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Studies on the flexural modulus of structural foams

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Abstract

An investigation based on I-Beam models was undertaken in this paper for extending knowledge regarding the flexural modulus of structural foam. The applicability of five I-Beams models (I-Beam A, B, C, D and E) including a newly developed one (I-Beam E) were investigated in this work. The square law model was used to predict Young's modulus of uniform density foam, which was subsequently utilized for the calculation of the I-Beam models. I-Beam A, B and E were observed from the configuration analysls of each I-Beam to be the more suitable models for predicting the flexural modulus of the structural foams having either an integral skin or a skin with limited residual bubbles, among which I-Beam E is considered to be better than I-Beam B and A. The comparison of the experimental and theoretical values of the flexural modulus of the structural foams molded with gas counter pressure structural foam (CPSF) and low pressure structural foam (LPSF) molding methods also confirmed that the newly developed I-Beam E is the most adequate model for predicting the flexural modulus of structural foams having either an integral skin or a skin with few residual bubbles. I-Beam B and A were also demonstrated to be in good agreement with the experimental data.

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Abbreviations

B:

width of I-Beam A, B, C and E

Bc:

core width of I-Beam A

Bc1 :

center core width of I-Beam

Bc2 :

half of center core width of I-Beam

C:

adjustable parameter for density distri-iion of structural foam

CPSF:

gas counter pressure structural foam injection molding

D:

thickness of I-Beam in foamed core sec tion or thickness of structural foam in foamed core section

Ds :

thickness of unfoamed beam

e:

ratio of skin thickness to half of the thickness of a specimen (reduced skin thickness)

E1 :

flexural modulus of structural foam

Ec :

average Young's modulus for foamed core of structural foam

Es :

Young's modulus of unfoamed solid

FLBF:

flexural load bearing factor

GASF:

gas assisted structural foam injection molding

HPSF:

high pressure structural foam injection molding

Ic :

equivalent moment of inertia of I-Beam

Is :

moment of inertia of unfoamed beam

LPSF:

low pressure structural foam injection molding

R:

reduced density for center core of structural foam

SCSF:

sandwich coinjection structural foam molding

T:

thickness of I-Beam in skin section or skin thickness of structural foam

Y:

half of the thickness of a specimen

Z:

dimensionless distance from neutral axis of a specimen subjected to pure bending

ρ:

local density of structural foam

ρ1 :

average density of structural foam

ρc :

average density of foamed core of structural foam

ρf :

density of uniform density foam

ρs :

density of unfoamed solid

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Authors and Affiliations

  1. Institute of Applied Chemistry, National Chiao Tung University, Hsinchu, Taiwan, Republic of China

    Jiann-Shing Wu & Tzong-Ming Yeh

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  1. Jiann-Shing Wu
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  2. Tzong-Ming Yeh
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Wu, JS., Yeh, TM. Studies on the flexural modulus of structural foams. J Polym Res 1, 61–68 (1994). https://doi.org/10.1007/BF01378595

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  • DOI: https://doi.org/10.1007/BF01378595

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