the hydrophilic nature of fibre surfaces is due to the presence of hydroxyl and polar groups of cellulose. it leads to swelling and agglomeration of fibres within the matrix when composites are formed. furthermore there is high moisture content which results in poor interfacial adhesion between fibres and matrix.
modification of the fibre surface can be exploited to enhance the mechanical and water absorption properties of the composites. an optimum result was obtained in koh treated sisal-fibre-reinforced homopolymer polypropylene composites. keywords: mechanical properties water absorption sisal- fibre chemical treatment . 1. introduction
as shown in figure 2 moisture absorption into epoxy resin is caused by the diffusion of water or clusters into the three-dimensional crosslinked structure of the resin. it is assumed that the moisture absorption progresses diffusing from the surface layer. as shown in figure 3 initially
diffusion direction ms is saturation absorption and k means initial gradient of the water absorption curve. since the diffusion in in-plane transverse direction and out-of-plane direction seems to be similar phenomenon same coefficients are used for those directions in present study. 3.2 impact test and damage inspection
water absorption behaviour like viscoelastic properties of food products is a time dependent behaviour figure 1 . therefore it is possible to model these two different properties of agricultural materials with the same model. according to figure 1 the water absorption behaviour of the agricultural products may be defined as mohsenin 1986 :
water absorption is the amount of water taken up by flour to achieve the desired consistency and create a quality end-product. it is the optimal amount of water you can add to a dough before it becomes too sticky to process. water absorption is usually defined by flour weight. for example 60% water absorption means 60 lbs of water is used to hydrate 100 lbs of flour.
the effects of various chemical treatments on the mechanical and thermal properties of natural fibers reinforcements thermosetting and thermoplastics composites were studied. a number of drawbacks of nfpcs like higher water absorption inferior fire resistance and lower mechanical properties limited its applications.
at the composite materials outer layers water absorption happens and decreases gradually into the bulk of the matrix. a generally high water intake by composite materials results in an increased weight of wet profiles a conceivable decline in their strength and increment in their deflection swelling and causing pressure on nearby structures.
water absorption. the type v tensile bars injection molded for each composite were dried in an oven for 24 hours at 100 2 o c and weighed. tests were conducted in an incubator at 25 2 o c under a photosynthetic photon flux density of 180 mol. m 2. s-1 using a photoperiod of 12 h light/12 h dark. tensile bars were placed in distilled water at room temperature for 872 h.
while intended primarily for laminated polymer matrix composite materials these procedures are also applicable to other materials that satisfy the assumptions of 1.2. 1.2 the calculation of the through-the-thickness moisture diffusivity constant in procedure a assumes a single-phase fickian material with constant moisture absorption properties through the thickness of the specimen.
plant water relations: absorption transport and control mechan isms 107 from one point with a lower concentration of solutes for example pure water to a point with a higher concentration. so the higher concentration of the solutes at a point which makes the system more negative will be the osmotic potential in this place. the water
coatings for composites. this solubility is undesirable for composite primers as it causes water absorption. chromate free primers will normally provide a better water barrier. another feature of chromate pigments is that they are classified as carcinogenic and as substances of very high concern svhcs under reach.
water absorption in three wood varieties 9 t/t ret mm m 1e kt to ret rel = 6 where krel is the rate of water absorption in the relaxation phase % / min . the time of retardation tret is the time required by the seed moisture content to
reasons. first during the life cycle of the material water absorption could induce a volume change of the fibers inside the composite leading to the development of internal stresses. on the other hand during the polymerization process of the matrix above 100 c a vaporization of water trapped inside fibers could occur leading to
the water absorption behavior of the composites mainly depends on the voids present in the composites interfacial adhesion between the fibre and matrix and type of fibres reinforced. the woven basalt fibre composites show higher absorption in normal water compared to sea water.
composite standards. these composites can be in the form of sandwich core materials honeycomb core materials polymer matrix composite materials and their laminates fiber-reinforced polymer-matrix composite plates and bars fiber reinforced metal matrix composites carbon fiber-epoxy prepregs continuous filament carbon and graphite fiber tows
water. the diffusion coefficient is the most important parameter for water absorption as it shows the ability of solvent molecules to penetrate inside the composite structure. water absorption of the composites increases with temperature since temperature activates the diffusion process. in addition the higher absorption of water may be due to
water absorption behavior of the composites and the neat resins are considered first followed by moisture and temperature effects on composite compressive strength 00 tensile strength and modulus ±450 tensile strength and modulus 900 tensile strength and modulus and interlaminar fracture toughness.
factors affecting water absorption include: type of plastic additives used temperature and length of exposure. the data sheds light on the performance of the materials in water or humid environments.
effect of water absorption on the mechanical properties of continuous carbon fibre reinforced polycarbonate composites. k. tanaka1 y. fukushima1 k. kashihara2 and t. katayama1 1department of biomedical engineering doshisha university japan. 2department of mechanical engineering doshisha university japan.
as a specimen a carbon fiber reinforced epoxy resin matrix composite cfrp with a curing temperature of 180 c and a fiber volume fraction vf of about 55% was used. as an examination of the accelerated moisture absorption condition the accelerated moisture absorption behavior was evaluated at each temperature.
the moisture content as a function of time of composite materials when mate-rial is either exposed to humid air or fully submerged in water. although the main interest in this investigation was in the moisture absorption and desorption of composite materials the results also apply to homogeneous materials.
effects of microfibrillated cellulose addition and water absorption on mechanical properties of jute/polylactic acid composites k. takemura s. takai and h. katogi kanagawa university japan abstract in this study the effects of microfibrillated cellulose mfc addition and water absorption on mechanical properties of jute fiber reinforced
abstract. high density polyethylene hdpe composites reinforced with short bamboo fibre bf were fabricated by compression moulding technique. bf were extracted from bamboo culm
composite materials exposed either on one side or on both sides to humid air or to water. the results apply during both moisture absorption and desorption when the moisture content and the temperature of the environ-ment are constant. test procedures are described for determining experi-
absorption. natural fibers absorb water from the air and direct contact from the environment. this absorption deforms the surface of the composites by swelling and creating voids. the result of these deformations is lower strength and an increase in mass. additionally with water absorption rates as high as 20 wt% the light weight advantage is often nullified.
water absorption in composites is more complex than in polymers alone. in the case of thermoplastic composites the extent of the water absorption into the polymeric matrix depends on the chemistry and morphology of the polymer as well as the volume fraction and configuration of the fibers present and whether any wicking at the interface occurs.
effect of water absorption on the mechanical properties of continuous carbon fibre reinforced polycarbonate composites k. tanaka1 y. fukushima1 k. kashihara2 and t. katayama1 1department of biomedical engineering doshisha university japan 2department of mechanical engineering doshisha university japan abstract
one of the main causes of mechanical properties loss in composites reinforced with fiberglass is their susceptibility to moisture absorption 14. the epoxy resins belong to the group of thermosetting resins and have a wide range of applications in the aerospace automotive and marine industries among others.
to determine certain physical properties viz. the thickness swelling and water absorption and mechanical properties viz. the tensile strength and izod impact strength of lignocellulosic filler reinforced polyolefin bio-composites polyolefin was used as the matrix polymer and rice-husk flour as the reinforcing filler.
wax is used in the engineered wood industry for two principal reasons: water absorption and lubrication. wax helps control water absorption and thickness swelling in a finished board especially along the edges. this temporary water resistance is important when boards are left outside at a job site or exposed to water prior to and after installation.
built-in moisture resistance where theres a pool theres apt to be water a lot of it. made in maine duralifes unique polypropylene and hardwood composite decking material features a co-extruded capped surface that allows water to easily drain from its surface. this provides a safer drier surface caused by rain and splash over from the pool and also greatly reduces off-season damage caused by expansion and contraction due to moisture absorption and temperature variation.
results and discussion water absorption. figure 1 shows the trend of water absorption of composites made up of pure epoxy and oil palm efb/jute fibres pure epoxy pure efb pure jute and hybrid composites . it is clear from fig. 1 that water absorption increased with immersion time.
water pickup data obtained during these studies are analysed in an attempt to develop an understanding of the absorption mechanism. there is evidence which indicates that voids and defects in the composite have a marked effect on the absorption process and may assume greater significance than the diffusion process through the resin.
water absorption test: water absorption test was done according to astm d570. specimens were molded in the shape of cylinder with 50.8 mm diameter and 3.2 mm thick and for each blend composition three specimens were produced. the picture of the specimens is presented in fig. 1. before immersion the specimens were conditioned by drying in an oven for 24 h at 50 c cooled in desiccators and immediately weighed to the nearest 0.0001 g.
water absorption on the distilled water is higher than the sea water for all the composites. this might be because of the salt content in the sea water which reduces the water molecules diffusion capability.
a five-week study on water absorption of dental composites suggested that the decrease in the mechanical properties was a result of residual stress between the wet and dry regions of the composite oshida et al. 1995 . whether this might be a carry over to possible breakdown of the resin matrix or separation of the filler particles from the resin matrix for complete sorption of water following a longer aging time was not discussed.
for their use as reinforcement the hydrophilic nature of plant fibers has to be considered with carefulness for several reasons. first during the life cycle of the material water absorption could induce a volume change of the fibers inside the composite leading to the development of internal stresses.
polymer composites is the engineering and scientific journal serving the fields of reinforced plastics and polymer composites including research production processing and applications. environmental damage and degradation of frp composites: a review report - ray - 2015 - polymer composites - wiley online library