Morphological and Performance Measures of Polyurethane Foams Using X-Ray CT and Mechanical Testing

Abstract

Meso-scale structure in polymeric foams determines the mechanical properties of the material. Density variations, even more than variations in the anisotropic void structure, can greatly vary the compressive and tensile response of the material. With their diverse use as both a structural material and space filler, polyurethane (PU) foams are widely studied. In this manuscript, quantitative measures of the density and anisotropic structure are provided by using micro X-ray computed tomography (microCT) to better understand the results of mechanical testing. MicroCT illustrates the variation in the density, cell morphology, size, shape, and orientation in different regions in blown foam due to the velocity profile near the casting surface. "Interrupted" in situ imaging of the material during compression of these sub-regions indicates the pathways of the structural response to the mechanical load and the changes in cell morphology as a result. It is found that molded PU foam has a 6 mm thick "skin" of higher density and highly eccentric morphological structure that leads to wide variations in mechanical performance depending upon sampling location. This comparison is necessary to understand the mechanical performance of the anisotropic structure.

Elaboration and Characterization of Advanced Biobased Polyurethane Foams Presenting Anisotropic Behavior

“…Several researchers have studied the elaboration and the physical characterization of biobased polymer foams by using different approaches . However, the mechanical and thermal properties of these materials have been less investigated.…”

Correlation of Materials Property and Performance with Internal Structures Evolvement Revealed by Laboratory X-ray Tomography

“…Research works are still very active and versatile in the experimental mechanics field. Deformation and fracture are still common interest for metals and alloys [ 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 ], foams and porous materials [ 11 , 14 , 43 , 44 , 45 , 46 ], and composites [ 13 , 47 , 48 , 49 ]. XRT has also been considerably extended with other in situ measurements including materials processing [ 50 , 51 , 52 , 53 , 54 , 55 ], materials interaction with specified conditions involving extreme temperature [ 56 , 57 ], corrosion [ 58 , 59 , 60 ], electrochemical environments, as in batteries [ 61 , 62 , 63 ], etc.…”

In Situ Imaging during Compression of Plastic Bonded Explosives for Damage Modeling

“…Each sample was compressed to identical engineering strain (10% and 20% displacement of the total sample height, or ε = 0.1 and ε = 0.2). They were held for 10−15 min after compression to allow any residual plastic flow to occur, then imaged at this strain [ 21 , 22 ]. Each full 3D measurement required approximately 26 h.…”