Longitudinal Compressive Strength Research Articles

The Effect of Adding the Mishraq Sulfur Ore on the Physical and Chemical Properties of Al-Angor and Al-Nahrawan Clays to Producing Lightweight Bricks

This paper aims to examine the possibility of producing lightweight laboratory clay Bricks by adding sulfur ore powder in different weight ratios ranging from 0, 10, 20, 30, 40, to 50% as supplementary materials to two types of clays taken from two different sites, which is the Al-Angor clay region near the city of Ramadi and the Al-Nahrawan clay region. The bricks burned at temperatures of 950 and 1050 C°٬ and the longitudinal Shrinkage tests, bulk density, water absorption, compression strength, and efflorescence were measured. The X-ray diffraction analysis was executed to determine the formed metal phases. The results of the tests showed a direct proportion between longitudinal contraction and water absorption ratio with the addition of sulfur ore and high burning temperature. While bulk density and compression strength are inversely proportional to the sulfur ratio and high burning temperature. Efflorescence tests showed a decrease in the efflorescence rate with an increase in the proportion of sulfur ore.

Consolidation and Dehydration Effects of Mildly Degraded Wood from Luoyang Canal No. 1 Ancient Ship

To ensure the conservation of waterlogged archaeological wood, sustainable, safe, and effective methods must be implemented, with consolidation and dehydration being crucial for long-term preservation to maintain dimensional stability and structural integrity. This study compares the permeability of 45% methyltrimethoxysilane (MTMS) and 45% trehalose solutions to evaluate the dimensional changes, hygroscopicity, and mechanical properties of treated wood. Since the collected samples (from an ancient ship, Luoyang Canal No. 1) were mildly degraded, the drying method had a slight impact on the properties of archaeological wood. Consolidated with trehalose and MTMS agents, the longitudinal compressive strength of the waterlogged wood’s cell walls increased by 66.8% and 23.5%, respectively. Trehalose proved to be more advantageous in filling pores and reducing overall shrinkage, while MTMS significantly reduced the hygroscopicity and surface hydrophilicity of the wood substance. Overall, the MTMS treatment has a smaller effect on the appearance of samples, making it more suitable for the consolidation of mildly degraded waterlogged archaeological wood.

Investigation and calculation of the longitudinal compressive strength of unidirectional glass fiber reinforced polymer considering the fiber orientation distribution

In this study, undulations and their influence on the longitudinal compressive strength of a unidirectional glass fiber reinforced polymer (GFRP) composite are investigated theoretically and experimentally. The objective of this research is to explore the failure mechanisms in FRP and to characterize the mechanical properties of FRP as a function of fiber orientation. For this purpose, a multiscale material model is developed that considers a stochastic fiber orientation distribution (FOD) and models matrix fracture-initiated failure. The relationship between compressive strength and undulation is investigated experimentally on standardized specimens made of unidirectional GFRP. The fiber orientations are measured using X-ray computed tomography and ImageJ image analysis, resulting in a binormal distribution of fiber orientations in the series of samples tested. To examine the failure process in detail, the compression tests are simulated using finite element analysis (FEA). Both the FEA results and the measured compressive strengths confirm the model assumption of matrix fracture-initiated failure under longitudinal compressive loading. The presented analytical model realistically represents the correlation of compressive strength with the FOD.

The role of constitutive properties on the longitudinal compressive strength of composites

The longitudinal compressive strength of fibre-reinforced composites is often a limiting factor for structural design. This paper uses micromechanical finite-element analyses to examine how the constitutive properties of the matrix, fibres, and interface affect the composite’s strength. For a typical carbon/epoxy composite, the matrix shear strength has a larger effect than the modulus; a linear-elastic perfectly-plastic approximation of the matrix shear curve may overestimate the composite’s strength by over 15%. A pressure-dependent and dilatant matrix plasticity response may strengthen the composite by 30%, considering current uncertainties in friction and dilation angles of epoxy matrices. The finite shear modulus of carbon fibres may weaken the composite by more than 10%. Considering a cohesive interface using traction–separation laws significantly affects the predicted response of the composite, even for interfaces stronger than the matrix. Opportunities for improving the characterisation, modelling and performance of the constituents in terms of matrix plasticity, fibre shear modulus, and interface response are discussed.

Relationship between mechanical properties and height-diameter ratio of moso bamboo

Systematic tests of longitudinal compression, bending, longitudinal shear, and longitudinal tensile strength of bamboo were conducted to study the variation of mechanical properties and the height-diameter ratio of bamboo. The predictive relations of mechanical properties and height-diameter ratio were fitted by linear regression analysis. The results showed that the mechanical properties of longitudinal compression, bending, longitudinal shear, and longitudinal tensile strength of bamboo increased with the increase of the height-diameter ratio. In this paper, the method of deducing the relationship between mechanical properties and height-diameter ratio of bamboo through the linear fitting relationship between mechanical properties and height-diameter ratio was shown to have high applicability and accuracy for bamboo. This paper has a certain reference value for the evaluation of mechanical properties of bamboo and has a certain practical value for reducing the testing cost.

Microstructure and mechanical properties of Ti6Al4V/W bimetallic structure via selective laser melting

The titanium alloy Ti–6Al–4V (TC4) and tungsten (W) possess excellent complementary properties that would be useful for a wide range of industrial applications if they could be suitably combined. Selective laser melting was applied to prepare TC4/W specimens with a bimetallic structure. A strong bond without interfacial macrocracks was obtained by adjusting the laser line energy density to <0.75 J/mm. The bond interface of the bimetallic structure reached a microhardness of 503 ± 20 HV, which was harder than that of the two base materials, and the transverse and longitudinal ultimate compressive strengths were 1510 ± 40 MPa at strains of 20%–22.5%. Three-point bending experiments showed that when TC4 was used as the base material, the flexural strength of the specimen was 2210.5 ± 44.5 MPa. The high strength of the bond interface was attributed to sufficient agitation of the molten pool and reinforcement by fine crystalline grains. The agitation was provided by the melting and elemental diffusion of TC4 owing to the high energy input during the formation of W, and the fine crystalline grains were obtained by the dispersed W particles providing multiple nucleation sites for liquid TC4. The bimetallic structure retained the strength of W and toughness of TC4, which bodes well for its industrial application.

Enhancing the Longitudinal Compressive Strength of Freeform 3D-Printed Continuous Carbon Fiber-Reinforced Polymer Composite Laminate Using Magnetic Compaction Force and Nanofiber Z-Threads.

Low fiber-direction compressive strength is a well-recognized weakness of carbon fiber-reinforced polymer (CFRP) composites. When a CFRP is produced using 3D printing, the compressive strength is further degraded. To solve this issue, in this paper, a novel magnetic compaction force-assisted additive manufacturing (MCFA-AM) method is used to print CFRP laminates reinforced with carbon nanofiber (CNF) z-threads (i.e., ZT-CFRP). MCFA-AM utilizes a magnetic force to simultaneously levitate, deposit, and compact fast-curing CFRP prepregs in free space and quickly solidifies the CFRP laminate part without any mold nor supporting substrate plate; it effectively reduces the voids. The longitudinal compressive test was performed on five different sample types. ZT-CFRP/MCFA-AM samples were printed under two different magnetic compaction rolling pressures, i.e., 0.5 bar and 0.78 bar. Compared with the longitudinal compressive strength of a typical CFRP manufactured by the traditional out-of-autoclave-vacuum-bag-only (OOA-VBO) molding process at the steady-state pressure of 0.82 bar, the ZT-CFRP/MCFA-AM samples showed either comparable results (by -1.00% difference) or enhanced results (+7.42% improvement) by using 0.5 bar or 0.78 bar magnetic rolling pressures, respectively.

Effect of strain rate on the in-plane orthotropic constitutive response and failure behaviour of a unidirectional non-crimp fabric composite

A comprehensive experimental campaign was performed to characterize the strain rate-dependent orthotropic constitutive response and failure behavior of a unidirectional non-crimp fabric (UD-NCF) carbon fiber/snap-cure epoxy composite. Shear and transverse compression strengths increased by 60% and 50%, respectively, over the range of strain rates considered, which is consistent with previously reported trends for unidirectional tape composites (UDTCs). The transverse tension strength increased by 18% with increasing strain rate, which is different from UDTCs. Owing to the distinct microstructure of UD-NCF composites, local damage mechanisms such as pullout of transverse supporting glass fibers and stitching were observed and are deemed to contribute to the rate dependency of transverse tension strength. The longitudinal compression strength increased by 35% with increasing strain rate. Observation of failed specimens revealed widespread inter-tow axial splitting and localized tow kinking, distinct from UDTCs. This important finding will aid in the development of failure criteria for UD-NCF composites.

Cold pressing and hot curing process for assembly of hexagonal pre-shaped bamboo culm sections

Bamboo is widely used in the construction industry due to its excellent mechanical properties, short production cycle, and environmental concerns. Reconstructing and processing bamboo into biomass-based composite materials that can replace wood alleviates the imbalance between wood supply and demand. This article uses cold press setting and hot press curing molding processes to prepare small samples of Hexagonal Recombinant Bamboo Material (glued HexBam). Through orthogonal analysis, the preparation process parameters, adhesive types, adhesive application amounts, and the relationship between the temperature and time of hot pressing solidification molding and the mechanical properties of glued HexBam were determined. A phenolic adhesive (PF) was used with a dosage of 200 g/m2, a heat setting and molding temperature of 130 °C, and a heat setting molding time of 10 minutes. Under these process conditions, the prepared glued HexBam had a longitudinal compressive strength of 73.8 MPa and a specific strength of 0.0535 N•m/kg, which is superior to ordinary steel.

Tensile and Compression Strength Prediction and Validation in 3D-Printed Short-Fiber-Reinforced Polymers.

In the current study, a methodology is validated for predicting the internal spatially varying strength properties in a single 3D-printed bead composed of 13%, by weight, carbon-fiber-filled acrylonitrile butadiene styrene. The presented method allows for the characterization of the spatially varying microstructural behavior yielding a local anisotropic stiffness and strength that can be integrated in a finite element framework for a bulk estimate of the effective stiffness and strength. The modeling framework is presented with a focus on composite structures made from large area additive manufacturing (LAAM). LAAM is an extrusion-based process yielding components on the order of meters, with a typical raster size of 10 mm. The presented modeling methods are applicable to other short-fiber-reinforced polymer processing methods as well. The results provided indicate the modeling framework yields results for the effective strength and stiffness that align with experimental characterization to within ∼1% and ∼10% for the longitudinal compressive and tensile strength, respectively, and to within ∼3% and ∼50% for the longitudinal compressive and tensile stiffness, respectively.

Compressive strength improvements from noncircular carbon fibers: A numerical study

The benefits of high-performance unidirectional carbon fiber composites are limited in many cost-driven industries due to the high cost relative to alternative reinforcement fibers. Low-cost carbon fibers have been previously proposed, but the longitudinal compressive strength continues to be a limiting factor or studies are based on simplifications that warrant further analysis. A micromechanical model is used to (1) determine if the longitudinal compressive strength of composites can be improved with noncircular carbon fiber shapes and (2) characterize why some shapes are stronger than others in compression. In comparison to circular fibers, the results suggest that the strength can be increased by 10%–13% by using a specific six-lobe fiber shape and by 6%–9% for a three-lobe fiber shape. A slight increase is predicted in the compressive strength of the study two-lobe fiber but has the highest uncertainty and sensitivity to fiber orientation and misalignment direction. The underlying mechanism governing the compressive failure of the composites was linked to the unique stress fields created by the lobes, particularly the pressure stress in the matrix. This work provides mechanics-based evidence of strength improvements from noncircular fiber shapes and insight on how matrix yielding is altered with alternative fiber shapes.

Effects of Heat Treatment under Different Pressures on the Properties of Bamboo.

To optimize the bamboo heat treatment process, the corresponding evolution rules under various heat treatment conditions must be determined. When the heat treatment time and temperature remained constant, the effects of different heat treatment pressures on the equilibrium moisture content, dimensional stability, mechanical properties, and chemical composition of bamboo were systematically investigated. In this experiment, bamboo without heat treatment was used as the control group. The experimental findings demonstrate the following: (1) The equilibrium moisture content of heat-treated bamboo gradually decreases with increasing treatment pressure. When the heat treatment pressure was set at 0.1, 0.15, 0.2, and 0.25 MPa, the bamboo's equilibrium water content decreased to 12.1%, 11.7%, 9.9%, and 8.6%, respectively, while that of the control group was 13.8%. (2) The dimensional stability of bamboo was enhanced with increasing heat treatment pressure. At pressures of 0.1, 0.15, 0.2, and 0.25 MPa, the radial air-dry shrinkage rates of the heat-treated bamboo decreased to 3.4%, 3.4%, 2.6%, and 2.3%, respectively, while the tangential air-dry shrinkage rates reduced to 5.6%, 5.1%, 3.3%, and 3.0%. In comparison, the radial and tangential air-dry shrinkage rates of the control group were measured as 3.6% and 5.8%, respectively. Similarly, the radial and tangential full-dry shrinkage of bamboo exhibited a similar trend. (3) With the increase in heat treatment pressure, the bending strength and longitudinal compressive strength of bamboo exhibited an initial rise followed by a decline. When it was at heat treatment pressures of 0.1, 0.15, 0.2, and 0.25 MPa, the corresponding bending strengths of the heat-treated bamboo were measured as 41.2, 26.7, 22.4, and 20.4 MPa, respectively; while the longitudinal compressive strengths were recorded as 42.6, 38.1, 29.1, and 25.3 MPa. In comparison, the bending and longitudinal compressive strengths of the control group were measured as 39.8 and 38.5 MPa, respectively. It is evident that the optimal heat treatment pressure for bamboo is 0.1 MPa, resulting in a significant increase of 3.5% and 10.6% in bending strength and longitudinal compressive strength, respectively, compared to the control group. (4) Based on the FTIR and XRD patterns of bamboo samples, a range of physical and chemical transformations were observed during the heat treatment process, including cellulose adsorb water evaporation, hemicellulose and cellulose degradation, as well as acetyl group hydrolysis on the molecular chain of hemicellulose. These changes collectively impacted the physical and mechanical properties of bamboo.

Mechanical performance of engineered bamboo subjected to accelerated aging with single and multiple durability exposures

Durability is a critical concern for engineered bamboo structures. The results of an experimental study of the mechanical performance of engineered glue laminated bamboo, bamboo scrimber and Douglas fir specimens subjected to accelerated aging under single and multiple durability exposures are presented. In total, nineteen specimen groups comprising almost 1200 samples were prepared and tested under conditions of ultraviolet radiation, alternating wet-dry cycles, alternating hot–cold cycles, and a combination of all three exposures. Specimen density, dimensional stability and discoloration were reported. Mechanical properties assessed were longitudinal compressive strength and modulus, and bending strength and modulus. Durability exposure related damage of the laminated bamboo and Douglas fir was greater than that of the bamboo scrimber under single and multiple durability exposures; the bamboo scrimber exhibited a better durability resistance. Analysis of variation of the results of the single and multiple exposures indicated that exposure to ultraviolet radiation had the greatest contribution to the durability performance of the three materials.

3D characterization of vascular bundle in moso bamboo node and its effect on compressive properties

Abstract The structure of the bamboo node obviously differs from that of the internode and largely affects the mechanical properties of bamboo. However, the node structure of moso bamboo, an important economic and ecologic bamboo species, was still unclear. Thus, in this study, the 3D structural changes of the vascular bundle (VB) in the moso bamboo node were visualized and quantified. The compressive properties and failure mechanisms of the bamboo node were discussed based on the structural changes. The results showed that the horizontal VB in bamboo node was classified into three types: branching, cross-linking, and thickening. The cross-sectional area of the vertical VB in bamboo node increased, and the vertical VBs shifted to the outer side after passing through the node. Due to the “wire hoop” effect of the horizontal VBs, the longitudinal compressive strength of the node was greater than that of the internode. The deflection of VBs caused slippage between VBs and resulted in the decrease of the node’s transversal compressive strength. This research provided key information for a deeper understanding of the structure and mechanical properties of bamboo for potential applications.

Numerical investigation on the ultimate strength behaviour and assessment of continuous hull plate under combined biaxial cyclic loads and lateral pressure

The ultimate strength of continuous hull plate under combined biaxial cyclic loads and lateral pressure is investigated in the present paper by using nonlinear finite element method. Geometric nonlinearity due to large deflection and material nonlinearity induced by kinematic hardening and isotropic hardening are both accounted for. A parametric study is designed and completed to examine the longitudinal ultimate compressive strength behaviours in the cycles on the basis of a large number of load-shortening curves. Effects of series of parameters especially the plate slenderness ratio, transverse cyclic compression, lateral pressure and cycle number are analyzed with details. It is found that the strength characteristic and collapse mode are highly affected by the coupling influence of the mentioned factors as well material behaviours. A dimensionless unified formulation as a function of the decisive factors is empirically proposed to accurately assess the ultimate strength of continuous hull plate in various cycles.

Identification of damage properties of glass/epoxy laminates using machine learning models

In the present research, the possibility of estimating damage properties of Glass/Epoxy woven laminates using machine learning (ML) models is investigated. The dynamic response of laminates under low-velocity impact (LVI) was characterized and used as training data sets for ML models. The suitability of four numerical models was investigated for LVI modeling, and based on their accuracy and simulation run-time, an appropriate method was selected. The MAT054 material model was selected for LVI simulations for two energy states (15 J and 20 J). After characterizing the results of these simulations a set of 13 dynamic characteristics were extracted from the dynamic response of each simulation. Moreover, for each energy state, four ML regression models, namely MLP, KNN, DT, and SVR, were performed with the numerical input sets and the random laminate damage properties in each simulation as the output sets. For each ML model the input vector was the same however only one damage property was set as an output vector. The trained ML models were able to estimate 4 out of 6 damage properties of Glass/Epoxy woven laminates namely Longitudinal modulus, Longitudinal tensile strength, Longitudinal compressive strength, In-Plane shear strength. Additionally, the output of the trained ML models was compared with damage properties obtained from experimental results and it was found that the trained models were able to estimate the said damage properties within 4% – 6% of the experimental results.

Enhanced longitudinal compressive strength of CFRP composites with interlaminar CNT film prepreg from hot-melt pre-impregnation

High strength, high modulus and the balance of compressive and tensile strength gradually became the main development goals of advanced CFRP composites. However, the low ratio of compressive and tensile strength of CFRP composites have limited the application as structural materials in aerospace field. In this study, CNT film prepreg (CNT-f-p) was prepared by hot-melt pre-impregnation and used to fabricate the interlayer stiffened and reinforced CFRP composites with enhancement of compressive strength, and the effect of CNT-f-p on longitudinal compressive strength and elastic-plastic failure mechanism of composites were firstly investigated from the experimental results and theoretical model. The tensile strength and modulus of CNT-f-p were enhanced due to sufficient and uniform infiltration of CNT network by resin matrix. The interlaminar shear strength and in-plane shear modulus of CFRP/CNT-f-p composites were improved due to effective CNTs bridging and riveted CNTs between resin and fiber in interlaminar region of composites. The compressive strength of CFRP/CNT-f-p composites was enhanced by 13.2%, showing a consistency with predicted results of Jumahat's combined model, which ascribed to restricted kink-band formation and avoided interface delamination during elastic-plastic compression process of composites from improved transverse support and interfacial adhesion. Consequently, this work presented a potential application in fabrication of CFRP composites with high compressive strength.

Splitting failure of a composite under longitudinal tension

AbstractSignificant variation can be found in measurements for the longitudinal tensile strength of the same unidirectional (UD) composite. A splitting failure is one of the main reasons. It is shown in this paper that the shear stress component resulted from a longitudinal tension and a fiber misalignment can cause the matrix to fail before fiber break. The misalignment angle consists of an initial off‐axial angle and a further fiber rotation during the loading. Based on the micromechanics Bridging Model and the matrix true stress theory established by the author, splitting failure has been analyzed and predicted rigorously in this paper, only using the fiber and matrix properties together with the fiber misalignment angle. The fiber initial misalignment angle of a unidirectional plate can be obtained from testing statistics, or deducing from measured longitudinal compression strength. Our research indicates that the longitudinal tensile strength and the relevant failure mode can be significantly affected by the fiber initial misalignment.

Mechanical Property Prediction of Larix gmelinii Wood Based on Vis-Near-Infrared Spectroscopy

Larix gmelinii is the major tree species in Northeast China. The wood properties of different Larix gmelinii are quite different and under strong genetic controls, so it can be better improved through oriented breeding. In order to detect the longitudinal compressive strength (LCS), modulus of rupture (MOR) and modulus of elasticity (MOE) in real-time, fast and non-destructively, a prediction model of wood mechanical properties with high precision and stability is constructed based on visible-near-infrared spectroscopy (Vis-NIRS) technology. The featured wavelengths were selected with the algorithms of competitive adaptive reweighted sampling (CARS), successive projection algorithm (SPA), uninformative variable elimination (UVE), synergy interval partial least squares (SiPLS) and their combinations. The prediction models were then developed based on the partial least square regression (PLSR). The predictive ability of models was evaluated with coefficient of determination (R2) and root mean square error (RMSE). It indicated that CARS performed the best among the four methods examined in terms of wavelength-variable selection. The combined featured wavelength selecting method of SiPLS-CARS showed better performance than the single wavelength selection method. The optimal models of LCS, MOR and MOE are the SiPLS-CARS-PLSR model, with the R2 of the calibration set and the validation set are both greater than 0.99, and RMSE the smallest. The NIR optimal models for wood mechanical properties predictions has high predictive accuracy and good robustness.

Experimental study on the low-temperature compression performance of 3D five-directional braided composites applied to extreme environments

• A low-temperature compression test method was designed for 3D5dB composites. • The effects of low-temperature on the compression strength and strain were revealed. • Results of the failure mode are guided for its application in extreme environments. 3D five-directional braided (3D5dB) composites with different braiding angles were designed and prepared, and their compressive properties in the longitudinal, out-of-plane and transverse directions were investigated at room temperature (RT) and liquid nitrogen temperature (LNT). The results of the stress-strain curves showed that the composites at LNT exhibited more pronounced brittle fracture failure and increased compressive strength in all directions compared to RT. The longitudinal compression strength decreased with increasing braiding angle, while the opposite effect was observed for transverse and out-of-plane. The effect of LNT on the failure of 3D5dB composites was mainly focused on the interfacial debonding of fibers and matrix, so the mechanical properties can generally be improved by modifying the fibers to increase the interfacial shear strength at low temperatures. 3D5dB composites with high mechanical strength at the temperature of LNT can be potentially used as cryogenic materials for aerospace applications.