI severity and prognosis.

Effect of recycled fibers and shredded intermediates variation on the mechanical properties and energy absorption of fiber‐reinforced composite panels

AbstractThe global composite industry generates large quantities of waste which mostly ends up in landfills due to a lack of established end‐use applications for multiple waste streams. The scrap from end‐of‐life (EoL) includes manufacturing waste such as dry chopped fiber tows, loose fibers, shredded fibers from fabric textile operations, cured/semi‐cured prepregs, and fully cured composite structure waste from aircraft, automobiles, wind blades, boats, and pressure vessels. In this work, different composite waste streams were reduced to shredded intermediates, followed by simple blending, and subjected to wet compression molding to produce composite panels. The panels/plaques were tested for mechanical properties (flexure and impact), fiber‐matrix wet‐out, and property bounds. It was found that wet‐compression molding was a viable and scale‐able approach to produce recycled panels from EoL composites shredded scrap. Furthermore, full‐scale size panels for use in truck bodies and intermodal shipping container flooring were manufactured and their impact resistance was tested using a drop weight impact test. They were tested both for high‐ and low‐velocity load. In the case of high‐velocity load, the average impact load was 14,673 N; the average absorbed energy was 101.6 J; the average elastic energy was 11.7 J and the impact resistance was 1065 J/m. In the case of the low‐velocity drop weight impact test, it was found that the average impact load was 7877.358 N; the average absorbed energy was 9.718 J; the average elastic energy was 9.14 J, and the impact resistance was 184.1 J/m. The shredded composite was shown to be a candidate material for the manufacture of truck bodies and intermodal containers’ flooring panels.Highlights By using shredded intermediates from different composite waste streams, it is possible to manufacture composite panels. Wet–compression process is an appropriate technique for manufacturing recycled fiber composite panels. Regardless of the source of scrap, the mechanical properties of the produced composite panels were improved. The recycling process technology can be transformed to commercial scale to produce full‐size transportation flooring panels. A product pathway is established in consideration of lower cost and improved recyclability.

A modified spring-mass model of low-velocity-impact on composite laminate including shearing deformation at delaminated region and reduction on membrane stiffness

A modified spring-mass model for response prediction of composite laminate subjected to destructive large mass impact was developed based on perturbation analysis on membrane stiffness and modified subsection superposition of bending stiffness. The reduction of the membrane effect caused by impact induced intraply matrix failure was evaluated by substituting the perturbated elastic modulus into the membrane stiffness. The subsection superposition method for calculating the bending stiffness of delamination-damaged laminate was modified by considering the transverse shear effect. According to the results of the finite element simulation, the accuracy of the first-order shear deformation theory (FSDT)-based subsection superposition method in evaluating the bending stiffness of delaminated laminates is obviously higher than the classical plate theory (CPT)-based one with the increase of laminate thickness. Destructive drop weight impact tests on the FRP laminate were conducted to validate the proposed model. The results show that the FSDT-based model is more accurate than the CPT-based one in destructive large mass impact response analysis.

Experimental Study on the Impact Resistance of Polymer-Modified Steel Fiber-Reinforced Recycled Aggregate Concrete

Recycled aggregate concrete (RAC), composed of aggregates sourced from construction solid waste, has garnered significant attention owing to its notable environmental friendliness. In this study, waterborne epoxy resin (WER) and steel fibers (SFs) were introduced into the RAC to enhance its performance. Orthogonal tests were meticulously designed, with the substitution rate of recycled aggregate (RA), SF dosage and WER dosage as variable factors, to comprehensively analyze the splitting tensile strength and impact resistance of concrete. The impact resistance of concrete was investigated via the drop weight test method. Furthermore, scanning electron microscopy (SEM) was employed to scrutinize the microstructure of concrete, investigating the modification mechanism of WER. The results indicated that the addition of SFs exerted the most pronounced influence on the properties of RAC. As the addition of SFs increased from 0 to 1.0%, there were significant enhancements in the splitting tensile strength and impact energy of the specimens. WER exhibited notable improvements, primarily on the splitting tensile strength, while demonstrating an adverse effect on the impact resistance. Utilizing the Weibull distribution theory, the results of the impact tests were fitted and analyzed to predict the impact life of different mixtures. The predicted results showed high correlations with the measured values.

Effect of fillers and weave architecture hybridization on the impact performance of 3D woven hybrid green composites

AbstractThe eco‐friendly characteristics of green composites not only make them economically and technically viable but also contribute to the reduction of pollution. Green composites are developed by combining degradable fibers (primarily cellulosic materials) with natural resins. A disadvantage of green composites is their lower mechanical strength. To address this issue, 3D woven reinforcement along with fillers can be used to enhance the mechanical properties of green composites. In the current study, three different types of novel 3D woven hybrid structures, that is, hybrid through the thickness (HB‐1 (TT), novel woven layer‐to‐layer structure (HB‐2 (LL)), and layer‐to‐layer structure with double warp yarn (HB‐3 (LL)) were developed. Composites were fabricated using the compression molding technique. Three different concentrations (2%, 5%, and 8%) of nano clay (nanoparticles) were used as fillers and mixed in the green epoxy resin. Pendulum (Charpy) and drop weight impact tests of the composites were performed. The results showed that by the addition of nano particles the impact properties were increased. Nanoparticles showed a significant effect on impact strength. Charpy impact test results showed that the HB‐3 (LL) composite sample with 8% nanofillers showed the highest impact performance, while the HB‐1 (TT) composite sample with 8% nanofillers showed the highest impact performance during the drop weight impact test. By comparing the impact strength of the present work with that of similar research previously published, it is evident that our study achieved a remarkable improvement of 19.17%. This increase is due to the novel structures and nano fillers in the composite.Highlights Eco‐friendly green composites: economically feasible, minimizes pollution. Adding 3D woven structures to green composites improves their mechanical properties. Composite materials with nano clay fillers have increased impact resistance. The highest impact performance is shown by HB‐3 (LL) composites with 8% nanofillers.

Experimental investigation on impact behavior of curved sandwich composites with chiral auxetic core

The purpose of this study is to evaluate and compare the capability of impact energy absorption of the sandwich panels with various chiral auxetic cores. To this end, flat and curved panels were subjected to impact testing at varying energy levels. Glass fiber-reinforced epoxy composites and PLA material were used as the skins and core of the examined sandwich panels, respectively. The face sheets were produced by the hand-layup method and the auxetic cores with tetrachiral, anti-tetrachiral, and hexachiral configurations were printed using a 3D printer. The wall thickness, node diameter, and ligament length of the cells, as well as the core thickness, were kept constant for all the studied core structures. Flat and curved sandwich panels were obtained by combining the skins and cores produced in flat, 100 mm, 125 mm, and 160 mm radii of curvature with the epoxy used in skin production. Drop weight tests were carried out at impact energies of 10, 25, and 80 J. The contribution of the auxetic core configuration and panel curvature to the impact behavior of the sandwich panel was evaluated by examining the relationships between contact forces and deflection and by the analysis of the energy absorption and failure mode. The comparative evaluations showed that the auxetic core structure and the curvature of the panel have a significant effect on the impact properties of the sandwich panels. It was also observed that the use of tetrachiral cores could be the ideal design option for flat panels loaded at the perforation energy level. For curved panels, it was determined that the use of a hexachiral core configuration was advantageous in terms of more energy absorption capability, while the use of an anti-tetrachiral core structure was more effective in terms of specific energy absorption.

Characteristics of a Heat Exchanger in a Liquid Rocket Engine Using Conjugate Heat Transfer Coupling with Open-Source Tools

Since a heat exchanger used in a gas generator of an open-cycle liquid rocket engine was operated in a high-temperature environment, the coupled analysis for heat transfer characteristics and structural integrity should be performed simultaneously. For these reasons, a numerical analysis of the heat exchanger in a liquid rocket engine was performed to elucidate the effects of heat transfer and structural deformation simultaneously using conjugate heat transfer (CHT) analysis and open-source tools. For the baseline heat exchanger, which had an inner helically coiled tube with nine turns (), the heat transfer characteristics were investigated and findings showed that the heat transfer performance was reduced from the sixth turn. Further analysis was performed to examine the effect of the number of turns in terms of heat flux and the corresponding pressure drop and the weight of the structure. The results indicated that the heat exchanger with had a significantly reduced outlet temperature due to an excessively shortened flow residence time. The heat exchanger with showed an outlet temperature similar to that of the baseline; it also presented advantages in terms of the pressure drop and structure weight. In addition, the thermal deformation and stress caused by temperature changes were numerically investigated to consider the structural integrity of the heat exchanger with . Further numerical analyses were performed at various flow rates. As the flow rate of helium increased, the amount of heat received from the high-temperature exhaust gas from the gas generator increased but the outlet temperature of helium decreased gradually. Finally, the temperature difference between the outer and inner walls increased due to the high heat flux in the region around the inlet, resulting in an increase in thermal stress. Based on these results, the optimal shape and flow rate of the system were identified. Furthermore, the heat transfer performance was found to correlate with the flow characteristics of the coiled tube.

IMPACT RESISTANCE ASSESSMENT OF INTERLOCKING COMPRESSED EARTH BRICKS (ICEB) INCORPORATING CRUMB RUBBER

Interlocking compressed earth bricks (ICEB) are a cleaner and sustainable alternative to conventional fired bricks and it has comparable strength to other masonry systems, making it feasible for both cladding and load-bearing purposes. However, it tends to be brittle and has poor performance under impact loading. Impact resistance of masonry walls are important as one of the main purposes of cladding is to protect its occupants from external projectiles. This study was commissioned to investigate the feasibility incorporating both crumb rubber (CR) and treated CR into ICEBs in place of sand to improve its impact resistance. The drop weight impact tests carried out concluded that ICEBs containing CR have better impact resistance and this was further improved with heat-treated CR. Heat-treated CR ICEBs also had less catastrophic failure compared to untreated CRs which had pieces of materials spalling off. Mechanical tests also show that this improvement in impact resistance comes at the expense of a minor loss in compressive and flexural strength at replacement levels higher than 7.5 %. Heat-treated CRs also showed higher losses of mechanical strength compared to untreated CRs.

Dynamic Mechanical Responses and Freezing Strengthening Mechanism of Frozen Sandstone with Single Flaw: Insights from Drop Weight Tests and Numerical Simulation

Dynamic Mechanical Responses and Freezing Strengthening Mechanism of Frozen Sandstone with Single Flaw: Insights from Drop Weight Tests and Numerical Simulation