| 摘要: | 本研究以短玻璃纖維強化聚縮醛(POM/GF)複合材料為對象，探討不同射出成型參數如充填時間、融膠溫度、模具溫度與保壓壓力等對於纖維排向、拉伸性質與磨耗性質之影響。藉由田口實驗設計法、變異數分析及主成分分析法，進行POM/GF單一機械性質與多重機械性質之製程條件最佳化分析。同時，採用掃瞄式電子顯微鏡觀察纖維排列方向及破壞斷面型態。 研究結果顯示，在顯微組織方面，拉伸試片之橫截面可明顯分為表皮層與核心層兩區域，表皮層的纖維排向平行於融膠流動方向，核心層的纖維排向垂直於融膠流動方向。磨耗試片之橫截面可明顯分為表皮層、剪力層與核心層三個區域，表皮層與核心層的纖維排向垂直於融膠流動方向，剪力層的纖維排向則平行於融膠流動方向。 POM/GF複合材料之纖維含量愈高，其強度愈高且其摩擦係數也愈高。摩擦方向與融膠流向平行時(P方向試片)摩擦係數與磨耗體積損失比兩者垂直時(AP方向試片)來得稍低。對POM/25wt.% GF而言，射出成型條件為充填時間1.5 s、融膠溫度215℃、模具溫度75℃與保壓壓力75MPa時，具有最佳的拉伸性質與磨耗性質。 在破壞機構方面，拉伸試片表皮層主要破壞模式為纖維被拉斷及纖維被抽離基材，核心層之主要破壞模式為纖維與基材介面分離。不含纖維的POM主要破壞型態為凹坑與紋溝。POM/GF複材的主要破壞型態為紋溝、碎屑、裂縫及纖維脫離。 在POM/25wt.% GF複材製程最佳化方面，針對不同單一品質時，其最顯著之控制因子亦不同。若同時考量抗拉強度、伸長率及摩擦係數等三項機械性質之多重品質特性時，其最佳化射出成型條件為充填時間1.5 s、融膠溫度230℃、模具溫度60℃及保壓壓力75 MPa。此時，影響最顯著之控制因子為保壓壓力，其貢獻度為50.99%。 This study investigates the influence of injection molding process parameters on fiber orientation and mechanical properties of short glass fiber reinforced polyoxymethlene (POM/GF) composites. Filling time, melt temperature, mold temperature and packing pressure were considered as the controllable factors during the injection molding process. Taguchi experimental design, ANOVA analysis and principle component analysis were adopted in order to optimize the process conditions. Moreover, the fiber orientation and fracture surfaces were observed with a scanning electron microscope (SEM). Two distinct layers existed in the cross section of the POM/GF tensile specimen. The fibers in the frozen layer were parallel to the tensile direction, while those in the core layer were perpendicular to the tensile direction. In addition, three distinct layers existed in the cross section of wear specimens. The fibers in the frozen and the core layer were perpendicular to the melt flow direction, but the fibers were parallel to the melt flow in the intermediate layer. The tensile strength and friction coefficient increased with the amount of glass fiber. The friction coefficient and the wear volume loss also depended on the sliding direction. The specimen with sliding direction paralleling the melt flow had low friction coefficient and wear volume loss. To obtain the best tensile strength and tribological properties POM/GF composites, the injection molding conditions were as follows: filling time 1.5 s, melt temperature 215℃, mold temperature 75℃, and packing pressure 65 MPa. Though the fiber-avulse and the fiber-snap were the major fracture mechanisms of frozen layer, the fiber-breakage and the pull-out were the major fracture mechanism of the core layer for the tensile specimens. In addition, SEM photographs revealed that peel-off and grooves were the major wear mechanisms of the neat POM. Grooves, debris, cracks and debonded fibers were the major wear mechanisms of the POM/GF composites. With respect to the optimum injection molding process of POM/25wt.% composites, it was found that the most influential factor depended on the target mechanical property. For a multi-response case with the tensile strength, elongation, and friction coefficients (P-type), the optimal injection molding process conditions were filling time 1.5 s, melt temperature 215℃, mold temperature 75℃, and packing pressure 65 MPa. Moreover, the most influential factor was packing pressure, and its contribution was 50.99%. |
