# Fiber-reinforced composite

A fiber-reinforced composite (FRC) is a composite building material that consists of three components: (i) the fibers as the discontinuous or dispersed phase, (ii) the matrix as the continuous phase, and (iii) the fine interphase region, also known as the interface.[1][2] This is a type of advanced composite group, which makes use of rice husk, rice hull, 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.

Fiber-reinforced composite

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.[1]

Difference between wood plastic composite and fiber-reinforced composite:

Features Plastic lumber Wood plastic composite FRC Wood
Recyclable Yes No Yes Yes
House Construction No No Yes Yes
Water Absorption 0.00% 0.8% and above 0.3% and below 10% and above

## Properties

 Tensile Strength ASTM D 638 15.9 MPa Flexural Strength ASTM D 790 280 MPa Flexural Modulus ASTM D 790 1582 MPa Failure Load ASTM D 1761 1.5 KN - 20.8 KN Compressive Strength 20.7MPa Heat Reversion BS EN 743 : 1995 0.45% Water Absorption ASTM D 570 0.34% Termite Resistant FRIM Test Method 3.6

## 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 ${\displaystyle \alpha }$ and ${\displaystyle \beta }$ phases of thickness ${\displaystyle l_{\alpha }}$ and ${\displaystyle l_{\beta }}$. and respectively. Thus, the volume fractions (${\displaystyle V_{\alpha }}$, ${\displaystyle V_{\beta }}$) of the phases are ${\displaystyle V_{\alpha }={\frac {l_{\alpha }}{l_{\alpha }+l_{\beta }}}}$ and ${\displaystyle V_{\beta }={\frac {l_{\beta }}{l_{\alpha }+l_{\beta }}}}$.

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/${\displaystyle L^{2}}$) is the same, but the strains (${\displaystyle \varepsilon _{\alpha }}$, ${\displaystyle \varepsilon _{\beta }}$) they experience are different. composite strain is a volumetric weighted average of the strains of the individual phases.

${\displaystyle \vartriangle l_{\alpha }=\varepsilon _{\alpha }l_{\alpha }}$, ${\displaystyle \vartriangle l_{\beta }=\varepsilon _{\beta }l_{\beta }}$

The total elongation of the composite, ${\displaystyle \vartriangle l_{c}}$ is obtained as ${\displaystyle \vartriangle l_{c}=N\vartriangle l_{\alpha }+N\vartriangle l_{\beta }}$

and the composite strain ${\displaystyle \varepsilon _{c}}$ is, ${\displaystyle \varepsilon _{c}}$=${\displaystyle {\frac {\vartriangle l_{c}}{N(l_{\alpha }+l_{\beta })}}}$=${\displaystyle V_{\alpha }\varepsilon _{\alpha }+V_{\beta }\varepsilon _{\beta }}$= ${\displaystyle \sigma {\biggl (}{\frac {V_{\alpha }}{E_{\alpha }}}+{\frac {V_{\beta }}{E_{\beta }}}{\biggr )}}$

Composite modulus ${\displaystyle E_{c}={\frac {E_{\alpha }E_{\beta }}{V_{\alpha }E_{\beta }+V_{\beta }E_{\alpha }}}}$

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. ${\displaystyle F=F_{\alpha }+F_{\beta }=NL(\sigma _{\alpha }l_{\alpha }+\sigma _{\beta }l_{\beta })}$

${\displaystyle \sigma _{c}=\left({\frac {\sigma _{\alpha }l_{\alpha }}{l_{\alpha }+l_{\beta }}}+{\frac {\sigma _{\beta }l_{\beta }}{l_{\alpha }+l_{\beta }}}\right)=\sigma _{\alpha }V_{\alpha }+\sigma _{\beta }V_{\beta }}$

${\displaystyle E_{c}=V_{\alpha }E_{\alpha }+V_{\beta }E_{\beta }}$

## 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 ${\displaystyle V_{f}}$, ${\displaystyle V_{m}}$; stress ${\displaystyle \sigma _{f}}$ , ${\displaystyle \sigma _{m}}$; strain${\displaystyle \varepsilon _{f}}$,${\displaystyle \varepsilon _{m}}$; and modulus ${\displaystyle E_{f}}$, ${\displaystyle E_{m}}$. And here ${\displaystyle \varepsilon _{f}}$=${\displaystyle \varepsilon _{f}}$=${\displaystyle \varepsilon _{c}}$. 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 ${\displaystyle \sigma _{c}=V_{f}E_{f}\varepsilon _{f}+V_{m}E_{m}\varepsilon _{m}=\varepsilon _{c}(V_{f}E_{f}+V_{m}E_{m})}$

${\displaystyle E_{c}=V_{f}E_{f}+V_{m}E_{m}}$

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

${\displaystyle \sigma _{c}=V_{f}E_{f}\varepsilon _{f}+V_{m}\sigma _{m}(\varepsilon _{m})=V_{f}E_{f}\varepsilon _{c}+V_{m}\sigma _{m}(\varepsilon _{c})}$

${\displaystyle E_{c}=V_{f}E_{f}+V_{m}({\frac {d\sigma _{m}}{d\varepsilon _{c}}})}$

In stage 3, when the matrix the fiber both deform plastically, the stress and strain relation is

${\displaystyle \sigma _{c}=V_{f}\sigma _{f}(\varepsilon _{f})+V_{m}\sigma _{m}(\varepsilon _{m})=V_{f}\sigma _{f}(\varepsilon _{c})+V_{m}\sigma _{m}(\varepsilon _{c})}$

${\displaystyle E_{c}=V_{f}({\frac {d\sigma _{f}}{d\varepsilon _{c}}})+V_{m}({\frac {d\sigma _{m}}{d\varepsilon _{c}}})}$

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

${\displaystyle \sigma _{c}=V_{m}\sigma _{m}(\varepsilon _{m})}$

However, it is not completely true, since the failure fibers can still carry some load.

## 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