Simulation of Long Semi-Flexible Fiber Orientation During Injection Molding

2016 ◽  
Author(s):  
Hongyu Chen ◽  
Peter Wapperom ◽  
Donald G. Baird
Keyword(s):  
Mechanical Properties ◽  
Injection Molding ◽  
Fiber Orientation ◽  
Fiber Length ◽  
Simple Shear Flow ◽  
Orientation Model ◽  
Rod Model ◽  
Flexible Fibers ◽  
Rigid Rod ◽  
Long Fibers

Fiber orientation simulation is conducted for the Center-Gated-Disk (CGD) geometry and compared with experimental data. Long-fiber thermoplastic composites (LFTs) possess competitive advantages over short glass fiber composites in terms of their mechanical properties while retain the ability to be injection molded. Mechanical properties of LFTs are highly dependent on the microstructural variables imparted by the injection molding process including fiber orientation and fiber length distribution. As the fiber length increased, the mechanical properties of the composites containing discontinuous fibers can approach those of continuous fiber materials. Several researchers have reported that flexural, creep and charpy impact properties increase as fiber length increases, while tensile modulus will plateau for glass fibers above 1 mm in length. Fibers less than the 1 mm threshold have been considered to be short while fibers with lengths greater than 1 mm are considered long. For long fibers, they will have the ability to deform, bend and even break during any stage of polymer processing. There is a lack of knowledge about the effects of fiber length and fiber length variation on fiber orientation kinetics. This lack of information provides an opportunity to understand the length effect inherent to long fibers systems. The Bead-Rod fiber orientation model takes into account the flexibility of semi-flexible fibers that show small bending angles. In this model, a flexibility parameter representing the resistive bending potential is fiber length dependent (detailed explanation can be found in the reference)1. This work is concerned with the effect of fiber length on the performance of the Bead-Rod fiber orientation model which takes into account the flexibility of semi-flexible fibers. Different averaging techniques are used to represent the average fiber length for the population of fibers, which give different fiber length parameters for the Bead-Rod model. The sensitivity of the Bead-Rod model is evaluated with regard to the fiber flexibility parameter, k, and length parameter, lb. The other phenomenal parameters within the orientation model are obtained via basic rheological measurements using simple shear flow. As the value of average fiber length Lav increases and the corresponding flexibility parameter value decreases, the core regions become wider and the flow direction orientation gradually decreases especially near the walls for the Bead-Rod model predictions. In addition, as the parameters favor longer fiber lengths, the predicted extent of fiber bending increases. The simulation results are also compared with the experimental obtained fiber orientation at different flow length along the thickness direction. The Bead-Rod model shows improvement over the rigid rod model.

scholarly journals Calibration of Fiber Orientation Simulations for LFT—A New Approach

2020 ◽  
Vol 4 (4) ◽  
pp. 163
Author(s):  
Fabian Willems ◽  
Philip Reitinger ◽  
Christian Bonten
Keyword(s):  
Mechanical Properties ◽  
Injection Molding ◽  
Process Simulation ◽  
Fiber Orientation ◽  
Model Parameters ◽  
Fiber Reinforced ◽  
Orientation Model ◽  
Fiber Microstructure ◽  
Reinforced Thermoplastics ◽  
Fiber Reinforced Thermoplastics

Short fiber reinforced thermoplastics (SFT) are extensively used due to their excellent mechanical properties and low processing costs. Long fiber reinforced thermoplastics (LFT) show an even more interesting property profile and are increasingly used for structural parts. However, their processing by injection molding is not as simple as for SFT, and their anisotropic properties resulting from the fiber microstructure (fiber orientation, length, and concentration) pose a challenge with regard to the engineering design process. To reliably predict the structural mechanical properties of fiber reinforced thermoplastics by means of micromechanical models, it is also necessary to reliable predict the fiber microstructure. Therefore, it is crucial to calibrate the underlying prediction models, such as the fiber orientation model, within the process simulation. In general, these models may be adjusted manually, but this is usually ineffective and time-consuming. To overcome this challenge, a new calibration method was developed to automatically calibrate the fiber orientation model parameters of the injection molding simulation by means of optimization methods. This optimization routine is based on experimentally determined fiber orientation distributions and leads to optimized parameters for the fiber orientation prediction model within a few minutes. To better understand the influence of the model parameters, different versions of the fiber orientation model, as well as process and material influences on the resulting fiber orientation distribution, were investigated. Finally, the developed approach to calibrate the fiber orientation model was compared with a classical approach, a direct optimization of the whole process simulation. Thereby, the new optimization approach shows a calculation time reduced by the factor 15 with comparable error variance.

Process comparison on the microstructure and mechanical properties of fiber-reinforced polyphenylene sulfide using MuCell technology

2018 ◽  
Vol 37 (15) ◽  
pp. 1020-1034 ◽  
Author(s):  
Christoph Lohr ◽  
Björn Beck ◽  
Frank Henning ◽  
Kay André Weidenmann ◽  
Peter Elsner
Keyword(s):  
Mechanical Properties ◽  
High Pressure ◽  
Injection Molding ◽  
Fiber Orientation ◽  
Polyphenylene Sulfide ◽  
Injection Molding Process ◽  
Fiber Reinforced ◽  
Molding Process ◽  
Glass Fiber Reinforced ◽  
Foam Injection Molding

The MuCell process is a special injection molding process which utilizes supercritical gas (nitrogen) to create integral foam sandwiches. The advantages are lower weight, higher specific properties and shorter cycle times. In this study, a series of glass fiber-reinforced polyphenylene sulfide foam blanks are manufactured using the MuCell injection molding process. The different variations of the process (low-pressure also known as structural foam injection molding) and high-pressure foam injection molding (also known as “core back expansion,” “breathing mold,” “precision opening,” decompression molding) are used. The sandwich structure and mechanical properties (tensile strength, bending strength, and impact behavior) of the microcellular and glass fiber-reinforced polyphenylene sulfide foams are systematically investigated and compared to compact material. The results showed that the injection parameters (injection speed, foaming mechanism) played an important role in the relative density of microcellular polyphenylene sulfide foams and the mechanical properties. It could be shown that the specific tensile strength decreased while increasing the degree of foaming which can be explained by the increased number of cells and the resulting cell size. This leads to stress peaks which lower the mechanical properties. The Charpy impact strength shows a significant dependence on the fiber orientation. The specific bending modulus of the high-pressure foaming process, however, surpasses the values of the other two processes showing the potential of this manufacturing variation especially with regard to bending loads. Furthermore, a high dependence of the mechanical properties on the fiber orientation of the tested specimens can be found.

INJECTION MOLDING OF FLAT GLASS FIBER REINFORCED THERMOPLASTICS

2010 ◽  
Vol 24 (15n16) ◽  
pp. 2555-2560 ◽  
Author(s):  
KAZUTO TANAKA ◽  
TSUTAO KATAYAMA ◽  
TATSUYA TANAKA ◽  
AKIHIRO ANGURI
Keyword(s):  
Mechanical Properties ◽  
Injection Molding ◽  
Glass Fiber ◽  
Cross Section ◽  
Fiber Length ◽  
Flat Glass ◽  
Circular Cross Section ◽  
Fiber Reinforced ◽  
Glass Fiber Reinforced ◽  
Fiber Attrition

During an injection molding of composite materials, fiber attrition occurs and the average fiber length is reduced. In order to control the breakage of fibers and degradation of mechanical properties during processing, Flat glass Fiber (FF), that has oval cross-section shape, has been developed to use for glass fiber reinforced thermoplastic (GFRTP). Using FF as reinforcement of GFRTP has advantages as following: (1) Fluidity of FF is better than conventional Normal glass Fiber (NF) with 'circular' cross-section; (2) Fiber breakage during the injection molding process using FF is smaller than that using NF. In this study, the mechanical properties of FF and NF were compared for reinforcement of long fiber thermoplastics pellets (LFT pellets). We have also investigated the effect of screw design on fiber damage and the mechanical properties. The mechanical properties of specimens molded by FF reinforcement LFT (FF-LFT) pellets were superior to these of NF reinforcement LFT (NF-LFT) pellets. The former could give composites with higher fluidity and longer residual fiber length. Moreover, FF was able to strengthen injection-molded samples with higher fiber content than NF. Low shear type screw was effective to prevent the fiber attrition during plasticization process, hence leads to better mechanical properties of GFRTP

Effect of the initial fiber alignment on the mechanical properties for GMT composite materials

2017 ◽  
Vol 31 (1) ◽  
pp. 91-109 ◽  
Author(s):  
Yuyang Song ◽  
Umesh Gandhi ◽  
Adam Koziel ◽  
Srikar Vallury ◽  
Anthony Yang
Keyword(s):  
Mechanical Properties ◽  
Fiber Orientation ◽  
Fiber Length ◽  
Initial Conditions ◽  
Length Distribution ◽  
Material Model ◽  
Bending Test ◽  
Process Conditions ◽  
Fiber Concentration ◽  
Finished Part

A glass-mat-reinforced thermoplastic (GMT) material is widely used in the automotive industry for components such as underbody shields, seat structures, front/rear bumper, and front-end modulus. Due to the higher residual length of the glass strands, GMT usually offers better mechanical properties than injection-molded fiber-reinforced thermoplastics. The GMT material is typically manufactured by compression molding (CM) of preimpregnated fibers–reinforced resin sheets called mat. Two types of mats, one with discontinuous random (RD) fibers and other with aligned continuous fibers, are considered in this study. A stack of such mats with different combinations is used to tailor the mechanical properties of the final part. During the CM, the fibers in the mat flow with the resin and change the alignment. In this study, we are presenting an approach to account for the initial condition, such as fiber length, orientation and concentration of the fibers in the mat, and process conditions used, to develop a material model for the finished part. First, a stack of mat with known fiber orientation, length, and concentration as initial conditions is simulated for CM to predict the fiber orientation in the finished part. Next, the material model for the finished parts is developed using a Mori–Tanaka homogenization approach. The fiber orientation in the finished part is mapped from the CM simulation. For the fiber concentration and fiber length distribution, we used an empirical approach. The cross section of the finished part is investigated under optical microscope, and the fiber length and concentration are estimated based on the microstructure and initial stacking of mats. The predicted fiber orientation tensor is verified with orientations measured using computerized tomography (CT) scan on actual parts. The material model is verified by comparing the predicted performance with the actual tensile and bending test results.

Mechanical properties and fiber characteristics of glass fiber/carbon fiber reinforced polyethylene terephthalate hybrid composites fabricated by direct fiber feeding injection molding

2018 ◽  
Vol 38 (6) ◽  
pp. 513-523 ◽  
Author(s):  
Wiranphat Thodsaratpreeyakul ◽  
Putinun Uawongsuwan ◽  
Akio Kataoka ◽  
Takanori Negoro ◽  
Hiroyuki Hamada
Keyword(s):  
Mechanical Properties ◽  
Carbon Fiber ◽  
Injection Molding ◽  
Glass Fiber ◽  
Polyethylene Terephthalate ◽  
Fiber Orientation ◽  
Mechanical Performance ◽  
Hybrid Composites ◽  
Fiber Distribution ◽  
Volume Fractions

Abstract Improving the applicability of polyethylene terephthalate (PET) by carbon fiber/glass fiber reinforcement is of great interest. Glass fiber (GF)/carbon fiber (CF)/PET hybrid composites were fabricated by direct fiber feeding injection molding (DFFIM) process. The aim of DFFIM is to obtain longer fibers in composites in order to improve their mechanical properties. In this study, the mechanical properties of GF/PET composites fabricated by conventional injection molding and hybrid GF/CF/PET composites fabricated by DFFIM process were investigated. The influence of GF and CF volume fractions on fiber distribution, fiber orientation, and fiber length is discussed. Fiber distribution status was quantitatively measured by the fiber distribution index. Fiber agglomeration problem was observed by scanning electron microscopy. The results indicate that incorporating CF in GF/CF/PET hybrid composites by the DFFIM process greatly enhances mechanical performance even when only a small amount of CF is added. Too high GF content leads to less effective CF hybridization because it causes poor fiber distribution and poor fiber orientation and intensifies fiber attrition. The ideal volume fractions of GF and CF for fabricating GF/CF/PET hybrid composites by using DFFIM are provided.

scholarly journals The Low Breaking Fiber Mechanism and Its Effect on the Behavior of the Melt Flow of Injection Molded Ultra-Long Glass Fiber Reinforced Polypropylene Composites

Polymers ◽  
2021 ◽  
Vol 13 (15) ◽  
pp. 2492
Author(s):  
Po-Wei Huang ◽  
Hsin-Shu Peng ◽  
Sheng-Jye Hwang ◽  
Chao-Tsai Huang
Keyword(s):  
Injection Molding ◽  
Glass Fiber ◽  
Fiber Length ◽  
Mold Cavity ◽  
Fiber Breakage ◽  
Melt Flow ◽  
Molding Machine ◽  
Glass Fiber Reinforced ◽  
Long Glass Fiber ◽  
Long Fibers

In this study, fiber breaking behavior, fiber orientation, length variation, and changes in melt flow ability of long glass fiber reinforced polypropylene (L-FRP) composites under different mold cavity geometry, melt fill path, and plasticization parameters were investigated. The matrix material used was polypropylene and the reinforcement fibers were 25 mm long. An ultra-long-fiber composite injection molding machine (with a three-stage plunger and injection mechanism design) was used with different mold cavity geometry and plasticization parameters. Different screw speeds were used to explore the changes in fiber length and to provide a reference for setting fiber length and parameter combinations. Flow-length specimen molds with different specimen thickness, melt fill path, and gate design were used to observe the effect of plasticizing properties on the flow ability of the L-FRP composite materials. The experimental results showed that the use of an injection molding machine with a mechanism that reduced the amount of fiber breakage was advantageous. It was also found that an increase in screw speed increased fiber breakage, and 25 mm long fibers were shortened by an average of 50% (to 10 mm). Long fibers were more resistant to melt filling than short fibers. In addition, the thickness of the specimen and the gate design were also found to affect the filling process. The rounded angle gate and thick wall product decreased the flow resistance and assisted the flow ability and fiber distribution of the L-FRP injection molding.

Injection molding of short fiber thermoplastic bio-composites: Prediction of the fiber orientation

2020 ◽  
Vol 54 (30) ◽  
pp. 4787-4797
Author(s):  
Fatima-Zahra Semlali AouraghHassani ◽  
Mounir El Achaby ◽  
Mohammed-Ouadi Bensalah ◽  
Denis Rodrigue ◽  
Rachid Bouhfid ◽  
...  
Keyword(s):  
Experimental Data ◽  
Mechanical Properties ◽  
Injection Molding ◽  
Fiber Orientation ◽  
Orientation Angle ◽  
Short Fiber ◽  
Thermoplastic Polymer ◽  
Molded Part ◽  
Practical Tool ◽  
Orientation Pattern

Injection molding of short fiber reinforced thermoplastic polymer results in a preferential fiber orientation in the part, which leads to an anisotropy in the material mechanical properties. To anticipate the molded part performances, it is necessary to predict the fiber orientation pattern. Our goal is to have a practical tool that accurately predicts fiber orientation patterns, and to use that information to estimate the final product properties. Consequently, an efficient way to determine the flow induced fiber orientation for different flow cases under real injection molding conditions is presented. The proposed approach allows the average orientation angle prediction in a section by considering the close interaction between the fibers and the flow rheology, the fibers aspect ratio and the mold geometry. Finally, to validate the model, experimental data were taken with different matrices, fibers and mold geometries, where good agreements (R2 ≥ 0.8) were obtained for the fiber orientations measurements.

Comparison of Mechanical Properties of Compression and Injection Molded PEEK/Carbon Fiber Reinforced Composites

2006 ◽  
Vol 306-308 ◽  
pp. 751-756 ◽  
Author(s):  
Dong Joo Lee
Keyword(s):  
Mechanical Properties ◽  
Carbon Fiber ◽  
Injection Molding ◽  
Fiber Length ◽  
Volume Fraction ◽  
Compression Molding ◽  
Fiber Volume ◽  
Creep Properties ◽  
Injection Molded ◽  
Initial Fiber

The tensile, fatigue and creep properties of carbon fiber filled poly(ether-ether-ketone) or PEEK were compared by employing injection and compression molding processes. The specimens with different initial fiber lengths were fabricated using compression and injection molding methods. The effects of fiber length on mechanical properties are evident in cases of specimens made by compression molding. But, the injection molded samples show no differences in tensile and fatigue strengths contingent on the initial fiber length. Similarly, the effects of fiber volume fraction on tensile and fatigue strengths are more evident for the compression molded specimens than the injection molded specimen. For the creep properties, even the injection molded specimens show some improvement for long reinforcing fibers especially as temperature is increased. When the influence of time and temperature is considered, the effects of fiber length on mechanical properties are very significant. Also, these results represent the significant fiber damage during injection molding.

Mechanical Properties of Short-Fiber-Elastomer Composites

1976 ◽  
Vol 49 (5) ◽  
pp. 1160-1166 ◽  
Author(s):  
S. R. Moghe
Keyword(s):  
Mechanical Properties ◽  
Aspect Ratio ◽  
Fiber Orientation ◽  
Fiber Length ◽  
Flow Direction ◽  
Length Distribution ◽  
Fiber Content ◽  
Constant Length ◽  
Composite Stiffness ◽  
Composite Properties

Abstract The reinforcement of rubber compounds with short fibers has, at times, become necessary in many product applications. Particularly compounds with relatively low fiber content have proven successful in improving hose and belt performance. This is mostly due to an increase in composite stiffness without a great sacrifice of basic processability characteristics of the compound. Too large a fiber content becomes a primary source of difficulties during manufacture and/or product performance. Therefore, an understanding of how various composite properties depend upon fiber and matrix properties, as well as on fabrication methods, will help design better products. The mechanical properties, such as modulus, strength, and ultimate elongation depend upon fiber orientation, aspect ratio, and adhesion between fiber and matrix compound. Unfortunately, the degree and type of adhesion cannot be estimated quantitatively at present even though its importance in the improvement of composite properties is well recognized. Aspect ratio is another parameter which can be used in improving composite properties. As a rule, a higher aspect ratio gives higher composite stiffness. During processing, fibers are buckled and crimped under large deformations, which results in a distribution of fiber lengths, rather than a constant length as before mixing, as shown, for example, in Figure 1. One can, therefore, expect to achieve the same composite properties regardless of the initial fiber length (up to, say, 15 mm) or fiber length distribution. Of the three parameters, fiber orientation affects composite properties the most. During processing (milling, extrusion, etc.) of rubber composites, the fibers tend to orient along the flow direction, causing mechanical properties to vary in different directions. Therefore, by changing or suitably controlling the flow direction, optimum properties can be generated for a given product. A good example is the balanced fiber orientation in a hose which gives optimum design strength. Milling or calendering is perhaps the most commonly used processing method in which fibers tend to orient along the mill direction. Since each mill or calender differs from any other in size, roll speed, and other characteristics, it is essential to determine the influence of these parameters on composite properties. Results of a systematic study to identify significant mill parameters which influence the composite properties are presented here.

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