Polypropylene Core Research Articles

Fatigue properties of spot joints of metal-plastic composites with DP 800 steel prepared by ultrasound resistance spot welding

The aim of this work is to analyze the properties of spot joints of metal-plastic composites (Litecor) with DP 800 steel. The joints were made using ultrasound resistance spot welding technology. A metallographic analysis of the joints was carried out, and the basic areas of the weld structure were determined. The separation and decomposition of the polymer core was also illustrated, with no observed diffusion between the Litecor covers and the polypropylene core. Fatigue tests were the main goal of this work, therefore a fatigue curve was determined and the mechanisms of fatigue failure at various levels of fatigue load were analyzed. The tests were carried out at a frequency of 30 Hz, the cycle asymmetry coefficient was R = 0.1 and the limit number of cycles was 2 × 106. Fatigue failure mechanisms specific to particular levels of fatigue load were demonstrated, which were: 2.2, 1.9, 1.5, 1.2, and 1 kN. For joints subjected to fatigue shear has been demonstrated that the boundary between low-cycle and high-cycle fatigue is located at a cyclic shear stress level of approximately 132 MPa. However, with the assumed limit number of fatigue cycles, the fatigue shear strength was 70.576 MPa. Macro- and microscopic fractographic analysis was carried out for joints after fatigue tests in order to demonstrate the mechanisms of failure at individual levels of cyclic load.

Impact Properties of Hemp Natural – Glass Fibers Hybrid Polypropylene Sandwich Composites

One way to improve the mechanical properties of composite structures is by hybridizing natural and synthetic fibers. Besides that, combined with sandwich structure composites consists of two relatively strong, thin, and stiff faces separated by a core, for example, balsa, foam, and honeycomb, a relatively thick lightweight. This research develops sandwich composites for structures that have able to withstand high loads and modulus-to-weight ratios but can absorb impacts through impact tests by utilizing the raw material of jute natural fiber, which is abundant in Indonesia so that this research study can predict the effect of variations in the hybridization of hemp natural fiber and the combination of hemp natural fiber with e-glass using polypropylene core sandwich composites by using hand lay-up and vacuum bagging methods. The current impact test results show that the hemp natural-e-glass fibers hybrid sandwich composites get a higher impact strength with a value of 0,019 J/mm² than the hemp-PP honeycomb hybrid sandwich composite with a value of 0,013 J/mm². It shows that by combining e-glass fiber in the composite, it can increase its impact strength and can be a lightweight structural material as being a new alternative material of jute and e-glass natural fiber hybrid sandwich composites with polypropylene cores to substitute conventional materials such as metals which is potential for applications in the automotive, building, and unmanned aerial vehicle industries.

Drop-weight impact responses and energy absorption of lightweight glass fiber reinforced polypropylene composite hierarchical cylindrical structures

A high spike force at the beginning of impact and the load fluctuations caused by unstable plateau deformation are disadvantages to avoid for impact resistance structures. Lightweight glass fiber-reinforced polypropylene composite hierarchical cylindrical structures (namely GFRP-CHCS, with a relative density of less than 0.1) have the potential to achieve low initial force and high crushing force efficiency under dynamic conditions. This work explores the drop-weight impact behaviors and energy absorption capacity of GFRP-CHCS. Deformation modes, failure conditions, and impact load history responses are discussed. Results showed that GFRP-CHCS has no initial load peak and achieves gentle response curves under the low-velocity impact when the load speed is less than 10 m/s. Among the experiments where the impact energy was beyond the range of static energy absorption, more than 94% of the impact energy was absorbed or dissipated when the impact energy ranged from 200 J to 300 J. After unloaded, GFRP-CHCS maintained good integrality and recovered a significant deformation which was over 93% initial structural height. With ideal isotropic material properties, numerical and theoretical predictions were conducted regarding the loading velocity effects on structural deformation mode and mean impact response force. This work utilized a thermoplastic composite consisting of GFRP face sheets and polypropylene core. The results have reference significance for the anti-impact design of thermoplastic composite hierarchical structures.

Effect of Poly(vinyl alcohol) Concentration on the Micro/Mesopore Structure of SBA15 Silica.

In this work, a series of micro/mesoporous SBA15 silica materials were synthesized using P123 and poly(vinyl alcohol) (PVA) as co-templates. The pore structure of the prepared SBA15 was observed to be a function of the PVA concentration. When the amount of PVA was relatively small, the specific surface area, micropore volume, and pore wall thickness of the synthesized SBA15 were considerably large. By contrast, when a large amount of PVA was added, the pore wall thickness was greatly reduced, but the mesopore volume and size increased. This is because the added PVA interacted with the polyethylene oxide (PEO) in the shells of the P123 micelles. Furthermore, when the amount of PVA was increased, the core polypropylene oxide (PPO) block also increased, owing to the enhanced aggregation of the P123/PVA mixed micelles. This research contributes to a basic comprehension of the cooperative interactions and formation process underlying porous silica materials, assisting in the rational design and synthesis of micro/mesoporous materials.

On the influence of manufacturing parameters on buckling and modal properties of sandwich composite structures

Sandwich structures with honeycomb cores are widely used in several applications given their promising properties, like high strength, light weight, and specific stiffness. However, these unique structures present complex behavior with failure modes that are not trivial when subjected to different loading conditions. Evaluation studies about the structural performance and failure modes of honeycomb sandwich structures with different face sheets and cores in static and dynamic conditions are scarce. Therefore, the structural behavior and failure modes of different honeycomb sandwich structures need to be evaluated to promote optimal performance in accordance with project requirements. This study seeks to characterize the structural behavior of different sandwich structures with honeycomb cores using a complete experimental comparative study. First, combinations of different types of cores and face sheets were elaborated using the Design of Experiments Method with Factorial Design, and then both the static and dynamic experimental tests were performed to obtain response variables and failure modes. The results showed that a polypropylene core in sandwich structures can increase damping. The sandwich structures manufactured with glass/aramid hybrid fabrics on the face sheets showed high strength under bending and buckling conditions, supporting a maximum bending loading of 1989 N and a maximum buckling loading of 12,700 N. Most sandwich structures had failure modes in “semi-circle” shapes. Only sandwich structures with glass fabric face sheets have failure modes in “V” shapes. Lastly, statistical results revealed that the type of core design variable contributed more to the response variability and was responsible for significantly changing the properties of stiffness, structural mass, and damping.

Energy absorption assessment of bio-mimicked hybrid Al/PP sandwich tube: Experimental and Numerical Investigation

This paper aims to investigate quasi-static and low-velocity impact responses of three manufactured bio-inspired hybrid multi-cell aluminum and polypropylene (Al/PP) sandwich tubes experimentally and numerically. The configurations are inspired by biological structures such as the horsetail, human tendons, and spongy bone. The crushing characteristics and axial collapse of sandwich tubes are discussed and compared with the quasi-static axial behavior of single Al and PP tubes. Further investigations, based on the accuracy of simulation results of the tested specimens, using the commercial nonlinear LS-DYNA software, on the effects of inner tubes diameter and material permutation are perceived through the full-factorial approach of FE parametric study. The results revealed that, packing the Al and PP tubes as hierarchical tubes generally improves the crushing patterns of individual hollow tubes. Also, specimens with aluminum and polypropylene cores have the highest amount of specific energy absorption under quasi-static and low-velocity impact loading, respectively. Finally, considering the interaction effects between the sandwich tube components, it can be seen that sandwiching single hollow tubes generally improves important crashworthiness indicators like peak crush force, crush force efficiency, energy absorption, and specific energy absorption when compared to the sum of these parameters in single hollow tubes.

Effects of core‐shell structured rubber on biobased polyamide 56 with stiffness and toughness balance

AbstractThere is great social awareness concerning the use of biobased materials of diminishing the rapid resource depletion and suppressing global warming. The inherent drawbacks of biobased polyamide 56 (PA56) such as poor notched impact strength limit its applications. Core‐shell structured impact modifiers consisting of a soft glycidyl methacrylate grafted poly(ethylene–octene) (POE‐g‐GMA) shell and a rigid polypropylene core were synthesized through the differences in interfacial tensions. Core‐shell rubber (CSR) particles were used to toughen biobased PA56 by melt blending. PA56/CSR composites exhibited a 560% increase in the impact strength, while the tensile performance loss was slight. This desirable toughness of biobased PA56 is attributed to the cavitation that occurred in POE‐g‐GMA shell which can induce shear bands and shear yielding, forming the fibrils. Characterizations, including X‐ray diffraction (XRD), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), melt rheological tests, and dynamic mechanical analysis (DMA) were conducted to study the toughening mechanism. The results indicated the massive shearing yielding, the cavitation of the CSR and interfacial debonding between the POE‐g‐GMA and the PP were the principal toughening mechanisms.

Sensitivity of the impact performance of nano reinforced sandwich structures to the material and geometrical variations

The low-velocity impact response of sandwich structures with aluminum face sheets and neat or nano-reinforced polypropylene core was studied. A strain-rate dependent micromechanics model (SRDM) was presented in the literature for predicting the dynamic behavior of nano-reinforced polymers. In the present study, the dynamic behavior of nano-reinforced polypropylene was simulated based on SRDM results. The finite element model was validated against the experimental results. It was shown that the results of the simulation performed by the SRDM model were in very good agreement with the experimental data. Then, the proposed finite element model was used for checking the sensitivity of the impact performance of nano-reinforced sandwich structures to the material and geometrical variations. A special sandwich structure with a core of 1 mm thickness and a face thickness of 1 mm was considered as the base structure. Different material and geometrical variations including doubling the thickness of the core or face sheets, a different weight ratio of graphene, and increasing material parameters of the face sheets up to 90%, were undertaken on the base structure. The results of the present study imply that the optimal amount of graphene should not exceed 0.5 wt.% to improve impact properties. The impact response of nano-reinforced sandwich structures was more sensitive to the variations of the face thickness in comparison to the variations of the core thickness. Moreover, the impact outputs were more sensitive to changes in the yield stress of faces compared to changes in Young’s modulus of faces.

Laboratory Study of Polypropylene-based Honeycomb Core for Sandwich Composites

Nowadays, a structure of sandwich composites can be reinforced by with hybrid materials such as polypropylene core. Due to its high strength properties, the polypropylene is widely used in various fields of science, technology and engineering including aerospace applications. This research studies the well-known hybrid composites of a carbon fiber (CF) and glass fiber (GF) to evaluate the mechanical properties under the presence of sandwich composites reinforced with such fibers. The different curing-pressure values of each material workpiece have been investigated to determine the curing pressure, resulting in the superior performances and properties. The specimens are moulded by the hand lay-up (i.e., cloth laying angle) of the carbon fiber. By changing direction, the specimens are determined the greatest load-bearing direction based on the bending test. According to the ASTM standard on the strength determination, it is found that when the curing pressure increases, the flexural stress increases. By placing the material orientation in the order (i.e., [CF90 / CF0 / GF0 / Core / GF0 / CF0 / GF0]) provides the highest strength. When the strain reaches its maximum value, the specimens actually fracture. The fracture propagation is generally followed the fiber orientation of the fabric. The experimental results are observed that the lower curing pressure the thicker of the work piece and the fiber volume fraction decreases. The obtained results show that changes in the curing pressure and laying angle significantly affect the mechanical properties of the sandwich composites

FEM Analyses of Low Velocity Impact Response of Sandwich Composites with Nanoreinforced Polypropylene Core and Alu-minum Face Sheets

Sandwich composites with nanoreinforced polypropylene core and aluminum face sheets were studied under low velocity impact using a finite element model. A three dimensional quarter model was implemented to simulate the drop weight impact response of sandwich structures. In order to consider the strain rate dependent behavior of the core and face sheets, the Johnson–Cook material model was used for both of the polypropylene and aluminum layers. Effects of the different weight ratio of nanoparticles, the core thickness and the impactor mass were studied on the impact outputs. Comparing the impact responses of the sandwich structures with different weight ratio of nanoparticles revealed that positioning a polypropylene layer with 0.5% weight ratio of graphene as the core of sandwich panel caused the minimum amounts of damage area and transverse displacement. Adding more amount of nanoparticles did not improved the mechanical response of the sandwich structures. Increasing the impactor mass caused an increase of the contact force and the contact duration. Increasing the core thickness caused a decrease of the contact duration and increase of the contact force. The finite element outputs were well validated against the experimental results.

Effect of Debonding on Stiffness and Long-term Creep of Sandwich panels IOP: Conference Series

The main objective of this study was to analyze the effect of debonding on the stiffness and long-term creep of sandwich panel. Sandwich panel is made of thermoplastic core which is viscoelastic in nature and debonding is the major failure mode of the sandwich panel. Sandwich beams were made of different types of materials and the different materials have different properties. Numerical modeling of sandwich beam with aluminium face sheet and polypropylene core is done. Analysis was performed by using ANSYS software and the element used in the modeling is SHELL181. Four-point load configuration was created for the model with loading of 60 % of core shear strength according to McCallum (2012) and the model were subjected to static deflection. Static deflection results were compared with experimental and theoretical results and stiffness of deboned sandwich beam was evaluated. Primary and Secondary creep was evaluated in ANSYS by using Time hardening and the Norton equations to the propylene core and Burger model was used to fit with the secondary creep of the bonded sandwich beam. The primary and the secondary creep of bonded and the deboned sandwich beams were compared and long-term creep of deboned sandwich beam was determined.

폴리프로필렌 중심 판재의 두께 변화에 따른 알루미늄 샌드위치 판재의 표면 거칠기 및 톱니 모양 거동의 변화

폴리프로필렌 중심 판재의 두께 변화에 따른 알루미늄 샌드위치 판재의 표면 거칠기 및 톱니 모양 거동의 변화

Experimental and numerical investigation of thermoplastic honeycomb sandwich structures under bending loading

Sandwich structures have attracted increasing attention in engineering applications due to their lightweight effect and energy absorbing capacity. In the current work, fully-thermoplastic honeycomb sandwich structures with 100% recyclability were developed, which consisted of continuous glass fiber-reinforced polypropylene (PP/GF) face sheets, polypropylene (PP) core and assembled using thermoplastic adhesive films. The experimental tests and numerical analysis were conducted to investigate the bending behavior and energy absorption of PP-based sandwich structures. Firstly, a series of three-point bending experiments were tested and the influences of structural factors on bending behaviors were investigated. The typical deformation modes were explored and the damaged microstructure of face-sheets were observed. Finite element models of the sandwich structures were developed to capture the deformation process, and the simulation results were validated with the experimental data. Afterwards, a multi-objective optimization was performed to seek for the maximum specific energy absorption together with the minimum initial peak force simultaneously. Response surface method was adopted to construct objective response functions and used for the defined optimization problem.

Collapse pressure of sandwich pipes with strain-hardening cementitious composite - Part 2: A suitable prediction equation

Abstract A comprehensive study on the collapse pressure and post-buckling behaviour of a sandwich pipe (SP) with a core of strain-hardening cementitious composite (SHCC) was carried out in Part 1 of two companion papers. The results in the Part 1 paper show that an SP with an SHCC core has a different collapse mechanism from an SP with a polypropylene core. Because of its weak inter-layer adhesion and a relatively hard core, the collapse pressure and the characteristic response of an SP with an SHCC core are more influenced by its strongest layer than by the summed strength of all its layers. Since this behaviour has never been reported before, current prediction equations for the collapse pressure of SP systems cannot capture the special behaviour of an SP with an SHCC core. Therefore, utilising the available prediction equations for an SP with an SHCC core may lead to unreliable estimates. This Part 2 paper is dedicated to addressing the challenge by proposing a suitable prediction equation. Based on the extensive simulation results carried out by the numerical model verified by experiments in the Part 1 paper, supervised machine learning techniques were applied to support the regression of different equation forms, which come from three sources: (a) equation forms proposed by previous researchers, (b) equation forms found by the automatic machine learning software EUREQA, and (c) equation forms proposed by us. Further, the performances of the equation forms in predicting accurate results for the collapse pressure were compared. Based on the comparative performances and accuracy, an equation was recommended for the design of SPs under external pressure.

Investigation of Thermal Conductivity of Wood Sandwich Panels with Aluminium and Polypropylene Core

Sandwich panels are obtained by placing thick but rather light core material between two thin and rigid lower and upper surface layers. Sandwich panels, especially due to their light weight, high "strength / weight" ratio and durability compared to conventional materials have many use areas such as aviation and space industry, maritime, automotive and building industry. It is one of the biggest advantages that sandwich materials can be obtained from different materials and geometric structures by choosing the lower and upper surface layers and the core for various applications. The aim of this study is to investigate the thermal conductivity values of the sandwich panels, which are manufactured with different types of surface and core materials in sandwich panels. An aluminium and polypropylene as a core materials and alder, birch and scots pine wood veneers were used as wood species for surface panels for manufacturing of sandwich panels. A polyurethane modified epoxy- adhesive were used for binding of core layer to both surface layers. Thermal conductivity of sandwich panels was determined according to ASTM C 518 & ISO 8301. As a result of the study, the highest thermal conductivity values were obtained from aluminium core sandwich panels. The highest values were obtained from alder for the aluminium core panels and scots pine for the polypropylene core panels as wood species.

Effect of peer ply and cooling rate on the tensile properties of Al/Gf/PP laminate prepared by hot pressing

The glass fiber-reinforced polypropylene/AA2024 hybrid composite (short for Al/Gf/PP laminate) was prepared by hot pressing with anodized 2024-T3 aluminum alloy as the skin and thermoplastic glass fiber-reinforced polypropylene core as a substitute of thermosetting glass fiber-reinforced polymer (based on epoxy) in order to increase the productivity and reduce the production costs during manufacturing procedure. The effect of peel ply (release cloth) and cooling rate on the laminate was investigated elaborately in this work. The orientation of glass fiber is mainly influenced by the peel ply structure, resulting in the resin’s overflow during hot press. Moreover, different cooling rates due to various cooling methods significantly affected both the degree of crystallization of the matrix and deformation of the metal skin during the curing process. Finally, a new peel ply structure was adopted to prevent the fiber from spilling during hot press process, while bubbles were allowed to flow out normally along with partial resin. Finally, a novel cooling method to reduce the degree of polypropylene crystallization and control metal deformation was proposed.

Buckle propagation of sandwich pipes under external pressure

Sandwich pipe (SP), consisting of two comparatively thin-walled metal tubes and a thick polymer or cement-based core, is believed to be a feasible conception to transport hydrocarbons in deep sea. In this paper, the buckle propagation experiments were carried out on small-scale SP test specimens composed of two aluminium tubes and the polypropylene (PP) core. In association with experimental efforts, dedicated finite element models of SP test specimens under external pressure were established to reproduce the local collapse and consequent buckle propagating scenarios using the software ABAQUS, and good agreements were observed between the experimental and numerical results. Then, influencing mechanisms of inter-layer adhesion behaviour on the stress state, cross-section deformation and buckle propagation pressure of SPs were systematically studied, and broad parameter correlation analyses were performed to explore geometric and material properties of two steel tubes and polymer core on the buckle propagation pressure of SPs. The results show that good interface bonding conditions can markedly enhance the buckle propagation pressure of SPs and improve the energy dissipation and the deformation capacity of the structures. The core layer thickness and the ratio of the wall thickness between inner and outer tubes have extremely noticeable effect on the buckle propagation pressure of SPs. Additionally, based upon extensive numerical results, an empirical design expression was developed to conservatively estimate the buckle propagation pressure of SP systems for the no inter-layer adhesion case.

Uniaxial tensile investigation of a porous compound nonwoven fabric

Carbon fiber (CF) nonwoven fabric possesses excellent chemical resistance, remarkable electrical properties, and low density, but its mechanical strength must be enhanced to facilitate its application. Therefore, a flexible compound nonwoven fabric (CEF‐NF) consisting of CF and a bicomponent polypropylene/polyethylene core/sheath fiber (known as ESF) was prepared using a 2‐step wet papermaking/thermal bonding process. Scanning electron microscopy observations indicated that the CEF‐NF fibrous network could be strengthened without blocking its pores by using a heat‐pressing temperature falling between the melting regions of the sheath polyethylene and core polypropylene. Additionally, uniaxial tensile experiments were conducted to investigate the failure mode and tensile properties of the CEF‐NF by varying the thermal bonding and structural parameters. The results showed that 3 failure modes of fiber physical contact separation, thermal bond breakage, and ESF fracture emerged and could be defined based on the variation in the heat‐pressing temperature. The tensile strength of the CEF‐NF was improved with increasing thermal bonding and structural parameters. Under a set of process parameters, ie, 180°C heat‐pressing temperature, 6‐MPa heat‐pressing pressure, 40 wt% ESF mass fraction, and 40‐gsm areal density, the tensile strength of CEF‐NF reached 5.7 MPa, which is much higher than that of pure CF nonwoven fabric.

Abstract: A Comparison of Epitendinous Repair Techniques for Flexor Tenorraphy

INTRODUCTION: The purpose of the epitendinous component of flexor tendon repairs was originally thought to just “tidy-up” the repair site but it is now recognized that it has a structural role and contributes approximately 20% to the strength of the repair. Polypropylene (Prolene™) has been the most popular material for epitendinous repairs yet little research has been carried out on other materials. We hypothesized that a polyester (Ethibond™) epitendinous suture would significantly increase the overall tensile strength of flexor repairs compared to a traditional polypropylene suture in an ex-vivo porcine model. METHODS: Eighty porcine tendons were transected and randomly assigned to one of four repair groups; Group 1: 3-0 polyester core and 5-0 polyester epitendinous; Group 2: 3-0 polyester core and 5-0 polypropylene epitendinous; Group 3: 3-0 polypropylene core and 5-0 polyester epitendinous; and Group 4: 3-0 polypropylene core and 5-0 polypropylene epitendinous. A cross-locked cruciate technique was used for all core sutures. A simple continuous suture was utilized for the epitendinous repair in all groups. Biomechanical testing was carried out with a tensiometer and the ultimate strength, 2mm gap-formation force and method of failure were recorded. RESULTS: Group 1 (96.3 ± 15.77N) with 3-0 polyester core and 5-0 polyester epitendinous repairs had significantly greater tensile strengths and 2mm gap forces than the Groups 2,3 and 4 (70.12 ± 11.4N, 62.9 ± 8.52N and 46.27 ± 9.18N respectively). The addition of a running 5-0 polyester epitendinous repair significantly improved the tensile strengths of both Groups 2 and 3. CONCLUSION: This study has demonstrated that a running polyester epitendinous suture significantly augments the strength of flexor repairs when compared to a traditional epitendinous polypropylene suture. Further study is certainly warranted in animal models looking at different types of epitendinous repair techniques. The authors feel that a 5-0 polyester suture should be considered for the epitendinous component of flexor tenorraphy as we have demonstrated that it produces a stronger repair with less gapping than traditional techniques in a porcine model.

The morphological properties of PP coextruded tape fabrics

In the field of self‐reinforced composites many researchers have focused their attention on the coextruded tapes composed of polypropylene core and PP/PE copolymer skin. Two similar commercial fabrics (P and T) have been compared in respect of their peel resistance. For both materials, peel resistance has a periodic trend that regularly follows fabric weave style. T has demonstrated an average peel resistance and a well‐bonded area slightly greater than P. Skin/core interfacial properties have been investigated and a crosscheck between differential scanning calorimetry (DSC) and Raman spectroscopy has been adopted to understand the influence of skin structure on consolidated laminate. DSC curves exhibit three melting peaks during first heating for both fabrics, corresponding to copolymer, skin/core interface, and core melting. After consolidation at 140°C stretching‐induced superstructure and PP crystallinity degree are preserved. The presence of PP/PE copolymer + PE blend only in fabric P has been pointed out and PE content has been calculated. POLYM. ENG. SCI., 56:727–734, 2016. © 2016 Society of Plastics Engineers