Experimental study on crack defects formation in polyarylacetylene composites and modification improvement of resin

Polyarylacetylene (PAA) resin is one among the ideal ablation materials, due to its high char yield and has been used to fabricate composite structures for solid rockets and missiles. However, the manufacturing quality of PAA composite is difficult to control. This article aims to reveal the formation mechanism of crack defect for PAA composite and presents an improvement method by resin modification. In this article, crack features and formation process of quartz fiber reinforced PAA composite were first studied, and the shrinkage and brittleness of PAA resin were evaluated to analyze the reason for crack formation. Furthermore, PAA resin modified by blending with phenolic resin was developed to reduce the crack defect. It is found that large curing shrinkage and extreme brittleness are the main reasons, which result in crack defect and poor mechanical performances of PAA. Moreover, PAA and phenolic (PF) blend was proved to be effective in raising ductility and reducing shrinkage, leading to the reduction of crack defect. Besides, the interlaminar shear strength of quartz fiber/PAA-PF blend composite increased twice as compared with quartz fiber/PAA composite.