《知識》飛機的機體材質「複合材料」成發展趨勢 The Trend of Composite Materials in Aircraft

波音787的特色之一,就是使用大量複合材料製成。
◎ photo credit: Luke Lai via photopin cc

本篇文章整理了飛機製造常使用的材質:

1. 鋁合金
為了讓飛機輕量化,機體材料很常會使用鋁合金。這種飛機用的鋁合金一般被稱為杜拉 (Duralumin),是由鋁、銅、鎂、錳等物質混合後製成。其特色就在於重量比鐵還要輕,而且性質強韌、堅固,是一種非常適合作為飛機材料的合金。

會產生高溫與壓力的引擎內部,使用了鎂合金、鈦合金、鎳合金等材料。另一種更新型的材質 - 鈦鋁合金(Titanium Aluminide),也開始採用來減輕引擎重量。


2. 鈦合金
鈦 (Titanium) 是現代飛機製造的重要材料。鈦具有高延展、抗熱、抗腐蝕,並具有高強度的特性。它提供了與鋼類似的強度,但重量卻輕很多。鈦合金可以應用在機身框架、發動機葉片、起落架等許多地方。鈦還可以與複合材料結合,變成更輕型的材料。

鈦在飛機製造中的使用程度持續增加。在 1960 年代開發的第一版波音 747 中,鈦的含量不到 3%,但在 90 年代中期的波音 777 的第一版中,鈦使用比例拉至近 9%。在波音 787-9 這樣的現代客機中,鈦的含量更接近 15%。

全球有超過一半的鈦都是應用在航太業。俄烏戰爭爆發後,鈦供應鏈面臨嚴重的問題,因為全球大部分的鈦都來自俄羅斯。俄羅斯的 VSMPO-AVISMA 公司,是世界上最大的鈦生產商。據估計波音使用的鈦金屬約有三分之一來自俄羅斯;空中巴士比例更高,約有一半所需鈦金屬來自俄羅斯,這也是歐盟需要思考的問題。

俄羅斯雖然不是鈦礦石的主要來源 (這些礦石來自中國、澳大利亞、哈薩克等國家)。俄羅斯在鈦供應鏈中的重要性是在後續加工的階段。VSMPO-AVISMA 是海綿鈦 (Titanium Sponge) 的主要生產商。海綿鈦是鈦加工材的原料,之後才會變成各種飛機零組件。

2022 年 2 月,俄羅斯入侵烏克蘭,波音和空中巴士都宣布重組他們的鈦供應鏈,停止向俄羅斯購買鈦金屬,進而轉向鈦市場主要主要參與者,像是日本的大阪鈦科技株式會社 (OSAKA Titanium) 和東邦鈦業 (Toho Titanium)。


3. 複合材料
隨著航太科技不斷的進步,也開始出現了新的製造材質,目前熱門的複合材料 (Composite Materials) 就為其中之一。複合材料是由纖維材料與塑化製品所組合而成,並被用來取代舊有的合金材料。複合材料因為擁有優異的彈性與耐久度,重量又更輕,所以多使用於飛機的起落架,以及飛機機翼當中的襟翼、水平、垂直等尾翼部位。

其實航空產業在 1970 年代就已經採用複合材料。從 1985 年起開始被用於製造機尾,例如空中巴士的 A310 廣體客機。但直到過去十年複合材料才有突破性的發展,並大量應用於波音 787 客機與空中巴士 A350。兩款飛機的機身幾乎有一半是由碳纖維塑膠及其它複合材料所製成,以材質更輕的碳纖維取代多數金屬零件,從而省下燃料費。金屬會有腐蝕與疲勞等問題,一定時間到了就要更換,複合材料不會有這樣的問題,可以延長飛機的壽命。

大量採用複合材料的飛機,組裝時必須格外小心。例如,以往金屬材料使用多,如果組裝過程稍微碰撞還可以修補,複合材料卻要求完全不能碰撞。

2024 年 1 月 2 日,日本航空 A350 客機與日本海上保安廳航機發生嚴重擦撞事故,是首度 A350 客機全毀事故,機上 379 人全數逃出,這場事故成為複合材料安全性的關鍵測試。

這起事故乘客和機組員得以在機體還完好的情況下全數平安撤離,讓人們對複合材料安全性增加了信心。鋁的熔點為攝氏 600 度左右且能導熱,碳纖維卻能承受約 6 倍的高溫,在當天的情況下,碳纖維提供了隔熱層保護。

至於複合材料的燃燒,究竟是否釋放出有毒物質,以至於對人體產生危害,目前仍無法判斷。這些傷害可能需要一段時間後才能顯現出來。

引擎製造商也想方設法降低引擎重量,大型噴射機平均重達 6,350 公斤。根據勞斯萊斯,若在風扇葉片與機殼等部分使用複合材料,廣體客機的引擎重量可望降低 340 公斤。

飛機製造商使用大量複合材料,已經是愈來愈明顯的趨勢。
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The Trend of Composite Materials in Aircraft

This article summarizes the materials commonly used in aircraft manufacturing.

1. Aluminum Alloys
To reduce the weight of aircraft, aluminum alloys are often used for the body material. This type of aluminum alloy used in aircraft is generally referred to as duralumin, which is made by mixing aluminum, copper, magnesium, and manganese. It is characterized by its lightness, strength, and durability, making it a very suitable alloy for aircraft materials.

The engine interior, which produces high temperatures and pressures, uses magnesium alloys, titanium alloys, and nickel alloys. Another newer material, titanium aluminide, is also starting to be used to reduce engine weight.


2. Titanium Alloys
Titanium is an important material in modern aircraft manufacturing. It has the properties of high ductility, corrosion resistance, heat resistance, and high strength. It offers strength similar to steel, but is much lighter in weight. Titanium alloys can be applied to many places, such as aircraft frames, engine blades, and landing gear. Titanium can also be combined with composite materials to create lighter-weight materials.

The use of titanium in aircraft manufacturing has been increasing. In the first version of the Boeing 747 developed in the 1960s, titanium content was less than 3%, but in the first version of the Boeing 777 in the mid-1990s, titanium use ratio reached nearly 9%. In modern passenger jets such as the Boeing 787-9, the titanium content is closer to 15%.

More than half of the world's titanium is used in the aerospace industry. After the outbreak of the Russia-Ukraine war, the titanium supply chain faced serious problems, as most of the world's titanium comes from Russia. VSMPO-AVISMA, a Russian company, is the world's largest titanium producer. It is estimated that one-third of the titanium used by Boeing comes from Russia; Airbus has a higher ratio, with about half of its titanium needs coming from Russia.

Although Russia is not the main source of titanium ore (these ores come from countries such as China, Australia, and Kazakhstan), its importance in the titanium supply chain is in the subsequent processing stage. VSMPO-AVISMA is the main producer of titanium sponge. Titanium sponge is the raw material for titanium processing, which will then be turned into various aircraft components.

In February 2022, after Russia invaded Ukraine, Boeing and Airbus both announced that they would reorganize their titanium supply chains, stopping buying titanium from Russia and turning to major players in the titanium market, such as OSAKA Titanium Technologies Co., Ltd. (OSAKA Titanium) and Toho Titanium Co., Ltd. (Toho Titanium).


3. Composite Materials
As aerospace technology continues to advance, new manufacturing materials have also emerged, with composite materials being one of the most popular. Composite materials are made up of fiber materials and plastics, and are used to replace traditional alloy materials. Composite materials have excellent elasticity and durability, and are lighter in weight, so they are often used in aircraft landing gear, as well as in aircraft wings, such as flaps, horizontal, and vertical tail wings.

The aerospace industry actually began using composite materials in the 1970s. From 1985, it began to be used to manufacture the tail, such as the Airbus A310 wide-body aircraft. However, it was not until the past decade that composite materials saw a breakthrough in development, and were widely used in the Boeing 787 and Airbus A350. The fuselages of both aircraft are almost half made of carbon fiber plastics and other composite materials. The use of lighter carbon fiber instead of most metal parts saves fuel. Metals can corrode and fatigue, and must be replaced after a certain period of time. Composite materials do not have these problems and can extend the life of the aircraft.

Aircraft that use a lot of composite materials must be assembled with extra care. For example, in the past, when metal materials were used more, if there was a slight collision during assembly, it could be repaired. However, composite materials require that there be no collisions at all.

On January 2, 2024, a Japan Airlines A350 passenger plane and a Japan Coast Guard aircraft collided in a serious accident. This was the first A350 passenger plane to be completely destroyed. All 379 people on board escaped. This accident became a critical test of the safety of composite materials.

The fact that passengers and crew were able to evacuate safely with the fuselage still intact gave people more confidence in the safety of composite materials. Aluminum melts at around 600 degrees Celsius and conducts heat, but carbon fiber can withstand about six times the heat. In this case, carbon fiber provided thermal insulation.

As for whether the burning of composite materials releases toxic substances that can harm the human body, it is still impossible to judge at present. These injuries may take some time to manifest.

Engine manufacturers are also trying to find ways to reduce engine weight. Large jet engines weigh an average of 6,350 kilograms. According to Rolls-Royce, if composite materials are used in parts such as fan blades and housings, the weight of wide-body aircraft engines could be reduced by 340 kilograms.

The use of large amounts of composite materials by aircraft manufacturers is becoming an increasingly clear trend.