In‐situ strain evolution mechanisms within a prestressed carbon composite

Abstract

AbstractThermal residual stress generated during curing is known to be detrimental to mechanical performance of a carbon composite. Fiber prestressing technique has been developed for decades to counterbalance these negative effects. Although there have been some achievements in development of the prestress mechanisms, these are mainly based on the extrapolations from macroscopic mechanical characterizations, lack of direct evaluation of the in‐situ in‐plane strain or stress evolution mechanisms, in order to reveal the impact induced by different prestressing methods. Here, we investigated the in‐situ strain evolution mechanisms in producing a prestressed carbon composite. Since clamping of the uncured prepreg is the most challenging, both the strain evolutions with and without precured prepreg edges were evaluated to reveal the underlying mechanisms induced by stress relaxation during fiber prestressing. Mechanical tests in terms of Charpy impact and three‐point bending, as well as fractured morphology were carried out to evaluate the prestress effects. The underlying mechanisms were then proposed to reveal the fundamentals in producing a prestressed composite. These are expected to revolutionize industrial production and applications of prestressed polymeric composites, indicating detrimental mechanisms on precuring strip ends following conventional prestress procedures.Highlights There is an optimal prestrain level to maximize properties of a composite. Internal strain development is dependent on the fiber clamping methods. Stress relaxation is beneficial to induce compressive stress within a composite. In‐situ strain evolution mechanics is revealed for prestressed carbon composite.