Investigation of Compression properties on E-Glass fiber reinforced polymer matrix composites used for micro wind turbine blades

: The main goal of this work is to understand the mechanical behaviour of composites to compression loads. A unidirectional (UD) fabric of E-glass fiber is the most common reinforcement in composite structural applications which exhibits excellent strength, modulus, resistance to water degradation and corrosive environments, durability, good and a quantitative and qualitative analysis is conducted on this model and the results are validated. An experimental test sample made of the E-Glass/Epoxy-resin composite is subjected to uniaxial compression test. The experimental results are validated with the multiscale mechanical model built. The FEA (Finite Element Analysis) is being utilized and the results obtained are validated through experimental approach. With such validated numerical model, application in micro wind turbine blade would result in faster prototype development.

In this paper, E-Glass fibre reinforced polymer matrix composite (epoxy-resin: Ly556 and Hardener 951) is modelled using FEA method (Finite Elements used at micro and macroscale), implementing a hierarchical multiscale modelling scheme. A representative volume element (RVE) is used to model the E-Glass/Epoxy-resin composite at microscale consisting of the uniaxial fibres embedded in epoxy-resin polymer matrix. The material properties derived from the microscale finite element analysis is applied to the nodal points of the elements of the macroscale finite element model. E-glass is a low alkali glass with a typical nominal composition of SiO2 54wt%, Al2O3 14wt%, CaO+MgO 22wt%, B2O3 10wt% and Na2OK2O less than 2wt% other than this some other materials may also be present as impurity.
A unidirectional (UD) fabric is one in which the majority of fibers run in one direction only. The Epoxy resin Araldite LY556 and Hardener HY951 combination gives laminate with excellent water resistance and very low cure shrinkage; hence the laminates of this epoxy are dimensionally stable and practically free from internal stresses. Araldite LY556 is an epoxy resin based on Bisphenol-A suitable for high performance composite FRP applications like Filament Winding, Pultrusion and Pressure Moulding etc.
Hardener HY951 an aliphatic primary amine and is used if curing is to take place at room temperature or within shorter time duration, at 50° to 120° C. The properties of the materials are listed in Table 1.

METHODOLOGY AND EXPERIMENTAL PROCEDURE
The objective of this study is to compare the behaviour of E-Glass/Epoxy composite material specimens under a compression test with the finite element analysis result. This study will help to determine the material properties of E-Glass fiber which is used in a wide range of engineering applications. The understanding from this study will help in the further development of the micro wind turbine blade.  Figure 1b.
The E-Glass fibers reinforced epoxy composite specimens were developed using Vacuum bagging process and then specimens of suitable dimensions were prepared from the composite Laminate for different mechanical tests according to ASTM standards. The test specimens were sized by using water jet cutting machine as shown in Figure 1c. Compression test specimens were prepared according to ASTM D3410.
Test specimen having dimension of length 150 mm, width of 25 mm and thickness of 2.8 mm. Two identical test specimens were prepared for carrying out Compression test. Figure.  Compression Specimen

Multiscale mechanical modelling
The dimension of the CAD model used for compression test simulation using FEA is same as that used for compression test (as per ASTM). Figure 3 shows Compression test is simulated using the explicit dynamic approach as the experimental tests are quasi-static in nature.

Multiscale modelling outcomes
The maximum principal stress and the reaction forces are extracted after the solution in FEA. The maximum principal stress is 165.39 MPa as shown in figure 6 and the reaction force is 6.29 kN as shown in Table 4. It is observed that the maximum principal stress and reaction force from FEA is very close to the test result. The error for stress is 2% and for the force is 4%.  System is utilized to determine parameters such as stiffness & Strength for composite specimens. The average standard deviation for the maximum principal stress is 168.33 MPa and for peak load it is 6.56 kN.
In Table 5 Compression strength and peak load of the E-Glass fiber-reinforced epoxy are shown for the applied load.