ABSTRACT
Polymer composites used in engineering structures are exposed to various types of mechanical stress. The most commonly used methods of assessing their strength are the ones based on static or dynamic testing. Rare attempts are made to assess reliability of composites under a given load. The influence of the manufacturing technique on the mechanical strength of composites is also a well-known fact. The production of fibre reinforced composites using an autoclave allows for the production of high strength composites and a very small number of structural defects. However, this method is expensive and available with restriction. Much more often composites are produced by cheaper methods like hand lay-up, infusion or vacuum bag. The aim of this study is to determine the influence of the technique of making selected polymeric composites on the probability of failure before achieving a certain tensile strength threshold. Composite materials reinforced with carbon and glass fabrics have been prepared as the most commonly used composites in aviation. Composites were made by such methods as hand-layup, vacuum bag and pressing. Static stretching was performed, followed by a statistical analysis and a reliability analysis. The reliability analysis was performed using the Weibull model. It was found that, in terms of tensile strength, the differences between the composites made by the compression method and the manual method are negligible. Vacuum bag composites exhibit the lowest tensile strength compared to other composites. On the other hand, the analysis of reliability indicates that the highest probability of maintenance of structure continuity under load is exerted by composites with fiberglass made by the pressing technique.
