Void Content Research Articles

Void content of polypropylene/carbon fiber wet‐laid nonwoven composites: Effect of fiber content and molding conditions, and void elimination mechanism

AbstractVarious wet‐laid nonwoven composites have been well‐developed in recent decades. However, studies that systematically investigate the factors affecting the void content of wet‐laid nonwoven composites are still missing. This paper aims to study the factors affecting the void content of wet‐laid nonwoven composites and propose a mechanism for void elimination in wet‐laid nonwoven composites. Polypropylene (PP) and carbon fiber (CF) were chosen to manufacture PP/CF wet‐laid nonwoven composites. An orthogonal experimental design found that the CF content and molding pressure can dominate the void content while molding temperature and time have non‐significant effects. Subsequently, this paper proposed that the void elimination mechanism is the compression of the impregnated CF network and the trapped air (compression mechanism) instead of the matrix's infiltration to the dry CF network (infiltration mechanism). In order to validate the compression mechanism, we developed an analytical model for predicting the void content of the PP/CF wet‐laid nonwoven composites. Good agreement between the predicted and the experimental void content suggests that void elimination follows the compression mechanism.Highlights An orthogonal experimental design reveals that the CF content and molding pressure can dominate the void content of the PP/CF wet‐laid nonwoven composite, while molding temperature and time have non‐significant effects. A mechanism (i.e., compression mechanism) is proposed to explain the effect of CF content and molding conditions on the void content of the PP/CF wet‐laid nonwoven composite. Good agreement between the experimental and the predicted void content validates the compression mechanism.

A novel performance-based method to design asphalt mixtures

Conventional asphalt mix design methods require numerous experiments to verify the efficacy of various recipes, resulting in significant time and labour costs. Therefore, there is a need for an alternative method that is both efficient and convenient. To address this issue, this paper proposes a novel asphalt mix design method that reduces the reliance on time-consuming and resource-intensive physical and mechanical tests to determine the properties of new asphalt mixtures. The method focuses on the quantity of aggregates and the volume of mortar to estimate the air voids content, resilient stiffness modulus, Marshall stability, and flow requirements in accordance with industry standards. Statistical analysis shows that the key properties of asphalt mixtures are primarily influenced by the number of aggregates and volume of mortar. Nomographs are provided to predict these properties based on the mixture’s gradation and mortar volume. The proposed method’s feasibility is demonstrated by accurately predicting the gradations and properties of six different mixtures. Additionally, the paper suggests the use of 3D models for asphalt mixtures, allowing for the observation of aggregate distribution and air voids before testing the mixtures’ mechanical properties.

Laboratory investigation on the use of wood waste fibres in SMA mixtures

This research investigates whether wood waste fibres, produced from the leftovers from the manufacture of wood panels for furniture, can be used to stabilize the binder (to absorb the excess binder) in stone mastic asphalt (SMA) mixtures rather than being disposed of in landfill or incinerated. In this research, SMA 8 S mixtures with different amounts (0.3%, 0.5%, 0.7%, 0.9% and 1.1%) of wood waste fibres were analysed. The reference mixture with 0.3% cellulose fibres was also produced. The ability of wood waste fibres to absorb the binder was determined by the binder drain down test, and the particle loss test was used as a primary indicator to evaluate the performance of the mixture. The influence of wood waste fibres on the performance of SMA mixtures was comprehensively evaluated with two amounts of wood waste fibres in terms of air void content, water sensitivity, stiffness, resistance to rutting, and resistance to fatigue. Research showed that 0.7% of the wood waste fibres is an optimal amount. It ensures both binder absorption and SMA 8 S mixture performance equivalent to that with 0.3% cellulose fibres.

Study on compaction characteristics and mechanical performance deterioration of large stone porous asphalt mixes

Large stone porous asphalt mixes (LSPM) have advantages in promoting pavement performance, including cracking resistance, rutting resistance, and moisture susceptibility. Engineering practice demonstrates that performance degradation is crucial and has an impact on the durability and service life of asphalt pavement. Therefore, this paper aims at investigating the damage characteristics of LSPM as well as proposing the corresponding control methods. Firstly, a simulation device is designed to carry out the temperature cooling testing of LSPM in the laboratory. Then, the variation of air void contents in LSPM was analyzed with different testing temperatures, loading times, and freeze–thaw cycles. LSPM macro-mechanical strengths and cracking resistance were measured during freeze–thaw cycles. The outcome demonstrates that different sections cool at various rates and for varying lengths of time. The effective compaction time and compactness are directly related to the ambient temperature. Paving at medium and high temperatures is an efficient way to increase the compactness of LSPM. The testing temperature, loading time, and freeze–thaw cycles have significant influences on the change of air void contents, while the influence of load strength is low. The penetration shear strength decreases as the number of freeze–thaw cycles increases, and the change trend gradually decreases. Freeze-thaw cycles will lessen the anti-cracking performance of LSPM. Strictly regulating construction parameters, air void content, and drainage conditions could increase the LSPM asphalt pavement's durability and service life. The change in pore structure composition is the primary factor influencing the damage performance of LSPM.

Laboratory evaluation of heavy metal removal from stormwater runoff by pervious concrete pavement containing seashell and oil palm kernel shell

One of the major issues related with impermeable surfaces such as impervious concrete pavement in urban area is the collecting of rain as stormwater runoff, which then moves harmful natural and man-made pollutant into the natural water bodies such as lakes, streams, rivers, etc. This study investigated the effect of pervious concrete containing palm oil kernel shell and seashell on removing dissolved heavy metals contaminants from stormwater runoff. Therefore, mixtures were made, which replaced 6.3–9.5 mm limestone with 25 and 50% of 6.3–9.5 mm and 4.75–6.3 mm of both shells. The specimens were cured in a fog room and void content were tested. Specimens with same void content (23%) are selected to reduce experimental variability from differing void content. Pervious concrete cylinders were loaded in the laboratory with collected stormwater runoff, and concentrations, volumes of influent and effluent evaluated. Ten consecutive storm events of 200 mL in 20 min of rain are simulated to test heavy metal removal performance. The range of heavy metal removal for pervious concrete mixture containing seashell was 37 and 93% which was higher than that of control mixture (39–73%). However, the rate of heavy metal removal for specimens incorporating kernel shell was between 14 and 63% which was lower than that of control mixture. The results showed that the waste materials can be considered as one of the sustainable runoff purification methods, respecting their effective heavy metal removal rate in runoff, as well as the reasonably low cost and consumption when used on the pervious concrete pavement.

An Experimental Investigation on Influence of Mixing and Compaction Temperature on Air Voids in Bituminous Mix

Abstract: The air void content and long-term performance of pavements are significantly impacted by the mixing and compaction temperature of bituminous mixtures, leading to potential failures such as premature aging, reduced durability, and issues like fatigue life, raveling, rutting, and vertical consolidation in Hot Mix Asphalt (HMA) pavements. To achieve optimal production and placement of HMA, it is crucial to carefully consider the mixing and compaction temperatures of the binder (bitumen) used. Notably, these temperatures vary based on the grade and origin of the bitumen, as different sources exhibit distinct properties affecting the mixing and compaction characteristics. Selecting an appropriate mixing and compaction temperature is vital to ensure effective aggregate coating and achieve the desired density. This experimental study aims to determine a reliable method for estimating the mixing and compaction temperatures for both modified and unmodified bitumen, thereby enhancing the overall performance and longevity of asphalt pavements.

Mechanical and dry sliding wear performance evaluation of marble dust particulates–lapinus fiber–polyamide 66 polymer composites with ranking analysis using hybrid AHP-R method

This research investigates the physical, mechanical, thermal, thermomechanical and dry sliding wear performance of marble dust particulates (0–20 wt.% @ step of 5%) and lapinus fiber (10 wt.% constant) reinforced polyamide 66 polymer composites, resulting in five hybrid polymer composite namely PLM-0, PLM-5, PLM-10, PLM-15 and PLM-20, respectively. A twin screw extruder and injection molding machine were used for the fabrication. Taguchi's method and ANOVA tools are used to optimize and determine the significant order of the input parameters for the sliding wear process, followed by surface morphology investigations. Finally, the hybrid AHP-R ranking method was applied to rank the compositions on their merits. It is observed that PLM-10 hybrid polymer composites have shown relative overall optimized performance. It shows the lowest density of 1.21 g/cc, voids content of 6.47%, water absorption of 4.51% and a specific wear rate of 1.03 × 10−3 mm3/Nm. In comparison, it shows the highest tensile strength of 112.64 MPa, flexural strength of 150.40 MPa, Rockwell hardness of 60.40 HRM, fracture toughness of 4.27 MPa√m, impact strength of 1.96 J, thermal conductivity of 0.98 W/mK and storage modulus of 1824.29 MPa. Finally, these subjective findings were found to be in tune with the findings of the hybrid AHP-R method.

Dry sliding wear and mechanical investigations on flyash particulates - Lapinus fibre - polyamide 66 polymer composites: Ranking analysis using hybrid Analytic Hierarchy Process-R method

This research work examines the physical, mechanical, thermal, thermo-mechanical, and dry sliding wear performance of hybrid waste flyash particulates (F-class; 0-20 wt% @ step of 5%) – Lapinus fibres (fixed 10 wt%) reinforced Polyamide 66 polymer composites fabricated using the twin screw extruder and injection moulding machine. This follows worn surface morphology to understand the prevailing wear mechanisms responsible for surface damage during sliding. Optimization of control parameters and identification of their order of significance in the dry sliding wear process is performed using Taguchi’s design of experiments and analysis of variance (ANOVA). Further, ranking optimization of the hybrid composite specimens based on their performance metrics is analysed using the hybrid AHP-R method. It has been observed that the hybrid composite specimens having 10 wt% flyash particulates optimize the overall performance metrics; therefore, it may be recommended to fabricate parts or components for industrial usage. It tends to have an experimental density of 1.18 g/cc, voids content of 7.11%, water absorption of 3.87%, tensile strength of 105.95 MPa, flexural strength of 144.86 MPa, Rockwell hardness of 58.12 HRM, fracture toughness of 4.11 MPa√m, Impact strength of 1.86 J, thermal conductivity of 1.08 W/mK, and specific wear rate of 1.12 × 10−3 mm3/Nm. This observation was attuned to the ranking analysis using the hybrid AHP-R method.

Physical and Mechanical Behavior of Ramie and Glass Fiber Reinforced Epoxy Resin-Based Hybrid Composites

ABSTRACT In this study, the compression molding technique was used to fabricate hybrid composites using different wt.% of the glass and ramie fibers in different stacking sequences. The physical (density, water absorption, and wear resistance) and mechanical (tensile strength, hardness, and impact strength) and morphology studies were performed for the glass and ramie fibers and the effect of stacking sequencing was studied. A technique for order of preference by similarity to the ideal solution model was used to determine the optimal reinforcement composition in the hybrid composites. The stacking sequence played a crucial role in the physical and mechanical characteristics of the hybrid composites. The GRG (stacking sequence: Glass (4 wt.%)-Ramie (4 wt.%)-Glass(4 wt.%)) hybrid composite showed optimal characteristics; tensile strength: 114 MPa, hardness: 41 HV, impact energy: 3.5 J m−1, void content: 1.09% and wear: 63 μm. However, if glass fibers were sandwiched between the ramie fiber layer, the composite showed lower physical and mechanical characteristics; tensile strength: 72 MPa, hardness: 28 HV, impact energy: 3 J m−1. The glass fiber reinforced composites (GG and GGG) exhibited better water absorption characteristics. The RRR composite’s impact strength was comparable with the GGG composites due to the stacking of the composites. Moreover, the glass fiber composites stacking (RR to RGR) exhibited lower tensile strength than ramie fiber composites stacking (GG to GRG). The microstructural analysis of the fractured composite surface revealed voids, de-lamination, interfacial bonding of the fibers with the matrix, fiber pull-out, and matrix distribution.

Fabrication and characterisation of polyester/hexagonal boron nitride/sisal fibre hybrid composites for microelectronic applications

ABSTRACT The main focus of the work is on developing a new class of hybrid composite with polyester as the continuous phase and micro-sized hexagonal boron nitride (hBN) and short sisal fibre as the discontinuous phases. The effect of loading of discontinuous phases on the different properties of the composites is analysed experimentally. The incorporation of either of the discontinuous phases unwillingly increases the void content and water absorption rate. With hBN content, the density increases, whereas, with sisal fibre content density decreases. The hybrid combination of fillers successfully improves the glass transition temperature (Tg) and coefficient of thermal expansion (CTE) of the polymeric resin. The maximum Tg reported is 106.2°C and the minimum CTE reported is 51.7 × 10−6/oC for the polyester reinforced with 40 wt. % hBN and 5 wt. % sisal fibre. The incorporation of hBN upsurges the thermal conductivity but also increases the dielectric properties. The dielectric properties gainfully reduce with the addition of sisal fibre. Dielectric properties also decrease with an increase in the working frequency. The incorporation of sisal fibre slightly reduces the thermal conductivity of the composites. The mechanical properties like tensile strength and flexural strength of the hybrid composite increase when the combination of hybrid fillers is judicially selected, whereas, the compressive strength and hardness of the composite increase with filler/fibre loading with maximum 131.4 MPa and 80.0 Shore D number, respectively. Due to the improved overall properties, the composite material under investigation can find its potential application in various microelectronic applications.

Hybrid wood-glass and wood-jute-glass laminates manufactured by vacuum infusion

Hybrid unidirectional wood-jute laminates manufactured by the vacuum infusion processing (VIP) may present some limitations, including high incidence of delamination failures, low interfacial adhesive strength and low transverse mechanical strength. This study proposes a way to overcome these issues by manufacturing wood-glass and wood-jute-glass laminates by VIP. Pine wood veneers, jute nonwoven fabrics, glass mats and a polyester resin were employed in the here studied five-layer laminates. Apparent density, compressive, longitudinal flexural, transverse flexural, short beam testing, morphology and water absorption were the characterization analyses. As expected, the higher the number of glass layers, the higher the apparent density (up to 30%), the thinner the laminates, the closer the longitudinal and transverse mechanical properties and the smaller the water uptake levels. Based on increases of up to 70% in short beam strength, the wood-glass interface bonding was more qualified than the wood-jute one. Among all laminates, those ones with glass mats as faces showed higher longitudinal and transverse flexural properties. Besides, the higher the number of jute layers, the higher the void content.

Investigating the Properties of Drainage Concrete Pavement through the Pore Creation Method: A Study

Background: Over the past decade, the pervious concrete pavement has become a popular innovation due to its highly porous spaces that allow for easy air and water flow from the surface to the underlying layers. However, the increased void content could potentially make the concrete weaker and less durable, which creates a need for alternative methods to maintain its strength while improving its drainage capabilities. Objective: This study aims to analyze the characteristics of drainage concrete pavement using a novel method for creating pore structures. Methods: To address the challenges of conventional concrete pavement, various pore patterns and diameters were examined, including a 2x2, 3x3, and 4x4 row arrangement with pore diameters of 2, 3, and 4 mm. The concrete mixture was formulated to comply with the standards established by the Department of Highways in Thailand. The study analyzed both the fresh concrete properties, such as slump test and setting time, and the hardened properties, such as compressive strength, flexural strength, and water absorption. The draining capability was evaluated through water permeability performance and the clogging effect was measured by very fine sand particles. Results: The test results showed that the slump value of concrete complied with the design specifications, and the initial setting time was recorded to be 230 minutes. The compressive strength and flexural strength tended to decrease while water absorption tended to increase as the pore pattern arrangement and pore diameter increased. However, the compressive strength of all mixtures exceeded 85% when compared to the control. Additionally, the water permeability coefficient ranged between 2.69-18.52 mm/s, and the permeability coefficient tended to decrease when the clogging effect occurred in the range of 18.18-37.27%. Conclusion: The findings of this study contributed to our understanding of the properties and behavior of concrete with pore creation. By refining our knowledge of the intricate correlation between porosity and compressive strength, it has become evident that reducing porosity is necessary to enhance the mechanical properties of concrete and ensure its long-term durability. Furthermore, sustainable infrastructure applications can improve the relationship between permeability and effective porosity through construction techniques.

Laboratory evaluation on performance of Polyurethane Porous Elastic Mixture

Poroelastic road surface (PERS)has high rubber particle content and air void, and its noise reduction performance is excellent. However, the performance of Polyurethane Porous Elastic Mixture (PUPEM) prepared with different contents of rubber particles and different types of polyurethane (PU) are rarely studied. This study aims to evaluate the comprehensive and functional performance of PUPEM and to analyze the influence of rubber particle content and PU type on PUPEM. PUPEM was prepared using different types of PU and different rubber particle content. The high-temperature performance, low-temperature bending performance, water stability performance, and skid resistance performance of PUPEM were evaluated by rutting test, low-temperature bending test, freeze–thaw splitting test, immersion Cantabro loss test, pendulum friction coefficient tester and sand patch method. The effects of air void content, rubber particle content, and thickness on the noise reduction performance of PUPEM were also studied by impedance tube test and dynamic modulus test. The results indicate that the PUPEM has excellent high-temperature performance, favorable low-temperature bending performance and skid resistance, and its water stability can meet the specification requirements. PUPEM also has favorable sound absorption and noise reduction performance through voids and noise reduction performance through elastic damping. In addition, the maximum sound absorption coefficient of PUPEM corresponds to a frequency that is influenced by the thickness. In order to balance the road performance and noise reduction of PUPEM mixture, it is recommended that the rubber particle content is 10%, and the polyurethane PU-Ⅰ with larger isocyanate index is used.

Performance evaluation of a HMA pavement longitudinal joint containing a void reducing asphalt membrane (VRAM)

Longitudinal joint cracking in Hot Mix Asphalt (HMA) pavements is a major issue that occurs because high density (low air voids) is not easily achieved during construction as compared to the mat away from the joints. High air voids allow water infiltration, which results in moisture-induced damage to the pavement and reduced pavement service life. The use of a Void Reducing Asphalt Membrane (VRAM) has been recommended and used at longitudinal joints of asphalt pavements as a preventative treatment to achieve good performance and increase density/reduce air void content at the longitudinal joint. The Void Reducing Asphalt Membrane material is sprayed on top of a tack coat at the longitudinal joint, 9 inches on each side of the joint below the Hot Mix Asphalt surface overlay, and is expected to migrate upward into the Hot Mix Asphalt overlay, filling 50%–70% of the air voids. This study evaluated and compared the performance of longitudinal joints constructed with Void Reducing Asphalt Membrane to that of a joint without Void Reducing Asphalt Membrane (control). Field cores were collected from 1) a section containing Void Reducing Asphalt Membrane and 2) a section without Void Reducing Asphalt Membrane that was paved for this research. Falling head permeability was carried out to determine the permeability coefficient of the specimen. Disk Compact Tension (DCT) and Semi-Circular Bend (SCB) tests were used to evaluate the cracking performance at low temperatures. A push-pull test was used to evaluate the improvement in adhesion between the top and bottom Hot Mix Asphalt layers at the intermediate temperature. The VRAM-containing samples show high values of fracture energy (Gf) and surface and joint bond energies as compared to the control sections. High surface and joint bond energies indicate that longitudinal cracking at the joints will be delayed as more energy is required to initiate cracks. Additionally, the VRAM-containing samples have a lower permeability coefficient compared to the control section. This indicates that the Void Reducing Asphalt Membrane reduces the possibility of water infiltration. The elastomeric polymer in the Void Reducing Asphalt Membrane increases the cohesion in the mixture, which increases the resistance to deformation and improves the bond strength of the joint Additionally, the Void Reducing Asphalt Membrane enhances the elasticity of the binder, thus increasing the cracking resistance of the joint.

Investigation on flow resistance of fluid in permeable asphalt mixture

Flow resistance distribution of fluid is the basis of comprehensively grasping the permeability of permeable asphalt mixture. This study aimed to investigate the flow resistance of fluid in permeable asphalt mixture. Considering the influence of anisotropy of permeable asphalt mixture, the vertical and transverse permeability tests of five types of permeable asphalt mixture were carried out using multidirectional permeability test instrument developed by our research group. The fitting equation of permeability was determined by comparing Darcy's law with Forchheimer equation. Moreover, the flow resistance is usually considered as an effective parameter to reveal the structural permeability. The connective void content of permeable asphalt mixture is important to calculate flow resistance. Accordingly, it is necessary to obtain the transverse and vertical connective voids of the asphalt mixture considering the influence of anisotropy. Therefore, a program for calculating the multi-directional connective void content was developed based on the theory of projection reconstruction. On this basis, a pore throat model was applied to reveal the variation of flow resistance of asphalt mixture. The results show that the weight of inertia resistance and viscous resistance is different in various seepage velocities. The viscous resistance is dominant when the fluid flow velocity is less than 0.0087 m/s under experimental conditions, and the inertial resistance is dominant when the fluid flow velocity is greater than 0.0087 m/s. The viscous resistance and inertia resistance of fluid are affected by the anisotropy and structure type of permeable asphalt mixture. When the vertical void content decreases by 3.3%, the corresponding viscous and inertial resistance increase by 7.92 kPa/m and 0.84 kPa/m, respectively. For the transverse void, the viscous and inertial resistance increase by 3.19 kPa/m and 2.02 kPa/m respectively as the content decreases by 3.5%. The influence of void structure of permeable asphalt mixtures on fluid flow is revealed from a microscopic perspective, which can be used to guide the optimization design of gradation of permeable asphalt mixtures.

MICROCAPSULES AND INDUCTION HEATING: TWO METHODS FOR CLOSING CRACKS IN ASPHALT POROUS PAVEMENTS

Asphalt concrete is widely known to be a self-healing material, by repeated loading the micro-cracks have appearing and disappeared when both faces of a fissure touch. This process is applied until the crack is completely gone and the material regains its prior resistance. In this study, two strategies are presented to boost of healing rate and applied in porous asphalt, one of them is induction heating. This method is used by mixing 1.1% of steel wool fiber to speed up this phenome, with 20mm aggregate size for porous asphalt mixture and 21% air voids content. Another approach is self-healing by 0.5% encapsulated agents using. These capsulate are incorporated within the asphalt mixture, then the capsules break when subjected to repeating loading on the asphalt surface. It has been discovered that there is a moment in the lifespan of an asphalt road where the capsules or induction heating applied can successfully self-heal the existing crack damage.

The Effect of Incorporating 100% of Undiluted and Diluted Reclaimed Epoxy Asphalt Materials into Pervious Cement Mixes

In order to improve the sustainability of road pavements, transportation agencies should consider designing pavements with recycled materials such as reclaimed epoxy asphalt pavement. Epoxy asphalt has recently attracted significant attention from the pavement community as a superior-performing binder that can help achieve long-lasting pavements. The recyclability of a proven long-life pavement material, such as epoxy asphalt, has now become one concern in promoting the use of epoxy asphalt binder in road pavements. Due to its thermosetting nature, the usual process of reclaiming asphalt pavement cannot be performed on epoxy asphalt pavement. Recent studies have investigated utilizing reclaimed epoxy asphalt materials in asphalt mixtures as black rock. In light of this, examining the use of reclaimed epoxy materials in cement-concrete mixes is important. The use of reclaimed epoxy asphalt materials in pavement construction is expected to gain more popularity and become a new sustainable construction option in various sustainable pavement applications in the near future. The main objective of this study is to investigate the effects of incorporating 100% reclaimed epoxy asphalt (hereinafter referred to as “epoxy RAP”) and reclaimed diluted epoxy asphalt materials (hereinafter referred to as “diluted epoxy RAP”) into cement-concrete mixes on the performance of the mixtures. The study also examined the effects of replacing cement with 5% silica fume on the performance of reclaimed mixtures. Five different mixtures were fabricated and tested in terms of density, void content, permeability, and compressive strength. Results of the density test revealed that replacing 100% natural aggregates with epoxy RAP and diluted epoxy RAP materials reduced density by an average of 10%. However, void content was found to increase with the incorporation of epoxy RAP, even when replacing Portland cement with silica fume. Regarding permeability, mixtures containing 100% epoxy RAP and diluted epoxy RAP materials have significantly higher permeability values compared with the natural mix value. However, adding 5% silica fume significantly reduced the permeability. Compressive test results indicated that substituting 100% of aggregates with epoxy RAP or diluted epoxy RAP materials would reduce compressive strength by 55% on average. Furthermore, adding silica fume to reclaimed mixes was found to have no apparent effect on compressive strength.

The combined impact of voids and thermal aging on the mechanical reliability of epoxy resin evaluated by statistical analysis

Epoxy resin is widely used in electrical engineering, and its long-term mechanical performance is directly related to the durability of the equipment. The issue might be aggravated when voids are introduced during manufacturing process and when the material is used under high temperature environment. This study aims to precisely reveal the effects of voids and thermal aging on mechanical strength of epoxy resin. Specimens with low and high void content were prepared and thermally aged at 105 ℃ for various lengths of time. Tensile test, scanning electron microscope (SEM) and the finite element simulation were employed to investigate the failure mechanism. The chemical change due to thermal aging was studied by Fourier Transform Infrared Spectroscopy (FTIR). The results illustrate the crack is initiated at the edge of the void due to stress concentration. With the increased void content, there was a slight decrease in the mean tensile strength but a large (108%) increase in the standard deviation. During thermal aging, the chain scission and oxidation were observed via FTIR, along with the inhomogeneity of chemical compounds. A defect density parameter ρ was proposed and integrated into the Weibull distribution to study the synergistic effect of voids and thermal aging on the mechanical properties. This statistical analysis quantitatively describes the decrease in average tensile strength and the increase in data scattering with ascending defect density ρ, due to higher void content and thermal aging. When 0.0005% failure probability is required, the predicted failure stress is significantly reduced from 49.6 MPa to 1.18 MPa for the specimen with high level of void after the long-term aging. In this work, we demonstrate that Weibull statistical analysis can quantitatively evaluate the impact of void defects and thermal aging and provide strength design for the high-reliability epoxy material.

Experimental Study of Sugarcane Bagasse Fiber with Rice Husk and Wood Powder Polymer Matrix Composite

ABSTRACT This research examines the mechanical, morphological, and moisture assimilation of composite materials built up from sugarcane bagasse fiber (SBF), rice husk (RH), and wood powder (WP) filler. Regular threads are now regarded as eco-friendly materials because of their sustainability. This article’s goal is to choose between two polymer structures with fiber and matrix: case 1 has epoxy (50%) plus sugarcane bagasse fiber (30%–45%) and wooden powder (5%–20%); case 2 has epoxy (50%) plus sugarcane fiber (30%–45%) plus rice husk (5%–20%). The impact of the mechanical test is compared to obtaining the best fiber volume fraction (Vf), and the failure of cracked surfaces and interfacial bonding analysis is done using SEM as a consequence of matrix cracking, void content, and fiber pullout. In order to get the characterization of materials, Thermo-Gravimetric Analysis (TGA) and X-Ray Diffraction (XRD) analyses were also performed. However, Sugarcane Bagasse Fiber, a single fiber, combined with an epoxy composite matrix demonstrated a strength of 14 to 18 Mpa and 230 to 250 g of weight. Nevertheless, when SBF was combined with hybrid materials like Rice Husk and Wood Powder, it demonstrated superior strength, with an estimate of 16 to 20 Mpa and a weight of 220 to 240 g.

Effect of Void Content on the Mechanical Properties of GFRP for Ship Design

Defects such as voids in composite materials often degrade the mechanical properties of laminates. Even if these materials are manufactured based on the design requirements, there is a possibility of instability occurring in these composite structures. In this study, several prototypes were developed based on changes in composite ship design conditions (glass fiber weight fraction and fabric combination type) using a hand lay-up approach. The fabrication quality was quantitatively defined using the burn-off test, and statistical analysis was performed. A combination of chopped strand mat and woven roving material laminates possessed relatively less void content in the entire glass content (Gc) region (30–70 wt%) compared to a chopped strand mat single-material laminate. The effect was more pronounced in the high-Gc region (50–70 wt%) than that in the normal-Gc region (30–50 wt%). The composite hull plate can be designed seamlessly according to changes in fabrication quality. To ensure safety, the thickness of the laminate must be greater than that specified in the ISO standards, regardless of the combination type in the normal-Gc region. As a result of the void content considered, the flexural strength in the single laminate decreased by 15.02%. Furthermore, 3.33% of the flexural strength calculation decreased in the combined laminate compared to that in the ISO rules. Thus, a single CSM material can be designed to be thicker than a combined-material laminate with the same Gc, while considering the void content on the mechanical properties.