**4. Sustainable product design**

#### **4.1 Case study: the use of biodegradable composites in the automotive industry**

Material selection processes are considered one of the most vital steps in the engineering and sustainable product design. This has become a necessary activity performed by automotive manufacturers and designers. Driven by the need to improve fuel efficiency, weight reduction has become a prime requirement. Accordingly, the fraction of lighter materials such as aluminum and plastic composites has progressively increased and substituted heavier steel alloys traditionally used. Other factors driving the search for alternatives are price, end-of- life vehicle legislation, and sustainability [16, 36]. Al-Oqla and Sapuan have emphasized on the importance of selecting the proper alternative biocomposite that meets all the requirements needed for environmental sustainability as well as compatibility to performance prerequisites [8]. Also, the authors added that considering the tremendous need and awareness of environmental issues, natural fiber-reinforced composites have become of major interest by researchers. Given their low density, good mechanical properties, renewability, and biodegradability, automotive interiors could be designed with high specific strength and stiffness properties, meeting design requirements while still meeting environmental criteria [37, 42].

#### *4.1.1 Materials and composites for interior panels*

Conventionally, polymers such as polyvinyl chloride (PVC) have been used for the interior panel structures [41]. Advantages such as easy processing and low cost have led to its extensive use in a wide variety of applications. However, it is a synthetic polymer with recycling and degradability issues making it an unfavorable choice. Subsequently, alternatives have been proposed in the literature with a recent review summarizing the selection criteria for biocomposites to be used in automotive structures [42]. **Figure 1** illustrates the use of hemp fibers in reinforcing polypropylene composites as a substitute in car doors.

*Design for Sustainability with Biodegradable Composites DOI: http://dx.doi.org/10.5772/intechopen.88425*

Holbery and Houston have indicated that the use of bast fibers and specifically flax fibers presents a strong competition against E-glass fibers commonly used in composites implemented in automotive applications [43], where the specific strength for flax fiber is 1200 compared to 1275 for E-glass fibers [43]. Other natural fibers suggested for reinforcing plastics are hemp and jute. Their use has been reported in reinforcing PP replacing fiber glass-reinforced plastics in commercial Mercedes-Benz and Ford cars [44]. **Figure 2** demonstrates the use of flax fiber composites in different components of the Mercedes-Benz A-Class vehicle.

However, these composites are argued to be only partially biodegradable due to the synthetic matrices and hence are not an environmentally friendly option. A rather more sustainable option is the use of natural polymers such as starch reinforced by natural fibers. Nevertheless, this option has not been investigated in the literature in applications related to the automotive industry in spite of the benefits these composites offer, which range from the low energy needed for production to being renewable and biodegradable. The case study presented in Section 4.1.2 evaluates the use of natural fiber-reinforced starch as a potential candidate for substitution.

#### *4.1.2 Performance indices and material requirements*

For interior panels, the material requirements needed are lightweight and high stiffness. Cost and environmental considerations are other factors considered for the decision-making process. Thus, the material performance index (m) for a stiff light structural member is calculated based on the consideration that a panel is

**Figure 1.** *Hemp fibers in vehicle doors [45].*

**Figure 2.** *Mercedes-Benz A-Class vehicle components made of flax fiber composites [46].*

rectangular of 100 cm in length (l), 50 cm width (b), and thickness (t) 3.7 mm for the PVC conventional material:

$$\mathbf{m} = \mathbf{E}^{1\beta} / \mathbf{\hat{p}} \tag{1}$$

The mass (*M*) of the panel is

$$\mathbf{M} = \rho tbl \tag{2}$$

The thickness is given by

$$\mathbf{t\_n} = \mathbf{t\_o} \left(\mathbf{E\_o/E\_n}\right)^{1/3} \tag{3}$$

where *t*<sup>n</sup> is thickness of alternative material, *t*<sup>o</sup> is thickness of the PVC conventional material, Eo is elastic modulus of alternative material, and En is elastic modulus of the PVC conventional material.

Calculations for each performance index are presented in **Table 6** for the different candidate materials.

#### **4.2 Cost of the panel**

The total cost (*C*t) of a panel is the summation of the cost of material, cost of manufacturing and finishing, cost over the entire life of the component (running cost), and cost of disposal and recycling.

#### *4.2.1 Cost assumptions*

The cost of the material in the panel is based on its weight and the price of material per unit weight. The manufacturing cost is roughly estimated based on the assumption that compression molding is used. According to Farag, the life of a car could be estimated to be 5 years, a total of 200,000 km traveled, \$3/gal of fuel, and 8.62 km/L for a 1782 kg vehicle; the total fuel cost savings of the vehicle is approximately \$6.6/kg. This amount can also be taken as the share in the running cost of a component weighing 1 kg over the entire life of the vehicle. Finally, the cost of disposal and recycling is estimated as being proportional to the weight of the panel and its material. Synthetic composites and matrices are difficult to dispose; thus the cost is assumed as \$0.7/kg, while natural composites are relatively easier, and the cost of disposal is assumed to be \$0.5/kg.

Finally, the cost of pure synthetic polymers is considered to be easy and estimated to be \$0.3/kg., while biodegradable natural fibers are easiest to dispose of with a cost of 0.15/kg.

#### **4.3 Environmental considerations**

Motorcar weight reduction is considered as the most important factor in reducing the negative impact on the environment. This is related to the reduction in fuel consumption and the reduction in carbon dioxide emissions [47]. Therefore, this study assumes that the environmental impact of the panel is directly proportional to its weight.

#### **4.4 Comparison of candidate materials using the compound objective function method**

**Material**

**51**

PVC PP and 40% GF PP and 40% flax Starch and 50% flax

**Table 6.** *Material properties and cost elements of candidate materials.*

 7.75

 4.65

 4.5

 1.4

 2.82

 1.34

 2.8

 1.78

 2.36

2

 1.3

 3.7

1.375 3.46 1.04 0.34

0.7

2

13

 0.3

2

2

12.4

 0.94

7.3

2

13.86

 1.47

3.3

2

15.84

 0.72

21.86 24.60 17.34

16

2.4

2.1

1.88

1.97

 **E (GPa) ρ (g/cc) t (mm) Cost of material /kg (\$)**

**Cost elements (\$)**

**Materials**

**Manufacturing**

 **Running**

 **Disposal**

**Total cost of panel (\$) Weight of panel (Kg)**

*Design for Sustainability with Biodegradable Composites*

*DOI: http://dx.doi.org/10.5772/intechopen.88425*

**Table 7** gives the normalized values for each of the computed cost and weight of the panel. The performance index of a panel made of a given material is taken as

#### *Design for Sustainability with Biodegradable Composites DOI: http://dx.doi.org/10.5772/intechopen.88425*


**Table 6.**

*Material properties and cost elements of candidate materials.*


#### **Table 7.**

*Ranking of candidate materials.*

the weighted sum product of the normalized values of its cost and environmental impact. Using the objective function method, two scenarios are considered: in the first scenario, the cost of the panel and its environmental impact are given equal weight, and in the second scenario, the cost of the panel is considered less important and is given a weight of 40%, and the environmental impact is considered more important and is given a weight of 60%. Both scenarios give the starch-flax composite the first rank. Its low cost more than compensates for its moderate weight.

## **5. Conclusion**

Conventional plastics are designed with little consideration for their ultimate disposability or recyclability. Accordingly, this has led to the growing environmental awareness and notion toward the use of alternatives to petrochemical-based polymers. Given the ubiquity of plastic use in everyday life, substantial progress was made in the development of a reliable substitute, and in recent years, significant advancement was achieved in the production of alternative biodegradable materials based on renewable resources, which can offer equivalent functionality and physical properties similar to their petrochemical-based counterparts. Products that are based on such materials can be designed to biodegrade at the end of their useful life using the design for a life approach which entails that the material used in making a given product will not last long after the end of its useful life. However, the challenge is to design polymers to provide the required functionality during use and naturally degrade after. Consequently, this chapter has elucidated the advancement achieved by researchers in fabricating biodegradable alternatives from starchbased composites.

**Author details**

**53**

Dina Fouad\* and Mahmoud Farag

The American University in Cairo, Cairo, Egypt

*Design for Sustainability with Biodegradable Composites*

*DOI: http://dx.doi.org/10.5772/intechopen.88425*

provided the original work is properly cited.

\*Address all correspondence to: dinafouad@aucegypt.edu

© 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

#### **Abbreviations**


*Design for Sustainability with Biodegradable Composites DOI: http://dx.doi.org/10.5772/intechopen.88425*
