Mechanical Characterization and Damage Analysis of Carbon/Flax Hybrid Laminates with Holes Machined by Abrasive Water Jet

ABSTRACT

This paper experimentally examines the influence of abrasive water jet (AWJ) machined holes on the mechanical performance and damage evolution of flax/epoxy and carbon/flax/epoxy hybrid composites. The specimens were made of unidirectional flax fiber (F) and woven carbon fiber (C) in four configurations: unidirectional flax [0 _F]₁₆ (UD-F), unidirectional hybrid [0–90_C2/0 _F6]_S (UD-CF), cross-ply [0–90_C2/(0/90)_F6]_S (CF [0/90]), and angle-ply [0–90_C2/($\pm$45)_F6]_S (CF [±45]). The specimens were subjected to static and quasi-static load-unload tensile tests until failure and the damage evolution and plastic strain were monitored. Results revealed severe delamination induced by AWJ at the entry and the exit of the hole in UD-CF and CF [±45] samples, and no delamination was evident in the flax/epoxy plies. The specimens with holes showed pronounced stiffness degradation compared to hole-free specimens. A similar trend was observed in their permanent plastic strain. The cross-ply hybrids showed the lowest increase in damage. While all hybrids exhibited failure by carbon fiber breakage and delamination at the carbon–flax interface, only the laminates with unidirectional flax plies failed by fiber splitting around the hole.

摘要

本文通過實驗研究了磨料水射流 (AWJ) 加工孔對亞麻/環氧樹脂和碳/亞麻/環氧樹脂混合複合材料的機械性能和損傷演變的影響。樣品由單向亞麻纖維 (F) 和編織碳纖維 (C) 製成，有四種配置:單向亞麻 [0 F]16 (UD-F)、單向混合 [0–90C2/0 F6]S (UD-CF)、交叉層 [0–90C2/(0/90)F6]S (CF [0/90]) 和角層 [0–90C2/(45)F6]S (CF [±45])。對試樣進行靜態和準靜態加載-卸載拉伸試驗直至失效，並監測損傷演變和塑性應變。結果表明，在 UD-CF 和 CF [±45] 樣品中，AWJ 在孔的入口和出口處引起嚴重分層，亞麻/環氧樹脂層沒有明顯分層。與無孔試樣相比，帶孔試樣顯示出明顯的剛度退化。在它們的永久塑性應變中觀察到類似的趨勢。交叉層混合顯示損壞的增加最低。雖然所有混合材料都表現出碳纖維斷裂和碳 - 亞麻界面分層的故障，但只有具有單向亞麻層的層壓板因孔周圍的纖維分裂而失敗。

KEYWORDS:

• Hybrid composites
• Flax fibers, Abrasive Waterjet machining
• Conventional drilling
• Damage evolution