**2.2 Flexural properties**

Flexural test is used to determine the capability of a material to resist bending forces applied perpendicularly to its longitudinal axis and often called the transverse beam test. Flexural test properties are among the major parameters used in assessing the suitability of composite materials for structural applications. Parameters such as flexural load, flexural Young's modulus, flexural strength and deflection at break are measured and used to interpret the mechanical behavior under flexural stress.

### **2.3 Impact properties**

Impact test is employed in assessing the impact strength, toughness and notch sensitivity of structural materials. In summary it is the capability of the material in question to withstand high rate loading. Toughness is the total of energy absorbed per unit volume of material before rupturing. The toughness is a measure of balance between strength and ductility of the material. Impact test is very critical for most polymer materials because it relates to the product performance and service life. It also influences other properties related to product safety and liability.

**115**

*Improving the Mechanical Properties of Natural Fiber Composites for Structural and Biomedical…*

Compressive tests evaluate the materials behavior when subjected to uniaxial compression load at a relatively low and uniform loading rate. These tests are very important for product design analysis, especially materials for building purposes. Compressive strength and compressive Young's modulus are the two major properties that are used; however, there are also compressive strain, deformation beyond

Hardness is that property of an engineering material which enables it to resist scratching, indentation, penetration and plastic deformation. It is a very significant property for any structural material from the engineering point of view, because hardness generally leads to increase in wear resistance by either erosion by water, oil

This is the degree to which a vehicle or aircraft will protect its occupant from the effect of an accident [34]. It is the most important concept in vehicle defect cases. That is, the ability to prevent injuries to the occupant in the event of collision. Therefore, crashworthiness focuses on occupant protection to reduce fatality in the case of an accident. Different criteria can be used to determine crashworthiness

In general for composites, these properties depend on other factors such as fiber length, fiber weight percentage content and the extent of polymer/fiber interac-

Natural fiber reinforced polymer composites are attracting widespread interest for purposes which are sensitive to the materials weight, because their strength and stiffness combine well with their low density, however, their toughness is a major concern [36]. NFPCs are prepared using plant fiber as fillers, which are hydrophilic in nature and do not interact well with hydrophobic polymer matrix [37–39]. NFPCs are a set of important materials developed for numerous areas application; medical, pharmaceutical, food packaging, electronics, aerospace, automobile, construction, building, transport and many more [40–43]. This is because of the many unique qualities these materials possess or can be designed to possess. Qualities which include, but are not limited to; light weight, resistant to chemical attraction, resistant to corrosion, ability to be molded to any shape, can be processed using existing technology, environmental friendliness and sustainability. That is why the interest in these materials has grown tremendously in the last two decades [36, 44–46]. Dweib et al. fabricated bio-based composites for roof structures in the form of paper sheets, entirely from cellulose fibers and soy oil-based resins [47]. These developed sheets were tested for structural unit beams and were established to have given the necessary strength and stiffness for consideration in roof construc-

depending on the nature of the impact and vehicle involved [35].

**3. Natural fiber polymer composites in structural purposes**

tion. Also Bektas et al. manufactured panels with a density of 0.7 g/cm3

required for general purpose-use particle board by normal standards.

sunflower stalks percentage of 25, 50 and 75% fiber contents [48]. From the results of the mechanical tests, the panels were observed to have the required properties as

with a

*DOI: http://dx.doi.org/10.5772/intechopen.85252*

yield point, and compressive yield stress.

**2.4 Compressive properties**

**2.5 Hardness properties**

and steam or friction.

**2.6 Crashworthiness**

tions as will be discussed later.

*Improving the Mechanical Properties of Natural Fiber Composites for Structural and Biomedical… DOI: http://dx.doi.org/10.5772/intechopen.85252*

## **2.4 Compressive properties**

*Renewable and Sustainable Composites*

for structural and biomedical applications.

**2. Mechanical properties of NFPCs**

elongation and ultimate tensile strength (UTS).

areas of applications.

**2.1 Tensile properties**

**2.2 Flexural properties**

under flexural stress.

**2.3 Impact properties**

those used in microelectronics, are designed to meet specific performance requirements. Structural requirements may vary based on end use; hence the requirement for a material to be used for vehicle part may differ widely from what is required for manufacturing casing for electronic equipment. Generally, of more interest are the following properties: mechanical, thermal, electrical conductivity, dimension stability, water absorbability, etc. [26–31]. This work intends to critically review the mechanical requirements and suggest ways of improving the mentioned properties

NFPCs are different depending on the type of polymers or fibers employed, the processing condition and the characteristic properties developed after processing [32, 33]. The use of these NFPCs for structural applications depends more on the mechanical properties. There are different mechanical evaluations carried out on a material and some are very specific to individual application. However, the general focus of most researchers is on a few tests including tensile test, flexural test, impact test, compression test and hardness. These few tests can describe the mechanical behavior of any material to a large extent and also gives an insight to other possible

Tensile test is one of the fundamental and common types of mechanical test widely used for testing polymeric materials. It is also known as tension testing; it is used to determine the stress-strain behavior under tension [32]. In tensile testing, tensile force (pulling force) is applied to a material and the specimens' response to that applied force (stress) is measured. Under this test condition, samples are subjected to controlled tension until failure occurs. Tensile test determines how strong a material is and how long it can be stretched. Important information that can be obtained from tensile test includes; Young's modulus, yield strength, percentage

Flexural test is used to determine the capability of a material to resist bending forces applied perpendicularly to its longitudinal axis and often called the transverse beam test. Flexural test properties are among the major parameters used in assessing the suitability of composite materials for structural applications. Parameters such as flexural load, flexural Young's modulus, flexural strength and deflection at break are measured and used to interpret the mechanical behavior

Impact test is employed in assessing the impact strength, toughness and notch sensitivity of structural materials. In summary it is the capability of the material in question to withstand high rate loading. Toughness is the total of energy absorbed per unit volume of material before rupturing. The toughness is a measure of balance between strength and ductility of the material. Impact test is very critical for most polymer materials because it relates to the product performance and service life. It

also influences other properties related to product safety and liability.

**114**

Compressive tests evaluate the materials behavior when subjected to uniaxial compression load at a relatively low and uniform loading rate. These tests are very important for product design analysis, especially materials for building purposes. Compressive strength and compressive Young's modulus are the two major properties that are used; however, there are also compressive strain, deformation beyond yield point, and compressive yield stress.

## **2.5 Hardness properties**

Hardness is that property of an engineering material which enables it to resist scratching, indentation, penetration and plastic deformation. It is a very significant property for any structural material from the engineering point of view, because hardness generally leads to increase in wear resistance by either erosion by water, oil and steam or friction.
