Unit Weight Research Articles

Effect of Using Recycled Colemanite Waste and Cathode Ray Tube Glass in the Cement Mortar on Physical and Mechanical Properties

In this study, the performance of colemanite, which is a valuable boron waste, and recycled cathode ray tube glass (CRT) in the cement mortar was examined by experimentally. Colemanite waste (CW) and CRT were replaced with cement and aggregate and used as mineral additives, and their effect on the physical and mechanical properties (PP and MP) of mortar was investigated. In addition to the reference sample that didn’t contain CW or CRT, seven more samples were used. In these samples, cement was used at a rate of 2.5% along with CW, and the aggregate was replaced with CRT at the rates of 10%, 20%, and 30%, and with the combination of CW and CRT. The workability, unit weight, and water absorption, compressive strength (CS), flexural strength (FS), and abrasion resistance properties of the mortars were compared. As a result of this study, it has been observed that the use of waste materials can make positive contributions to some of the PP and MP of the mortar. Thus, the goal of both improving the properties of the mortar and making it affordable by using waste materials were achieved.

Study Of High Performance Concrete Using Local Materials (Fly Ash Of Pltu Labuhan Angin, Mount Sinabung Volcanic Ash And Silica Sand) On The Mechanical Properties Of Concrete

Currently in Indonesia a lot of construction work and concrete is one that is widely used. In the development of concrete construction technology, especially in Indonesia, it is necessary to have concrete capable of carrying high loads using available materials. The development of high quality concrete has 3 levels, namely High Strength Concrete (HSC), High Performance Concrete (HPC) and Ultra High Performance Concrete (UHPC). Against the background of future needs, in this study experiments were carried out in a concrete laboratory to obtain high performance concrete mixes with local materials. At the experimental stage, testing of tools and materials, concrete mix, casting, slump test, manufacture of specimens, maintenance, checking of unit weight, compressive strength test, split tensile strength and modulus of elasticity was carried out. In that study there were 11 variations. Furthermore, the test results were analyzed by the data to draw conclusions. The results showed that the average compressive strength of concrete at 3 days of age was relatively high, namely 53.8 MPa which could be used for fast precision work. In variation 11 mixture (PCC Cement, Silica Fume, Sand Mesh 35-60, Silica Mesh 325, Water, Viscocrete Superplasticizer 8670 MN, Fly Ash 7% and Polypropylene Fiber 0.2%) tested for 28 days, the compressive strength reached 87.5 MPa, so it can be said as HPC concrete. In this study it was concluded that the use of local materials, Sinabung Volcanic Ash waste and fly ash can improve the quality of concrete and can also reduce environmental pollution.

Rock - soil transition during weathering of rhyolite

Concentric layers of weathered materials around core-stones show the rhyolite to experience sequential, but gradational, changes in visible features, textures and mineralogy as it transforms from ‘rock’ into ‘soil’. The changes start with the opening-up of grain boundaries and micro-cracks (stage 1) followed by their dark brown staining (stage 2) and the subsequent alteration (to sericite and clay minerals) of plagioclase feldspar groundmass grains and phenocrysts (stage 3). Biotite flakes are then bleached and altered (to chlorite and clay minerals) (stage 4) before there starts alteration (to sericite and clay minerals) of groundmass alkali feldspar grains (stage 5) and finally alteration of alkali feldspar phenocrysts (stage 6). Quartz grains are not altered during these stages of weathering but disaggregate and reduce in size due to continual opening-up of grain boundaries and micro-cracks. Increasing stages of weathering are marked by decreasing dry unit weights, dry densities and uniaxial compressive strengths, but increasing apparent porosities. The transition between ‘rock’ and ‘soil’ occurs during weathering stage 6 when all plagioclase groundmass grains and phenocrysts have been altered as have been all alkali feldspar groundmass grains and most phenocrysts. Stage 6 is marked by large apparent porosities (>14%) but low values of dry unit weight (<21.90 kN/m3) and dry density (<2,232 kg/m3).

A critical review of municipal solid waste hydraulic conductivity: A mini review.

This study is a critical review of municipal solid waste (MSW) hydraulic conductivity that includes investigation of the influence of vertical stress, dry unit weight and degradation. A total of 56 studies were compiled that included laboratory-, pilot- and landfill-scale hydraulic conductivity experiments. Compacting waste and increasing vertical stress reduce MSW hydraulic conductivity via reshaping the pore networks throughout the waste matrix, reducing the void ratio and increasing tortuosity. However, the magnitude of reduction in hydraulic conductivity is dependent on stress, waste composition and decomposition. Solid waste decomposition can have opposing effects on hydraulic conductivity. Some studies have indicated that an increase in MSW decomposition results in particle size reduction and settlement that reduces the void ratio and decreases hydraulic conductivity. Conversely, some studies indicate that waste decomposition reduces the solid mass, which increases the void ratio and creates larger flow paths that increase hydraulic conductivity. The data compilation, observations and key findings from this study are beneficial for solid waste practitioners to improve design, analysis and operation of MSW landfills.

SMART MINING: JOINT MODEL FOR PARAMETRIZATION OF COAL EXCAVATION PROCESS BASED ON ARTIFICIAL NEURAL NETWORKS

<p>In the present paper we propose a new artificial neural network model for the estimation of coal cutting resistance and excavator performance as a nonlinear relationship between the examined input (excavator movement angle in the left and right direction, slice height and thickness, coal unit weight, compressive and shear strength) and output factors (excavator effective capacity, maximum current/power/force/energy consumption, linear and areal cutting resistance). We analyze the dataset collected from three open-pit coal mines in Serbia: Field D, Tamnava Eastern Field and Tamnava Western Field (all part of the Kolubara coal basin). The model is developed using a multilayer feed-forward neural network, with a Levenberg-Marquardt learning algorithm. Results of the preformed analysis indicate satisfying statistical accuracyof the developed model (R>0.9). Additionally, we analyze the individual effects of input factors on the properties of coal cutting resistance and performance of the excavator, by invokling the multiple linear regression. As a result, we single out the statististically significant and physically possible interactions between the individual controlling factors</p>

THE SOIL CARBON STOCK IN THE TOURISM AREA OF GILI TRAWANGAN

This study aims to determine the distribution of carbon stocks in various land uses and total carbon stocks in the tourism area of ​​Gili Trawangan. This research was conducted in the Gili Trawangan area, Physics and Soil Conservation Laboratory, and Soil Chemistry and Biology Laboratory, Faculty of Agriculture, University of Mataram, in June-October 2022. The method used in this study was a descriptive method with a survey technique. The descriptive method can start with data collection, analysis and interpretation. Carbon in the soil in this study was obtained from the results of C-organic laboratory analysis (Walcky and Black) supported by measurements of soil unit weight (BV), soil porosity and soil texture. Meanwhile, aboveground carbon stocks were obtained through direct sampling in the field by measuring tree biomass. The results showed that the total carbon stocks in various land uses have different carbon stocks. The mixed garden had the highest carbon stock of 840.27 ton.ha-1, forest land of 83.76 ton.ha-1, and shrubs of 15.76 ton.ha-1, and the lowest carbon stock was a settlement of 3.01 ton. ha-1. Overall, carbon stocks in the tourist area of ​​Gili Trawangan are 942.8 ton.ha-1.

Effect of aggregate type on the elastic modulus and compressive behavior of concrete: A case study in Colombia

The modulus of elasticity Ec, the specified compressive strength fc', the measured concrete strength, fcr', and the axial strain of the concrete at peak strength εc0 are key parameters for the analysis, design, and construction of reinforced concrete (RC) structures. These parameters require precise laboratory control, which makes routine testing and consistent reporting in the literature challenging. Therefore, in some developing countries, numerical modeling for RC structural analysis relies on results or equations proposed by international building codes as reference values, ignoring the mechanical contribution of locally available materials. This study used five gravel sources from different mineralogical origins in Colombia to evaluate the mechanical properties of twenty concrete mixtures at four water-cement ratios (0.60, 0.55, 0.49, 0.35). Analyses and comparisons of aggregate properties, including mineralogical origins, unit weight, aggregate surface, absorption, and Los Angeles Abrasion Loss (LAAL), are conducted in relation to Ec, fcr', and εc0 and are contrasted against existing literature. Two groups of concrete were defined as normal and high-strength (NS- and HS-concrete), and compressive stress-strain curves were recorded during the tests of 220 cylinders, from which Ec, fcr', and εc0 were obtained. A statistical analysis was conducted to study the main effects and interactions of the aggregate type and water-cement ratio on the modulus of elasticity. It was found that the aggregate type had a significant impact on Ec with no interaction with the water-cement ratio. It led to the development of new expressions to account for the different available aggregates, potentially improving future local building code provisions for Ec. Values of fcr' ranged from 20 MPa to 95 MPa, with the corresponding Ec / √fcr' ratio varying from 4870 to 6140 MPa for the NS-group, while being approximately 25% smaller, on average, for the HS-group. The greatest Ec values are produced by an igneous aggregate type exhibiting the lowest LAAL, while a metamorphic aggregate with 40% LAAL produces the lowest Ec values. However, both aggregates had 100% fractured faces, resulting in the highest fcr' values at 56 days (42 ≤ fcr' ≤ 44 MPa), with the fractured faces of the aggregate being the critical parameter for compressive strength. The εc0 results showed negligible median variations among the aggregate types, except for the aggregate with a smooth surface with fewer fractured faces. Median εc0 values are 0.0019 and 0.0026 for the NS- and HS-group, respectively.

Assessment of Bohme surface abrasion resistance of natural stones by simple and nonlinear multiple regression methods

Natural stones are widely used in the construction sector and the physico-mechanical features are very important for them in terms of areas of use. Abrasion is an important phenomenon for causes to decrease in aesthetical and mechanical properties. The Bohme surface abrasion (BSA) test is the widely used test method to determine abrasion resistance, but it is time-consuming, very difficult, and expensive to apply. Because of such difficulties, this study has been conducted to indirectly determine the BSA value of natural stones by some practical methods. For this purpose, BSA, Point load index (Is50), Shore Schlerescope hardness (SSH), Brinell hardness (HB), Rock impact hardness number (RIHN), Coefficient of rock strength (CRS), Crushability index (CI), Impact strength index (ISI), Water absorption (WA), Unit weight (UW), and Porosity (Pg) properties of a total of up 119 rocks, mainly of Turkish rocks, were determined. The main objective of this article is to develop some estimation models for the BSA of different rocks. Two different methods have been utilized in the modeling of data, including simple regression analysis (SRA), and nonlinear multiple regression analysis (NMRA). In addition to the SRA performed using all data sets, the SRA analysis was deepened by classification according to origin, porosity, and strength. A large number of estimation equations were obtained by NMRA performed by applying three different models. The actual BSA values obtained from the laboratory study and the BSA values obtained from the models analyzed with SPSS software were compared using ANOVA analysis and various graphics. The most successful SRA equations derived using the entire dataset were obtained with HB, Is50, and SSH parameters, respectively. In general, there is a significant correlation between various rock properties and BSA, except CRS and CI. For NMRA models constructed with at least three independent variables, the highest predictive power belongs to the equations using (Is50 / HB / UW), (Is50 / HB / CRS), and (Is50 / UW / WA / Pg) parameters, respectively. Rock abrasion has a complex nature. The results of this study strongly support that it is an accurate approach to seek a solution to this complex problem by using parameters such as hardness, strength, and physical properties in the same model.

Upper Bound Analysis of Ultimate Pullout Capacity for a Single Pile Using Hoek–Brown Failure Criterion

As a typical pullout foundation, the uplift pile has been widely used in ocean projects or geotechnical engineering, but the accurate prediction of its ultimate pullout capacity has always been a difficulty in engineering design. This study focused on a single pile in rock formation, and constructed a curved uplift failure mechanism in the case that the whole rock mass around the pile was damaged. In this mechanism, the rock mass failure was assumed to comply with the Hoek–Brown failure criterion. Then, the theoretical prediction formulas for the rock failure surface and the ultimate pullout capacity of the pile were derived by using the upper bound theorem. The influence laws of factors such as different rock mass parameters, pile parameters and additional surface load on the pile capacity and failure range were analyzed. Further, the proposed method was validated by comparing with the numerical simulation results. The results show that the ultimate pullout capacity of the pile increases with the increase in the length/diameter ratio, rock empirical parameter A, tensile strength, compressive strength, unit weight and additional surface load, but decreases with the increase in rock empirical parameter B. Empirical parameters A and B are key factors affecting the pile capacity and rock failure range, and should be attached importance to in engineering design. The research work in this study can provide some theoretical reference for the design of the uplift pile in rock formation.

Reaction kinetics and properties of pumice-based geopolymer systems cured at room temperature

This research investigated the kinetics of pumice-based geopolymer systems and their physical and mechanical properties. The effect of the Na2SiO3/NaOH ratio of geopolymer systems on the rate of heat evolution and total heat of reaction were examined via isothermal calorimetry of geopolymer pastes prepared with Na2SiO3/NaOH ratios of 2.5, 3, and 3.5. Hardened pastes were also studied with thermo-gravimetric analysis to determine weight loss. In addition, the unit weights and compressive strengths of the pastes prepared using pumice were measured. Although the hydration process starts the earliest in pumice-based geopolymer pastes with a Na2SiO3/NaOH ratio of 2, they have the lowest total hydration temperature. Na2SiO3/NaOH ratio of 2.5 by mass, shows higher weight loss obtained from TGA results. The compressive strength of the paste sample, prepared with a Na2SiO3/NaOH ratio of 3.5 by mass, was the highest, with 36.30 MPa at 28d. Depending on the Na2SiO3/NaOH ratio, it is thought that as the amount of Na2SiO3 increases in the samples, silica gel formation increases in later ages.

Research on the descaling characteristics of a new electrochemical water treatment device.

In recent years, chemical water treatment equipment has gained significant attention due to its environmental-friendly features, multifunctionality, and broad applicability. Recognizing the limitations of existing chemical treatment equipment, such as challenges in scale removal and the high water content in scale deposits, we propose a novel drum design for both anode and cathode, enabling simultaneous scale suction and dehydration. We constructed a small experimental platform to validate the equipment's performance based on our model. Notably, under the optimal operating parameters, the hardness removal rate for circulating water falls within the range of 19.6-24.46%. Moreover, the scale accumulation rate per unit area and unit time reaches 13.7 g h-1 m-2. Additionally, the energy consumption per unit weight of the scale remains impressively low at 0.16 kWh g-1. Furthermore, the chemical oxygen demand (COD) concentration decreased from an initial 106.0 mg L-1 to a mere 18.8 mg L-1, resulting in a remarkable total removal rate of 82.26%. In conclusion, our innovative electrochemical water treatment equipment demonstrates exceptional performance in scale removal, organic matter degradation, and water resource conservation, offering valuable insights for future research and development in chemical treatment equipment and electrochemical theory.

Performance enhancement of ice storage capsules by biomimetic fins

Ice storage enhanced by biomimetic fins in spherical capsules is studied numerically based on enthalpy-porosity method. The evolution of water/ice interface, the temperature variation, and the cooling energy storage capacities are examined quantitatively to gain further insight into the solidification process in capsules. Especially, the geometrical configurations of fins, including the maximum bifurcate level and fractal dimension of length, are investigated. In addition, four evaluation criteria are employed to determine the optimum design for the biomimetic fins. The results show that the biomimetic fins are significantly effective in enhancing the heat transfer in the stage of cooling energy storage through sensible heat in ice. The performance enhancement is facilitated as the level of fins is increased that average 24% reduction in solidification time is achieved by the fin-Ⅲ series with only 1.24% loss of cooling energy storage capacity averagely. An optimum design for biomimetic fins is the fin-Ⅲ with a fractal dimension of 3, which results in a 30.01% increase in dimensionless cooling energy storage capacity per unit time and weight compared to the case without a fin. Aluminum is a favorable fin material considering both the enhancing performance and material cost of the capsule. A prediction formula of ice volume under different cooling conditions is generalized.

Effect of the use of retardant chemical additive in concrete on rebar corrosion

Reinforced concrete (RC) is one of the most widely used building materials. However, RC, especially in coastal seaside or humid environments, can suffer reinforcement corrosion with the result that the reinforcement fails to perform its function over time. The effect of a retarder additive used to eliminate loss of consistency in hot, windy and humid weather on the corrosion of RC elements was investigated in this work. Four different concrete types were assessed, with 0%, 1%, 1.5% and 2% additions of the chemical additive. Along with accelerated corrosion and pressure tests, physical properties such as electrical resistivity, water absorption, porosity, unit weight and capillary water absorption were also determined. The results of this work indicate that the use of up to 2% of the setting retarder did not pose a problem in terms of the physical and mechanical properties of the concrete. However, in terms of the frequently encountered corrosion problem, the use of 1.5% is more appropriate. Many chemical additives are used for different purposes in concrete and it is suggested that, alongside physical and mechanical properties, durability characteristics should also be examined when determining the suitable ratios of these additives.

Dynamic prediction of over-excavation gap due to posture adjustment of shield machine in soft soil

The probability analysis of ground deformation is becoming a trend to estimate and control the risk brought by shield tunnelling. The gap parameter is regarded as an effective tool to estimate the ground loss of tunnelling in soft soil. More specifically, ω, which is a gap parameter component defined as the over (or insufficient) excavation due to the change in the posture of the shield machine, may contribute more to the uncertainty of the ground loss. However, the existing uncertainty characterization methods for ω have several limitations and cannot explain the uncertain correlations between the relevant parameters. Along these lines, to better characterize the uncertainty of ω, the multivariate probability distribution was developed in this work and a dynamic prediction was proposed for it. To attain this goal, 1 523 rings of the field data coming from the shield tunnel between Longqing Road and Baiyun Road in Kunming Metro Line 5 were utilized and 44 parameters including the construction, stratigraphic, and posture parameters were collected to form the database. According to the variance filter method, the mutual information method, and the value of the correlation coefficients, the original 44 parameters were reduced to 10 main parameters, which were unit weight, the stoke of the jacks (A, B, C, and D groups), the pressure of the pushing jacks (A, C groups), the chamber pressure, the rotation speed, and the total force. The multivariate probability distribution was constructed based on the Johnson system of distributions. Moreover, the distribution was satisfactorily verified in explaining the pairwise correlation between ω and other parameters through 2 million simulation cases. At last, the distribution was used as a prior distribution to update the marginal distribution of ω with any group of the relevant parameters known. The performance of the dynamic prediction was further validated by the field data of 3 shield tunnel cases.

Improving the Landslide Susceptibility Prediction Accuracy by Using Genetic Algorithm Optimized Machine Learning Approach

Landslide susceptibility prediction is critical in open pit mines and geotechnical fields. Prediction accuracy is very essential to reduce the risk of slope instability. Traditional statistical learning methods have been widely used in early warning systems, but they cannot thoroughly explore the coupling effect among related factors, which often results in low prediction accuracy. This paper establishes an ensemble learning prediction model optimized by a genetic algorithm (GA) to determine landslide susceptibility more quickly and efficiently. The model is based on 290 sets of slope cases containing height (H), slope angle (α), unit weight (γ), cohesion (c), friction angle (φ), and pore water pressure (ru). Two common algorithms are incorporated into the ensemble learning model: Xgboost and gradient boosting decision tree (GBDT). The area under the curve (AUC) of GA-GBDT and GA-Xgboost were found to be 0.928 and 0.933, respectively, both of which could predict landslide susceptibility better. Compared with multiple logistic regression and other machine learning algorithms, both GA-GBDT and GA-Xgboost models perform better in terms of accuracy and applicability. The study results demonstrate that the developed optimized machine learning model can accurately predict landslide susceptibility and that the parameters should be optimized on a case-by-case basis to achieve more accurate results after building a suitable machine model. The optimization model proposed in this paper can be an effective new method for the intelligent prediction of landslide susceptibility.

Effects of Hemp Fibers on Durability and Strength Properties of Concrete to be Used In Agricultural Buildings

Concrete is the most common construction material used worldwide. It is also commonly used in construction of agricultural buildings. With the rapid developments in technology, different building materials with superior properties are being researched in order to improve different properties of concrete and eliminate its disadvantaged aspects and to obtain lighter, insulated, more economical and useful construction materials. One of the applications to improve the negative properties of concrete with low tensile strength is to add various fibers into the concrete mixtures. Hemp stalks play an important role in recycling vegetable wastes. Therefore, it is highly significant to recycle or transform these materials. In this study, hemp fibers were supplemented into concrete mixtures in different ratios (1, 2.5 and 5%). Slump and unit weight tests were conducted on fresh samples and compressive strength, tensile strength, water absorption, freeze-thaw resistance, thermal conductivity and ultrasound pulse velocity tests were conducted on 28-day cured cube specimens. Compressive strength, specific gravity, ultrasound pulse velocity and thermal conductivity coefficients decreased, but tensile strengths and water absorption ratios increased with increasing hemp fiber ratios. Hemp fiber supplementation into concrete mixtures yielded a material with higher tensile strength, lower thermal conductivity and suitable for cold climate conditions

The experimental procedures of sand and lime as base soil stabilization materials on the modified proctor values for flexible pavement construction

During road construction, one of the major challenges encountered is dealing with weak subgrade soil, specifically expansive soil that experiences volume changes due to variations in moisture content. Lime stabilization is a widely used method for improving post-construction stability, offering cost savings, and reducing environmental impact. This study reviews various methods for creating soil-lime mixtures, comparing testing methods. Effective soil stabilization leads to improved construction outcomes, cost reduction, and minimized environmental impact. Soil characteristics, including Maximum Dry Density (MDD) and Optimum Moisture Content (OMC) value, are important factors in determining suitability for construction. Therefore, this study focused on soil characterization, grain analysis, Atterberg limits, and modified compaction before and after lime as well as sand stabilization. This study also determined soil characteristics, grain gradation, Atterberg limit, and modified compaction, and also developed implementation methods and budget plans for stabilized earthworks. Subsequently, the tests included moisture content, density, specific gravity (Gs), sieve analysis, grain analysis with a hydrometer, Atterberg limits, and modified compaction. The tests were conducted with varying percentages of sand (20 %) and lime (5 %, 10 %, 15 %, and 20 % of soil dry weight). Original soil moisture content value (w) = 53.70 %, Wet soil unit weight (γ) = 1.69 gr/cm3, Gs = 2.69, The original soil is classified into A-2–7 as (silty gravel or clay and sand) according to AASHTO.•This method shows the effect of sand and lime as base stabilization materials.•This method examines the roles of modified proctor on the flexible pavement.•This study explores MDD and OMC for curing times of 1, 7, and 14 days.

Bayesian Mixture Analysis of a global database to improve unit weight prediction from CPTu

Empirical correlations between different geotechnical parameters are frequently sought after by exploiting multivariate databases. An example are estimations of total unit weight from cone penetration tests (CPTu), which are very useful in earlier design stages. If the underlying soil database includes data from many different soils a single correlation may lack precision. Precision is gained when the underlying database is narrowed down to some specific soil type, but the applicability of a soil-specific correlation is also limited. A way out of this dilemma is to apply clustering techniques to a general database before developing separate correlations for different clusters. Projecting the clustered data back to a convenient classification space (e.g., one spanned by normalized CPTu metrics) new data can be easily assigned to different clusters and the appropriate correlation used. This idea is illustrated here using Bayesian Mixture Analysis (BMA) to identify hidden soil classes within a general geotechnical database that supports correlations between soil total unit weight and CPTu readings. It is shown that BMA supported clustering improves the accuracy of previous regressions, and, more importantly, facilitates the formulation of novel and more accurate regressions. A simple discriminant criterion is developed to facilitate application of cluster-based regressions to new sites. The good performance of the method is illustrated with application to a deltaic site.

Use of Waste Polythene in Bituminous Concrete Mixes for Highways

Abstract: Bituminous Concrete (BC) normally used in construction projects like road surfacing, airports ,parking lots etc is a composite material . It consists of asphalt or bitumen (used as a binder) and mineral aggregate which are mixed together & laid down in layers then compacted. In these days the large increment in high traffic intensity in terms of commercial vehicles, and the compelling variation in daily and seasonal temperature put us in a demanding situation to think of some alternatives for the improvisation of the pavement characteristics and quality by applying some necessary modifications which shall satisfy both the strength as well as economical aspects .Also considering the environmental approach, due to excessive use of polythene in day to day life the pollution to the environment is increased significantly . Since the polythene is non-biodegradable the need of the current hour is to use the waste polythene in some beneficial purposes .This paperpresents a research conducted to analyse the behavior of BC mix modified with waste polythene. Various percentages of polythene are used for preparation of mixes with a selected aggregate grading as given in the IRC Code. By preparing Marshall samples of the concrete mix the role of polythene in bituminous is studied for various engineering properties BC mixtures with and without polymer. Marshall properties such as stability, flow value, unit weight, air voids are used to determine optimum polythene content for the given grade of bitumen (80/100).

Mechanical Performance and Failure Analysis of a 3D-Printed "Continuous Layer-Lattice Layer-Continuous Layer" Sandwich Structure.

Sandwich structures are engineered with continuous layers surrounding the inner lattices, which combines the advantages of the high strength of the continuous layer and the light weight of the lattice layer. They are widely employed in weight-critical energy-absorbing engineering fields such as aerospace, automobile, and robotics. However, the application of sandwich structures made of polymer matrix composites is still limited due to lack of essential performance investigation and adequate reference data. The following innovative works are accomplished in this paper: (i) Continuous long glass fiber (CGF) is employed within the continuous layer of the sandwich structure, with composite short carbon fiber/polyamide (SCF/N) applied within the lattice layer. (ii) Sandwich structures with different cell types and orientations of the lattice infills are designed and prepared by additive manufacturing. (iii) The basic mechanical properties of the sandwich structures, i.e., the bi-directional tension/compression compound performance, failure modes and mechanisms in characteristic directions, are analyzed systematically. (iv) The effects of geometric features on the three-point bending properties of L-shaped sandwich structures are investigated and compared with those of pure SCF/N structures. The results show that the bending resistance per unit weight was up to 54.3% larger than that of pure SCF/N, while the weight could be decreased by 49%, and the bending flexibility before fracture could be increased by 44%. These studies contribute fundamental research data to the application of sandwich structures prepared by fiber reinforced polymer matrix composites.