Mechanical Properties Of Fiber-reinforced Composites Research Articles

Effect of Fiber Content on the Mechanical Properties of Jute Fiber Reinforced Perlite/Gypsum Composites

Fiber reinforcement is one of the ways for the improvement of the mechanical properties of composite materials. Previously, it was seen that the fiber content in composites played a vital role in the mechanical properties of fiber-reinforced composites. Considering the benefits of natural fiber, in this work, jute fiber reinforced perlite/gypsum composites were manufactured with five different fiber contents ranging from 2.41 % to 4.82 %. The ratios of gypsum to perlite and gypsum to water were kept constant, and only fiber content was varied. The compression and flexural tests were conducted to investigate the effect of jute fiber content on the mechanical properties of jute fiber-reinforced perlite/gypsum composites. Results showed that both the compressive and flexural properties were improved up to certain jute fiber content. The compressive strength, modulus, and energy absorption of the jute fiber-reinforced composite were found to be the maximum at 3.01 % fiber content. The compressive strength of the composite with 3.01 % jute fiber content was 35.23 % higher than the composite with 2.41 % fiber content. The flexural strength, modulus, and energy absorption were maximum at 3.61 % jute fiber content. This study demonstrated that the addition of jute fiber to perlite/gypsum composites results in improved mechanical properties up to a certain percentage of jute fiber, beyond which the properties deteriorate.

Global sensitivity analysis for degraded braided composite with interval process

Global sensitivity analysis has predominantly focused on examining the effect of time-invariant parameters on the mechanical properties of fiber-reinforced composites, while ignoring degradation. However, fiber-reinforced composites are subject to degradation, which means that the physical system is dynamic. It is important to consider this dynamic behavior in sensitivity analysis. This paper presents a set of sensitivity indices based on the interval method to measure the influence of the time-invariant and time-variant parameters on the synthetic uncertainty of output in global sensitivity analysis for 2D triaxially braided composites (2DTBCs) considering degradation. To achieve this purpose, we represent time-variant uncertain parameter using an interval process and describe them with multiple uncorrelated interval variables using the interval Karhunen-Loève explansion method. We then introduce a two-dimensional interval process and similarity degree to define a new sensitivity index for time-invariant uncertain parameters. For time-variant uncertain parameter, a novel sensitivity index combining multi-dimensional interval process and similarity degree is proposed which considers the synthetic influence of the group of multiple uncorrelated interval variables. Additionally, an efficient sampling-based method is presented to estimate the global sensitivity analysis indices using the Monte Carlo method and Newton-Cotes formula. Finally, the feasibility and potential benefits of the proposed sensitivity indices are demonstrated by applying them to a 2DTBC made of carbon fiber reinforced polyether ether ketone with thermal ageing consideration.

Enhancing the Thermal Comfort of Woven Fabrics and Mechanical Properties of Fiber-Reinforced Composites Using Multiple Weave Structures

In this study, the different effects of weave structure on the comfort properties of fabrics and the mechanical properties of fiber-reinforced composites were investigated. Fabrics were developed using one type of material (flax spun yarn) in the warp direction and three different materials (flax, sisal and cotton spun yarn) in the weft directions. Four different types of weaves (plain, twill, matt and mock leno) were produced in each type of material. Twelve specimens were produced on a sample weaving machine. These fabrics with multiweave combinations give the wearer a comfort zone for sportswear and outdoor applications. These fabrics maintain the temperature of wearers in extreme weather conditions. But these weaves have different effects when interlaced with different types of weft yarns. Air permeability, overall moisture management, stiffness and thermal resistance were investigated for these fabric specimens. The hybrid fabric produced with pure flax warp and weft cotton/sisal exhibited the highest value of air permeability, overall moisture management capability and thermal resistance followed by flax–sisal and flax–flax. The hybrid fabric produced with the mock leno weave also presented a higher value of air permeability compared to the twill, mat and plain weaves. Bending stiffness was observed to be higher in those fabrics produced with flax/sisal compared to pure flax and flax–cotton. The outerwear fabric produced with a blend of flax yarn in the warp and cotton/sisal spun yarn in the weft exhibited improved properties when compared to the fabric produced with flax/sisal and pure flax yarns. In composites, flax/flax showed enhanced mechanical properties, i.e., tensile and flexural strength. In other combinations, the composites with longer weaves possessed prominent mechanical characteristics. The composites with enhanced mechanical properties can be used for window coverings, furniture upholstery and sports equipment. These composites have the potential to be used in automotive applications.

Automated Industrial Composite Fiber Orientation Inspection Using Attention-Based Normalized Deep Hough Network

Fiber-reinforced composites (FRC) are widely used in various fields due to their excellent mechanical properties. The mechanical properties of FRC are significantly governed by the orientation of fibers in the composite. Automated visual inspection is the most promising method in measuring fiber orientation, which utilizes image processing algorithms to analyze the texture images of FRC. The deep Hough Transform (DHT) is a powerful image processing method for automated visual inspection, as the “line-like” structures of the fiber texture in FRC can be efficiently detected. However, the DHT still suffers from sensitivity to background anomalies and longline segments anomalies, which leads to degraded performance of fiber orientation measurement. To reduce the sensitivity to background anomalies and longline segments anomalies, we introduce the deep Hough normalization. It normalizes the accumulated votes in the deep Hough space by the length of the corresponding line segment, making it easier for DHT to detect short, true “line-like” structures. To reduce the sensitivity to background anomalies, we design an attention-based deep Hough network (DHN) that integrates attention network and Hough network. The network effectively eliminates background anomalies, identifies important fiber regions, and detects their orientations in FRC images. To better investigate the fiber orientation measurement methods of FRC in real-world scenarios with various types of anomalies, three datasets have been established and our proposed method has been evaluated extensively on them. The experimental results and analysis prove that the proposed methods achieve the competitive performance against the state-of-the-art in F-measure, Mean Absolute Error (MAE), Root Mean Squared Error (RMSE).

Interplay of manufacturing-induced thermal residual stresses and microvoids in damage and failure of fiber-reinforced composites

Fiber-reinforced composites have inherent thermal residual stresses (TRS) and microvoids that are both generated during the manufacturing process. While the two factors are naturally included in experimental measurements as they preexist in the specimens for testing, theoretical and computational modeling of composites usually neglect these two or include only one. Such simplifications inevitably introduce errors to the predicted mechanical properties of composites, which may further influence the reliability of subsequent modeling and design efforts. Using a micromechanics-based failure modeling approach, this work investigates the effects of both TRS and microvoids on the mechanical properties of fiber-reinforced composites. The TRS is generated when composites are cooled down from the curing temperature. The microvoids are assumed to take realistically existing circular, triangular, square, and pentagonal shapes. Damage progression is systematically studied in six representative loading modes, five voids, and two TRS conditions. All results are statistically extracted to account for geometric uncertainties. The study unravels the interplay of TRS and microvoids in determining the mechanical properties of composites along with the corresponding failure mechanisms. This investigation provides high-fidelity predictions and theoretical insights to improve our understanding of TRS and microvoids in composites, mitigate their impacts, and guide future modeling and design efforts.

Experimental investigation on mechanical properties of Ramie, Hemp fiber and coconut shell particle hybrid composites with reinforced epoxy resin

This paper presents the study of the mechanical characterization of the Ramie, Hemp fibers and coconut shell particle reinforced with epoxy hybrid composites. The Ramie and Hemp fibers will be canned with alkali NaOH (5%) at distinct treatment times. Composite laminates were developed through the compression moulding technique with Ramie and Hemp fibre treated conditions with different Weight fraction of fibers as 30 wt% addition of coconut shell with epoxy resin and hardener. The fabricated samples are prepared as per ASTM standards. The prepared samples were further studied under different conditions to know its mechanical properties such as tensile test, impact test, flexural test and water absorption test. It is conveyed that properties of epoxy composites were improved by hybridization with Ramie and Hemp fibers. The improved mechanical properties of fiber-reinforced composites were noticed in increment of percentage composition of Hemp fibers.

Enhanced mechanical properties in Cf/LAS composite with yolk-shell structure interface

A new approach to improve the interfacial matching of carbon fiber-reinforced lithium-aluminum-silicon(Cf/LAS) composites is proposed, which is achieved by Ni nanoparticles catalyzing the formation of a tunable graphite layer on the surface of Cf. The interfacial structure between the composites can be effectively improved by tuning parameters such as Ni2+ content and sintering holding time, and ultimately, the mechanical properties of the composites can be improved. Interestingly, due to the introduction of Ni2+, a yolk-shell type graphite layer is formed between the Cf and LAS, and the bridging effect of the graphite layer improves interfacial bonding. The highest flexural strength (515 ± 30 MPa) and fracture toughness (14.7 ± 1.6 MPa·m1/2) were obtained. Taking Cf/LAS as an example, the relationship between interfacial matching and mechanical properties of composites is systematically investigated and may provide a new idea for the improvement of mechanical properties of fiber-reinforced composites.

Electrostatic incitation on fiber surface for enhancing mechanical properties of fiber-reinforced composite

The excellent wettability contributes to the formation of mechanical interlocking morphologies at the interface as well as to the reduction of the internal defects in the composite for enhancing the mechanical properties of the fiber-reinforced composites. Herein, a facile and effective electrostatic method is proposed, where a small proportion of negative charges are merely sprayed on the fiber surface to modulate wettability. The results revealed that negatively charged fibers exhibit superior wettability for resin. Furthermore, the interfacial shear strength (IFSS) of the electrostatically treated T800H carbon fiber (T800H-ES)-based composite is 29.9% higher than that of the untreated-fiber composites. The improvement in interfacial properties is mainly ascribed to the formation of mechanical interlocking induced by surface charge-triggered Cassie-Baxter (CB) to Wenzel (WZ) transition of a liquid resin on the fiber surface, as verified by molecular dynamics (MD) simulations of carbon fiber–resin interfacial wetting. In addition, T800H-ES based composite has a 41.2% increase in tensile strength, a 22.5% increase in interlaminar shear strength (ILSS), and a 100.5% increase in fracture energy compared to as-received composite. These increases were mainly attributed to the improved interfacial adhesion and the reduction in internal composite defects. Consequently, this study reveals that the electrostatic charge-assisted wetting method is a green, cost-effective, and promising method for preparing composites with outstanding interfacial characteristics and mechanical properties.

Evaluation the interface damage influences on mechanical properties of fiber-reinforced composites based on subdomain boundary element theory

In this paper, a novel microscopic method is presented to investigate the effective mechanical properties and local stress distribution of the composites with respect to some specific interfacial cracks. To this end, a subdomain boundary element method (SBEM) is combined with the asymptotic homogenization theory to calculate their effective mechanical properties. In order to accurately capture the stress distribution on the boundary and inside points (Gaussian integral points) of representative volume element (RVE), the parametric sub-cell is firstly constructed to discretize the RVE. On this basis, a node-pair decoupling method is introduced with consideration of unilateral and bilateral damage. The influence on mechanical properties of composites is revealed, which provides a solid foundation for the design and manufacture of the composite interface.

Binocular Vision-Based Yarn Orientation Measurement of Biaxial Weft-Knitted Composites.

The mechanical properties of fiber-reinforced composites are highly dependent on the local fiber orientation. In this study, a low-cost yarn orientation reconstruction approach for the composite components’ surface was built, utilizing binocular structured light detection technology to accomplish the effective fiber orientation detection of composite surfaces. It enables the quick acquisition of samples of the revolving body shape without blind spots with an electric turntable. Four collecting operations may completely cover the sample surface, the trajectory recognition coverage rate reached 80%, and the manual verification of the yarn space deviation showed good agreement with the automated technique. The results demonstrated that the developed system based on the proposed method can achieve the automatic recognition of yarn paths of views with different angles, which mostly satisfied quality control criteria in actual manufacturing processes.

High-Performance Dental Composites Based on Hierarchical Reinforcements

Use of high-performance fibers such as poly(p-phenylene-2,6-benzobisoxazole) (PBO) improves the mechanical properties of dental fiber-reinforced composites (FRCs). However, the surfaces of high-performance fibers are relatively inert, and the interface with the resin matrix is poor. This has become a limitation restricting the performance of PBO FRCs in dentistry. Nanomaterials were introduced onto PBO fibers to construct various hierarchical reinforcements to obtain a dental FRC with higher flexural performance and optimized interface bonding. Four hierarchical reinforcements were constructed: PBO-ZnO nanoparticles (NPs), PBO-ZnO nanowires (NWs), PBO-ZnO NPs–cage silsesquioxane (POSS), and PBO-ZnO NWs-POSS. Performance following this optimized method was evaluated at macroscale and microscale levels, including measurement of the interfacial properties and mechanical properties of FRCs. The physicochemical characteristics of PBO fibers before and after modification were measured to determine the interfacial bonding mechanisms and to verify the connection between the microinterface and macromechanical properties. The cytotoxicity of the preferred PBO FRC was evaluated using the CCK8 assay. In comparison to other designs, the interfacial shear strength (IFSS) of PBO-ZnO NWs-POSS was the highest (29.31 ± 2.40 MPa). The corresponding FRC had the highest flexural strength under a static load (925.0 ± 39.2 MPa), the flexural modulus (39.39 ± 1.41 GPa) was equivalent to that of human dentin, and in vitro cytotoxicity was acceptable. The interfacial bonding mechanisms of PBO-ZnO NWs-POSS resulted from mechanical interlocking, chemical bonds, hydrogen bonds, and van der Waals forces. In summary, the PBO-ZnO NWs-POSS hierarchical reinforcement was introduced in dental FRCs and showed remarkable enhancement of the IFSS and flexural properties. We verified that the PBO-ZnO NWs-POSS hierarchical reinforcement was successful. This PBO FRC may be applied in dentistry as a new option for endodontic posts. Our study provides an interface design strategy for developing high-performance FRCs reinforced with high-performance fibers for dental applications.

Enhanced interfacial shear strength in ultra-high molecular weight polyethylene epoxy composites through a zinc oxide nanowire interphase

The mechanical properties of fiber-reinforced composites are largely dictated by fiber-matrix interactions, where a well-adhered interface is desired. Ultra-high molecular weight polyethylene (UHMWPE) fibers suffer from poor interfacial properties due to their smooth and inert surface. Therefore, enhancing the interfacial properties of such composites will lead to an increased use in structural applications where high modulus, tenacity, low density, high impact and abrasion resistance properties are needed. In this work, an interfacial modification process consisting of an oxygen plasma surface functionalization followed by the grafting of zinc oxide nanowires (ZnO NWs) onto the UHMWPE fiber surface is investigated to improve the fiber-matrix interaction in UHMWPE composites. The UHMWPE fiber surface is subjected to varying oxygen plasma treatment durations such that the surface oxygen content can be increased to improve ZnO NW adhesion. Through single fiber pullout testing, the interfacial shear strength (IFSS) of oxygen plasma functionalized and ZnO NW coated UHMWPE fibers was shown a maximum increase of 135% with a 30 s plasma treatment prior to ZnO NWs. This increase in IFSS is attributed to an increased surface area interaction and mechanical interlocking between the fiber and matrix. The results detailed in this work demonstrate a benign, simple, and effective way to significantly improve the interfacial properties of UHMWPE fiber reinforced composites.

Synthesis of a self-assembly amphiphilic sizing agent by RAFT polymerization for improving the interfacial compatibility of short glass fiber-reinforced polypropylene composites

This experimental study focuses on the development of an amphiphilic sizing agent to improve the interfacial adhesion and the mechanical properties of short glass fiber (GF)/polypropylene (PP) composites. To solve the critical compatible issue between the hydrophilic GF and the hydrophobic PP, we strategically utilized the reversible addition-fragmentation chain-transfer (RAFT) polymerization to self-assemble and synthesize an amphiphilic sizing agent. This surfactant-free sizing agent can create hydrogen bonds and electrostatic adsorption on GF surfaces and meanwhile can form molecular entanglements, alkyl cations, and σ-π conjugates with PP matrix. The FT-IR analysis shows that a large number of hydrogen bonds are formed on the sizing agent-GF interface. Additionally, the SEM micrographs of the composite fracture surfaces demonstrate strong interfacial compatibility between the sized-GF and the PP matrix. Comparing with the neat GF/PP composites, the tensile and flexural strength of the sized-GF/PP composites are increased by 25.8% and 33.1%, respectively. Their tensile strength and young's modulus are in close agreement to the analytical calculations. In short, this paper presents a new RAFT-based methodology to develop the amphiphilic sizing agents that are able to improve the interfacial compatibility of GF/PP composites and also can be transferred towards real applications for enhancing the mechanical properties of fiber-reinforced composites.

Comprehensive investigation of mechanical and thermal properties of vetiver grass and red mud reinforced hybrid composites

ABSTRACT The study deals with the mechanical and thermal characterization of novel composite consisting of vetiver grass fiber (Chrysopogon zizanioides) (VF) and red mud (RM) as reinforcement in epoxy resin. Five types of composites were fabricated using hand lay-up technique by varying the weight percentage (wt%) of vetiver grass and red mud. Various mechanical properties like tensile strength, impact strength, and flexural strength of the said composites were evaluated and discussed. The thermal properties in terms of thermo gravimetric analysis (TGA) were evaluated whereas the chemical composition characteristics were analyzed using FTIR and XRD spectroscopy. The fractured surfaces of the tested specimens were studied using a scanning electron microscope. From the results, it was observed that properties of polymer composites were improved by hybridization with vetiver grass fibers and red mud. The improved mechanical properties of fiber-reinforced composites were noticed in increment of wt% of red mud. Highest tensile strength of 51.78 MPa, flexural strength of 35.92 MPa and impact strength of 29 KJ/m2 was obtained for C5 composite which contains highest wt% of red mud. TGA shows better resistance to thermal degradation for the composites containing higher percentage of red mud. Looking at the results it can be concluded that the developed composites in this work can be an efficient alternative for building and automotive application which requires high strength and thermal stability.

EFFECTIVE DISSIPATIVE PROPERTIES OF A WHISKERED LAYER IN MODIFIED FIBROUS COMPOSITES WITH WHISKERED FIBRES

It is known that the mechanical properties of fiber-reinforced composites are controlled by the conditions of contact between the fiber and the matrix. In this regard, great efforts of mechanics are directed to developing various techniques to improve the quality of the interface. The most common are: modification of the fiber surface, improvement of chemical interactions, or the addition of a third phase (interfacial layer) between the fiber and the matrix. The most common are: modification of the fiber surface, improvement of chemical interactions, or a third phase (interfacial layer) between the fiber and the matrix. In this study, the authors aim to examine the effective dynamic properties of a whiskered layer of fibers in modified composites, taking into account the structural characteristics of the interfacial layer – its thickness – length of whiskers, volumetric content of whiskers, and their mechanical properties. The dynamic performance of the whiskered layer surrounding the base fiber in modified composites was estimated. The whiskered layer is considered a fibrous composite formed by nanoscale whiskers grown on the surface and a matrix. An epoxy binder or a viscoelastic polymer is considered as a matrix. An approximate model was used. The effective characteristics of the whiskered layer were modeled and determined as the properties of a transversally isotropic fibrous system with the isotropy axis coinciding with nanowhiskers in the whiskered layer. A feature of the whiskered layer is that the density of whiskers varies with distance from the fiber surface. Therefore, it depends on the length of the nanowhiskers (the thickness of the interfacial layer). In this case, it turns out that the bulk for the matrix in the whiskered layer, even at the maximum density of nanowhiskers grown on the fiber surface and for sufficiently thin interfacial layers, is very significant. Fuzzy fiber composite, nanofibers, epoxy binder, damping properties.

Mitigations of machine-damaged free-edge effects on fiber-reinforced composites

The carbon fiber-reinforced composites were prepared in a vacuum oven using pre-preg composites, and the edge surfaces of the composite coupons were treated using high performing adhesives to eliminate the free-edge effects. The primary objective of the study was to usefully address the free-edge effects of composites used in aircraft and other manufacturing industries. The mechanical test results conducted on the untreated and edge-treated test coupons showed that the edge treatment and fiber orientations significantly affected the tensile strength and quality of the composites. It is determined that applying adhesives on the edges of the coupons could improve the mechanical properties of the composites, about 11%. Successful testing and evaluation of materials can lead to the precise analysis of a structure, and predictable behavior of the end design. This study may open up new possibilities to enhance the overall mechanical properties of fiber-reinforced composites for various manufacturing industries.

Viscoelastic characteristics of carbon fiber-reinforced epoxy filament wound laminates

The mechanical properties of fiber-reinforced composites are time-dependent due to the viscoelastic nature of polymers. This study covers the creep/recovery and dynamic mechanical properties of high-performance composites under low-stress loading. Flat unidirectional 6-layer laminates are manufactured by dry-filament winding and cured under hot compression. Four different laminates are studied: [0]6, [30]6, [60]6, and [90]6. Dynamic mechanical curves and creep behavior are highly dependent on the ply angle up to 60°. The fiber orientation does not influence significantly the glass transition temperature, except for the [0]6 laminate, which has a higher Tg compared to the other samples. Normalized dynamic mechanical curves are plotted aiming to study the behavior of the material passing through the glass transition temperature (Tg). The modulus decreases for fiber angles toward the transverse direction, but the energy dissipation occurs in a broader temperature range. Creep/recovery also demonstrates a dependency on the fiber orientation, in which the sample [0]6 (highest storage modulus) has the lowest strain, leading to higher molecular hindrance compared to the other laminates.

Covalent functionalization of aramid fibers with zinc oxide nano-interphase for improved UV resistance and interfacial strength in composites

Improving the resistances of organic high-performance fibers to harsh environments and enhancing the interfacial interactions of fiber-reinforced composites have become crucial in various applications. In this report, ZnO nanoparticles (NPs) and ZnO nanowires (NWs) were successfully “grown” on the surfaces of aramid fibers (AFs) by grafting with γ-aminopropyl triethoxysilane (KH550) followed by the growth of nano-ZnO. The surface functionalized AFs exhibited improved UV-resistances. After 168 h of ultraviolet exposure, the tensile retention rates of the ZnO-NP- and ZnO-NW-grafted AFs reached 95.6% and 97.7%, respectively, which were significantly higher than the value of 79.1% of the bare fiber. Meanwhile, the introduction of the KH500 and ZnO formed a nano-interphase, enhancing the interfacial strength of the fiber-reinforced epoxy resin composites. The interfacial shear strengths (IFSSs) of the composites with AF-g-ZnO NPs and AF-g-ZnO NWs were 42.9 and 47.8 MPa, respectively, whereas that of bare AF-reinforced epoxy resin was only 31.2 MPa. Nano-ZnO was physically deposited on the AF surfaces without KH550. The IFSS was 36.4 MPa for the AF-ZnO NP and 38.8 MPa for the AF-ZnO NW, which were lower than those of the grafted composites. Therefore, the chemical grafting nano-ZnO on high-performance fibers provides a new strategy for improving the UV-resistances of advanced fibers and to enhance the mechanical properties of fiber-reinforced composites.

Extraction and characterization of vetiver grass (Chrysopogon zizanioides) and kenaf fiber (Hibiscus cannabinus) as reinforcement materials for epoxy based composite structures

The study deals with the mechanical characterization of vetiver grass fiber and kenaf fiber reinforced epoxy-based hybrid composites. Five types of composite laminates were developed through the hand lay-up process by varying the percentage of vetiver grass and kenaf fibers. The tensile, flexural, compression and impact tests were conducted as per ASTM. The fractured surfaces of the tested specimens were studied using a scanning electron microscope. From the results, it was shown that properties of epoxy composites were improved by hybridization with vetiver grass and kenaf fibers. The improved mechanical properties of fiber-reinforced composites were noticed in increment of percentage composition of kenaf fibers.

Size Effect on Microbond Testing Interfacial Shear Strength of Fiber-Reinforced Composites

Microbond tests have been widely used for studying the interfacial mechanical properties of fiber-reinforced composites. However, experimental results reveal that the interfacial shear strength (IFSS) depends on the length of microdroplet-embedded fiber (le). Thus, it is essential to provide an insight into this size effect on IFSS. In this paper, microbond tests are conducted for two kinds of widely used composites, i.e., glass fiber/epoxy matrix and carbon fiber/epoxy matrix. The lengths of microdroplet-embedded glass fiber and carbon fiber are in the ranges from 114.29 µm to 557.14 µm and from 63.78 µm to 157.45 µm, respectively. We analyze the representative force–displacement curves, the processes of interfacial failure and frictional sliding, and the maximum force and the frictional force as functions of le. Experimental results show that IFSS of both material systems monotonically decreases with le and then approaches a constant value. The finite element model is used to analyze the size effect on IFSS and interfacial failure behaviors. For both material systems, IFSS predicted from simulations is consistent with that obtained from experiments. Moreover, by analyzing the shear stress distribution, a transition of interface debonding is found from more or less uniform separation to crack propagation when le increases. This study reveals the mechanism of size effect in microbond tests, serving as an effective method to evaluate the experimental results and is critical to guidelines for the design and optimization of advanced composites.