What is a composite?
steel elements
H He Li Be B C N O F Ne Na Mg Al Si P S Cl Ar K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe Cs Ba La Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn Fr Ra Ac Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr Rf Db Sg Bh Hs Mt Ds Uuu Uub Uut Uuq Uup Uuh Uus Uuo human-body elements
H He Li Be B C N O F Ne Na Mg Al Si P S Cl Ar K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe Cs Ba La Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn Fr Ra Ac Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr Rf Db Sg Bh Hs Mt Ds Uuu Uub Uut Uuq Uup Uuh Uus Uuo plant elements
H He Li Be B C N O F Ne Na Mg Al Si P S Cl Ar K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe Cs Ba La Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn Fr Ra Ac Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr Rf Db Sg Bh Hs Mt Ds Uuu Uub Uut Uuq Uup Uuh Uus Uuo "The word 'composites' has a modern ring. But using the high strength of fibres to stiffen and strengthen a cheap matrix material is probably older than the wheel. ...almost all natural materials which must bear load--wood, bone, muscle--are composites. ... The composite industry, however, is new. It has grown rapidly in the past 30 years with the development of fibrous composites..." 1
Natural composites
- spider webs
- fish fin
- bird wing
- muscle
- wood
- your nose (pretensioned flexible composite with shape memory)
Engineered composites 2
Composite materials are like sandwiches. A good sandwich contains a variety of ingredients to yield a taste that no single ingredient could provide by itself. Similarly, composite materials are those which are formed from two or more materials producing properties or characteristics that could not be obtained from any one material. All of the above natural composites are typified by two or more phases, one of which is stronger and stiffer that the others and serves as the primary load carrying component.
Composites consist of one or more discontinuous phases embedded in a continuous phase. The discontinuous phase is usually harder and stronger than the continuous phase and is called the reinforcement or reinforcing material, whereas the continuous phase is termed the matrix.
fiberglass bars and plates laminated-carbon bars and plates aluminum-honeycomb sandwich panel from aircraft honeycomb carbon-polymer sandwich panel kevlar-foam sandwich panel from S&T solar car body tested in flexure fiberglass-carbon sandwich panel with drilled hole tested in tension synthetic fiber reinforcement for concrete polymer-sawdust lumber
Fiber-pullout failures
Fibers toughen by pulling out of the fracture surface, absorbing energy as the crack opens. 1
Matrix failures
The stress-strain curve of a continuous fibre composite (heavy line), showing how it relates to those of the fibres and the matrix (thin lines). At the peak the fibres are on the point of failing. 1
Kinking failures
Composites fail in compression by kinking, at a load which is lower than that for failure in tension.1
Crushing failure of Norway spruce in the L, R-plane: 100X earlywood tracheid wall.3
Classification of Composite Materials 4
The seven hierarchical levels in the [Euplectella] sponge skeleton represent major fundamental construction strategies, such as laminated structures, fiber-reinforced composites, bundled beams, and diagonally reinforced square-grid cells, to name a few. -- Aizenberg et al., Science (2005) 309, 275
