No abstract

Lightweight composites produced from renewable and biodegradable materials have been very promising to find wide applications in automotive industries and to lessen the dependence on exhausting petroleum resource. In this chapter, various natural fibers, traditional polymer and bio-polymer matrix systems are presented. Potentials and limitations of modification methods on natural fiber and manufacturing techniques for lightweight composites are reviewed in details. Major technical concerns and challenges regarding natural fiber reinforced composites are addressed. Examples of recent automotive industrial applications are given and future trends are outlined.

Traditional multifunctional composite structures are produced by embedding parasitic parts, such as foil sensors, optical fibers and bulky connectors. As a result, the mechanical properties of the composites, especially the interlaminar shear strength (ILSS), could be largely undermined. In the present study, we demonstrated an innovative aerosol-jet printing technology for printing electronics inside composite structures without degrading the mechanical properties. Using the maskless fine feature deposition (below 10 μm) characteristics of this printing technology and a pre-cure protocol, strain sensors were successfully printed onto carbon fiber prepregs to enable fabricating composites with intrinsic sensing capabilities. The degree of pre-cure of the carbon fiber prepreg on which strain sensors were printed was demonstrated to be critical. Without pre-curing, the printed strain sensors were unable to remain intact due to the resin flow during curing. The resin flow-induced sensor deformation can be overcome by introducing 10% degree of cure of the prepreg. In this condition, the fabricated composites with printed strain sensors showed almost no mechanical degradation (short beam shearing ILSS) as compared to the control samples. Also, the failure modes examined by optical microscopy showed no difference. The resistance change of the printed strain sensors in the composite structures were measured under a cyclic loading and proved to be a reliable mean strain gauge factor of 2.2 ± 0.06, which is comparable to commercial foil metal strain gauge.

As a new kind of manufacturing technology developing rapidly, Material Increasing Manufacturing, scilicet 3D printing technology is that the popularity of various fields. In this paper, under the background of the desktop 3D printing gradually enter the family. To solve the printing material problem scilicet 3D printing technology development bottleneck, come up with a bamboo-plastic composite made of Bamboo powder and poly lactic acid (PLA), can be used on desktop 3D printing. Due to bamboo resources is abundant, low cost, and also have the advantages of friendly of environment, have a good potential for development. In this paper, the right formula is used in the study on preparation of materials, through the material blending; extrusion process to produce the 3D printing wire can meet the requirements. Through further studies on the ratio of bamboo and plastic, the amount of additives added, extrusion processing temperature and material situation, optimizing the ratio of bamboo and plastic, the amount of Additives, adjust the extrusion temperature in the formulation. Tests showed that through the improved technology, wires have further enhanced performance, continuous printing more than 300 meters, the printing effect is smooth, jam does not appear, and the molded parts have good quality.

To overcome the disadvantage of large suction requirements, the suction control for drag reduction is optimized. Computational fluid dynamics (CFD), in conjunction with multi-island genetic algorithm (MIGA), is employed to achieve the optimization. An E387 airfoil is employed as the physical model. The suction location and mass flux of a slot are set as the design parameters. The goal is to minimize both the airfoil drag and suction requirement by identifying the optimal suction location on the upper airfoil surface. The effects of different numbers of suction slots were investigated. Results show that the suction control for drag reduction could be optimized using MIGA. For a single-suction slot, the reduction in airfoil drag is up to 8.3%, and the mass flux of a slot reaches the lower limit of the optimization interval. The increase in suction slot number results in a better drag reduction effect, which is accompanied by larger suction requirement and slower convergence. The main reason for airfoil drag reduction is the decrease in the pressure drag.