The crystallization behavior of polyetheretherketone (PEEK) is essential for the interfacial properties of its carbon fiber (CF) reinforced composites. It has already been well known that the transcrystalline (TC) layer at the CF/matrix interface is beneficial of improving the interfacial shear strength (IFSS). However, not all CF can induce the formation of TC layers in the PEEK matrix. This study aims to compare the effects of cooling rates on the IFSS of CF/PEEK composites with and without existence of the TC layer. In comparison to the original PEEK matrix (PEEK-O), we applied both physical (PEEK-A) and chemical (PAEK) modifications to increase the nucleation ability of the matrices. As a result, obvious TC layer was only observed in CF/PEEK-O composite. We further found that the effects of cooling rates on the IFSS of CF composites were opposite for samples with and without the TC layer. For CF/PEEK-O composite which contains the TC layer, the fast-cooling sample showed a smaller IFSS than the slow-cooling sample. This work reveals the key role of crystallization behavior at the interface in modulating the effects of cooling rates on IFSS, which is beneficial for the customized manufacturing and processing of different CF/PEEK composites.

中文翻译：

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冷却速率对存在和不存在跨晶层的碳纤维/PEEK复合材料界面剪切强度的反向影响

聚醚醚酮（PEEK）的结晶行为对其碳纤维（CF）增强复合材料的界面性能至关重要。众所周知，CF/基体界面处的跨晶（TC）层有利于提高界面剪切强度（IFSS）。然而，并非所有 CF 都能诱导 PEEK 基体中 TC 层的形成。本研究旨在比较冷却速率对存在和不存在 TC 层的 CF/PEEK 复合材料的 IFSS 的影响。与原始 PEEK 基体 (PEEK-O) 相比，我们应用物理 (PEEK-A) 和化学 (PAEK) 改性来提高基体的成核能力。结果，仅在CF/PEEK-O复合材料中观察到明显的TC层。我们进一步发现，冷却速率对 CF 复合材料 IFSS 的影响对于有和没有 TC 层的样品是相反的。对于含有 TC 层的 CF/PEEK-O 复合材料，快速冷却的样品表现出比缓慢冷却的样品更小的 IFSS。这项工作揭示了界面结晶行为在调节冷却速率对 IFSS 影响中的关键作用，这有利于不同 CF/PEEK 复合材料的定制制造和加工。