Transverse Compressive Strength Research Articles

Effect of hollow glass microspheres on transverse properties of carbon fiber reinforced epoxy composites

AbstractHollow glass microsphere (HGM)—based composites are gaining popularity in materials research due to their ability in altering material characteristics drastically. The current study investigates HGMs filled carbon fiber reinforced epoxy (CE) composites on transverse properties, aiming for aerospace and defense applications mainly in composite pressure vessels. Unidirectional laminates of Carbon/Epoxy with varying HGM percentages (0.2, 0.4, 0.6, 0.8, 1.0 wt. %) were wounded onto a flat‐plate mandrel using a 4‐axis filament winder, along with a baseline sample without HGM for comparison. The glass transition temperature (Tg) and thermal stability were analyzed by carrying out dynamic mechanical analysis and thermogravimetric analysis. The fracture mechanism of the samples loaded under tension was investigated using FESEM. Experimental results indicate reduction in density with increase in HGM content, up to 0.4% HGM there is increase in transverse tensile strength of 25% compared to baseline and further increase in HGM content, decrease trend is observed. 30% decrease in transverse compressive strength is observed compared from baseline to 1.0 wt. % of HGM. No significant change was noticed in the thermal stability and Tg on introduction of HGM. Microscopy images of fractured samples revealed effective physical interaction and dispersion of the HGM within the matrix.Highlights Transverse mechanical properties are tested to know the influence of HGM filler on filament wound composites. Density of the composite decreases with increase in HGM content. Thermal stability and Tg shows less change on introduction of HGM in composites.

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.

Effect of Pulping Waste Liquid on the Physicochemical Properties and the Prediction Model of Wheat Straw Residue Granular Fuels.

Herein, wheat straw residue and pulping waste liquid were collected from pulping mill and mixed to prepare bio-based granular fuels by using compression molding technology, and to explore the comprehensive utilization of the industrial waste of pulping and papermaking. The effects of pulping waste liquid on granular fuel properties were analyzed systemically. Further study of the function of pulping waste liquid, cellulose and hemicellulose was used to replace wheat straw residue and avoid the interference factors. Therefore, the prediction models of granular fuels were established with influencing factors that included cellulose, hemicellulose and pulping waste liquid. The granular fuels had the best performance with 18.30% solid content of pulping waste liquid. The highest transverse compressive strength of granular fuel was 102.61 MPa, and the activation energy was 81.71 KJ·mol-1. A series of curve fitting prediction models were established to clarify the forming process of granular fuel, and it turned out that the pulping waste liquid could improve the adhesion between solid particles and increase their compression resistance.

A transverse failure criterion for unidirectional composites based on the Puck failure surface theory

Puck criterion, a transverse failure criterion for composites, has more applications in engineering, but the empirical nature of its mathematical expression and the complexity of its parameters hinder its further development. In this work, a failure function is proposed based on the Puck hypothesis. According to the parameters of composites in special states, two modes of transverse tension and compression are distinguished, the pending coefficients in the failure function are derived, and then a transverse failure criterion for composites is formulated. The proposed criterion was evaluated experimentally in terms of envelope curves and off-axis strength using the existing data in the literature, and was compared with several other criteria. The results show that the proposed criterion is in good agreement with the experimental data, and its prediction accuracy ranks high among several criteria, demonstrating the rationality of the proposed criterion. Additionally, the effect of material parameters on the proposed criterion is analyzed and the results show that changes in transverse tensile and compressive strength can change the strengthening effect of transverse compression against in-plane shear, while changes in in-plane shear strength cannot change the strengthening effect. This work provides a correction method for the Puck criterion, which has a more rational mathematical expression with fewer parameters and can be used in the design of engineering composite structures, which has significant design reference value and theoretical significance.

Effects of Growth Ring Width, Height from Tree Base, and Loading Direction on Transverse Compression of Plantation Japanese Larch Wood

This study aimed to investigate the effects of growth ring width, height from the tree base, and loading direction on the transverse compressive strength of Japanese larch wood, which is commonly used in wood structures in China. Plantation wood is often used to replace natural forest woods for reconstruction purposes, despite significant differences in properties (e.g., growth rings, density, strength) between them. The ends of transversely compressed wood members in such structures are prone to damage by breaking or crushing. A transverse compressive test was conducted following Chinese national standards, which revealed the following key findings. (1) There was a significant difference in the transverse compressive strength of wood with different growth ring widths (p &lt; 0.05). The radial and slant compressive strength of wood increases with growth ring width, while the tangential compressive strength decreases as growth ring width increases. (2) The transverse compressive strength of wood decreases as the height from the tree base increases. The radial, tangential, and slant compressive strength at a lower height were 18.39%, 22.58%, and 18% higher than those at a greater height in the stem, respectively, with significant differences at the 0.05 level. (3) The load–displacement curve of Japanese larch wood under radial and slant compression follows a “three-segment” form. In contrast, the load–displacement curve of tangential compression is a continuous curve that drops sharply upon reaching its highest point. (4) There is a significant difference in the transverse compressive strength of Japanese larch wood in different loading directions when growth ring width and height from the tree base are constant (p &lt; 0.05), which fall into order as tangential &gt; radial &gt; slant.

Liquid nitrogen temperature effects on the mechanical behaviors of three-dimensional seven-directional braided composites

Three-dimensional (3D) braided composites are broadly adopted in aerospace cryogenic fuel tanks. This work designed and fabricated 3D seven-directional braided composites (3D7dBCs) with different braiding angles, and their compression properties at room and liquid nitrogen temperatures (RT and LNT) were explored and discussed, while the mechanical properties were compared with other braided structural composites. Temperatures and braiding angles considerably influenced the properties of 3D braided composites. The multi-directional compression strength of 3D7d21-LNT and 3D7d34-LNT was 392.7 MPa, 426.1 MPa, 270.3 MPa, 210.3 MPa, and 268.8 MPa, 204.1 MPa, which was 18.1% and 18.6% higher than that of 3D7d21-RT and 3D7d34-RT in the out-of-plane direction, 5.1% and 6.5% in the longitudinal direction, 74.2% and 9.7% in the transverse direction, whereas the longitudinal strength decreased as braiding angles increased, and the out-of-plane and transverse compression strength increased. Additionally, shear cracking was the main reason for the failure of 3D7dBCs at RT, while fiber loosening, pulling-out, and interfacial debonding were exhibited at LNT. Compared to 3D five-directional and 3D six-directional braided composites (3D5dBCs and 3D6dBCs), the incorporation of seventh yarns significantly improved the out-of-plane properties of 3D7dBCs.

Test on shearing performance of concrete filled square CFRP-steel tube

Taking layer of the transverse CFRP and compressive strength of the concrete as the main factors, the shearing behaviour of overall 8 concrete filled square CFRP-steel tubular (CF–S-CFRP-ST) specimens and 3 concrete filled square steel tubular specimens are tested. On the basis of test results, the shearing force-displacement curves of all specimens can be classified three stages. Increase of layer of the transverse CFRP can improve the shear capacity of the specimens, while the elastic stiffness of the curve changes a little. Increase of compressive strength of the concrete can improve both the shearing load carrying capacity and the elastic stiffness. The shape of the curve of the specimens is not sensitive to the layer of the transverse CFRP and the compressive strength of the concrete. It is found that the simulated shear loading-displacement curves agree reasonably well with the experimental ones by using software ABAQUS. Using this verified numerical model, parametric study is conducted to explore the influence of principle factors on shear behaviour of concrete filled square CFRP-steel tube. Finally, the calculation formula of CF-S-CFRP-ST shear capacity is established, and the calculated results of this formula are in good agreement with the experimental results.

Numerical investigation on the role of out-of-plane fiber direction on impact resistance of composite target

In high-velocity projectile impacts, the contact duration is very short and the response of the target is governed by the local behavior of the material in the impact zone. On impact, a compressive stress wave is generated in the target, which travels in the thickness direction. This compressive stress wave plays a significant role in the failure of thick composite targets. In conventional laminates, the out-of-plane (transverse) compressive strength of composite resists the generated compressive stress wave which is not efficient since out-of-plane compressive strength is significantly lower than the fiber direction strength value. In the current numerical study, a non-conventional approach has been adopted by orienting the fibers in the impact direction to utilize the high compressive strength in the fiber direction to resist the projectile impact. In this regard, unidirectional composite rod segments are considered with fiber aligned in the projectile impact direction. The resulting effect on the impact energy absorption and the overall mechanical impact response is numerically studied and compared with conventional woven fabric laminates. Several configurations of these unidirectional fiber rod segments and the role of lateral confinement are also studied to understand their effect on the impact energy absorption. The numerical simulation results indicate an advantage for the proposed arrangement of composite (segments) rods with fiber in impact direction over the conventional woven fabric laminates.

Machine learning and materials informatics approaches for predicting transverse mechanical properties of unidirectional CFRP composites with microvoids

The mechanical properties of composites are traditionally measured using numerical and experimental approaches, which impede the innovation of materials due to the cost, time, or effort involved. This study for the first time develops a machine learning-assisted model, which aims at predicting the transverse mechanical properties of unidirectional (UD) carbon fiber reinforced polymer (CFRP) composites with microvoids. To this end, the stochastic microstructures are generated by random sequential expansion (RSE) and hard-core model. And the transverse elastic modulus, transverse tensile strength and transverse compressive strength are computed by micromechanics-based finite element (FE) method. Then, the reduced order representation of microstructures is determined using 2-point spatial correlations and principal component analysis (PCA). Finally, a genetic algorithm (GA) optimized back propagation (BP) neural network is implemented to capture the potential nonlinear relationship between microstructure and transverse mechanical properties. The presented data-driven techniques can reproduce the FE simulation results with an R-value of 0.89 or greater. The excellent agreement between the predicted results and test datasets verifies the successful application of data science methodologies in elucidating the microstructure-property linkages of UD-CFRP composites with microvoids, and thus provides a promising tool for accelerating the smart design and optimization of composites.

Prediction of temperature-dependent transverse strength of carbon fiber reinforced polymer composites by a modified cohesive zone model

A temperature-dependent micromechanical model was proposed in this study by the representative volume element model with the fibers randomly distributed, the law of temperature-dependent Young’s modulus of polymer and the plasticity model of polymer. Considering the thermal effect, a modified cohesive zone model with temperature-dependent parameters was presented for simulating the fiber/polymer interface. Validations by other’s experimental results indicate that the proposed model is reliable and accurate to estimate the transverse mechanical properties, including Young’s modulus and strength of carbon fiber reinforced polymer composites. Compared with those at room temperature, values of the transverse tensile strength and transverse compressive strength at 80 °C are reduced by 9.1% and 4.8%, while both values at −196 °C greatly increase by 16.1% and 8.8%, respectively, showing that the temperature plays a more influencing role on the transverse tensile strength. Failure behaviors of composites were investigated for the temperature from −196 °C to 80 °C. Moreover, parametric sensitivity analysis was carried out to evaluate the effect of interface properties on the strengths of carbon fiber reinforced polymer composites. It was found that the interface strength significantly affects mechanical behavior of composites at different temperatures, while the influences of interface stiffness and fracture energy are fairly minimal.

Data-driven soft sensors of papermaking process and its application to cleaner production with multi-objective optimization

Papermaking industry can hardly monitor the dynamic of certain variables in the process when the test can only be conducted offline or destroy samples. Soft sensor is a predictive model that maps the measurable variables to the unknown measurements. In order to address the caused uncertainty, promote the papermaking process, a couple of soft sensors are developed with the industrial data by means of random forest (RF), gradient boosting regression (GBR), ridge regression and K-nearest neighbor (KNN) to monitor folding endurance, bursting strength, smoothness, and transverse ring compressive strength. The optimal models hold accuracy ≥0.839 (R-square) in general, and are applied to the multi-objective of cleaner papermaking production with regard to cost, energy consumption, and greenhouse gas (GHG) emission. The optimized results show that, when process is qualified with soft sensors' support, the possible reduction of cost, energy consumption and GHG emission could be up to 17.3% in total.

Tar induced deactivation and regeneration of a commercial V2O5-MoO3/TiO2 catalyst during selective catalytic reduction of NO with NH3

Tar species on catalyst’s surface promote the deposition of NH4HSO4/(NH4)2SO4 leading to the complete deactivation of V2O5-MoO3/TiO2 catalyst utilized in a glass kiln. The proposed pyrolysis method in this work effectively removes the poisoning substances. TG-IR and TG-MS results indicate that the pyrolysis products are mainly CO2 and SO2 representing the pyrolysis of tar species and NH4HSO4/(NH4)2SO4. The heating rate and pyrolysis temperature are the critical factors to keep a superior mechanical property. The axial and transverse compressive strength remained 1.77 MPa and 0.53 Mpa falling only by 4.8% and 13.1% respectively through the optimized treatment at 420 °C for 2 h with heating rate of 3 K min−1. The characterizations indicated that the surface area, pore volume and acid property were apparently restored after the heat treatment. As a result, the regenerated powder catalyst showed 100% NO conversion and more than 94% N2 selectivity at 250 – 300 °C and the regenerated honeycomb catalyst exhibited 91.6% NO conversion at 260 °C. The TPR and XPS results indicated changes of the redox behavior, which contracted the temperature range of excellent performance. Typically, the redox cycles shifting to high temperatures narrowed this temperature range, while the excessive oxidation ability decreased the N2 selectivity. The schematic of tar induced deactivation and regeneration was proposed. Overall, the tar induced deactivated catalyst was successfully regenerated by proper pyrolysis and can be reutilized in the original glass kiln at 260 °C.

Effect of Strain Rate on the Transverse Tension and Compression Behavior of a Unidirectional Non-Crimp Fabric Carbon Fiber/Snap-Cure Epoxy Composite.

The strain rate-dependent behavior of a unidirectional non-crimp fabric (UD-NCF) carbon fiber/snap-cure epoxy composite loaded along the transverse direction under quasi-static and dynamic conditions was characterized. Transverse tension and compression tests at quasi-static and intermediate strain rates were performed using hydraulic testing machines, while a split Hopkinson pressure bar (SHPB) apparatus was used for transverse compression tests at high strain rates. A pulse shaper was used on the SHPB apparatus to ensure dynamic equilibrium was achieved and that the test specimens deformed homogenously with a nearly constant strain rate. The transverse tensile strength at a strain rate of 16 s−1 increased by 16% when compared to that at quasi-static strain rates, while distinct localized fracture surface morphology was observed for specimens tested at different strain rates. The transverse compressive yield stress and strength at a strain rate of 325 s−1 increased by 94% and 96%, respectively, when compared to those at quasi-static strain rates. The initial fracture plane orientation for the transverse compression tests was captured with high-speed cameras and found to increase with increasing strain rate. The study provides an important data set for the strain rate-dependent response of a UD-NCF composite material, while the qualitative fracture surface observations provide a deeper understanding of the failure characteristics.

Size Effect in Transverse Compressive Strength of Composites Analyzed by the Fixed Crack Model

AbstractPresented in this study is a numerical analysis of the size effect in the transverse compressive strength of unidirectional (UD) composites by employing the fixed crack model. The model is ...

Investigation of the Impact of Aging Upon the Mechanical Properties of Cocoa Pod Husk

The husk of fresh cocoa pods has traditionally been considered a waste by-product in the production of chocolate and other related confectionaries. However, in recent times new research has shed light on an increasing number of uses for this material. Of particular interest are applications that utilize the cocoa pod husk (CPH) for its mechanical properties. In most instances, the CPH raw material is allowed to age for several days before pre-processing or utilization in the intended application. Despite this, the impact of aging on its mechanical properties is an area that has not been well investigated. Consequently, this work seeksto determine the impact of aging upon the mechanical properties of CPH. To investigate this, several CPH properties were identified and selected for evaluation. These included CPH tensile strength, CPH compressive strength, cocoa pod transverse compressive strength, cocoa pod longitudinal compressive strength, CPH cutting force, cocoa pod cutting force, CPH hardness, and CPH colour. These properties were subsequently assessed over an aging period of seven days. The results obtained indicated that most CPH mechanical properties vary significantly with aging time. Moreover, CPH colour was found to bestrongly related to the mechanical properties of pod longitudinal compressive strength and CPH hardness, with correlation coefficients of -0.71 and 0.86 respectively. Further, these relationships were found to be strongly linear in nature and regression analyses indicated that up to 83% of the variation in longitudinal compressive strength can be accounted for by changes in colour, hardness and aging time. These results provide the basis for the potential development of image analysis and computer vision approaches to CPH sorting and grading.

Investigation of the Impact of Aging Upon the Mechanical Properties of Cocoa Pod Husk

The husk of fresh cocoa pods has traditionally been considered a waste by-product in the production of chocolate and other related confectionaries. However, in recent times new research has shed light on an increasing number ofuses for this material. Of particular interest are applications that utilize the cocoa pod husk (CPH) for its mechanical properties. In most instances, the CPH rawmaterial is allowed to age for several days before pre-processing or utilization in the intended application. Despite this, the impact of aging on its mechanical properties is an area that has not been well investigated. Consequently, this work seeksto determine the impact of aging upon the mechanical properties of CPH. To investigate this, several CPH properties were identified and selected for evaluation. These included CPH tensile strength, CPH compressive strength, cocoapod transverse compressive strength, cocoa pod longitudinal compressive strength, CPH cutting force, cocoa pod cutting force, CPH hardness, and CPHcolour. These properties were subsequently assessed over an aging period of seven days. The results obtained indicated that most CPH mechanical properties vary significantly with aging time. Moreover, CPH colour was found to bestrongly related to the mechanical properties of pod longitudinal compressive strength and CPH hardness, with correlation coefficients of -0.71 and 0.86 respectively. Further, these relationships were found to be strongly linear in natureand regression analyses indicated that up to 83% of the variation in longitudinal compressive strength can be accounted for by changes in colour, hardness andaging time. These results provide the basis for the potential development of image analysis and computer vision approaches to CPH sorting and grading.

Study on Glass Fibre Concrete Roof Tiles

The main objective of the fibre glass in concrete roof tile is to obtain good strength, heat resistant, &amp; water seepage resistant roof tile. To ensure that the roof tile produced plays a role development with minimum cost, and high flexure strength. To draw an analogy between the normal concrete roof tile with glass fibre concrete roof tile. The sizes of short fibres used were 25mm and the glass fibres were alkali resistant. The effect of these short fibres on wet transverse strength, compressive strength and water absorption was carried out.

Numerical modelling of spoolable thermoplastic composite pipe (TCP) under combined bending and thermal load

ABSTRACT Spoolable thermoplastic composite pipe (TCP) consisting of fibre-reinforced laminate with inner and outer liners is an ideal candidate to replace steel counterparts in deepwater. In this paper, a 3D finite element (FE) model is developed to analyse stresses in TCP under combined bending and uniform temperature change illustrative of spooling in different environments. Thermal load causes deviation from the stress symmetry expected at the top/bottom of the pipe in simple bending. Maximum stress, Tsai–Hill and Hashin failure responses are analysed for [±55]4, [±42.5]4, [±30]4 and [(±55)2/(±30)2] laminates at low and high temperatures. The [±42.5]4 configuration displays superior spooling capacity as layers orientated at ±55° and ±30° exhibit high utilisation of relatively weak transverse tensile and fibre compressive strengths, respectively. The failure criteria are in closest agreement at the top of the pipe (under axial tension) but differ more significantly at the bottom (axial compression).

Effects of loading rate and loading direction on the compressive failure behavior of a 2D triaxially braided composite

The effects of loading rate and loading direction on the compression failure behavior of a typical 0°/±60° two-dimensional triaxially braided composite (2DTBC) were studied by compressing brick specimens cut from an eight-layer 2DTBC panel along the axial and transverse directions. Quasi-static tests were conducted using an electronic universal testing machine, and a novel Electromagnetic Split Hopkinson Pressure Bar (E-SHPB) was employed to carry out dynamic tests. High-speed cameras were employed to monitor the progressive failure process in the specimen during the tests, and the failure morphology was examined using an optical microscope. The test results show that both axial and transverse compression strength noticeably increase under dynamic loading conditions. Moreover, different failure mechanisms for the 2DTBC under axial and transverse compression were observed, and the influence of loading rate on the compressive failure behavior of the 2DTBC was systematically investigated.

An improved methodology of constructing inter-fiber failure criteria for unidirectional fiber-reinforced composites

Based on Mohr’s failure theory and physical mechanisms of unidirectional (UD) fiber-reinforced composites, an improved methodology of constructing inter-fiber failure (IFF) criteria is proposed. The expression of the failure criteria is a quadratic polynomial, in which the variables are the normal and shear stress components (σn,τnl,τnt) on the potential failure plane. The coefficients of the quadratic polynomial are independent of empirical parameters and calibrated only by four basic strengths of a UD composite, i.e. transverse tensile and compressive strengths, Yt and Yc, as well as transverse and longitudinal shear strengths, S23 and S21. It avoids some deficiencies of the previous criteria for IFF in which some parameters may need to be determined by multiaxial stress tests or by empirical data-fitting operation. Compared with the theoretical prediction results and the experimental data of various UD composites, the present IFF criteria show good prediction accuracy.