Studies on the flexural modulus of structural foams

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.Nomenclature 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 - D_s 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 - E_c average Young's modulus for foamed core of structural foam - E_s 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 - I_c equivalent moment of inertia of I-Beam - I_s 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 Greek symbols local density of structural foam - ¹ average density of structural foam - _c average density of foamed core of structural foam - ^f density of uniform density foam - _s density of unfoamed solid