Influence Of Water Absorption Research Articles

Influence of water absorption on the interlaminar behavior of carbon fiber-reinforced composites containing halloysite nanotubes

Polymer matrix composites deteriorate during prolonged exposure to water, especially at the fiber–matrix interface. Herein, water absorption and interfacial mechanical property degradation were evaluated after the addition of halloysite nanotubes (HNTs), which are inexpensive tube-shaped nanofillers. The water absorption ratio of the composite containing HNTs was lower than that of the reference. The mechanical properties, including flexural strength and interlaminar shear strength, were also less degraded in the composite containing HNTs. This improvement was attributed to the HNT nanofiller reinforcing the matrix and bridging propagating cracks. Concurrently, the HNTs acted as a water absorbent and water barrier, thereby preventing damage to the fiber–matrix interface by water. Halloysite nanotubes are suitable as a filler for applications exposed to high humidity or aqueous environments.

Understanding water absorption effect on molecular dynamics, microstructures and relaxation behavior of segmented polyurethane elastomers

The influence of water absorption on molecular dynamics, microstructures and relaxation behaviors of polyurethane (PU) elastomers with polyether (poly(tetramethylene glycol), PTMG) soft segments has been studied. Kinetics of water absorption of PU elastomer can be well fitted by Fick's model. However, non-Fickian absorption behavior was observed in the late stage at 60 °C, which was presumed to be related to the plasticization of some hard domains. Broadband dielectric relaxation spectroscopy was used to investigate the molecular dynamics of PU elastomers. The analysis of α-relaxation and Maxwell-Wagner-Sillars interfacial polarization indicated that the water absorption has a great influence on the molecular mobility of soft segment and the interface regions between soft domains and hard domains. Microphase separation structures of PU elastomers consisted of loose, partially regular and compact hard domains. Water molecules could interact with loose hard domains and lead to the plasticization. The results of stress relaxation behavior indicated that water absorption leaded to remarkable increase in the stress relaxation ratio. The deterioration of relaxation properties caused by water absorption was not only related to the soft segments, but also caused by the plasticization of the interface regions and the hard domains.

Experimental Study on Disintegration of Guilin Red Clay

In order to study the disintegration characteristics of red clay under different moisture content and temperature, red clay taken from Guilin was prepared into samples with different moisture content, and the disintegration test of red clay was carried out by self-made test equipment. Considering the influence of water absorption and weight gain in red clay, a parallel water absorption test was carried out for each disintegration test, and the disintegration amount–time relationship curve was corrected with the results of the water absorption test so as to propose a new disintegration amount calculation formula. In this experiment, the disintegration characteristics of red clay under different moisture content and temperature were investigated. The experimental results show that the disintegration amount decreases with the increase in moisture content, the moisture content exceeds 25%, and the red clay basically does not disintegrate within 2 h. The amount of disintegration increases with increasing temperature, but the disintegration of red clay in natural environments is not sensitive to temperature. The comprehensive analysis of moisture content and temperature shows that in the natural climate range, moisture content is the main influencing factor of soil disintegration.

The influence of water absorption on reinforced polymers (FRP) using MWCNT and HGB

In the current paper, different MWCNTs filler amounts, containing PA6 and HGBs were prepared by injection moulded. The water uptake at saturation, normalized to the polyamide mass, decreases; hence the diffusion rate in both MWCNTs is slower, respectively HGBs which is faster. Injected moulded polymer samples can take less (6%) water uptake than neat polymer granules (11%). The addition of 15 wt% of multi-walled carbon nanotubes (sample 3) led to a minimum water absorption rate of 5%; this value is 15% less than the majority of the polymer composite mixtures and 1% less than pure PA6, mainly because other polymer composites which contained the HGB filler, absorbed more water. The best results highlight the improved water resistance of polyamide composite (sample 3), which reduces the impact of water on the component and expresses better applicability in the water environment than other polymer composites or even pure PA6.

Effect of Water Absorption on the Mechanical Properties of Alkaline Treated Bamboo and Flax Fiber Reinforced Epoxy Composites

Untreated and alkaline treated bamboo and flax fiber reinforced epoxy composites are processed using a hand layup process. The effect of alkaline treatment on the mechanical properties of the composites has been analysed. Alkaline treatment of the fiber has enhanced the mechanical properties of the developed composites. Composite reinforced with 5 % NaOH treated fiber show better performance when compared with untreated fiber reinforced composites. Alkaline treatment of the bamboo and flax fiber with 5 % NaOH has improved the hardness by 3.57 and 2.43 %, tensile strength by 47 and 20.72 % and flexural strength by 7.36 and 13.85 % in bamboo and flax fiber reinforced composites, respectively. The increase in the percentage NaOH in the alkaline treatment of the fibers resulted in weakening of fiber resulting in a drop in the properties of the developed composites. Water absorption tests of the developed composites were conducted as per ASTM D570 by immersion in distilled water at room temperature. The influence of water absorption on mechanical properties of developed composites is also examined. The quantity of water absorption and diffusion coefficient are reduced with alkaline treatment of fiber. Mechanical properties of the composite were found to decrease by the water absorption, which can be controlled by alkaline treatment of fiber and thereby reducing water absorption rate and improve the mechanical properties of the composites.
 HIGHLIGHTS
 
 Reinforcing natural fiber in polymer resin is highly beneficial because it helps to improves the strength and toughness of the polymer
 Moisture absorption rate and lack of interfacial adhesion between the polymer and natural fiber made natural fiber reinforced composites less attractive compared to synthetic fiber reinforced composites
 Alkaline treatment of the natural fiber increases the fiber surface roughness, which results in improved mechanical interlock between fiber and matrix, resulting in improved mechanical and water resistance properties of the developed composites
 
 GRAPHICAL ABSTRACT

Influence of water absorption on the mechanical behavior of CFRPs manufactured by RTM at room temperature

Deterioration of the physical properties of fiber-reinforced composites is inevitable under a high temperature and humidity environment. The resin transfer molding (RTM) process for large composite parts is often accompanied by micropore formation, making the composite more sensitive to water absorption. In this study, carbon fiber-reinforced composite specimens were manufactured using the RTM process at room temperature, and their water absorption and mechanical properties were investigated. The water absorption was saturated after about 40 d, and the absorption ratio was higher at 75 °C than at 50 °C. The tensile strength of water-soaked specimens was decreased by 15%, exhibiting interlaminar delamination. However, plasticization of the cured epoxy resin by water increased interlaminar fracture toughness. These results indicate that water absorption accelerated interlaminar cracking initiated by micropore and interfacial failure in toughened resin, especially under low-temperature curing condition.

Effect of Water Absorption on Flexural Properties of Kenaf/Glass Fibres Reinforced Unsaturated Polyester Hybrid Composites Rod

This study investigates the effect of water absorption on the flexural strength of kenaf/ glass/unsaturated polyester (UPE) hybrid composite solid round rods used for insulating material applications. Three volume fractions of kenaf/glass fibre 20:80 (KGPE20), 30:70 (KGPE30), and 40:60 (KGPE40) with three different fibre arrangement profiles of kenaf fibres were fabricated by using the pultrusion technique and were aimed at studying the effect of kenaf fibres arrangement profile and its content in hybrid composites. The fibre/ resin volume fraction was maintained constant at 60:40. The dispersion morphologies of tested specimens were observed using the scanning electron microscope (SEM). The findings were compared with pure glass fibre-reinforced UPE (control) composite. The water absorption results showed a clear indication of how it influenced the flexural strength of the hybrid and non-hybrid composites. The least affected sample was observed in the 30KGPE composite type, wherein the kenaf fibre was concentrated at the centre of a cross-section of the composite rod. The water absorption reduced the flexural strength by 7%, 40%, 24%, and 38% of glass/UPE (control), 20KGPE, 30KGPE, and 40KGPE composites, respectively. In randomly distributed composite types, the water absorption is directly proportional to the volume fraction of kenaf fibre. At the same time, flexural properties were inversely proportional to the volume fraction of kenaf fibres. Although the influence of water absorption on flexural strength is low, the flexural strength of pultruded hybrid composites was more influenced by the arrangement of kenaf fibre in each composite type than its fibre loading.

Prediction of statistical life time for unidirectional CFRTP under water absorption

Carbon fiber reinforced plastics (CFRP) with the matrix of thermoplastic resin called as carbon fiber reinforced thermoplastics (CFRTPs) has been widely used in the industrial fields. Recently, a thermoplastic epoxy resin (TP-EP resin) has been developed as the matrix of CFRTP and carbon fiber reinforced TP-EP strands (CF/TP strands) molded by pultrusion method began to be used as tension rods for infrastructure under water absorption. On the other hand, an accelerated testing methodology (ATM) for predicting statistically long-term creep and fatigue strengths of CFRP was established by the authors. This study examines the prediction of statistical life time for these developed CF/TP strands at creep and fatigue tension loadings under the wet condition of water absorption with comparison to similar prediction under a dry condition by using our developed ATM. First, the static, creep, and fatigue tensile strengths of CF/TP strands were measured statistically at various constant temperatures under wet and dry conditions. The statistical long-term creep and fatigue tensile strengths for CF/TP strands under wet and dry conditions are predicted by substituting the measured data into the formulations of these strengths on our developed ATM. Finally, the influences of water absorption on the statistical long-term creep and fatigue strengths of CF/TP strands are cleared. In particular, the degradation of relaxation modulus of matrix TP-EP resin with increasing of elapsed time is accelerated with the water absorption, and the degradation of creep strength of CF/TP strand with increasing of elapsed time is also accelerated with the water absorption in the similar manner of matrix resin. On the other hand, the fatigue strength of CF/TP strand decreases scarcely with water absorption although this fatigue strength depends remarkably on the number of cycles to failure.

Influence of water absorption on mechanical properties and glass transition temperatures of polyamide6/hexagonal boron nitride composites

PurposeThe absorption of moisture/water can affect the mechanical and thermal properties of polymers and polymer composites as many polymers, mainly polyamide thermoplastics, are sensitive to environmental humidity and can absorb a large amount of moisture. This paper investigates the effect of water molecules' absorption on mechanical and thermal properties of polyamide6/hexagonal boron nitride (PA6/h-BN) composites.Design/methodology/approachThe PA6/h-BN composites were exposed to an open environment and water for 15 days to analyse the effect of humidity/water molecules' absorption on mechanical and thermal properties. The tensile strength, hardness and impact strength of materials were measured and compared. The scanning electron microscopy (SEM), x-ray diffraction (XRD) and differential scanning calorimetry (DSC) analyses were utilized to see the influence of water absorption on microstructure, crystallinity and glass transition temperatures.FindingsAfter exposing materials to an open environment and water, the tensile strength and hardness were found to decline, while improvement in impact strength was noticed. SEM characterization revealed the formation of voids/pockets in water-immersed materials. DSC analysis revealed the loss in glass transition temperatures, and XRD analysis revealed the loss in crystallinity of water-immersed materials.Originality/valueEnvironmental conditions vary according to the geographical areas, and it varies in many countries throughout the year. Polyamides are sensitive to the environmental humidity and can absorb a large amount of moisture from the environment. It becomes necessary to test these materials in their original working conditions, and sometimes it is mandatory to see the effects of extreme environmental conditions on a component. In this article, efforts have been made to investigate the influence of extreme humidity/water conditions on thermo-mechanical properties of PA6/h-BN composites.

Influence of water absorption on friction, wear and abrasion resistance of PA6-hBN composites

Investigations on the tribological properties, i.e., abrasion resistance, friction coefficient, and wear of water conditioned polyamide6/hexagonal boron nitride composites were carried out in this research. Polyamide6 and polyamide6/hexagonal boron nitride composites were fabricated with the help of a twin-screw extruder and injection moulding machine. Fabricated materials were water immersed for 15 days to analyse the effect of water absorption on the tribological properties of materials. Tribological tests were carried out on a pin-on-disc tribometer, and abrasion resistance tests were performed on a TABER abrader. The SEM analysis was carried out to analyse the wear tracks of water conditioned composites. Testing on TABER abrader revealed the loss in abrasive resistance of composite materials, while tribological testing of composites with steel as the other mating and rubbing surface revealed improvements in COF and wear after water absorption. The SEM images revealed less depth of wear in water conditioned materials compared to dry ones. The causes of wear were found as the stick and slip, i.e., adhesive wear in which material tends to stick during matting with steel disc, and due to the continuous movement, it slips. Water absorption was found supportive in the formation of smooth lubricating transfer film on a steel disc. Bonding between the polyamide matrix and water molecules plus the formation of boric oxide & orthoboric acid were found advantages in decreasing the friction coefficient and wear of water conditioned composites.

Hygrothermal Ageing Influence on BVI-Damaged Carbon/Epoxy Coupons under Compression Load.

Composite materials usage in several industrial fields is now widespread, and this leads to the necessity of overcoming issues that are still currently open. In the aeronautic industry, this is especially true for Barely Visible Impact Damage (BVID) and humidity uptake issues. BVID is the most insidious kind of impact damage, being rather common and not easily detectable. These, along with the ageing that a composite structure could face during its operative life, could be a cause of fatal failures. In this paper, the influence of water absorption on impacted specimens compressive residual strength was studied. Specimens were impacted using a modified Charpy pendulum. Two different locations were chosen for comparison: Near-Edge (NE) and Central (CI). Accelerated hygrothermal ageing was conducted on impacted and reference nonimpacted coupons, placing them in a water-filled jar at 70 °C. Compressive tests were performed in accordance with the Combined Loading Compression (CLC) test method. A Dynamic Mechanical Analysis (DMA) was performed as well. The results showed the influence of hygrothermal ageing, as expected. Nevertheless, the influence of impact location on compressive residual strength is not clearly noticeable in aged specimens, leading to the conclusion that hygrothermal ageing may have a greater effect on composite compressive strength than the analysed BVI damage.

Influence of Groundwater pH on Water Absorption and Waterproofness of Polymer Modified Bituminous Thick Coatings.

Polymer modified bituminous thick coatings are increasingly used in the construction industry to protect underground parts of buildings from groundwater. When assessing their durability, one vital issue related to their functional properties is the influence of water absorption on the waterproofness of the applied solution as a result of the action of groundwater with different pH values. As part of the research, the water absorption of the products in question was assessed using the method of total immersion in water with pH of 4.0, 7.0 and 7.5 as well as comparatively, as a result of one-way exposure to demineralized water under successively increasing pressure up to 0.5 MPa. The moisture susceptibility of the coatings was assessed both concerning the local surface damage and the continuous waterproofing coating. It was established that the coatings show the highest water absorption when the water pH is 4.0, which simulates the groundwater aggressiveness on construction products. It was proven that moisture absorbed by the coatings is retained within this layer and is not transferred to the substrate on which the coatings are laid. It was also found that water in contact with the tested coatings changes its reaction to alkaline, which can result in contamination of groundwater in the area of waterproofing coating. A modification of the method of assessing the water absorption of polymer modified bituminous thick coatings was proposed, taking into account their use in conditions of use.

Effect of water absorption and curing period on strength and porosity of triple blended concrete

Water absorption and porosity are the two main factors which are directly related to strength and durability property of concrete. The present work is mainly focused on the influence of water absorption on the compressive strength and effect of curing period on porosity, investigated on concrete specimens triple blended with fly ash, egg shell powder and steel fibres. Fly ash and waste egg shell powder are being used as one of raw material in concrete. In addition to both, a small amount of steel fibers is also added to examine the change in the properties of concrete. Fly ash and egg shell powder are used as a substitution in place of cement in various proportions and initially the experiments were performed to examine the results, with 0%, 0.25%, 0.5% and 0.75% addition of steel fibres by volume of concrete, after 7 days and 28 days of curing period. It is observed that water absorption percentage decreased with the rise in the amount of steel fibers and porosity decreased with the increase in curing period but increased with the rise in the amount of steel fibers. It was also confirmed that a combined mix of 35% fly ash, 6% egg shell powder reinforced with 0.75% steel fibers exhibited the maximum compressive strength.

The Influence of Moisture Absorption on the Mechanical and Thermal Properties of Chemically Treated DPL Reinforced Hybrid Composite

Moisture absorption of natural fiber-based composites is one of the major problems in outdoor applications. The present study deals with the effect of moisture absorption on mechanical and thermal properties of unmodified/modified Date Palm Leaf (DPL) with glass fiber-based hybrid composites. Natural fibers were modified with alkaline treatment to improve fiber and matrix bonding. Conventional hand lay-up technique is used to fabricate the composites with varying different wt.% of treated and untreated short DPL with constant wt.% of glass fiber and prepared with random oriented manner. The combine effect of hydrophilic and hydrophobic nature find out as the study based upon the natural with synthetic fiber hybrid composites. Mechanical behaviour of the epoxy-based hybrid composites were characterized by using tensile, flexural and hardness test. The results revealed that significant improvement in mechanical properties by the addition of different weight percentage of modified DPL. Different thermal properties of the composites were described by using Thermo Gravimetric Analyzer (TGA) and Differential Scanning Calorimetric (DSC). Morphological investigation was carried out to by using scanning electron microscope. All the properties of untreated natural fiber reinforced composites were mostly affected by the influence of water absorption as compared with chemically treated based composites.

Influence of Water Absorption on the Low Velocity Falling Weight Impact Damage Behaviour of Flax/Glass Reinforced Vinyl Ester Hybrid Composites.

Due to rigorous new environmental legislations, automotive, marine, aerospace, and construction sectors have redirected their focus into using more recyclable, sustainable, and environmentally friendly lightweight materials driven by strengthening resource efficiency drive. In this study, the influence of moisture absorption on flax and flax/glass hybrid laminates is presented with the aim to investigating their low velocity impact behaviour. Three different types of composite laminates namely, flax fibre reinforced vinyl ester, flax fibre hybridised glass fibre and glass fibre reinforced vinyl ester composites were fabricated using resin infusion technique. The moisture immersion tests were undertaken by immersing the different specimens in sea water bath at room temperature and 70 °C at different time durations. The low velocity falling weight impact testing was performed at 25 Joules of incident energy level and impact damage behaviour was evaluated at both ageing conditions using scanning electron microscopy (SEM) and X-ray microcomputed tomography (micro CT). The percentage of moisture uptake was decreased for flax vinyl ester specimens with glass fibre hybridisation. The maximum percentage of weight gain for flax fibre, flax/glass hybrid and glass fibre reinforced composites immersed at room temperature for 696 h is recorded at 3.97%, 1.93%, and 0.431%, respectively. The hybrid composite exhibited higher load and energy when compared flax/vinyl ester composite without hybridisation, indicating the hybrid system as a valid strategy towards achieving improved structural performance of natural fibre composites. The moisture absorption behaviour of these composites at room was observed to follow Fickian behaviour.

Evaluation of a biodegradable color concentrate in bags for coffee seedlings

The aim of this study was to evaluate different formulations of a biodegradable black concentrate obtained from cassava starch and carbon black, on the mechanical properties, color, and water absorption of a film destined to the production of biodegradable bags for coffee seedlings. The modulus of elasticity, tensile strength and elongation properties is found to show significant variation due to the pigment, plasticizer, and lubricant concentration, both longitudinally and transversely of the film, the treatment being 40% pigment with the absence of plasticizer and lubricant for the pigment, which presented greater integrity in the mechanical properties evaluated in both directions. It is also noticeable that the different masterbatch formulations had an influence on the changes in the color parameters and weight gain of the film by the influence of water absorption.

The influence of water absorption on unidirectional and 2D woven CFRP composites and their mechanical performance

This paper discusses a key parameter ‘fibre architecture’ that is believed to play a major part in the performance of CFRP composites when subjected to water absorption. Unidirectional, plain, and twill weave CFRP specimens were immersed in water at 70 °C for 40 days. The condition of the matrix was examined using a Scanning Electron Microscope (SEM). The mechanical properties dominated by the condition of the matrix and interfacial regions such as compression, shear, and impact resistance were assessed for un-aged and aged specimens. A reduction in strength was observed for all aged specimens. However, the observed reduction in strength varies depending on both the fibre architecture used and the specific load case. The largest effect on properties was observed in unidirectional materials, which leads to the recommendation that less conservative safety factors should be used for woven fibre architectures.

Water absorption characteristics of cement-based materials based on the chemical reaction

With the development of urban infrastructure, subway and other underground projects are gradually being constructed in various cities. The influence of water absorption on surface of cement-based materials has therefore become more and more important. A mathematical model and the relative experiment of water absorption in cement mortar were investigated. The results showed that the change of radius of pore was decreased and absorption mass fraction was increased with the increased of absorption time. The possibility and direction of reaction during this process were studied, and the result showed that hydrolysis was not merely occurred in this process.

Influence of Water Absorption on Static Friction of Pure and Friction-Modified PA6 Polymers

In the present study, static coefficients of friction of pure and friction modified (FM) polyamide 6 (PA6) polymers against primer-coated steel surfaces were investigated under a series of nominal contact pressures and by considering the influences of water absorption by the polymer, temperature, counter-body surface roughness and lubrication conditions. Under the majority of the test conditions investigated, FM PA6 exhibited lower static friction than pure PA6. Under unlubricated conditions, this was due to the low adhesion of the FM PA6 provided by its friction modifying inclusions; while under lubricated conditions, a combination of softening due to water absorption and decreased adhesion provided by its friction modifiers enabled lower static friction, especially at medium and high contact pressures.

Influence of Water Absorption and Temperature on the Mechanical Properties of Discontinuous Carbon Fiber Reinforced Polyamide 6

Carbon fiber reinforced thermoplastics (CFRTP) show relatively high mechanical properties and are expected to be feasible materials for mass production of light-weight structures. In particular, discontinuous CFRTP (DCFRTP) with affordable resins have been developed to realize excellent formability and mechanical properties. Currently, polyamide 6 (PA6) is a promising matrix for CFRTP in mass-produced automobiles. However, due to the hygroscopic and viscoelastic properties of polyamide resins, the influence of water absorption on the mechanical properties of CFRTP under varying temperature is necessary to be investigated. In this study, the influence of water absorption on the mechanical properties of discontinuous CF/PA6 composites was investigated. Chopped carbon fiber tape reinforced thermoplastics (CTT), which are randomly oriented strand (ROS) composites, were selected as DCFRTP. The mechanical properties of the composites were investigated by a three point bending test between −40 and 125 °C, as a function of water absorption. The flexural modulus were calculated using the Timoshenko beam equation to predict degradation by water absorption. The mechanical properties of CTT have a relatively high sensitivity to water absorption.