Mechanical properties of silicon breast implants

Breast augmentation with silicone implants is one of the most common aesthetic procedures. Rupture of the implant is the main reason for repeated surgery and for the removal of the implant. The aim of the study is to investigate the changes in toughness and deformability of the shell of breast implants leading to their rupture depending on the conditions of mechanical loading. The methods of continuum mechanics used in the study of elastomers were applied. Cyclic stretching and cyclic stretching with increasing amplitude were performed on the implant shell. The mechan-ical tests were carried out on a silicone breast implant manufactured by Eurosilicone. The initial parts of the strain curves up to 200% are shown for the shells of Mentor (8 years of use in the body), Eurosilicone (8 years) and Motiva (2 years). The obtained experimental results were com-pared with the data for the unused (control) implant shell. Cyclic stretching showed that after the first elongation to a given strain, the implant shell softens and the next stress-strain curve is much lower than the first. At a strain greater than the previous strain, the stress-strain curve returns to the initial curve of the unstretched specimen. In the presence of microdamage, the shells of the breast prostheses soften (Mullins effect) and the curves fall below the curve of the control test. It is shown that the toughness of the prosthesis decreases with time due to the accumulation of microdamage under systematic cyclic deformation during its use in the range of 100–130%. In the case of large deformations of implant shells, the strength of the prosthesis decreases significantly and fracture can occur much earlier than the shelf life.