1:30 pm – 7:00 pm:
W13-Composites: Modelling, Numerical Studies and Long Fiber Composites-Room S320D
1:30 pm – 2:00 pm:
Fundamental Understanding of Tribological Behavior of Multiphase Polymeric Systems using FEM Modeling
Mohammad Hossain, Texas A&M University-Kingsville
Three-dimensional finite element method (FEM) modeling has been carried out to study the influence of dispersed particles on tribological behavior of multiphase polymeric systems. Specifically, effects of particle type and volume fraction on scratch behavior of multiphase polymeric systems have been investigated. The FEM findings correlate well with the experimentally observed scratch-induced damages. The results show that type and concentration of particles can drastically affect the stress and strain field development during the scratching process.
2:00 pm – 2:30 pm:
Experimental Verification on MoldEx3D Fiber Orientation Prediction in High Fiber Concentrations
Huan-Chang Tseng, CoreTech System (Moldex3D) Co., Ltd.
An accurate predictive analysis of fiber orientation is crucial for practical injection molded fiber composite applications. Recently, an objective model, iARD-RPR (Improved Anisotropic Rotary Diffusion and Retarding Principal Rate), has been significant to provide anisotropic distribution of fiber orientation, such as the well-known skin-shell-core structure. The micro-computed tomography (micro-CT) scan is state-of-the-art technique for measuring a very high 3D resolution of a specimen’s fiber orientation data. According to the micro-CT experiments and injection molding simulations with the iARD-RPR computation, we investigate changes in fiber orientation distributions for different fiber concentrations in rectangle plate. Comparisons of the fiber orientation predictions with the validated experimental data are also presented herein.
2:30 pm – 3:00 pm:
In-Situ Synthesis of Poly(Ethylene Terephthalate) Graphene Nanocomposites
Vahid Shabafrooz, Oklahoma State University
Fabrication of graphene-based poly(ethylene terephthalate) (PET) nanocomposites through in-situ polymerization is demonstrated. With the goal of improving the incorporation and dispersion of graphene in the PET matrix, an ultrasonic exfoliation method was employed in ethylene glycol (EG), a raw material used in PET synthesis. The graphene EG dispersions were used as precursors to fabricate PET nanocomposites. Transmission electron microscopy (TEM) was used to evaluate the level of exfoliation of graphene in the dispersions. Mechanical testing showed at 2 wt. % concentration of graphene, the elastic modulus and the tensile strength of PET increased by 22% and 10%, respectively. Differential scanning calorimetry (DSC) measurements were performed to evaluate the percent crystallinity, and it was observed that addition of graphene at 2 wt. % increased the crystallinity of PET by 33%. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were used to study morphology and microstructure of the PET nanocomposites, respectively.
3:30 pm – 4:00 pm:
Draping Behavior of Uni-directional tape laminates – Experimental and Numerical Studies
Sandeep Kulkarni, SABIC
Today continuous fiber thermoplastic composites are used in various applications across the industry due to its excellent mechanical properties, which offer significant weight saving potential. In addition, thermoplastic composites are well suited for mass production and easily integrated in a hybrid overmolding processes. This enables the industry to manage cost while delivering performance. Forming or draping is an important step in the manufacturing of continuous fiber prepreg or tape based thermoplastic material forms. Different studies indicate that forming of multi-layer unidirectional (UD) laminates may result in out-of-plane wrinkling and in-plane fiber misalignment. Thus, understanding the forming behavior and having a simulation method in place for its prediction is essential for widespread acceptance of this new material. This paper presents experimental forming studies on multi-layer GF-PP UD thermoplastic composite laminates. The influence of the tool geometry and the laminate layup on forming behavior are studied. The results show that the current GF-PP UD composites are easy to shape, resulting in a large processing window. However, in some cases process induced defects arise, such as out of plane deformation, fiber waviness, ply splitting, bridging, etc. whose influence on part performance needs to be assessed and quantified. Forming simulations are performed on UD tape based laminate composites in PAM-FORM software using a visco-elastic material model, dedicated to continuous fiber composites. Numerical studies show that the predicted process induced defects such as fiber waviness and wrinkling patterns are in good agreement with experiments. With increased confidence on such a computational framework, thermo-forming simulations can help identify critical spots in the product and process design at an early stage and reduce costly product development times.
4:00 pm – 4:30 pm:
Virtual Characterization of Prepreg Platelet Length Effect on Tensile Properties of Coupons with Stochastic Morphology
Sergey Kravchenko, Composites Manufacturing & Simulation Center
Progressive failure analysis is herein used to study the damaged deformation up to ultimate failure in prepreg platelet-based tensile coupons with stochastic morphology. Computational damage mechanics approaches (continuum and discrete) are utilized for constitutive modelling and addressing complex interacting/competing damage mechanisms. The developed failure analysis allows for virtual characterization of how the composite structure details, meaning the platelet geometry and system morphology (geometrical arrangement and orientation distribution of platelets), define the effective properties of a platelet-molded composite system, its stiffness, strength and variability in properties.
4:30 pm – 5:00 pm:
Geometrical Effects on Fiber Micro-structure Variations and the Influences on Long Fiber Reinforced Thermoplastics (FRT) Parts
Chao-Tsai Huang, Tamkang University
Due to its great potential and capability, the fiber-reinforced thermoplastics (FRT) material and technology have been applied into industry recently. However, due to the microstructures of fiber inside plastic matrix are very complex, they are not easy to be visualized. The connection from microstructures to the final shrinkage/warpage is far from our understanding. In this study, we have performed a benchmark with three standard specimens based on ASTM D638 where those specimens have different gate designs. Due to the geometrical effect, the warpage behaviors are quite different for those three specimens. Although we expect long fiber reinforced to enhance strength, it causes one specimen warped downward and bended inward, another warped upward, and the other slightly upward at the same time. The difference might be due to the interaction of the entrance effect of molten plastic with fiber content to cause high asymmetrical fiber orientation distribution (FOD). Moreover, the experimental study is also performed to validate the simulation results. From short shot testing to the warpage and bending measurement for each individual model, overall, the tendency for both numerical simulation and experimental results is in a reasonable agreement. However, some deviation still existed which needs for further study.
5:00 pm – 5:30 pm:
An Investigation of Rheological Properties of Polypropylene Single-polymer Composites
Mingxing Yu, Beijng Institute of Technology
Polypropylene single-polymer composites (PP SPCs), whose matrix and reinforcement came from identical type of polymers, were fabricated by an approach of applying undercooled polymer melt. The undercooling method could enlarge the processing temperature windows thus realize the fabrication of SPCs without destroy the reinforcement structures. Rheology could be used in the processing of the SPCs, however there is little investigations. This work was done with the aim to investigate the effect of undercooling compaction temperature from 125 oC to 145 oC on rheological properties of PP SPCs by dynamic rheological measurements. The linear viscoelastic range (LVE) was measured for strain sweep. And it was found that complex viscosity of PP SPCs increased as the temperature increased, whereas the storage modulus decreased during frequency sweep. Moreover, the photography of morphology before and after tests revealed a positive correlation between the degree of shrinkage and the compaction temperature. Overall, the effects of temperature on rheological and morphology properties of PP SPCs are strictly dependent upon the molecular structure parameters.
5:30 pm – 6:00 pm:
Suppression of Necking in LLDPE/SEPS Rubber Bilayer Laminates
Sachin Velankar, University of Pittsburgh, Chemical Engineering Dept
Semicrystalline plastics often show necking and drawing behavior in tension. In contrast, rubbery materials do not show necking, but instead stretch homogeneously. We examine the behavior of bilayer laminate composites of linear low density polyethylene (LLDPE) and styrene-ethylene/propylene-styrene (SEPS) rubber to test the extent to which the SEPS can modify the necking behavior of the LLDPE. Video recordings of tensile tests on dog-bone shaped samples were analyzed by a Digital Image Correlation (DIC) technique to quantify the degree of non-homogeneity in deformation. The LLDPE showed severe necking with a natural draw ratio exceeding 5. Upon bonding it to a rubber layer, the natural draw ratio reduced significantly. With a sufficiently large SEPS thickness, the neck was almost completely eliminated and the sample reverted to nearly-homogeneous deformation. We present a simple 1D model of the mechanics of the bilayer laminate in which the force within the bilayer is treated as a sum of the force of a Mooney-Rivlin rubber layer and an elastoplastic layer. The model predicts the decrease in natural draw ratio and the elimination of necking as rubber thickness increases, consistent with experiments.