Prestressing effects on the ultimate flexural strength of composite box sections

Application of prestresssing as an effective means of enhancing the structural performance of composite box sections is presented. A primary objective of prestressing, in application to composite structures subjected to flexural loading, is to reduce the compressive stresses developed under critical loading conditions. This would increase the flexural strength of composite structures by delaying the prevalent compressive modes of failure. Theoretical models were developed for predicting the contributions of prestressing to the flexural performance of composites. Methodologies were developed for prestressing composite box sections. Flexure tests performed on prestressed (and similar non-prestressed) composite box sections verified the theoretical predictions. In the example composite structure considered here, prestressing produced 74% gain in flexural strength when compared with a similar non-prestressed box section (which embodied the prestressing tooling). The prestressed section produced 89% gain in flexural strength when compared with the box section without the prestressing tooling which carried 15% weight penalty.