梯度特性結構可使材料提升抗衝擊性。從自然界中能夠觀察到一些生物的硬組織具有功能梯度特性以形成自我保護機制，例如鐵甲魚的鱗片。其中功能梯度特性中之其中一項為連續性梯度結構之特性，為材料內部具有連續性的性質變化，藉此提升材料韌性與抗衝擊性，在魷魚喙與動物牙齒皆可觀察到此梯度特性。實驗室團隊先前對不同動物牙齒進行詳細的研究，觀察到動物牙齒中從牙釉質至EDJ之間具有硬度梯度特性，並利用此特性來延長使用壽命。在梯度材料之製程進展中，從傳統的鑄造或粉末冶金法演變至近代快速發展的積層製造技術，使功能梯度材料之應用更加廣泛。因此，藉由先前實驗室之研究成果與生物硬組織之文獻研究，本研究將著重在梯度特性對於材料性質的影響，並透過DLP列印技術仿照生物硬組織之梯度強度特性，主要探討梯度特性如何影響材料機械性質之穩健性，其次探討奈米材料提升光固化樹脂之硬度的效果。
實驗中透過微觀量測儀器與機械性質量測儀器對添加氧化矽奈米材料後之複合材料進行量測，首先針對氧化矽奈米材料對硬度提升的效果進行探討，再觀察材料在微觀性質中是否具有梯度特性；最後結合機械性質之量測結果，可得到梯度特性對機械性質之影響，再以電子顯微鏡觀察斷裂面及材料黏彈性之變化來補充其影響之原因。
由實驗結果顯示，氧化矽奈米材料確實有助於提升光固化樹脂材料之硬度，但添加過量會導致材料脆化的負面效果；再來從微觀硬度與微觀動態機械性質之結果顯示出DLP列印技術確實能夠成功製造梯度材料，且能經由改變光照時間來控制梯度性質的幅度。此外，經由機械性質之綜合比較後，能得到梯度性質的增加確實有助於提升材料抗衝擊性，但提升至一定程度時即到達高原期，並失去其提升的效果。從材料黏彈性之趨勢可得知，材料內部儲存能量的能力隨著梯度性質增加而提升，亦可作為造成抗衝擊性提升的原因。結合觀察斷裂面的電子顯微鏡圖像以及從分子鍵結之觀點切入，可充分解釋梯度性質與材料抗衝擊性之間的關聯。本研究中闡明梯度特性與材料機械性質的關聯性，並探討其影響之機制與原因，為製造梯度材料的進展提供指引。

Gradient features of a structure can provide impact resistance, and it has been observed from nature that the hard tissues of some animals have functional gradient features to form self-protection mechanism, such as the scales of the ancient fish ‘Polypterus senegalus’. One of the functional gradient features is the property of the continuous gradient structure, which is a continuous change of the material property to improve the toughness and impact resistance of the material, which can be observed in squid’s breaks and animal teeth. Our laboratory team previously conducted detailed studies on different animal teeth and observed a hardness gradient property from enamel to EDJ in animal teeth, and used this feature to extend lifespan. In the manufacturing process of gradient materials, the evolution from traditional casting or powder metallurgy to the rapidly developed of additive manufacturing technique makes the application of functional gradient material more extensive. Therefore, based on the literature research of the biological hard tissues and the previous research of our laboratory team, this dissertation will focus on the effect of gradient features on material properties, and employ DLP printing technique to mimic the gradient feature of the hard tissues, and mainly to investigate how the gradient feature affects the robustness of the mechanical property, and secondly to investigate the effect of the nanoparticle on improving the hardness of photocurable resin.
In the experiment, different proportions of the silica nanoparticle are added to the resin, and observe whether the hardness of the composite material is improved and the limitation of materials about brittleness. Additionally, the composite materials are measured by microscopic measuring instrument to observe whether the composite materials have the gradient feature in micro-mechanical properties. Combined with the results of measuring mechanical properties, the influence of the gradient feature on impact resistance can be obtained, and then the electron microscopic images of the fracture surface and the change of material viscoelasticity are used to supplement the reason for its influence.
The experimental results show that the silica nanoparticle does help to improve the hardness of the photocurable resin, but adding too much will have the negative effect of brittleness. Secondly, the results from the nano-hardness and micro-viscoelasticity show that DLP printing method can successfully produce materials with gradient features, and the magnitude of gradient features can be controlled by the curing time gap. In addition, after comparing the gradient features with the impact resistance of the material, it can be found that the increase of the gradient features does help to improve the impact resistance of the material, but when it increases to the limitation of the manufacturing method, it will reach a plateau period and lose its improving effect. It can be obtained from the trend of the viscoelasticity of material that the decreasing trend of viscoelasticity represents an increase trend in the ability of the material to store energy, which can also be used as an explanation for the improvement in impact resistance. Combined with the observation of electron microscope images of the fracture surface and the supplement of the dimension of molecular bonding, the correlation between gradient characteristics and impact resistance of materials can be fully explained. In this study, we elucidate the relationship between gradient features and mechanical properties of materials, and investigate the mechanisms and causes of the effects, so as to provide guidance for the progress of manufacturing gradient materials.

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