Monday, August 11, 2008

3.4.2 FLEXURAL PROPERTIES (ASTM D-790)

3.4.2 FLEXURAL PROPERTIES (ASTM D-790):

The flexural strength test was performed as per the procedure explained in the chapter 2 and the results were tabulated as shown in table 3.6. The properties that were evaluated as a part of flexural strength test are flexural strength at peak load, flexural modulus, percentage elongation and Youngs modulus. From the results, regression analysis had been performed to get the regression equations, which are shown in the tables 3.7, 3.8, 3.9, 3.10. Then using the equations contour plots and response surfaces were generated for each of them as shown in the figures 3.5 to 3.12. The plots obtained are saddle shaped.

Table 3.6 Results for flexural properties for CaCO3 – HDPE system:

Trial no.

X1

X2

Flex Strength @ peak load (kg/cm2)

%Elongation

Flex Modulus (M Pa)

Youngs Modulus

(kg/cm2)

1.

60

5

4.4

15.7

182

16.2

2.

60

25

4.91

19

325

25.7

3.

80

5

4.96

21.4

288

22.8

4.

80

25

4.85

23.3

233

20.7

5.

56

15

4.63

16.4

292

25.9

6.

84

15

4.72

13.7

347

30.8

7.

70

1

4.67

23.6

363

32.2

8.

70

29

4.58

22.16

360

32

9.

70

15

4.86

22.9

416

36.9

10.

70

15

4.86

22.9

416

36.9

11.

70

15

4.86

22.9

416

36.9

Table 3.7 Estimated Regression Coefficients for Flexural Strength

Term

Coef

SE Coef

T

P

Constant

4.8581

0.07613

63.812

0.000

X1

0.07904

0.04686

1.687

0.152

X2

0.03460

0.04686

0.738

0.494

X1*X1

-0.05923

0.05626

-1.053

0.341

X2*X2

-0.08474

0.05626

-1.506

0.192

X1*X2

-0.155

0.06594

-2.351

0.066



















S = 0.1319 R-Sq = 69.9% R-Sq (adj) = 39.8%

The regression equation is

Y = 4.8581+ 0.07904 X1 – 0.03460X2 - 0.05923X12 - 0.08474X22 -0.155X1 X2.


Table 3.8 Estimated Regression Coefficients for Flexural Modulus

Term

Coef

SE Coef

T

P

Constant

417.09

31.33

13.312

0.000

X1

11.49

19.29

0.596

0.577

X2

10.58

19.29

0.549

0.607

X1*X1

-70.69

23.15

-3.053

0.028

X2*X2

-49.26

23.15

-2.128

.087

X1*X2

-49.50

27.14

-1.824

0.128

S = 54.28 R-Sq = 75.0% R-Sq (adj) = 50.1%

The regression equation is

Y = 417.09+ 11.49 X1 +10.58X2 -70.69X12 -49.26X22 -49.50X1 X2.

Table 3.9 Estimated Regression Coefficients for Youngs Modulus

Term

Coef

SE Coef

T

P

Constant

37.0165

3.271

11.317

0.000

X1

1.0682

2.013

0.531

0.618

X2

0.8990

2.013

0.447

0.674

X1*X1

-6.6499

2.417

-2.751

0.040

X2*X2

-4.7366

2.417

-1.960

0.107

X1*X2

-2.9000

2.833

-1.024

0.353

S = 5.666 R-Sq = 68.0% R-Sq (adj) = 35.9%

The regression equation is

Y = 37.0165 +1.0682X1 +0.8990X2 - 6.6499X12 - 4.7366X22 -2.9X1 X2.

Table 3.10 Estimated Regression Coefficients for Percentage Elongation

Term

Coef

SE Coef

T

P

Constant

22.8871

1.4627

15.647

0.000

X1

0.7854

0.9004

0.872

0.423

X2

0.4020

0.9004

0.447

0.674

X1*X1

-3.7524

1.0808

-3.472

0.018

X2*X2

0.2425

1.0808

0.224

0.831

X1*X2

-0.3500

1.2669

-0.276

0.793

S = 2.534 R-Sq = 74.6% R-Sq (adj) = 49.2%

The regression equation is

Y = 22.8871+ 0.7854X1 +0.4020X2 -3.7524X12 +0.2425X22 -0.35X1 X2.

No comments: