Development of Novel 3D Woven Reinforcements for High Performance Applications

Abstract

Three-dimensional (3D) fibre reinforced polymer composites (FRPC) are attractive and preferred in high performance applications because of their resistance against delamination and better out of plane properties due to the presence of fibres/yarns in the z direction. However, the ability to withstand damage depends on weave design, z-binder yarn and interlocking pattern. A substantial amount of research has been performed to understand in plane properties of 3D woven composites as well as under different mechanical loads. But there is limited research on the damage tolerance and out of plane properties of 3D woven warp, weft, bidirectional and novel hybrid interlock composites as well as on mechanical and time dependent compression and recovery properties of 3D woven spacer composites. In view of present research in 3D woven composites, two different types of 3D woven reinforcements i.e. 3D woven solid and 3D woven spacer were developed. In 3D woven solid reinforcements i.e. warp, weft, bidirectional and hybrid interlock structures were produced. In the first stage, 3D orthogonal layer to layer warp, weft and bidirectional interlock composite structures were fabricated. It was found that alone warp and weft interlock composites showed better tensile behaviour as compared to bidirectional interlock composite in warp and weft direction, due to the presence of less crimp as compared to bidirectional interlock. However, bidirectional interlock composite exhibited considerably superior impact resistance and three-point bending strength as compared to the individual warp and weft interlock composites. In the second stage, mechanical performance of seven different types of 3D woven composites i.e. orthogonal layer to layer (OLL), orthogonal through thickness (OTT), angle interlock layer to layer (ALL), angle interlock through thickness (ATT), hybrid 1 (H1, combination of OTT and ATT), hybrid 2 (H2, combination of OTT and ALL) and bidirectional interlock (H3) were studied. Overall, during in plane testing (tensile), OTT composite samples behaved mechanically well due to the least crimp in binder yarn, while during out of plane characterizations (flexural, interlaminar shear strength, low velocity impact and compression after impact), both through thickness structures (OTT and ATT) and H3 samples showed highest and comparable mechanical results. In the third stage, 3D woven spacer composites with three different thicknesses i.e. 4mm, 10mm and 20mm were characterized. Flexural, low velocity impact and flat compression performance of the 3D woven spacer composites were reduced with the increase of sample thickness. The highest amount of energy was absorbed during fracture of 4mm thick composite. Compressibility (%) and resiliency (%) was highest in 4mm thick composite but recovery (%) was found a bit lower as compared to the 10mm and 20mm thick composites. While in 10mm thick composite recovery percentage was highest. Three dimensional (3D) woven fibre reinforced polymer composites (FRPC) are currently receiving a great deal of attention in numerous applications such as interior parts of vehicles, light weight furniture, automotive, sporting goods, aerospace, civil infrastructure, etc., due to their favourable mechanical properties. Despite their several advantages over traditionally used structures, they tend to be susceptible to the different static and dynamic mechanical loads (in plane and out of plane), resulting in the failure of the structure. A substantial amount of experimental and theoretical work has been performed to understand the in-plane properties as well as out of the plane performance of 3D woven composites exposed to different mechanical loads. However, the use and influence of individual 3D warp and weft interlocks and their combination with novel hybrid 3D interlocking on the in-plane, as well as the out of plane properties of different 3D woven composites and, time dependent performance of the 3D woven spacer composites has not yet been explored. The behaviour of 3D woven (Solid and Spacer) composites under static and time dependent loads are studied in this work. Chapter 1 In this chapter, the literature survey is presented, and this is divided into five sections. The first section deals with the general background of this study with a certain application area and their significance. The second section deals with different classes of textile preforms/reinforcements (2D and 3D), Advantages of three dimensional (3D) woven structures over the two dimensional (2D) woven structures. Designing of 3D woven structures on the conventional weaving machines. In the third section, types of the matrix with their significance and composite fabrication techniques are explained. In the fourth section, literature regarding the 3D woven composite with different reinforcement systems is described in detailed. This also covers damage/failure mechanisms under tensile, flexural, compression, compression after impact, impact testing, and the effect of test parameters on the subsequent damage mechanism. In the fifth section of this chapter, the research problem is defined, and the objectives of this study are stated. Chapter 2 In this chapter, designing and fabrication of warp, weft and bidirectional (combination of warp and weft) interlock 3D woven structures using the orthogonal layer to layer (OLL) 3D multilayer technique on a conventional weaving loom, is described. Influence of the interlocking patterns on the mechanical properties (in plane and out of plane) of the composite structures is explained in both warp and weft directions. Chapter 3 In this chapter, designing and fabrication of 3D woven warp interlock structures using the orthogonal layer to layer (OLL), orthogonal through thickness (OTT), angle layer to layer (ALL), angle through thickness (ATT) interlocking and their combination (hybrid interlock) with extra stuffer yarns in warp direction, is discussed. Also, the Influence of the interlocking patterns on the mechanical properties (in plane and out of plane) of the composite structures is clarified in both warp and weft directions. Microscopic images are added for clarification of the 3D structures. Chapter 4 In this chapter, designing and fabrication of the 3D woven spacer composites with different thickness levels (4mm, 10mm, 20mm) and their influence on the mechanical (flexural, impact, compression) as well as on the time dependent compression/recovery properties, is explained. Effect of pile height on different mechanical properties is explained. The cyclic load is applied to the composite structures to determine dynamic compression and recovery behaviour. Chapter 5 In this chapter, general conclusions and future perspectives of this work are given.