Issue 41

Y. Yang et alii, Frattura ed Integrità Strutturale, 41 (2017) 339-349; DOI: 10.3221/IGF-ESIS.41.45 345 That is: ε ε = + 2 2 1 2 / 3 / 3 p p t t M E bh E bh (10) The plane hypothesis: ε ε = 2 1 / / t p h h (11) Where, ε p is the compressive strain of the upper surface; ε t is the tensile strain of the lower surface; other symbols have the same meanings as above. Equilibrium condition: σ σ σ σ − = ⇒ = ∫ ∫ 0 1 1 2 0 2 1 2 h p t p t h bxdx bxdx h h h h (12) As the tensile modulus σ ε = / t t t E and the compression modulus σ ε = / p p p E , by combining Formula (10), (11) and (12), we obtain: ε ε ε = + 2 2 3 ( ) / t p t t E M b h (13) ε ε ε = + 2 2 3 ( ) / p p t p E M b h (14) Where, E t is the tensile modulus; E p is the compression modulus. Therefore, the tensile - compression modulus ratio is: ε ε = = 2 2 1 2 2 2 p t p t E h E h (15) The mid-span bending moment of the specimen: = / 6 M PL (16) By substituting Eq. (16) into Formula (13) and Formula (14), we obtain the tensile and compression modulus calculation formulas as follows: ε ε ε + = t p 2 2 t ( ) 2 t pL E bh (17) ε ε ε + = t p 2 2 p ( ) 2 p pL E bh (18) A NALYSIS ON TENSILE , COMPRESSION AND FLEXURAL MODULI TEST RESULTS Analysis on the change rules of the three moduli with the loading rate ccording to the deduced tensile, compressive and flexural modulus calculation formulas, we use the triple mean variance to eliminate the abnormal test results and calculate the test mean value of 9 groups of specimens. The test results of the three moduli under different loading rates are shown in Tab. 2. A