材料科學與工程基礎(chǔ)：第5章 合成物1

1、5 Composites5.1 Introduce5.2 Fiber-Reinforced composites5.3 Polymer-matrix composites 5.4 Metal-matrix composites5.5 Ceramic-matrix composites5.6 Carbon-matrix compositesWhy Study Composites?Improve the properties of materials, for example: Mechanical(力學) , optical(光學), magnetic(磁性),electric (電)and

2、so.(2) Reduce the cost (成本)of materials(3) Reduce the density(密度) of materials5.1 IntroduceLearning Objectives1. Name the three main divisions of composite materials, and cite the distinguishing feature of each.2. Cite the difference in strengthening mechanism for large-particle and dispersion-stren

3、gthened particle-reinforced composites.3. Name the three different types of fiber-reinforced composites on the basis of fiber length and orientation; comment on the distinctive mechanical characteristics for each type.4. Calculate longitudinal modulus and longitudinal strength for an aligned and con

4、tinuous fiber-reinforced composite.5. Compute longitudinal strengths for discontinuous and aligned fibrous composite materials.6. Note the three common fiber reinforcements used in polymer-matrix composites, and, for each, cite both desirable characteristics and limitations.7. Cite the desirable fea

5、tures of metal-matrix composites.8. Note the primary reason for the creation of ceramic -matrix composites.9. Name and briefly describe the two subclassifications of structural composites.A composite is a multiphase（多相） material that is artificially （人造）made, as opposed to one that occurs or forms n

6、aturally（自地）. In addition, the constituent （連續(xù)）phases must be chemically dissimilar（不同的） and separated by a distinct（明顯） interface.What is Composite?metallic alloys（金屬合金） and many ceramics（陶瓷）1. 定義 (1)種類不同，性質(zhì)差異很大的幾種材料及其界面相（層） 所組成（組成上） (2)多相固體材料（結(jié)構(gòu)） (3)經(jīng)設(shè)計復合而成（制備上） (4)通過復合效應獲得原組份材料所不具備的性能，或產(chǎn)生 性能協(xié)同作用，

7、與簡單混合有本質(zhì)的區(qū)別（性能上）簡言之：復合材料由連續(xù)基體相(matrix phase)和分散增強相(disperse phase)及界面相(interface phase)所構(gòu) 成復合材料系統(tǒng)組合分 散 相連 續(xù) 相金屬材料無機非金屬材料有機高分子材料金屬材料金屬纖維(絲)纖維金屬基復合材料鋼絲/水泥復合材料增強橡膠金屬晶須晶須/金屬基復合材料晶須/陶瓷基復合材料金屬片材金屬/塑料板無機非金屬材料陶瓷纖維纖維/金屬基復合材料纖維/陶瓷基復合材料晶須晶須/金屬基復合材料晶須/陶基復合材料顆粒彌散強化合金材料粒子填充塑料玻璃纖維纖維/村脂基復合材料粒子碳纖維碳纖維/金屬基復合材料纖維/陶基復合材

8、料纖維/樹脂基復合材料炭黑顆粒/橡膠顆粒/樹脂基復合材料有機高分子材料有機纖維纖維/樹脂基復合材料塑料金屬/塑料橡膠2. 分類：(1)按來源：天然、 人工復合材料等(2)按基體：樹脂基、 金屬基、 無機非金屬基復合材料等(3)按增強體形態(tài)：顆粒增強(particle-reinforced) 短纖或晶須增強(chopped fiber or whiskers reinforced) 連續(xù)長纖增強(continuous fiber-reinforced) 多維編織布增強(braided fabric or filament winding-reinforced) 三維編織體增強等(4)按應用：結(jié)構(gòu)

9、、功能、智能復合材料等(5)按增強材料品種：玻纖、碳纖、有機纖維復合材料等(6)按特定含義：通用、先進、現(xiàn)代、 近代、混雜、納米、 原位、分子、宏觀復合材料等FIGURE 15.2 A classification scheme for the various composite types discussed in this chapter.The matrix phase is constituent （連續(xù)）phases of compositesMatrix phase（基體相）Metal(金屬), polymer（聚合物), ceramic（無機金屬）Titanium(鈦)+ bor

10、on fiber(硼纖維)Nature rubber (天然橡膠)+ carbon black (碳黑)Alumina(A12O3)+silicon carbide (SiC)Dispersed phase(分散相）PARTICLE (顆粒)：Nanorod(棒);spherical(球型); disk(盤狀);triangular(三角) interaction: on the atomic or molecular level（原子或分子水平） (2) harder and stiffer（堅硬和堅固）.(3) bears the portion of an applied load(4)

11、 Mechanism of Reinforcement（增強機理） large-particle strengthened composites and dispersion-strengthened compositesDifferences FIGURE 15.3 Modulus of elasticity （彈性模量）versus volume percent tungsten（鎢） for a composite of tungsten particles dispersed within a copper（銅） matrix. Upper and lower bounds are a

12、ccording to Equations 15.1 and 15.2; experimental data points are included.Fiber（纖維） On the basis of diameter and character, fibers are grouped into three different classifications: whiskers(晶須）, fibers（纖維）, and wires（線）.WhiskersGraphite(石墨), silicon carbide(碳化硅), silicon nitride(氮化硅), and aluminum

13、oxide(氧化鋁).They are very thin single crystals(單晶)that have extremely large length-to-diameter ratios(長徑比)The characterizations of Whiskers(1)In spite of these high strengths（高的力學強度）, (2)they are extremely expensive（非常昂貴）. (3) it isdifficult and often impractical to incorporate whiskers into a matrix

14、(很困難或幾乎不可能的被摻雜到基體材料中).Materials that are classified as fibers are either polycrystalline or amorphous（是一種多晶或非晶體材料）and have small diameters; the polymer aramids(聚酰亞胺), glass(玻璃), carbon, boron(硼), aluminum oxide, and siliconcarbide.fibrous materials are generally either polymers or ceramicsFibersFine

15、 wires have relatively large diameters; typical materialsWiresSteel(鋼), molybdenum(鉬),and tungsten(鎢). Tires(輪胎), in filament-wound rocket casings(火箭) and in wire-wound high-pressure hoses(軟管).復合材料的特性(character) 一般特性： a. 可設(shè)計性 b. 構(gòu)件復合與成型一次性完成，整體性好 c. 性能分散性大，性能對工藝工程及工藝參數(shù)甚至一些 偶然性因素都十分敏感，難以精確控制結(jié)構(gòu)和性能 d.

16、復合效應（多種復合效應）(principle of combined action) 一般性能特點： a. 比強度、比模量大 b. 破壞安全性高 c. 耐疲勞性好 d. 阻尼減震性好 e. 耐燒蝕性能好5.2 Fiber-Reinforced composites5.2.1 Structural composites 5.2.2 Fiber-Reinforced composites 5.2.1 Structural composites Laminar composites (片狀結(jié)構(gòu)) Sandwich panels (夾層結(jié)構(gòu)) Laminar compositesA laminar c

17、omposite is composed of two-dimensional sheets (薄片)or panels（板） that have a preferred high-strength directionaligned fiber-reinforced plastics. Sandwich panels Sandwich panels, considered to be a class of structural composites, consist of two strong outer sheets, or faces, separated by a layer of le

18、ss-dense（低密度） material, or core, which has lower stiffness （硬度）and lower strength（強度）5.2.2 Fiber-Reinforced composites Influence of fiber length Influence of fiber orientation and concentration Influence of fiber length For a number of glass and carbon fibermatrix combinations, this critical length

19、ison the order of 1 mm, which ranges between 20 and 150 times the fiber diameter.critical length lc(臨界長度)fiber diameter (直徑) dtensile strength (纖維拉伸強度)*fshear yield strength of the matrix(基體剪切強度),cAs fiber length l increases, the fiber reinforcement becomes more effective; this is demonstrated in Fi

20、gure Influence of fiber orientation and concentration Continuous and aligned (排列)fiber composites Discontinuous (不連續(xù)) and aligned fiber composites Discontinuous and randomly oriented (雜亂無章)fiber composites Continuous and aligned fiber compositesFIGURE 15.9 (a) Schematic stressstrain curves for britt

21、le fiber and ductilematrix materials. Fracture stresses and strains for both materials are noted. (b)Schematic stressstrain curve for an aligned fiber-reinforced compositeElastic Behavior(彈性行為)Longitudinal Loading(縱向施加外力)modulus of elasticity(彈性模量)Example problem 15.1A continuous and aligned glass f

22、iber-reinforced composite consists of 40 vol% of glass fibers having a modulus of elasticity of 69 GPa (10106 psi) and 60 vol% of a polyester resin that, when hardened, displays a modulus of 3.4 GPa (0.5 106 psi).(a) Compute the modulus of elasticity of this composite in the longitudinal direction.(

23、b) If the cross-sectional area is 250 mm2 (0.4 in.2) and a stress of 50 MPa (7250 psi) is applied in this longitudinal direction, compute the magnitude of the load carried by each of the fiber and matrix phases.(c) Determine the strain that is sustained by each phase when the stress in part b is applied.Elastic BehaviorTransverse Loading(橫向施加外力)Compute the elastic modulus of the composite material described in Example Problem 15.1, but assume that the stress is applied perpendicular to the direction of fiber alignment