Assessment Of Fiber Orientation Research Articles

Fast characterization of in-plane fiber orientation at the surface of paper sheets through image analysis

The in-plane fiber orientation distribution has a decisive impact on paper mechanical and dimensional properties (e.g., tensile stiffness, hygroexpansion). It is usually estimated offline through relatively expensive bench instrumentation such as diffusion-based optical methods and ultrasonic devices. In this work we present an alternative methodology that is fast, portable, inexpensive and able to provide the complete surface polar fiber orientation profile. The proposed technology combines an image acquisition setup, consisting of a digital camera with a low angle illumination system, with the gradient-segmentation method (GSM), a robust image analysis algorithm. This camera-GSM methodology presented high internal consistency, accurately identifying the angles of samples subjected to known rotations at the imaging step. The methodology also produced comparable results to the TSO (tensile stiffness orientation) technique, used as reference. The methodology is easily transferable to plant operation, including for the online assessment of fiber orientation.

Self‐compacting high performance fiber concrete for foundations: Part 2—Fiber orientation and distribution

AbstractAn investigation was executed into the applicability of self‐compacting high performance fiber concrete in foundations. The applied concrete has a concrete cube strength of about 110 MPa and contains 60 kg/m3 hooked‐end steel fibers (LF = 30 mm, DF = 0.38 mm). This publication consists of two parts: (1) Experimental assessment and verification of design rules and (2) assessment of fiber orientation and distribution. In the first part, experiments are described which were carried out to determine the pre‐ and post‐cracking strength properties, the shear resistance of short beams, the anchorage length of rebars, and the shear capacity of foundation slabs supported on piles. The test results were used for a verification and extension of design rules for fiber reinforced concrete (FRC) found in the fib Model Code 2010. The application of the FRC developed can lead to substantial savings in concrete and reinforcing steel. In the present second part, cross‐sections of two slabs and a beam of this testing series have been analyzed with regard to fiber orientation and distribution. An image analysis, executed on 111 concrete areas, indicates that a preferred fiber orientation could not be identified throughout the assessed elements. The data supports the conclusion of a good fiber distribution as well; a strong correlation was obtained for the data set of full images between measured and theoretical relation of fiber orientation and fiber density.

Phase-contrast and dark-field imaging for the inspection of resin-rich areas and fiber orientation in non-crimp vacuum infusion carbon-fiber-reinforced polymers

In this work, we present a multimodal approach to three-dimensionally quantify and visualize fiber orientation and resin-rich areas in carbon-fiber-reinforced polymers manufactured by vacuum infusion. Three complementary image modalities were acquired by Talbot–Lau grating interferometer (TLGI) X-ray microcomputed tomography (XCT). Compared to absorption contrast (AC), TLGI-XCT provides enhanced contrast between polymer matrix and carbon fibers at lower spatial resolutions in the form of differential phase contrast (DPC) and dark-field contrast (DFC). Consequently, relatively thin layers of resin, effectively indiscernible from image noise in AC data, are distinguishable. In addition to the assessment of fiber orientation, the combination of DPC and DFC facilitates the quantification of resin-rich areas, e.g., in gaps between fiber layers or at binder yarn collimation sites. We found that resin-rich areas between fiber layers are predominantly developed in regions characterized by a pronounced curvature. In contrast, in-layer resin-rich areas are mainly caused by the collimation of fibers by binder yarn. Furthermore, void volume around two adjacent 90°-oriented fiber layers is increased by roughly 20% compared to a random distribution over the whole specimen.

Assessment of Fiber Orientation on the Mechanical Properties of PA6/Cellulose Composite

Cellulose is being considered as a suitable renewable reinforcement for materials production. In particular, cellulose based composites are attracting global interest for their unique and intrinsic properties such as strength to weight ratio, dimensional stability and low thermal expansion and contraction. This article investigates the preparation of cellulose pulp fibers with polyamide-6 (PA6) polymer and the effect of fiber orientation within the matrix on the final properties of the biocomposite. Cellulose pulp fibers were melt compounded with PA6 using a thermo-kinetic mixer. Different formulations were prepared and the compounds were manufactured into test samples by injection molding. Mechanical characterization revealed that elastic modulus and the flexural properties increased linearly with the fiber composition. The effect of fiber orientation was examined from square samples out of which individual specimens were cut at different directions with respect to the flow direction. The contributions related to fiber content and effect of fiber orientation on the tensile properties assessed lent positively towards parallel oriented samples (0°) with respect to flow direction. Furthermore, the cellulose network within the biocomposite revealed the superior interfacial properties between the cellulose and PA6 matrix when observed under a scanning electron microscope.

Process characterization for molding of paper bottles using computed tomographyand structure tensor analysis

Packaging products find their significance in almost all classes of consumer goods and products. The use of plastic and metal based packaging for beverages is highly dominant. However, there is a constant urge for development of eco-friendly packaging alternatives. The paper focuses on characterizing an inflatable core assisted paper bottle molding process with respect to the obtained fiber distribution in the bottle. Distribution of paper fibers affect product characteristics such as thickness and mechanical strength of the bottle. Assessment of fiber orientation using structure tensor analysis is therefore performed. The results confirmed non-uniform fiber compaction in the paper bottle. This gives rise to non-conformities such as non-uniform thickness distribution. The approach discussed in the work can be used as a Non Destructive Testing technique to evaluate the quality of paper bottles.

Comparative study on point and line thermographic inspection for fiber orientation assessment of randomly oriented strand material

Composite materials are being successfully used in aeronautics for more than two decades. This great success is mainly because this kind of materials is typically lighter when compared to metals and more resistant to corrosion. Resistance and stiffness of composite materials are usually related to their fiber orientation. The development of non-destructive methods is required to assess this kind of property without damaging the sample. In this work, a non-destructive method based on infrared thermography is presented for fiber orientation assessment. More specifically, two approaches are presented and results are compared for fiber orientation assessment of randomly oriented strand parts. The first one is a point-by-point inspection based on pulsed thermal ellipsometry and the second one is a line approach based on flying laser spot inspection combined with neural artificial networks. Results showed that the second approach provides similar accuracy when compared to the first one; however, it is much faster which makes the second approach very interesting for industrial applications.

Machine Learning and Infrared Thermography for Fiber Orientation Assessment on Randomly-Oriented Strands Parts.

The use of fiber reinforced materials such as randomly-oriented strands has grown in recent years, especially for manufacturing of aerospace composite structures. This growth is mainly due to their advantageous properties: they are lighter and more resistant to corrosion when compared to metals and are more easily shaped than continuous fiber composites. The resistance and stiffness of these materials are directly related to their fiber orientation. Thus, efficient approaches to assess their fiber orientation are in demand. In this paper, a non-destructive evaluation method is applied to assess the fiber orientation on laminates reinforced with randomly-oriented strands. More specifically, a method called pulsed thermal ellipsometry combined with an artificial neural network, a machine learning technique, is used in order to estimate the fiber orientation on the surface of inspected parts. Results showed that the method can be potentially used to inspect large areas with good accuracy and speed.

Nondestructive testing based on scanning-from-heating approach: application to nonthrough defect detection and fiber orientation assessment

Today, industries ensure the quality of their manufactured products through computer vision techniques and nonconventional imaging. Three-dimensional (3-D) scanners and nondestructive testing (NDT) systems are commonly used independently for such applications. Furthermore, these approaches combined constitute hybrid systems, providing a 3-D reconstruction and NDT analysis. These systems, however, suffer from drawbacks such as errors during the data fusion and higher cost for manufacturers. In an attempt to solve these problems, a single active thermography system based on scanning-from-heating is proposed in this paper. In addition to 3-D digitization of the object, our contributions are twofold: (1) the nonthrough defect detection for a homogeneous metallic object and (2) fiber orientation assessment for a long fiber composite material. The experiments on steel and aluminum plates show that our method achieves the detection of nonthrough defects. Additionally, the estimation of the fiber orientation is evaluated on carbon-fiber composite material.

Fiber orientation assessment on randomly-oriented strand composites by means of infrared thermography

In this paper, an infrared thermography technique is used to assess the fiber orientation on the surface of carbon fiber reinforced polymer (CFRP) moulded with randomly-oriented strands (ROS). Due to the randomness of the material, a point by point inspection would be very time consuming. In this paper it is proposed to use a flying laser spot technique to heat a line-region on the surface of the sample instead of a spot. During our experiments, a flying laser spot inspection was performed in 30 s while a point by point inspection of the same area would require about 25 min. An artificial neural network (ANN) was then used to estimate the fiber orientation over the heated line. The classification rate obtained with the network was 91.2% for the training stage and 71.6% for the testing stage.

An active infrared thermography method for fiber orientation assessment of fiber-reinforced composite materials

Fiber orientation in composite materials is an important feature since the arrangement or orientation of the fibers relative to one another has a significant influence on the strength and other properties of fiber reinforced composites. In this paper we present a method to assess the fiber orientation on the surface of carbon fiber reinforced polymer (CFRP) laminates. More specifically, a diode-laser beam is used to locally heat a small spot on the surface of the sample. Observation of the heat pattern in the infrared spectrum enables the assessment of the fiber orientation. Different samples and different regions on the surface of the samples are tested in order to estimate the precision of the method.

Fiber orientation assessment in complex shaped parts reinforced with carbon fiber using infrared thermography

The use of composite materials is growing more and more every day in several applications. The arrangement or orientation of the fibers relative to one another have a significant influence on the strength and other properties of fiber reinforced composites. Thus, evaluation techniques are needed for measuring material fiber orientation. In this work infrared thermography is employed to assess the material’s fiber orientation. More specifically a pulsed infrared diode laser heating spot technique combined with a 3D model of the part is used in order to assess fiber orientation on the surface of carbon fiber-reinforced polymer complex shaped parts made of carbon/PEEK (Polyether ether ketone) randomly-oriented strands.