Testing standards assessment for silicone rubber

Skin biomechanics has become an emerging area in research as its interest covers a wide range of applications such as product design, surgery, animation and materials engineering. Based on literatures, silicone rubber is one of the best candidate materials that exhibit desirable skin characteristics, thus making it the right material for skin substitute. Nonetheless, there is no specific standard that has been used to measure the mechanical properties and deformation behaviour of synthetic skin. This paper for the first time aims to assess two standard testing methods for silicone rubber. The work is carried out in 2 stages involving uniaxial testing and quantifying the material constants using a Matlab programme. Mechanical tests are conducted on 2 types of materials (different grades of silicone rubber) using uniaxial tensile test with two different standards (ASTM D2209 and ASTM D412). The raw testing data (load-extension) are then input into an in-house developed Matlab programme to compute and plot stress-stretch value based on neo-Hookean model. Based on statistical analysis, the testing data is found valid, since the sample variance is found to be less than 1%. The neo-Hookean constants, C₁, are found to be 0.7819 (ASTM D2209) and 1.3786 (ASTM D412) for Material 1; and 0.927 (ASTM D2209) and 1.4396 (ASTM D412) for Material 2 revealing a difference of 59.67% and 51.21% for Material 1 and Material 2 respectively. As a conclusion, the significant difference of the quantified Material constants suggests a dedicated testing standard must be used.