LIMIT STRESS SPLINE MODELS FOR GRP COMPOSITES

Abstract

This paper focuses on the use of Spline functions in modelling the critical stress - strain responses of polyester matrix GRP Composites. Spline functions were established on the assumption of three intervals and fitting of quadratic and cubic splines to critical stress-strain responses data. Quadratic and Cubic spline models for three intervals of data points 0.024 £ x£ 0.036, 0.036 £ x £ 0.061and 0.061 £ x £ O. 12 were established. The optimization of quadratic and cubic models by gradient search optimization gave the critical strain as 0.024, which resulted to strength of approximately 26 MPa. Strain hardening was observed to occurr within a strain range of 0.03 to 0.12 leading to strength of about 62 MPa predicted by Cubic spline. Splines were found to accurately predict the functional values at subinterval, 0.024 £ x £ 0.036 of data points. Spline model is therefore recommended as it evaluates the function at subintervals, eliminating the error associated with wide range interpolation.