Structural Integrity and Monitoring for Composite Materials

Composite materials, thanks to their high-performance mechanical properties, have progressively replace metallic materials in various industrial sectors, in particular for aerospace. Composite structures may be prone to sequential or simultaneous damage modes occurring at different scales, such as matrix cracking, fiber failure or delamination and the earlier damage detection and identification constitute a significant challenge necessary to prevent the consequences of the damage modes on the overall structural health. Structural Health Monitoring (SHM) aims to improve the safety of structures and reduce the control downtime by integrating on-board inspection technologies adapted from Non-Destructive Evaluation (NDE), which the fully-grown techniques such as ultrasonics, X-rays or thermography inspections have definitively demonstrated their reliability in damage analysis for structural engineering applications. The SHM approaches are not restricted to in-service data acquisition mostly given by a distributed sensors network permanently attached on the surface or embedded within the monitored structure and required to diagnose its damage state using sophisticated algorithms and damage models. They also have to evaluate the remaining useful life of the structure. SHM process highly depends on the way to accurately detect damage at the incipient occurrence, thus it is necessary to know and understand the on-line monitoring tools allowing to investigate the damage state of the monitored structures. Thus, this chapter sets out to review the main SHM technologies restricted to laminated composites for aerospace applications, by presenting their respective advantages and drawbacks, in order to seize the potential of these techniques in accordance with the considered damage modes.

The discrete damage modelling technique is applied to the investigation of progressive failure in laminated composites subjected to fatigue loading. Discrete damage modelling uses the extended regularized finite element method to simulate matrix cracking in unknown directions and locations irrespective of the mesh alignment. A material history variable is introduced and updated in each integration point after each loading increment, corresponding to a certain load amplitude and cycle count, to assess the lamina level evolution of deterioration in composite material. In this chapter, it will be revealed how fiber-reinforced composite structures behave when they sustain damage based on a local measure of damage that builds up over time. In order to effectively assess the damage-accumulation process in composite structures, which affects the effective properties of the composite material, it is also preferable to take into account both the initiation and propagation phases of microcracks concurrently.

One of the most important failure modes in fiberglass laminated composites (FGLC) is called impact-induced delamination (IID). Static and dynamic load response required the transducer to be contacted to the sample and was not suitable due to random defect location. Thus, the ultrasonic classification signal approach with help from an artificial neural network has a good potential method to be implemented. This approach can be used to characterize the IID in FGCL type 7781 E-Glass fabric and as a reference during inspection procedures. In this study, the increasing delamination area against the changes of impact energy has been obtained between 23 and 45%. In addition, the damage diameter and area increase significantly to the impact energy between 21 to 46% and 24 to 42% respectively. The difference between DT and NDT measurement is at an acceptable rate which is 4.72% only. Based on the classification performance result, the average accuracy is in the range of 99% and indicates the classification is successful for IID in the FGCL application.

Due to the unique sound absorption characteristics of microperforated panel (MPP), many acousticians start to do further research on how to improve its performances as it may outperform the sound absorption performance of conventional porous sound absorber. Most of the conventional MPP available is made out of common metal based material such as aluminium and steel. The production of metal based material is known to be very costly and harmful to the environment. To overcome that issue, natural fibre composite is used on this study for the production of biodegradable natural fibre composite micro-perforated panel (BNFC-MPP). BNFC-MPP was produced by employing conventional method such as mixing, pelletizing, drilling, and hot compression process. The assessment on the sound absorption of BNFC-MPP was done and determined by using impedance tube. The sound absorption performance of BNFC-MPP will be analysed and compared with traditional MPP. The distinct difference between BNFC-MPP and traditional MPP was that BNFC-MPP possessed porous structure that conventional MPP did not exhibit. It can be noted that BNFC-MPP has excellent sound absorption properties mostly due to the porous structure of BNFC-MPP. BNFC-MPP is also more sustainable due to its biodegradability properties as it does not impose any adverse effect towards the nature.

When aluminum alloys are deployed in the industry, the load bearing capacity are key to selection. Fractographic study of new aluminum alloys cast using Recycled Beverage Cans (RBCs) with the focus of relating the mechanical properties with the fracture characterization is relevant in deploying 7xxx alloys for automobile applications. This chapter assessed the effect of variation in wt.% Zn (4.0–5.0), artificial ageing temperature (100 and 120 °C) and soaking time (6, 10 and 15 h) on the nature of fracture with elemental characterization of the alloys. Ductile dimples, tear ridges, quasi-cleavage surface were characterized. Mechanical properties were better with cup cone fractures as fracture surface were about 45° to the tensile plane. Prolonged ageing time and temperature were detrimental to mechanical properties of alloys from RBCs. The novelty of this study is the characterization of a new Al–(4–5)Zn–1.5 Mg–1.0Mn–0.35Cu alloy cast from about 85% recycled materials. Future studies should concentrate on reducing the contaminants and unintended constituents during laboratory experiments of this alloys.

Composites such as Wood Polymer Composites (WPCs) comprised of polymer matrix and natural fiber is expected to increase in market growth due to its sustainable and environment-friendly nature. Polymers are widely utilized in the different types of fields and contributing the plastic waste in the atmosphere. The knowledge of this product regarding its long-term efficiency is still vague. Properties of recycled polymers, virgin polymers, and effects of weathering are aspects to be considered of WPCs in civil engineering study. Various weight percentage of fillers such as rice husk (RH) as well as recycled /waste polypropylene polymer (WPP) were incorporated together to influence its mechanical characteristics. The condition monitoring of the fabricated composites materials is treated through Ultra-Violet irradiation exposure to reveal its photodegradation. WPC specimens with several compositions of WPC pellets obtained from the industry were each mixed with 10%, 20% and 30% of homopolymer polypropylene (HPP) and later exposed to 1000, 2000, 3000, 4000, 5000 and 6000 h of UV irradiation under accelerated weathering. In this case of studies, WPP, RH and HPP are denoted by the letter A, B and C respectively. The specimens were then subjected tensile test, flexural test, FTIR analysis and morphological study of the fractured surface using Optical Microscope. The study revealed the WPC made from HPP recorded the highest tensile and flexural strength. On the other hand, the modulus of elasticity continued to increase alongside the decrease of HPP constituent. The Carbonyl Index (CI) value were calculated after FTIR to study the rate of photodegradation the specimens went through after UV irradiation exposure which give overall perspective for the civil engineering application. All the mechanical properties as well as decreased in values after they were being subjected to accelerate weathering which is important for building services interest. This is also in agreement with the CI value obtained after specimens were subjected to UV irradiation exposure. From the morphological study of fractured surface, it was observed that all WPC specimens experienced clean surface crack before UV irradiation. Formation of voids occurred after UV irradiation. Increased hours of UV irradiation and RH content caused larger voids formed which outcome in the reduce of mechanical characteristics of the specimens. However, for specimens made from WPC pellets, it was noticed that the tensile strength alongside the flexural strength fluctuates as the percentage of RH content raised. The total opposite however was observed for modulus of elasticity and flexural modulus. As RH content increased, these two properties also increased. The addition of HPP definitely helped to improves the mechanical properties and reduced the rate of photodegradation after the specimens were subjected to accelerated weathering. This is due to the RH fillers became less exposed to UV irradiation and humidity. Mixing HPP with WPP pellets helped in controlling the matrix pull outs. HPP also helped increase the interface bonding of RH and polymer matrix in the WPC pellet. In conclusion, adding optimum percentage of RH as fillers and HPP as additional reinforcements to WPP can improved the mechanical properties of WPC as well as reducing the rate of photodegradation when subjected to UV irradiation exposure.

Composite materials have been the subject of many researchers due to their relatively superior properties and suitability for industrial studies. When composites are classified, researchers may encounter multiple classifications. However, they can basically be classified as natural, synthetic and hybrid composites. In this classification, reinforcement materials can be selected as natural, synthetic or hybrid for their usage area and it depends on the polymer matrix which has different interface parameters. Reinforcement materials, generally in the form of fibers, obtained from plants, animals or cultures, are called natural reinforcements. For example, jute, banana peel, hemp, coconut shell, silk, bamboo, wool etc. can be given. Materials such as carbon, kevlar, glass, etc., which are produced by various artificial processes and generally used as fibers, are called synthetic reinforcements. Compared with synthetic supplements, natural supplements appear to be environmentally friendly, renewable, inexpensive and easily available. But the disadvantage of using natural supplements is that they have lower mechanical properties compared to synthetics. It can be applied in a structure called hybrid reinforcement by using both natural and synthetic reinforcement materials. With the hybrid method, various properties of synthetic and natural reinforcements are combined and the manufactured composite is tried to have the desired properties (Khan et al. in Hybrid fiber composites: materials, manufacturing, process engineering. Wiley–VCH, Weinheim [1]). In this part of the book, basic information about the classification of composites and information about composite fabrication process, which is the main subject of the chapter, will be given.

Natural fibres have nowadays been famously investigated as alternative fibres due to the source depletion of petroleum. There are several natural fibres such as jute, hemp, sisal, kenaf, and pineapple leaf that have been actively researched in terms of their mechanical properties. This chapter presents the research conducted on composites for engineering applications. The discussion focuses on the automotive application and the potential of composite technology. The mechanical characteristics data of earlier studies were examined to comprehend the potential of synthetic fibre, natural fibre, and hybrid composites for the automotive and agriculture industries.

Natural fibre can be bio-based fibres or fibres of plant and vegetable origin. In some countries, natural fibre is not appropriately used in textile or engineering industries, making the fibres waste and useless. Natural fibre such as jute, kenaf, and pineapple have significant potential in composite due to its high strength, environmentally friendly nature, low cost, and sustainability. This chapter will give an overview of the potential of natural fibre in the aviation industry. The discussion will emphasize on application of kenaf, bamboo and pineapple leaf in the radome of an aircraft. The previous investigation will be presented for comparison and study of the problem related to the natural fibre. Understanding natural fibre behavior can help researchers explore the structural health monitoring application in detail.

The use of synthetic material in manufacturing materials increase some awareness among people about the disadvantages due to the environmental effects. A lot of researchers have shown an interest in developing materials based on natural fibres. This is also due to the demand for commercial use of natural fibres. Natural fibres are fibres that have properties of eco-friendly materials such as easy to degradable, low-cost, not harmful to the environment and contribute green living practices. Several natural fibre such as cotton, silk, bamboo, jute plant contributes to the structural application product. This is enhanced with polymeric materials to increase the properties of natural fibres or vice versa. Indirectly, make both of them unique in terms of structural properties. The application can be seen in the manufacturing product, bioplastics, production of paper, furniture materials and more. This article reviews the use of natural fibre in bioplastics and paper applications.

In Malaysia, the demand for agriculture drones is rising rapidly as drones can enlarge the efficiency of the farmer’s production. The agriculture industries in Malaysia are welcoming the drones to assist their work field. The drones used for this sector should be comply by the airworthiness certification as approval to operating the drone. The materials used to build the drone framework necessity to be compatible with Malaysian’s farmer’s expectation as it is light in weight, high intensity, and low in cost. If the structure of each part of the drone is being tested efficiently, a higher stability and high specifications drone can be produced. The materials used for the agriculture drone is one of the most important parts to been focused on. The failure of the drone can highly affect the farmer cost which can cause a harm to the crops in a wide range. Once the crops are totally blemished, it will affect the farmer daily production for their farm. Selecting the suitable materials are needed to enhanced this situation. Carbon fibre and aluminium material are reviewed in this chapter for drone arm application. These two materials have a big potential to employ in drone arm.

Direct conversion process of recycling aluminium chip has recently been applied without the melting process to avoid the disadvantages of present method. Excellent recycling processes need to be focused to expand the contribution of aluminium to the industry. Aluminium recycling saves energy, which benefits both current and future generations. Aluminium matrix composite (AMC) is aluminium produced by the addition of reinforcement that beneficial to improve its physical and mechanical behaviors. Rice husk ash is a potential source of reactive silica in amorphous phase since it is produced through the combustion of rice husk. The AMC was produced using an AA7075 aluminium chip and varying amounts of semi-amorphous rice husk silica (2.5–12.5%) particles with the method of cold compaction. The effect of physical and mechanical properties of semi amorphous rice husk silica reinforced aluminium chip AA7075 was investigated. The highest density value was 2.31 g/cm² at 10 wt% of rice husk silica, while porosity and water absorption were similar. The best composition for hardness is 10 wt% at 68.33 Hv which increased 55.4% from fully aluminium chips specimen. The highest compression strength is 312.63 MPa at 7.5 wt% of rice husk silica. The increasing value of compression strength is 6.68% from fully aluminium chips specimen.

Nowadays, pineapple leaves are commonly known as a waste product from pineapple cultivation. Therefore, this paper explores the potential of pineapple leaf to be used in polymer composite. This paper investigates the effect of adding pineapple leaf fibre to polypropylene composites using tensile and flexural testing. Pineapple leaf fibre (PALF) and polypropylene (PP) composites were prepared using an injection moulding process by varying the weight percentage (wt.%) of PALF from 2 to 6 wt.%. The results show a significant increase in tensile and flexural properties of PALF/PP composites compared to pure PP composites regardless of PALF weight percentage (wt.%). The experimental results show that composites made from 6%PALF + 94%PP have 6.48% more tensile strength and 11.33% more flexural strength than pure PP composites.

In Malaysia, an abundance of PEFB of biomass waste with the amount of 23 million tonnes is produced annually in landfills. Malaysia’s oil palm sector has grown rapidly because of abundant oil palm biomass and cheap labor cost can be beneficial for bio-product production, thus promoting a green environment. The potential of PEFB as natural fiber for reinforcing materials into LDPE plastic waste to produce a deck panel has sustainable and environmentally friendly properties. The research presents the utilization of deck panels made from Palm Empty Fruit Bunches (PEFB) fiber mixed with Low-Density Polyethylene (LDPE) plastic waste to produce PEFB-LDPE polymer composites. The main objective of this study is to determine the optimum ratio of PEFB fiber mixed LDPE plastic waste to produce PEFB-LDPE polymer composites for deck panel application. To produce PEFB-LDPE polymer composites, the main objective is to determine the optimum ratio of PEFB fibers and LDPE plastic waste into polyurethane resin and hardeners. The preparation of the samples involved the process of grinding PEFB fibers into small particles sizes ranging from 1.30 to 1.50 mm. In the process of mixing at different ratios of PEFB fibers by weight of 0.0, 0.1, 0.2 0.3,0.4, 0.5, and 0.6 (wt/wt) mixed with a constant ratio of 0.2 LDPE plastic waste, the polyurethane resin binder and hardener resin (3:1). The samples of PEFB-LDPE polymer composites will be transferred to 200 mm × 200 mm aluminum by using the close-mold method at room temperature (24 ± 2 °C) for 24 h for the curing process. For tensile results, the ratio PEFB/epoxy resin of 0.3 produces higher tensile strength at 18.18 MPa with stress–strain at 3.28%. Similar to flexural results, the ratio of 0.3 PEFB/epoxy resin at 26.20 MPa. In terms of impact strength, 0.3 PEFB/epoxy resin shows the highest impact at 159.89 J/m with energy absorption at 10.10 kJ/m². It is also supported by compression strength, 0.3 PEFB/epoxy resin reveals a high value at 12.59 MPa. In conclusion, the ratio of 0.3 PEFB/epoxy resin is the optimum composition to be applied to polymer composite applications.

Calcium Carbonate (CaCO₃) is widely used as one of main materials in bone tissue engineering. The use of porous material scaffolds made from bioceramic and polymer components to support bone cell and tissue growth is a longstanding area of interest in biomedical field. The aim of this research is to extract CaCO₃ from cockle shells and analyze the mechanical and physical properties of powder and samples built by mixing CaCO₃ with synthetic polymer High Density Polyethylene (HDPE) to produce stronger and more flexible composite for bone replacement application. Unused cockle shells were collected and cleansed before crushed to make 100 µm-sized CaCO₃ powder. The process of mixing HDPE and CaCO₃ is by using brabender mixing machine in temperature of 170 °C based on differences in their weight percentages. Samples were produced using injection molding method and tested for mechanical testing. The powder and samples were analyzed using SEM, EDX and FTiR analysis to observe the microstructure and content of CaCO₃ as well as the sample structure to determine which ratio sample is the most suitable to be used in the mentioned field. The flexural modulus of the composite from flexural test for sample 1 to sample 3 was between 2.4 and 2.77 GPa while Young’s modulus achieved from tensile test samples was between 0.43 and 0.59 GPa. The impact strength achieved for samples 1–3 was between 0.69 and 0.74 J/mm². Results show the weight percentage of CaCO₃ affected the mechanical and physical strength of samples greatly.