Material characterization and computer model simulation of low density polyurethane foam used in a rodent traumatic brain injury model

• Published in: Journal of neuroscience methods 2011-05, Vol.198 (1), p.93-98
• Main Authors: Zhang, Liying, Gurao, Manish, Yang, King H., King, Albert I.
• Format: Article
• Language: English
• Subjects: Animals; Brain Injuries; Compression test; Computer Simulation; Disease Models, Animal; Finite element modeling; Low density polyurethane foam; Polyurethanes; Rate dependency; Rodent head impact acceleration device; Rodentia; Species Specificity; Stress, Mechanical; Traumatic brain injury
• ISSN: 0165-0270; 1872-678X
• DOI: 10.1016/j.jneumeth.2011.03.024

► A low density open-cell polyurethane foam which serves as an energy absorber has been tested in compression at various strain rates. ► The stress–strain relationships, stiffness, elastic modulus, strain rate dependency, and rate recovery have been characterized. ► The foam (density of 14 kg m −3) used in the Marmarou rat TBI model is rate dependent up to 15 s −1. ► The foam is reusable even after multiple loadings (9 cycles). A 1 h recovery time is recommended for a repeated test. ► It is also noted that the stress resistance of used foam is found to be reduced to 70% of the new foam. ► The FU_CHANG_FOAM material model in a finite element solver has been found to be adequate to simulate this rate sensitive foam. Computer models of the head can be used to simulate the events associated with traumatic brain injury (TBI) and quantify biomechanical response within the brain. Marmarou's impact acceleration rodent model is a widely used experimental model of TBI mirroring axonal pathology in humans. The mechanical properties of the low density polyurethane (PU) foam, an essential piece of energy management used in Marmarou's impact device, has not been fully characterized. The foam used in Marmarou's device was tested at seven strain rates ranging from quasi-static to dynamic (0.014–42.86 s −1) to quantify the stress–strain relationships in compression. Recovery rate of the foam after cyclic compression was also determined through the periods of recovery up to three weeks. The experimentally determined stress–strain curves were incorporated into a material model in an explicit Finite Element (FE) solver to validate the strain rate dependency of the FE foam model. Compression test results have shown that the foam used in the rodent impact acceleration model is strain rate dependent. The foam has been found to be reusable for multiple impacts. However the stress resistance of used foam is reduced to 70% of the new foam. The FU_CHANG_FOAM material model in an FE solver has been found to be adequate to simulate this rate sensitive foam.