Static structural testing of trans-tibial composite sockets

The purpose of this investigation was to quantify the structural strength o f various trans-tibial composite sockets. To conduct the study, loading par ameters and methods were developed that emulate the International Standards Organisation (ISO) standards for structural testing of lower limb prosthes es since specific guidelines for the testing of the trans-tibial socket por tion of a prosthesis have not yet been established. The experimental set-up simulated the instant of maximum loading during the late stance phase of g ait. Ten trans-tibial sockets were evaluated. Five different reinforcement materials and two resin types were used to construct the sockets. A standar d four hole distal attachment plate was used to connect the socket and pylo n. Each sample was loaded to failure in a servo-hydraulic materials test ma chine at 100 N/s. None of the composites in the study met the ISO 10328 standards for level A 100, loading condition II (4025 N), as required for other prosthetic compon entry. All failures occurred at the site of the pyramid attachment plate. U ltimate strength and failure type were material dependent. Load point defle ction was significantly different for the resin variable (p<0.05). Statisti cal differences according to reinforcement material were noted in composite weight and strength-to-weight ratio (p<0.05). The fibre volume fraction wa s also estimated and recorded. Reinforcement material type was the primary determinant of performance for the tested samples. Carbon reinforcements pe rformed better than fibreglass reinforcements of similar weave type. The gr eatest ultimate strength and strength-to-weight ratio was observed with the unidirectional carbon reinforcement.