Study Of Some Mechanical Properties For Epoxy / SiO 2 Nano Particles Reinforced With 6 Layers Of CM E-Glass Fibers Composites

In this study, the neat epoxy and nanocomposites with volume fraction (1, 3, 5, 7 and10%) of nano SiO2 particles reinforced with six layers of chopped mat E-glass fibers (CM) specimens were prepared by molding method. The results of Impact strengths of EP/SiO2 nanocomposites reinforced with 6 layers of CM E-glass fibers showed that Impact strength has a random behaviour with increasing volume fraction of SiO2 nanoparticles. The results showed an increase of Impact strengths with increasing the SiO2 nanoparticles volume fraction at 1% vol. of SiO2 nanoparticles, then decreases with increasing volume fraction at 3% vol. of SiO2 nanoparticles, then the Impact strength increases with increasing volume fraction of SiO2 nanoparticles until the Impact strength reach to maximum values (78.93KJ/m2) at 7% vol. of SiO2 nanoparticles. And then Impact strength decreases with increasing volume fraction at 10% vol. of SiO2 nanoparticles. Also the results of shore D hardness of EP/SiO2 nanocomposites reinforced with 6 layers of CM E-glass fibers showed that Hardness No. an increase with increasing the SiO2 nanoparticles volume fraction at 1% vol. of SiO2 nanoparticles, then decreases with increasing volume fraction at 3% vol. of SiO2 nanoparticles, then the Hardness No. increases with increasing volume fraction of SiO2 nanoparticles until the Hardness No. reach to maximum values (85.03) at 10% vol. of SiO2 nanoparticles.


INTRODUCTION
Polymer nanocomposites are defined as an interacting mixture of two phases, a polymer matrix and a solid phase which is in the nanometer size range in at least one dimension. Solid phase are fillers such as carbon nanotubes, layered graphite nanofillers, silica nanoparticles, titania nanoparticles etc. Very important feature of polymer nanocomposites is that the small size of the fillers leads to a dramatic increase in interfacial area as compared with traditional composites [1]. There are many factors that affect the polymer nanocomposite properties such as; (i) Types of nanoparticles and their surface treatments, dispersion and distribution of nanoparticles in the polymer matrix, shape and size. (ii) The types of synthesis methods. (iii) Polymer nanocomposite morphology.(iv)Polymer matrix such as degree of crystallinity, molecular weight, polymer chemistry and the type of polymer; thermoplastic, thermosetting or elastomers [2,3,4].
Sands cover a large quantity of the Earth and are the source from which most silica is made. The crystalline and non-crystalline forms of silicon dioxides are well known to be named as quartz and fused silica, respectively. Two methods have been used in preparing nano scale silica: the gas-phase (or the drying method) and the deposition preparation method (or the wet method). The particle sizes in both the gas-phase and the deposition methods are quite different in that the former produces silica with a smaller particle size than that produced by the latter method [5,6].
Some characteristic of silica nanoparticles; (i)Swelling behavior and cation exchange performance. (ii) Porosity, particle porosity structure and pore distribution are of importance, the diameters of micropores and mesopores are all less than 50 nm, and the diameter of macropores or large pores is above 50 nm. Particles with pore diameter less than 100 nm should be thought of as nanomaterials. (iii) Dispersion phase and media, the smaller the particle size the more difficult is its dispersion into the polymermatrix [5,7].
Nanocomposite materials have become increasingly important due to their extraordinary properties, which arise from the synergism between the properties of the parent components and their unique interfacial characteristics. These properties appear to be quite different from those of the conventional micrometer-sized composites. This mainly results from the nanometer-sized component which dramatically increases the available interacting surface area [20].
The general Applications of nanocomposite have recently attracted increasing interest because of the possibilities of synthesizing materials with unique physical-chemical properties. Highly sophisticated surface related properties, such as optical, magnetic, electronic, catalytic, mechanical, chemical and tri biological properties can be obtained by advanced nano structured manufacturing, making them attractive for industrial applications in high-speed machining, optical applications and magnetic storage devices because of their special mechanical, electronic, magnetic and optical properties due to size effect [9].

2-1 RAW MATERIALS
Raw materials used in this experimental work are listed below:

2-1-1 MATRIX MATERIALS
Epoxy as a matrix (Nitofill, EPLV with Nitofill EPLV hardener from Fosroc Company) was used to prepare composites. The weight ratio of the epoxy resin to the hardener was 3:1 and gelling time 40 minutes at 35°C, mixed viscosity 1.0 poise at 35Cᵒ. The properties of epoxy resin are given in Table (1).

2-1-2 FIBER MATERIAL
E-glass fibers were used as reinforcements, chopped mat E-glass fibers of surface density 300 g/cm2.The fiber materials used in this work are shown in Figure (

2-1-3 REINFORCING PARTICLE
SiO2 nanoparticles (Aerosil-200) from Aerosil pharma (hydrophilic silica) with average diameter of 12nm, a specific surface area of 200±25m2/g. Atomic force microscopy (AFM) was used (CSPM scanning probe microscope) to measured the average particles size of SiO2 nanoparticales, the particles size distribution is shown in Figure (2).Some properties of the reinforcing particulate are given in Table (3).

2-2 PREPARATION METHOD
Impact test and Shore D hardness test specimens were prepared by hand lay-up technique and mixing process which can be summarized by the following steps:

Chopped mat random (CM)
Fast wet-out

2-2 -1 PREPARATION OF NEAT EPOXY
The neat epoxy specimens were prepared by simple direct mixing of epoxy resin with the hardener, epoxy resin and hardener are weighted for suitable mixing ratio by using electronic balance type (Sartorius BL 210S/Germany) with sensitivity of 10-4g and with rang up to 2Kg, and mixed in container by mechanical stirring for 15 minutes to get good homogeneity between epoxy resin and hardener before casting it as sheets (of dimensions 15x15cm2), by using clean glass mould (cleaned by distilled water to remove the dirt and dust present on the surfaces) were used for casting. The casting was cured at room temperature for 24 hours. Sheets were casted in an oven for 1hour with temperature 50 oC, it was left for 48 hours before pulling out from molds and then left at room temperature for 7 days before processing further and kept then in vacuum chambers.

2-2-2 PREPARATION OF THE LAMINATED COMPOSITES
Sheets of E-glass/epoxy composites were prepared from epoxy resin (as a matrix) and E-glass fibers(as reinforcement) with the chopped strand mat CM by using hand lay-up method sometimes called wet lay -up or contact moulding, is a simple method and the most widely used for fiber reinforced polymer (FRP) process. In its simplest form, the process consists of applying layers of reinforcing material against a single sided mould and working resin into the material with a brush and roller, after a suitable period of time to allow the resin to cure, the moulding with one smooth surface, is removed from the mould and trimmed to size, which can be summarized by the following steps: The epoxy resin was mixed with the hardener in weight fraction of 3:1 both were thoroughly mixed to be ready to composite construction. Fiber glass sheets of dimensions 15 × 15cm2 were cut from chopped mat.
The first layer of mat was laid and epoxy resin spread uniformly over it by means of a paint brush. A second layer of mat was laid and spread again with paint brush. After the second layer, to enhance wetting and impregnation, a teethed aluminum roller was used to roll over the fabric before applying resin. It was made sure that there is no air bubbles entrapped inside the mixture applied on sheet otherwise it would create a flow there. This process was repeated till all the six fabric layers were placed. The casting was cured at room temperature for 24 hours. The specimens were casted in an oven for 1hour with temperature 50°C and finally removed from the mold to get a fine finished composite sheet after 48 hours and then left at room temperature for 7 days before processing further and kept then in vacuum chambers.

2-2-3 PREPARATION OF EPOXY NANOCPMPOSITES
Nanocomposites with different volume fraction (1, 3, 5, 7 and10%) of nano SiO2 particles and reinforced with six layers of E-glass fibers(CM) were prepared by molding method. Since properties of composite depend upon the volume fraction of reinforcement, mass for a given volume fraction of SiO2 was determined from the volumes of individual components matrix and SiO2 fillers by using: Where, Vf is the volume fraction of SiO2 fillers, Vm is the volume fraction of epoxy matrix, Wf & ρ f is the mass and density of fillers for the prepared composite, Wm & ρ m is the mass and density of epoxy matrix for the prepared composite.
The nanocomposites were prepared in more complicated method such that; The nanoparticles were preheated at 120 oC for 2 h in order to eliminate possible absorbed water on their surface,to prepare homogenous mixture of epoxy and the nanoparticles, a volume fraction percent of nanoSiO2 particles weighted with electronic balance of four digits type (Sartorius H51) then mixed with epoxy resin, the mixture put inside a container, an oil bath was used to heat up the mixture to desired (75 oC ) temperature so the viscosity of epoxy base is reduced. Proper mechanical stirring (2h) at this stage resulted better dispersion of nanoparticles, then the mixture was cooled to room temperature after that the hardener was added to the formulation being mixed by mechanical stirring (10 minutes). Sheets were left at room temperature for 24hours for curing, and was cast in an oven for 1 hour at 50 oC for post curing, it was left for 48 hours before pulling out from molds and left for 7 days before any test to get better curing conditions and kept then in vacuum chambers.

IMPACT TEST SAMPLE CUTTING
The sheets of the nanocomposites reinforced with six layers of chopped mat E-glass fibers (CM) are cutting into specimens, by using a circular iron saw, pluses from the samples were removed by using the iron rasp, the samples were polished by using abrasive emery papers of grade 400.The shape and dimension of the samples cut for impact test according to [

CHARPY IMPACT TEST
This instrument consists mainly of pendulum and energy gauge. Charpy impact test consists of standard test piece that would be broken with one flow of a swinging hammer. The test piece is supported at both its ends in a way that the hammer strikes it at the middle.
The testing method of this instrument includes lifting of the pendulum to its maximum height and fixing it firmly. The specimen is fixed in its pertaining place, and then the energy gauge is initialized (on zero position), after that, the pendulum is freed whereas its potential energy would be changed to kinetic energy. Some of this kinetic energy is utilized to fracture the specimen, while the energy gauge reads the value of fracture energy (Uc) for the sample under test. Impact strength (I.S) is calculated by applying the relationship: [11] I.S =Uc/A(KJ/m2) ……………………. (3) Where Uc: is the fracture energy (Joule) which is determined from charpy impact test instrument.
A: is the cross-sectional area of the specimen.

4-2 HARDNESS TEST
Shore D Durometer Hardness instrument, fabricated by TIME GROUP INC Company, was used to carry out the hardness test by using pointed dibbing tool. The pointed dibbing tool penetrate the material surface by the pressure applied on the instrument where the dibbing tool head touching quite the surface of the samples then calculate the hardness values for the samples.

5-1 IMPACT STRENGTH OF COMPOSITES
The results of Impact strengths of EP/SiO2 nanocomposites reinforced with 6 layers of CM E-glass fibers in Table (4) showed that Impact strength has a random behaviour with increasing volume fraction of SiO2 nanoparticles of EP/SiO2 nanocomposites reinforced with 6 layers of CM E-glass fibers. The results show an increase of Impact strengths with increasing the SiO2 nanoparticles volume fraction at 1% vol. of SiO2 nanoparticles, then decreases with increasing volume fraction at 3% vol. of SiO2 nanoparticles, then the Impact strength increases with increasing volume fraction of SiO2 nanoparticles until the Impact strength reach to maximum values (78.93KJ/m2) at 7% vol. of SiO2 nanoparticles. Increases Impact strength due to Increase of crack deflections (creating more than one crack propagation direction) which means crack propagation resistance and increase of chains supporting resulting from nanoparticles existence. And then Impact strength decreases with increasing volume fraction at 10% vol. of SiO2 nanoparticles.
In general all the results obtained still higher than the neat epoxy and the neat composites specimen. Figure (4) shows the variation of Impact strengths of EP/SiO2 nanocomposites reinforced with 6 layers of CM E-glass fibers vs. SiO2 nanoparticles volume fraction.
Photographs under 40X magnification for Charpy Impact specimens of EP/SiO2 nanocomposites with 1, 3, 5, 7and 10% volume fraction nanocomposites reinforced with 6 layers of CM E-glass fibers after the test showed in Figure (

5-2 HARDNESS TEST
The results of shore D hardness of EP/SiO2 nanocomposites reinforced with 6 layers of CME-glass fibers showed in  (6) shows the variation of Hardness No. of EP/SiO2 nanocomposites reinforced with 6 layers of CME-glass fibers vs. SiO2 nanoparticles volume fraction.