Fiber-reinforced composite
A fiber-reinforced composite (FRC) is a composite building material that consists of three components: This is a type of advanced composite group, which makes use of rice husk, rice hull,rice shell, and plastic as ingredients. This technology involves a method of refining, blending, and compounding natural fibers from cellulosic waste streams to form a high-strength fiber composite material in a polymer matrix. The designated waste or base raw materials used in this instance are those of waste thermoplastics and various categories of cellulosic waste including rice husk and saw dust. Introduction. FRC is high -performance fiber composite achieved and made possible by cross-linking cellulosic fiber molecules with resins in the FRC material matrix through a proprietary molecular re-engineering process, yielding a product of exceptional structural properties. Through this feat of molecular re-engineering selected physical and structural properties of wood are successfully cloned and vested in the FRC product, in addition to other critical attributes to yield performance properties superior to contemporary wood. This material, unlike other composites, can be recycled up to 20 times, allowing scrap FRC to be reused again and again. The failure mechanisms in FRC materials include delamination , intralaminar matrix cracking, longitudinal matrix splitting, fiber/matrix debonding, fiber pull-out, and fiber fracture. Difference between wood plastic composite and fiber-reinforced composite: Basic principles. The appropriate "average" of the individual phase properties to be used in describing composite tensile behavior can be elucidated with reference to Fig. 6.2. Although this figure illustrates a plate-like composite, the results that follow are equally applicable to fiber composites having similar phase arrangements. The two phase material of Fig. 6.2 consists of lamellae of formula_1 and formula_2 phases of thickness formula_3 and formula_4. and respectively. Thus, the volume fractions (formula_5, formula_6 ) of the phases are formula_7 and formula_8. Case I: Same stress, different strain A tensile force F is applied normal to the broad faces (dimensions Lx L) of the phases. In this arrangement the stress borne by each of the phases (= F/formula_9) is the same, but the strains (formula_10, formula_11) they experience are different. composite strain is a volumetric weighted average of the strains of the individual phases. formula_12, formula_13 The total elongation of the composite, formula_14 is obtained as formula_15 and the composite strain formula_16 is, formula_16=formula_18=formula_19= formula_20 Composite modulus formula_21 Case II : different stress, same strain Fibers that are aligned parallel to the tensile axis, the strains in both phases are equal (and the same as the composite strain), but the external force is partitioned unequally between the phases. formula_22 formula_23 formula_24 Deformation behavior. When the fiber is aligned parallel to the direction of the matrix and applied the load as the same strain case. The fiber and matrix has the volume fraction formula_25, formula_26; stress formula_27 , formula_28; strainformula_29,formula_30; and modulus formula_31, formula_32. And here formula_29=formula_29=formula_16. The uniaxial stress-strain response of a fiber composite can be divided  into several stages. In stage 1, when the fiber and matrix both deform elastically, the stress and strain relation is formula_36 formula_37 In stage 2, when the stress for the fiber is bigger than the yield stress, the matrix starts to deform plastically, and the fiber are still elastic, the stress and strain relation is formula_38 formula_39 In stage 3, when the matrix the fiber both deform plastically, the stress and strain relation is formula_40 formula_41 Since some fibers do not deform permanently prior to fracture, stage 3 cannot be observed in some composite. In stage 4, when the  fiber has already become fracture and matrix still deforms plastically, the stress and strain relation is formula_42 However, it is not completely true, since the failure fibers can still carry some load. Reinforcement with discontinuous fibers. For discontinuous fibers (also known as whiskers, depending on the length), tensile force is transmitted from the matrix to the fiber by means of shear stresses that develop along the fiber-matrix interface. Matrix has displacement equals zero at fiber midpoint and maximum at ends relative to the fiber along the interface. Displacement causes interfacial shear stress formula_43 that is balanced with fiber tensile  stress formula_27. formula_45 is the fiber diameter, and formula_46 is the distance from the fiber end. formula_47 formula_48 After only a very small strain, the magnitude of the shear stress at the fiber end becomes large. This leads to two situation: fiber-matrix delamination or matrix having plastic shear. If matrix has plastic shear: interfacial shear stress formula_49. Then there is a critical length formula_50 that when formula_51, after certain formula_46, formula_27 remains constant and equals to stress in equal-strain condition. formula_54 formula_55 The ratio, formula_56 is called the "critical aspect ratio". It increases with composite strain formula_16. For  the mid-point of a fiber to be stressed to the equal-strain condition at composite fracture, its length must be at least formula_58. Then calculate average stress. The fraction of the fiber length carrying stress formula_59 is formula_60. The remaining fraction formula_61 bears an average stress formula_62. formula_63 For formula_64, average stress is formula_65 with formula_66. formula_67 The composite stress is modified as following: formula_68 formula_69 The above equations assumed the fibers were aligned with the direction of loading. A modified rule of mixtures can be used to predict composite strength, including an orientation efficiency factor, formula_70, which accounts  for the decrease in strength from misaligned fibers. formula_71 where formula_72 is the fiber efficiency factor equal to formula_73for formula_74, and formula_75for formula_76. If the fibers are perfectly aligned with the direction of loading formula_70 is 1. However, common values of formula_70 for randomly oriented are roughly 0.375 for an in-plane two-dimensional array and 0.2 for a three-dimensional array. Appreciable reinforcement can be provided by discontinuous fibers provided their lengths are much greater than the (usually) small critical lengths. Such as MMCs. If there is fiber-matrix delamination. formula_79 is replaced by friction stress formula_80 where formula_81  is the friction coefficient between the matrix and the fiber, and formula_82 is an internal pressure. formula_83 This happens in most resin-based composites. Composites with fibers length less than formula_50 contribute little to strength. However, during composite fracture, the short fibers do not fracture. Instead they are pulled out of the matrix. The work associated with fiber pull-out provides an added component to the fracture work and has a great contribution to toughness. Application. There are also applications in the market, which utilize only waste materials. Its most widespread use is in outdoor deck floors, but it is  also used for railings, fences, landscaping timbers, cladding and siding, park benches, molding and trim, window and door frames, and indoor furniture. See for example the work of "Waste for Life", which collaborates with garbage scavenging cooperatives to create fiber-reinforced building materials and domestic problems from the waste their members collect: Homepage of Waste for Life References. 3. Thomas H. Courtney. "Mechanical Behavior of Materials". 2nd Ed. Waveland Press, Inc. 2005.