Void Content Research Articles

Effect of micro‐sized blast furnace slag on physical, mechanical, and thermo‐mechanical properties of bi‐directional date palm fiber reinforced polymer composite

AbstractThis present research work focuses on studying the physical, mechanical, and thermo‐mechanical behavior of blast furnace slag (BFS) in bi‐directional date palm fiber reinforced hybrid polymer composites. During this investigation, the different weight percentage of blast furnace slag filler (from 3 wt.‐% to 7 wt.‐%) was added to date palm fiber to fabricate epoxy‐based composite by vacuum assisted resign transfer molding (VARTM) technique under controlled pressure conditions. The fabricated composite were characterized for physical (density, void content, hardness), mechanical testing (tensile, flexural, inter‐laminar shear strength, impact strength and fracture toughness) and thermal properties. The experimental result indicated varied rate of deterioration for tensile strength of the composites and the maximum tensile strength 69.51 MPa was obtained for blast furnace slag (3 wt.‐%) and date palm fiber (30 wt.‐%) hybrid composite. The optimum flexural and inter laminar shear strength has been obtained to be 85.72 MPa and 9.43 MPa for 7 wt.‐% blast furnace slag‐filled date palm fiber‐epoxy hybrid composite. Similarly, in case of fracture toughness, blast furnace slag‐filled composites, fracture toughness increases by approximately 20 %, 28 %, and 38 % respectively over unfilled composites. Based upon the results of the present research work can be afterward prolonged for automobile components and low‐grade structural application in addition to optimal waste utilization to reduce environmental degradation.

HIGH VOLUME BRICK POWDER CONCRETE SYNERGISTIC WITH METAKAOLIN: PHYSICOMECHANICAL PROPERTIES AND DRYING SHRINKAGE

Currently, sustainability of the construction and building industry taken a priority. This study investigates the feasibility of using a high volume (up to 50%) of blended waste brick powder (BP) and metakaolin (MK) as ordinary Portland cement (OPC) replacements. The binder of the control mixture was a blend of 50% OPC and 50% BP, while the other two mixes were prepared by substituting 10% and 20% of BP with MK. The characteristics of fresh concrete were assessed depending on measuring the mixture temperature, the fresh density, and the workability. The bulk density, and the mechanical properties were investigated and tested at 7 and 28 days. In the line of durability parameters, the void content and drying shrinkage up to 90 days of all mixtures were evaluated. The findings have demonstrated that the control mixture achieved high workability (slump =180 mm), structural compressive strength (34 MPa) at 28 days, low void content (<3%), and acceptable shrinkage strain. The workability of the mixes containing 10%MK:40%BP and 20%MK:30%BP has slightly decreased, while the mechanical properties were increased and the drying shrinkage were declined. However, the inclusion of This study highlighted an ecological technique toward waste management of construction materials and confirmed the possibility of including a high volume of BP as a cementitious material to synthesize more sustainable concrete.

Study on moulding control factors to reduce void contents in manufacturing CFRP parts by HP-RTM

Study on moulding control factors to reduce void contents in manufacturing CFRP parts by HP-RTM

A study on the overall variance and void architecture on MEX-PLA tensile properties through printing parameter optimisation

This study investigates the influence of printing parameters on the tensile properties and void architecture of poly(lactic) acid (PLA) parts fabricated using the fused filament fabrication (FFF) technique. Two Taguchi optimisation methods were employed to identify the optimal parameter combinations for maximising tensile performance. The results revealed a positive correlation between tensile performance and nozzle diameter (ND). Notably, the analysis of the coefficient of variance (COV) studies revealed that both tensile strength and modulus exhibited minimal variation within a tight range of 5.5%, suggesting a high degree of process consistency in achieving desired mechanical properties regardless of the chosen parameters within the investigated range. Micro-computed tomography (micro-CT) analysis was used to quantify void characteristics within the as-printed samples. Micro-CT analysis confirmed the influence of ND and layer thickness (LT) on void architecture. By establishing structure–property relationships, the study revealed that larger NDs paired with finer LTs yielded superior tensile properties due to reduced void content. This work highlights the interplay between printing parameters, void architecture, and the resulting mechanical behaviour of MEX-based PLA parts.

Mix Design Method and Void Performance of Concrete for Pervious Concrete Pavement

Pervious concrete pavement is drawing increasing attention for its high content of interconnected voids which is expected to reduce the environmental impact as concrete is often counted as a causal factor of the urban heat island phenomenon. Performance of pervious concrete can be measured by water permeability, water retentivity and noise reduction effect. Although active research is being made, no established standards or indicators for pervious concrete are available in Japan. Terms are not defined yet, and no method has been established for mix design. The purpose of this study is to present a mix design method that provides pervious concrete with a design void content and required performance level. The authors developed a theoretical model of pervious concrete under different void conditions, derived theoretical equations of void content from the model, and proposed a mix design method using the theoretical equations for pervious concrete for pavement. The proposed method takes into account the physical properties of the aggregate including solid volume percentage in addition to the densities of the materials. The close relationship between the strength and water permeability of pervious concrete and the physical properties and void structures of the materials was confirmed both experimentally and analytically.

A safe highway driving surface using an open graded concrete

The use of open graded asphalt wearing courses for highway pavements is established technology but the opportunities to use a similar cementitious based surface type for concrete pavements has been limited by material technology and costs. Research work in Australia using new generation concrete admixtures and placing techniques has allowed the development of a stiff open graded concrete material which is expected to meet the same durability requirements as standard concrete used for roads. Open graded surface textures absorb vehicle noise emissions and minimise water film build up during rain events, thus resulting in quieter and safer driving conditions. In addition, experience has shown that high void contents at the surface assist in reducing water spray generation and glare reflection. This paper details the laboratory mix design test results and three field trials using hand placing techniques to define the limits of a wet on wet construction process. The concrete developed in the trials has high compressive strength with air voids in the range of 20 to 30%. The next stage in the development of the open graded concrete surfacing is in the use of mechanised placing techniques to make the process cost competitive to other asphalt alternatives and yet meet similar durability requirements to those currently expected in concrete road surfaces over a 40 year design period.

The effect of semi-cured elements on the quality of integrated composite structures

There is a demand to ramp up the rate of production of primary aerostructures and as such new processing methods are required. This study investigates a two-stage process for integrating composite structures. In Stage 1, a series of doublers are infused and semi-cured to a target degree of cure (α). In Stage 2, these doublers are integrated into a preformed stiffened panel, to increase thickness locally, followed by infusion. The impact of this integration on quality in terms of thickness and void content of the semi-cured doublers is assessed through the processing stages. The results indicate that semi-curing elements to a higher degree of cure (α = 0.74) around the gel point (α = 0.70) of the epoxy matrix have minimal impact on the relative quality of the final structure. However, at a lower semi-cure (α = 0.47), the void (> 100 µm) content increased from 0.8 to 1.92% during the secondary stage. Tracking the thermal profile of the semi-cured elements through the stages combined with a Cure-Temperature-Transition diagram shows that at a lower degree of cure, the resin in the semi-cured doublers will be in a liquid phase during Stage 2 leading to the potential for resin reflow.

Potential use of high-volume of slag in pervious concrete: technical assessment and sustainability analysis

ABSTRACT Large porosity and interconnected pore structure allow pervious concrete to find interesting applications in urban pavement. At the same time, accounting for the exorbitant greenhouse gas emissions associated with Portland cement production, the application of supplementary cementitious materials (SCMs) in pervious concrete has received significant attention in studies. This research investigates the feasibility of developing pervious concrete by substituting a high volume of Portland cement with slag. Different mixtures were made to investigate the effects of high-volume slag content (60% and 80%), fine aggregate incorporation (10% and 15%) and combined use of SCMs (high-volume slag + silica fume) in pervious concrete. Concretes were tested for void content, compressive strength, permeability and abrasion resistance. Based on the results, although the compressive strength of pervious concrete was decreased by the inclusion of high-volume slag, it can be compensated to some extent by increasing the curing age. Furthermore, by decreasing the material cost and CO2 emissions up to 8.2% and 61.2% over plain pervious concrete, respectively, utilisation of high-volume slag can produce relatively more cost-effective and eco-friendly pervious concrete. In general, combined use of slag + silica fume or incorporation of fine aggregate at the optimum replacement ratio can be suggested to obtain higher strength and acceptable permeability in high-volume slag pervious concrete.

Effect of Heat-Shrinkable Tape Application on the Mechanical Performance of CFRP Components Obtained by a Filament Winding Process

Carbon Fiber Reinforced Polymers (CFRPs) are widely used in aerospace, automotive, and other sectors for their high strength-to-weight ratio and adaptability. In order to reach high mechanical performance and quality for CFRP components in which a thermosetting resin is used, the curing process plays a key role, and the optimal conditions have to be identified. In this context, the present study aims to study the effect of heat-shrinkable tape application on the mechanical performance of CFRP tubular components obtained by a filament winding process. To this purpose, CFRP hoop-wound components were realized with a laboratorial filament winding machine. Half of them were directly cured in a muffle oven, while the other half were cured after the application of heat-shrinkable tape around the external surface of the component. To evaluate the effect of the heat-shrinkable tape use on the mechanical properties of the CFRP wound parts, ring specimens, obtained by the tubular components according to the ASTM D2290 standard, were subjected to ring tensile tests. The thickness uniformity and void content of the components were evaluated by means of X-ray computed tomography, whilst the fracture surfaces were observed using scanning electron microscopy. It was demonstrated that the heat-shrinkable tape application around the external surface of the CFRP tubular components allows for improved mechanical performance of the wound parts due to the enhanced material compaction, resulting in stronger and more cohesive structures characterized by a uniform thickness and reduced void content.

Process parameters optimization of double‐vacuum‐bag technology for carbon fiber/resin composites

AbstractDouble‐vacuum‐bag (DVB) process, as an effective out‐of‐autoclave (OoA) technology, can manufacture composite materials with low void content and high mechanical properties. Therefore, this paper aimed to achieve low void content, the effects of pressure difference between inner and outer bags, dwelling temperature, and dwelling time on the void of composite laminates were studied based on orthogonal experimental method. The void content and morphology of laminates were statistically analyzed, by observing the microscopic images of the samples on cross‐section. The results show that the pressure difference between the inner and outer bags has a significant impact on the void content and morphology, while the dwelling temperature and dwelling time have little effect. In addition, with the variance analysis and extreme difference analysis, the optimal process parameters were determined as follows: pressure difference between inner and outer bags was 0 MPa, dwelling temperature was 110°C, and dwelling time was 15 min. The void content of composite laminates manufactured under these parameters is 0.07%, less than 1% requirement for aerospace components, and interlaminar shear strength (ILSS) is 110 MPa, which is 54.93% higher than the single‐vacuum‐bag (SVB) process. Generally, the void content and ILSS reached the level of hot press process with 0.6 MPa.Highlights Influence of different DVB process parameters on void were studied. Void content manufactured with the optimal DVB process parameters was less than 1%. ILSS of laminate with the optimal DVB process parameters was equal as hot press process.

Development and Investigation of Biodegradable Hybrid Fiber Sandwiched Composites Using Ultrasonication

ABSTRACTLightweight and highly strong polymer composites are popular and used in a variety of industries, such as consumer products, electronics, packaging, healthcare, textiles, and aviation. This study examines the production of hybrid polymer nano composites (HPNCs) and their mechanical and physical characterization. HPNCs were developed by embedding eight layers of bidirectional Banana and Kevlar fiber along with nano‐graphene oxide (GO) and epoxy as the matrix material. The novelty in this research was done by employing an ultrasonication machine for uniform dispersion of nano‐sized GO particles and varying the stacking sequence of fiber (KKBKKBKK) followed by variation in GO (0, 0.25, 0.50, 0.75, and 1) wt.% in HPNCs. The optimum values of various mechanical properties such as flexural strength, tensile strength, hardness, and inter‐laminar shear strength were found for the 0.50 wt.% of GO which are 532.13, 552.42, 88.12, and 53.08 MPa, respectively. The optimum impact strength of 878.87 J/m was obtained at 0.25 wt.% of GO. Densities, void content, and water absorption tests were done under physical characterization. The surface morphology and homogeneity of HPNC were done using the FE‐SEM test.

Recycling of waste E-cigarette butts as engineered pelletized fibres for sustainable stone mastic asphalt

The disposal of discarded E-cigarette butts (E-CBs) presents significant environmental challenges due to their detrimental impacts on ecosystems. To find an environmentally sustainable method for managing this waste, the potential for recycling E-CBs in asphalt pavements was investigated in this study. By focusing on the two primary components of E-CBs, namely cellulose fibre and polylactic acid (PLA), this research introduced a novel approach for recycling E-CBs in stone mastic asphalt (SMA) as a fibre additive in engineered pellet form. The prepared fibre pellets were directly added to aggregates to produce the SMA mixture. The resulting mixtures underwent a comprehensive evaluation through a series of standardized laboratory tests, including assessments of volumetric properties, indirect tensile strength (ITS), stiffness modulus, moisture susceptibility, and rutting resistance. The results were compared with SMA mixtures containing conventional cellulose fibres. Additionally, to examine the potential influence of PLA, a third mixture was prepared, incorporating both cellulose fibre and PLA. The findings indicate that the SMA using pelletized fibre can satisfy the technical specifications regarding the tests performed in this study, showing higher ITS and rutting resistance compared to the reference mixture. Moreover, the incorporation of PLA plastic reduced air void content and improved tensile strength, stiffness, and rutting resistance. This study highlights the potential for recycling E-CBs in asphalt mixtures, offering technical support for further development of sustainable recycling methods for this waste.

Optimization of Resin Infusion Processes in Composite Manufacturing: An Experimental Study on Void Formation

This research aims at determining the effect of the process parameters namely the vacuum pressure, resin viscosity, temperature and flow rate on formation of voids in the composite manufacturing during resin infusion process. Thus, the study executes controlled experiments and quantitatively examines void content under different parameter configurations to determine that certain conditions substantially reduce voids, improving composite quality. The study reveals that selected vacuum pressure of about 100 kPa, resin viscosity of 200-250 cP at higher temperature and carefully regulated flow rates of 10- 15mL/min help to reduce air bubbles to the barest minimum. These findings provide significant advantages to composite producers on aspects of productivity, mechanical properties and material costs. Similarly, the results indicate the following from secondary research and comparative analysis: Further investigation of real-time void monitoring, exploring advanced optimization with machine learning models. This research is relevant for the enhancement of low-cost and efficient manufacturing techniques in industries that incorporate high-performance composites

Mechanical and tribological characteristics of glass fiber and rice stubble-filled epoxy-LD sludge hybrid composites

In this work, bidirectional rice stubble fiber (RS), Glass fiber (GF), and Linz-Donawitz sludge (LDS) are used as reinforcement for the fabrication of epoxy (EP) based hybrid composite materials. The mechanical (tensile, flexural, compressive strength), and physical (density, void content) characteristics were evaluated as per ASTM standards. The tensile, compressive and flexural strength values of neat epoxy increased from 45 to 111 MPa, 22.5 to 58 MPa and 84 to 140 MPa respectively, with the addition of 6 % RS in EP-LDS-GF-RS composites. With the continuous addition of RS content, the density of the EP-LDS-GF composite gradually decreases, while void content increases gradually within 0.1 %, but both are higher than pure resin. Dry sliding wear tests are carried out on the composites to acquire the specific rate of wear (SWrate). Taguchi’s design of experiment analysis is used to highlight the effect of various dependent parameters on SWrate. Artificial Neural Network (ANN) tool is used to predict the combined effect of different input parameters on the SWrate. From the SEM analysis, it is observed that material removal is significantly less near the region of filler content and hence the RS content is found to be the predominant control factor affecting the wear rate of the composites.

Investigating physical and mechanical properties of alumina/acrylonitrile butadiene styrene composites manufactured by fused deposition modeling

AbstractIn recent years, 3D printing technologies or additive manufacturing have gained significant attention in research and other industries. Among the various 3D printing techniques, fused deposition modeling has been the most widely adopted. This study focused on developing composite filaments by incorporating acrylonitrile butadiene styrene (ABS) with different volume percentages of aluminum oxide (alumina). The mechanical and physical properties of parts printed with these composite filaments were thoroughly evaluated. Tensile testing revealed that increasing the alumina content led to a reduction in tensile strength. At 20 vol%, tensile strength dropped by 72%. A heat deflection temperature (HDT) test indicated an 11% reduction in HDT, likely due to the defective composite structure. Thermogravimetric analysis test demonstrated improved thermal stability as alumina content increased. Linear shrinkage was measured in three directions, revealing anisotropic shrinkage patterns. Hardness tests were conducted, and a decrease was observed when the polymer was filled with alumina. Finally, the warpage was reduced by 91% as alumina content increased to 20%.Highlights Alumina/ABS composite filaments were manufactured and 3D‐printed very well. The void content in composite samples increases with alumina powders. The mechanical properties of 3D‐printed composite parts were decreased The alumina powder improves the warpage issues in 3D‐printed parts.

Fatigue life prediction of hybrid carbon-flax-epoxy laminates using progressive failure analysis and cohesive zone model

A 3D progressive fatigue damage model was incorporated into ABAQUS software to predict the fatigue life of hybrid carbon-flax-epoxy composites. A cohesive zone method was employed to simulate delamination damage at carbon/flax interface. To evaluate the accuracy of the finite element model, two different layups, namely, unidirectional [0–90C2/0 F6]S (UD) and angle-ply [0–90C2/(±45) F6]S (AP), consisting of 12 flax fibers layers (F) sandwiched between four woven carbon fibers layers (C) were created using hand lay-up technique and then placed in compression molding. There is a good agreement between experimental and predicted fatigue life. It was observed that the predicted fatigue life is reduced by about 14% by changing the void content from 0.38% to 3.83%. The finite element analysis revealed that the matrix in the flax region of the AP layup failed at 12% of fatigue life, followed by delamination at the carbon/flax interface, consistent with SEM results.

Sugarcane bagasse for sustainable development of thermoplastic biocomposites

The potential of agricultural waste residues, such as sugarcane bagasse, as natural fiber reinforcement in thermoplastic biocomposites, is of significant interest. This study investigates the physical and mechanical behavior of PLA and HDPE composites reinforced with chemically modified sugarcane bagasse fibers. The fibers underwent alkali treatment with sodium hydroxide, silane treatment with 3-glycidoxypropyltrimethoxy silane and acid treatment with oxalic acid. Density and void percentage variations in the composites were assessed to determine the effects of the modifications, revealing that silane-treated samples of both thermoplastics had the lowest void content, indicating better compatibility between the fibers and the matrix. Mechanical tests, including impact, hardness, flexural and tensile properties, were conducted on various composites, and it was observed that chemical treatments enhanced the mechanical properties of the reinforced samples. The morphology of the composite fractured surfaces was assessed using scanning electron microscopy, revealing that chemical treatments significantly affect the failure modes of the composites. Moreover, the thermal response of the composites was characterized using thermogravimetric analysis and differential scanning calorimetry. The maximum thermal degradation temperatures, glass transition temperature, melting temperature, weight loss rate, melting enthalpy and activation energies were reported. Additionally, wettability studies and moisture absorption tests were performed. Results indicated that unreinforced composite samples had the lowest moisture absorption, while contact angle measurements demonstrated that different chemical treatments impart varied hydrophobicity and water barrier properties to the composites.

Role of fiber clustering and resin bleeding on voids and evolution of fiber volume fraction for additively manufactured continuous carbon fiber thermoset composites with dual-cure resins

Additive manufacturing of continuous fiber-reinforced thermosets is enhanced by producing a core–shell structured tow, where admixed UV and thermal cure resin (dual-cure) forms an interpenetrating polymer network. Such material can be produced by rapid interlayer curing assisted (RICA) 3D printing, a process that impregnates a fiber tow with epoxy and then applies a dual-cure resin coating hardened by UV exposure. A challenge of this novel process is the fiber volume fraction control and void content minimization after dual-cure coating, UV curing and consolidation. Here we reveal towpreg properties at RICA processing points of interest via a continuous model setup. We also put in place metering of the resin during the process which increased the fiber volume fraction and provided better layer thickness control. Two new numerical models were introduced that investigate (i) the void formation during impregnation of clustered carbon fibers and (ii) void filling accompanied by resin bleeding from core-shell structured tows during compaction. Experimental results revealed clusters in the carbon fiber tow during roller-assisted epoxy impregnation, with a void content between 3% and 5%. The clustering model showed that large clusters entrapped bigger voids. After consolidation, void content was reduced to 2.1–2.7% when the shell only contained UV resin, thanks to resin entrapment by the cured shell. Resin bled from the dual-cure shell, which reduced void filling but increased the fiber volume fraction from 0.29 up to 0.37. Ultimately, this work demonstrates that the dual-cure coating mixture utilized for RICA 3D printing has an effect on the final void content that is amplified during high-speed consolidation and reduced when the incoming initial voids are small.

Stochastic analysis of dynamic fracture of concrete using CT-image based mesoscale models with a rate-dependent phase field method

Concrete structures are commonly exposed to dynamic loads spanning a wide range of strain rates, and the inherent mesoscale heterogeneities complicate stochastic dynamic fracture mechanisms even more. This work develops a numerical framework using mesoscale concrete models based on micro computed tomography (CT) images to investigate such mechanisms with meaningful stochastic analyses. A rate-dependent phase field model is proposed to characterise the dynamic initiation and propagation of cracks by incorporating both micro-viscosity and macroscopic viscoelasticity, which is described by two standard Maxwell elements with different relaxation times to consider a wide range of strain rates. Moreover, the viscoelastic constitutive relation is formulated in the full strain space, which allows for a spectral decomposition of the strain tensor to determine the effective damage driving force, thus effectively addressing the issue of compressive fracture. A numerical implementation scheme is developed by combining user-defined element and material subroutines in ABAQUS/Explicit solver. Extensive Monte Carlo simulations of dynamic tension up to a strain rate of 200 s−1 are performed with statistical analyses. This work reveals the intricate dynamics associated with mesoscale heterogeneities and identifies the critical transition state at 20 s−1. The transition is characterised by changing modes of fracture patterns, stress wave propagation, and load-carrying capacities. A new TDIF–strain rate–standard deviation relation is also proposed and aligns well with the increasing dispersion of experimental data. The relationship between void content and tensile strength reflects the formation characteristics of crack networks, with the void content exhibiting a positive correlation with the TDIF from 20 s−1 to 100 s−1.

Evaluating the impact of post-processing on the wear and friction properties of polyamide 6 carbon fiber composites produced by fused deposition modeling

The current research addresses the challenges encountered in polyamide 6 carbon fiber composites synthesized by fused deposition modeling. It specifically investigates issues such as inadequate interlaminar bonding and increased void content compared to conventionally manufactured composite components and as-built printed parts. The study focuses on printing pin samples via fused deposition modeling and explores various thermal post-processing methods to reduce void content while preserving dimensional accuracy. To evaluate wear and friction behavior, a pin-on-disc tester was used to test both as-built samples and samples post-heat-treated at 70 °C, 140 °C, and 210 °C. The results indicate that as the applied load increases from 5 to 20 N, both wear rates and friction coefficients increase across all speeds (1–5 m/s). Heating the samples to 70 °C and 140 °C strengthens the interlayer bonding. This significantly improves the maximum wear rates and friction coefficients compared to the as-built samples. However, samples heated to 210 °C do not show much of a change in wear rates or friction coefficients. Samples heated to 210 °C exhibit a decrease in wear rate of 16.87%, 15.82%, and 15.73% for loads ranging from 5 to 20 N, at speeds of 1, 3, and 5 m/s, respectively. This is likely due to pores sealing off and structures binding tightly. The worn surfaces were analyzed using a scanning electron microscope and measured the Shore D hardness of the samples before and after wear testing and documented the results for further analysis. In a scanning electron microscope, samples treated at 210 °C displayed smoother, less worn surfaces. Shore D hardness tests revealed a slightly higher hardness in samples heated to higher temperatures, followed by higher loads and sliding speeds in tribometer tests. This showed that the material was more stable. These post-processing methods significantly advance the development of functional composite elements for superior structural or dynamic performance.