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The hybrid single shot method is an innovative manufacturing technique that allows thermoset composite sheets to be formed and cured while they are also bonded into an injected thermoplastic body all in a single integrated operation. This integration concept is complex in nature but promising to overcome the drawbacks of the traditional procedures for manufacturing such multi-material structures by reducing the cycle time, energy consumption, and cost of the required tools and machinery. In this study, CF/Epoxy prepreg sheets are selected as the inserted material which is then later deformed and bonded to an injected body made of a polypropylene compound. The bonding between these two dissimilar materials is mostly achieved by taking the advantages of the melt penetration and the tackiness of the prepreg sheet. Therefore, an experimental study is here designed and carried out to evaluate the bonding conditions of the final hybrid parts regarding several influential process parameters. To better monitor the process and analyze the physics behind this integration, a set of real-time process variables are measured and analyzed using an instrumented experimental setup. The results show that the pre-heating time has the largest effect on the bonding strength, and the best combination of the deformation and bonding strength is achieved when the cavity pressure and temperature are at the highest level compared to the other experiments. The maximum bonding strength attained in the optimum process settings was 6.8 MPa which shows a 51% improvement compared to the average value of the other experiments.

Delignified wood (DW) is natural wood’s cellulosic skeleton. It has highly ordered anisotropic architecture, permitting solute accessibility to modify its abundant interior surfaces. Herein, we demonstrate a facile method to coat polydopamine (PDA) conformally on DW’s interior surfaces. The PDA layer not only introduced heteroatom (N), but also facilitated the generation of silver particles by in situ reduction. The prepared DW skeletons were freeze-dried and pyrolyzed at 850/1200 °C to create carbonized DW (CDW) and then embedded in the epoxy matrix to prepare a composite for the application of electromagnetic interference (EMI) shielding. It was found that the PDA coating converted to a highly conductive carbon species on the surface of a DW-derived carbon scaffold. As a result, the PDA modification increased the electrical conductivity (EC) of the plain epoxy/CDW from 0.32 to 0.46 S/m, and accordingly the EMI shielding effectiveness (SE) increased from 18.2 dB for epoxy/CDW to 24.0 dB for epoxy/CDW-PDA, and 30.6 dB for epoxy/CDW-Ag. This work provides a facile and universal methodology to enhance the EC and EMI SE performance of open-porous carbon.

Although the mass production of cellulose nanocrystals (CNC) shows the possibility of their use in scalable nanocomposite manufacturing, the low compatibility between the CNC-hydrophobic matrix and...

In this study, the effect of epoxidized soybean oil (ESO) on the thermomechanical properties of foams based on epoxidized pine oil (EPO) was investigated. To obtain homogeneity in microstructure, an in-house developed, delayed addition approach was adopted for foaming compositions with polymethylhydrosiloxane (PMHS) while varying ESO content from 10% to 50%. The resulting foams were characterized with respect to microstructure, mechanical and thermal properties. The influence of rheology of blend compositions before gelation on the cell morphology was examined and a prospective approach was proposed for optimality in cell size. Although pure ESO did not cure at room temperature, blending with EPO facilitated processing the foams at room temperature, thereby curtailing the overall energy input in commercially manufacturing such composite systems. The behavior of foams under compressive loading was studied, and the compressive strength was observed to exhibit a decrease from 5.24 to 1.13 MPa with increase in ESO content. The nature of collapse plateau however suggested an increase in the fraction of load supported by the fluid in this region. This juxtaposed with a decrease in foam density deviated from Rehkopf's evaluation of load distribution between polymer and fluid. The foams were shown to exhibit high thermal stability, which increased from 182 to 208 °C with the amount of ESO present in the matrix.

In this paper, we set to examine the inter-laminar shear strength of a fiber-reinforced composite part manufactured via a stepped-concurrent ultraviolet curing and layering process. This process was specifically proposed for making epoxy-based thick parts, whereby a layer-by-layer, model-based, optimal layering time and ultraviolet control scheme is set up with the objective of minimizing the degree of cure deviation across the final thick part. We focus on a cationic curing process wherein additional energy savings are possible by switching off the ultraviolet source after initiating the curing reaction with the ultraviolet source at each layer addition. Since the inter-laminar sheer strength of parts made via a layering process is often a concern, we consider the application of in-situ consolidation pressure in the layering process. We then characterize the inter-laminar shear strength by manufacturing samples with application of different in-situ consolidation pressures and measuring the inter-laminar shear strength of each sample by the short-beam shear test. The results showed that the inter-laminar shear strength of composite parts fabricated with the proposed stepped-concurrent curing, and layering process increases with the applied consolidation pressure up to a point. Scanning electron microscopy of samples cured at different in-situ consolidation pressure showed that the sample with optimum consolidation pressure has relatively uniform fiber to resin distribution and hence improved inter-laminar shear strength.

The authors detail the creation of a hybrid multi-material structure via the injection of polypropylene (PP) with high ductility into a robust CF/Epoxy thermoset sheet. The purpose of this hybrid method involves combining the inherent properties of both thermoset and thermoplastic materials in a new hybrid structure while reducing the cycle time and tooling system. Specifically, the effect of pre-heating time, injection temperature, and injection speed rate on the deformation of the prepreg and polymer penetration through prepreg sheets were evaluated. The results of the experimental design indicated that the hybrid structures were manufactured with no penetration present in any combinations of parameters. An inadequate deformation characterized the samples created at a lower injection temperature, and pre-heating time, with insufficient adhesion as a result. High injection speed resulted in enhancing the formability and joinability. Also, the effect of the mentioned process parameters on the curing of prepreg sheet and bending behavior of final hybrid component were investigated through Differential Scanning Calorimetry (DSC), and the Three-point flexural test, respectively. Both DSC and Three-point test results illustrated the increase in pre-heating time, and the injection temperature enhanced the amount of curing and an increase of stiffness on the hybrid component.

Reactive extrusion was used for dicumyl peroxide (DCP)-initiated grafting of glycidyl methacrylate (GMA) to poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV). The effects of GMA and DCP content and their weight ratio on the GMA grafting percentage (GP%), the polymer melt viscosity, and the PHBV molecular weight were investigated. FTIR spectroscopy determined that the DCP did indeed initiate GMA grafting. However, the changes in both the zero-shear viscosity (η0) and the molecular weight suggested the existence of crosslinking products in the extruded polymers. A negative correlation between the degree of crystallinity (χc) of the PHBV-g-GMA and the GP% suggested the influence of chain branching on crystallinity. In addition, the GMA content was found as a key factor determining the GP%. The PHBV-g-GMA was used as a matrix polymer in cellulose nanocomposites to evaluate its effects on CNC dispersion and CNC-matrix adhesion relative to the unmodified PHBV matrix. The SEM images and the change in crystallization temperature suggested enhanced dispersion of CNC in a PHBV-g-GMA matrix. However, little increase in strength properties were found with CNC addition suggesting inadequate stress transfer between the matrix and CNCs.

CF/Epoxy sheet with injected thermoplastic is a hybrid structure that combines high mechanical properties of thermoset composite with the toughness and complex geometries of injected thermoplastic into a single component. To overcome the high cycle time and production cost associated with the manufacturing of such hybrids, the authors undertook a feasibility study for developing an integrated technology for the manufacturing of thermoset CF/Epoxy prepreg sheet and injected thermoplastic polypropylene. First, several demonstrator parts were manufactured to elucidate the effect of the process parameters on the process performance and the appearance of the final hybrid component. Then, to have a better understanding about the curing condition of prepreg sheet during this hybrid process, a set of numerical simulation was conducted to study the relationship between the initial preset machine parameters (i.e., holding time, injection speed rate,) on the temperature distribution and history of the prepreg sheet. The results show that the proposed technology is capable of manufacturing hybrid components in a single operation under different process and design conditions.

In this work two material systems, epoxidized pine oil (EPO) and acrylated epoxidized soybean oil (AESO), both previously individually experimented on, were blended in varying ratios, foamed, and characterized with respect to their microstructure, physical properties, mechanical performance, and thermal stability. Intermediate systems were created bearing a broad range of properties derived from both the parent material systems. The structure–property relations were studied, and the effect of process parameters on the resulting thermomechanical behavior was analyzed. Finally, the degradation kinetics of the developed foams was studied, and activation energies were calculated for a comprehensive understanding of behavior of foams at high temperatures. The obtained foams exhibited high thermal stability and mechanical strength varying from 0.4 to 11.3 MPa for densities ranging from 0.76 to 0.50 g/cm3, respectively, which enables them to be employed in a variety of applications based on product requirements.

The present work reports on the synthesis of foams from epoxidized pine oil (EPO) with polymethylhydrosiloxane (PMHS) used as a foaming agent. The effect of two different processing methods involving modifications of curing agent and foaming agent addition timings was also analyzed. Resultant foams were characterized via density, mechanical and thermal testing, and microstructure. Foams produced using a modified processing method displayed properties that deviate from the Ashby–Gibson models, resulting in superior compressive strengths over many synthetic and biobased epoxy foams, ranging from 6.1 to 11.3 MPa. The impact of the method on cellular microstructure was also significant, with 20- and 30-fold increase in cell density from the original processing method for the same levels of foaming agent in both the methods. Glass transition temperatures of the foams ranged from 61.8 to 97 °C, higher than those of many foams in their class.

In this study, the thermal, wetting and viscoelastic properties of biodegradable poly(butylene succinate)–isora nanofibril (PBS–INF) composites were investigated. Optical polarizing microscopy showed that incorporating INF in PBS enhanced the number of nucleation sites while also reducing its spherulitic size. Wide-angle X-ray diffraction results showed the influence of INF on the crystal structure of PBS. Dynamic mechanical analysis results revealed increases in storage and loss moduli with increasing INF content. Differential scanning calorimetry analysis showed that incorporating INF facilitated crystallization at higher temperatures. INF slightly enhanced the melting behavior of PBS matrix. Thermogravimetric analysis results demonstrated no definitive change in the thermal stability of PBS upon inclusion of INF. Contact angle studies showed enhancement in the hydrophilic nature of PBS–INF composites. Overall, INF had a positive influence on the thermophysical properties of PBS providing a feasibility for using PBS–INF composites in automotive interiors, food packaging and related applications.

Thermal properties of yttria stabilized zirconia (YSZ) were investigated using molecular dynamics (MD) simulation. Several YSZ samples were designed to elucidate the effect of porosity on thermal conductivity of the designed YSZ systems. Mean square displacement (MSD), vibrational density of state (VDOS) and atomic movement in designed YSZ and other samples were also investigated. Results of MD simulation indicated the key role of pores in preventing thermal transport behavior. For same volume of a single pore, samples with larger pore volume showed smaller thermal conductivity ( κ ), while for same amount of total porosity, samples with small-sized pores displayed a smaller thermal conductivity. The latter was due to the presence of relatively larger number of smaller-sized pores as compared to larger-sized ones. Samples with smaller-sized pores in greater numbers also exhibited lower vibration frequency and lower amplitude of single atoms, suggesting smaller thermal conductivity ( κ ) values. For constant pore volume, YSZ samples were observed to have a decrease in thermal conductivity with increasing number of pores. Among YSZ samples with same levels of porosity, those with smaller pores displayed smaller thermal conductivity. Similar levels of thermal conductivity could be acquired in samples with smaller pore amounts and/or smaller porosity as compared to those with larger pores.

In this paper, a theoretical approach to model free deformation of sheet metal via polymer injection pressure is presented. It is a general methodology that can be applied for any situation where a nonuniform pressure distribution is responsible for free deformation of sheet metal within a circular cavity. This approach is composed of two iterative approximation loops. In the outer loop, the radius of curvature at the tip of dome shape was optimized based on the boundary condition at the edge of clamped area while in the inner successive loop, principal stresses determined from plasticity theories were used to satisfy the equilibrium equations. While forming sheet metal via polymer injection is a revolutionary yet complex process, its modeling is challenging. Hence, before implementing this general approach to this process, the modeling methodology as such necessitates a simplified solution for melt flow analysis to obtain a pressure distribution encompassing the entire cavity. To evaluate the proposed model, a customized experimental setup was designed and fabricated, which allows sheet metal bulging with the plastic injection. The deformation of the AA1100-O sheet was investigated during the injection of the polypropylene–olefin compound. The comparison of the theoretical and experimental results shows that the general approach formulated here can be successfully applied to predict the surface strains and thickness distributions with maximum error of 6% while the deformed geometry remains within ±0.35 mm deviation in the final deformation stage.

We demonstrate the potential of polymer-derived ceramics (PDC) as next-generation sustainable thermoelectrics. Thermoelectric behavior of polymer-derived silicon oxycarbide (SiOC) ceramics (containing hexagonal boron nitride (h-BN) as filler) was studied as a function of measurement temperature. SiOC, sintered at 1300 degrees C exhibited invariant low thermal conductivity (similar to 1.5 W/(m.K)) over 30-600 degrees C, coupled with a small increase in both Seebeck coefficient and electrical conductivity, with increase in measurement temperature (30-150 degrees C). SiOC ceramics containing 1 wt % h-BN showed the highest Seebeck coefficient (-33 mu V/K) for any PDC thus far.

Single Point Incremental Forming (SPIF) is a sheet forming process characterized by advantages that include low-cost and part-shape-independent tooling, higher formability and greater process flexibility as compared to conventional sheet forming. While recent work has demonstrated the possibility of SPIF of polymers the effects of incremental depth and tool rotation speed, key process parameters in SPIF, have rarely been examined. This work experimentally examines how incremental depth and tool rotation speed affect the failure mode during forming, forming forces as well as the void structure and crystallinity of the formed material in polymer SPIF. The dependence of both tearing and wrinkling on the incremental depth and tool rotation speed is uncovered. It is shown that contrary to SPIF of metals, greater incremental depths result in increased formability in polymer SPIF, but this advantage is limited by the occurrence of sheet wrinkling at excessively high incremental depths. Further, the occurrence of sheet wrinkling depends not just on the incremental depth but also on the part shape being formed. Microstructural examination of the formed material shows that greater incremental depth results in greater void densities and that the material formed with SPIF has greater crystallinity than the unformed material. Additionally, it is shown that higher tool rotation speed can cause earlier onset of wrinkling. The implications of these observations on SPIF of polymers are discussed.

Using natural cellulosic fibers as fillers for biodegradable polymers can result in fully biodegradable composites. In this study, biodegradable nanocomposites were prepared using nanofibrillated cellulose (NFC) as the reinforcement and poly (3-hydroxybutyrate-co-3-hydroxyvalerate, PHBV) as the polymer matrix. PHBV powder was dispersed in water, mixed with an aqueous suspension of NFC fiber, and freeze-dried. The resulting PHBV/15 wt% NFC was then used as a master batch in a subsequent melt compounding process to produce nanocomposites of various formulations. Its properties such as its mechanical properties, crystallization behavior, solubility of carbon dioxide (CO2), foaming behavior, and thermal stability and degradation of PHBV due to NFC were evaluated. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to study the dispersion of NFC fibers. Adding NFC increased the tensile modulus of the PHBV/NFC nanocomposites nearly twofold. Differential scanning calorimetry (DSC) analysis showed that the NFC served as a nucleating agent, promoting the early onset of crystallization. However, high NFC content also led to greater thermal degradation of the PHBV matrix. Dynamic mechanical analysis (DMA) showed an increase of the storage modulus in the glassy state with increasing NFC content, but a more significant increase in modulus was detected above the glass transition temperature. The solubility of CO2 in the PHBV/NFC nanocomposites decreased and the desorption diffusivity increased as more NFC was added. Finally, the foaming behavior of PHBV/NFC nanocomposites was studied and the addition of NFC was found to inhibit foaming.

This paper first discusses some experimental verification of proposed ultraviolet (UV) radiation curing process models and then it outlines a robust process optimization and control scheme for layer-by-layer UV processing of a thick composite laminate. The experiments include UV transmission, cure kinetics, and in situ temperature measurements for UV curing of a one-dimensional (1D) composite material sample. The validated models are used to motivate how optimizing the layer-by-layer curing process can help address the challenge of maintaining through-cure due to the in-domain attenuation of the UV input during thick-part fabrication. The key insight offered is to model the layer-by-layer deposition and curing process as a multimode hybrid dynamic system with a growing spatial domain, where the interlayer hold times and the UV intensity at each layer addition can be taken as the augmented control variables to be selected optimally. Specifically, the control input is set to have feed forward and output feedback components, which act on the UV intensity at each layer and are constructed to track a reference surface temperature trajectory. The feedback gains at each layer addition are designed by posing a robust optimization problem that penalizes the sensitivity of the objective function to process uncertainties. It is illustrated using simulation analyses that augmented control with robust optimal static feedback of UV intensity at each layer and nominal optimization of the interlayer hold times gives very close tracking of a desired final cure level distribution in the presence of parametric uncertainty.

Fully biobased composite materials were fabricated using a natural, lignocellulosic filler, namely oak wood flour (OWF), as particle reinforcement in a biosynthesized microbial polyester matrix derived from poly(β-hydroxybutyrate)- co -poly(β-hydroxyvalerate) (PHBV) via an extrusion injection molding process. The mechanisms and effects of processing, filler volume percent (vol%), a silane coupling agent, and a maleic anhydride (MA) grafting technique on polymer and composite morphologies and tensile mechanical properties were investigated and substantiated through calorimetry testing, scanning electron microscopy, and micromechanical modeling of initial composite stiffness. The addition of 46 vol% silane-treated OWF improved the tensile modulus of neat PHBV by 165%. Similarly, the tensile modulus of MA-grafted PHBV increased 170% over that of neat PHBV with a 28 vol% addition of untreated OWF. Incorporation of OWF reduced the overall degree of crystallinity of the matrix phase and induced embrittlement in the composites, which led to reductions in ultimate tensile stress and strain for both treated and untreated specimens. Deviations from the Halpin–Tsai/Tsai–Pagano micromechanical model for composite stiffness in the silane and MA compatibilized specimens are attributed to the inability of the model both to incorporate improved dispersion and wettability due to fiber–matrix modifications and to account for changes in neat PHBV and MA-grafted PHBV polymer morphology induced by the OWF.

The effects of incorporating hyperbranched polymers (HBPs) and different nanoclays [Cloisite® 30B and halloysite nanotubes (HNT)] on the mechanical, morphological, and thermal properties of solid and microcellular poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) were investigated. According to the X-ray diffraction (XRD) and transmission electron microscopy (TEM) analyses, Cloisite 30B exhibited a combination of exfoliation and heterogeneous intercalation structure for both solid and microcellular PHBV–12% HBP–2% Cloisite 30B nanocomposites. TEM images indicated that HNTs were uniformly dispersed throughout the PHBV matrix. The addition of 2% nanoclays improved the thermal stability of the resulting nanocomposites. The addition of HBP+poly(maleic anhydride-alt-1-octadecene) (PA), Cloisite 30B, and HNT reduced the average cell size and increased the cell density of the microcellular components. The addition of (HBP+PA), Cloisite 30B, and HNT also increased the degree of crystallinity for both solid and microcellular components in comparison with neat PHBV. Also, with the addition of 12% (HBP+PA), the area under the tan-δ curve, specific toughness, and strain-at-break of the PHBV–HBP nanocomposite increased significantly for both solid and microcellular specimens, whereas the storage modulus, specific Young's modulus, and specific tensile strength decreased. The addition of 2% nanoclays into the PHBV–HBP nanocomposites improved the storage modulus, specific Young's modulus, and specific tensile strength of the PHBV–HBP–nanoclay-based nanocomposites, but they were still lower than those of the neat PHBV. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers

Poly(ethylene terephthalate) (PET) resin is one of the most widely used thermoplastics, especially in packaging. Because thermal and hydrolytic degradations, recycled PET (RPET) exhibits poor mechanical properties and lacks moldability. The effects of adding elastomeric modifiers, chain extenders (CE), and poly(butylene adipate-co-terephthalate), PBAT, as a toughener to RPET on its moldability and mechanical property were investigated. Melt blending of RPET with CE, thermoplastic elastomer (TPE), and/or PBAT was performed in a thermokinetic mixer (K-mixer). The blended materials were then injection molded to produce tensile specimens. Various techniques were used to study the mechanical properties, rheological properties, compatibility, and crystallization behavior of the RPET blends. By melt blending with proper additives, recycled PET regained its moldability, thereby enabling the recycling of RPET. Furthermore, the addition of CE greatly enhanced the mechanical properties of RPET. While the RPET and TPE blends also showed improved mechanical properties, the improvement was less significant and the blends were often immiscible due to the difference in polarities between RPET and TPE. Finally, it was found that the mechanical properties of RPET blends depended on the prior thermal history of the material and could be improved with an extra annealing step that increased the degree of crystallinity. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers

Solid and microcellular components made of poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV)/poly (butylene adipate-co-terephthalate) (PBAT) blend (weight ratio of PHBV:PBAT = 30:70), recycled wood fiber (RWF), and nanoclay (NC) were prepared via a conventional and microcellular-injection molding process, respectively. Morphology, thermal properties, and mechanical properties were investigated. The addition of 10% RWF (both untreated and silane-treated) reduced the cell size and increased the cell density of the microcellular components. Also, the addition of 10% RWF (both untreated and silane-treated) generally increased the specific Young’s modulus and tensile strength, but decreased the specific toughness and strain-at-break in both solid and microcellular components. Moreover, unlike the neat PHBV/PBAT blend, microcellular PHBV/PBAT/RWF (both untreated and silane-treated) composites showed higher specific toughness and strain-at-break compared to their solid counterparts. In addition, higher specific toughness and strain-at-break was observed in the PHBV/PBAT/untreated-RWF composite compared with the PHBV/PBAT/silane-treated RWF composite, particularly in the microcellular components. The degree of PHBV crystallinity increased significantly in both solid and microcellular PHBV/PBAT/RWF composites although the degree of PHBV crystallinity in the solid components was slightly higher than that of their microcellular counterparts. The effects of adding 2% nanoclay on the properties of the PHBV/PBAT/silane-treated-RWF composite were also investigated. The nanoclays exhibited an intercalated structure in the composites based on XRD analysis and did not induce significant changes in the cell morphology and mechanical properties of the PHBV/PBAT/silane-treated-RWF composite. However, it did improve its thermal stability.

Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV)/coir fiber composites were prepared via both conventional and microcellular injection-molding processes. The surface of the hydrophilic coir fiber was modified by alkali- and silane-treatment to improve its adhesion with PHBV. The morphology, thermal, and mechanical properties were investigated. The addition of coir fiber (treated and untreated) reduced cell size and increased cell density. Further decrease in cell size and increase in cell density was observed for treated fibers compared with PHBV/untreated-fiber composites. Mechanical properties such as specific toughness and strain-at-break improved for both solid and microcellular specimens with the addition of coir fibers (both treated and untreated); however, the specific modulus remained essentially the same statistically while the specific strength decreased slightly. The silane-treated coir fiber composites showed the greatest improvement in specific toughness and strain-at-break among the treated-fiber composites. In addition, adding coir fibers (treated and untreated) also increased the degree of crystallinity of the PHBV composites. PHBV with treated coir fibers showed a higher degree of crystallinity compared with untreated coir fibers.

Solid and microcellular specimens made of poly (3-hydroxybutyrate-co-3-hydroxyvalerate)(PHBV)/ poly(butylene adipate-co-terephthalate) (PBAT) blends with three different weight ratios (i.e., PHBV/PBAT = 98.5/1.5 (Y1000P), 45/55 (5010P), and 30/70 (6010P), respectively) were prepared via conventional and microcellular injection molding process, respectively. Various properties such as miscibility, cell morphology, thermal, and mechanical properties were investigated. Compared with the microcellular specimens, the solid specimens showed better miscibility. Increasing the PBAT content led to higher specific toughness and strain-at-break, but lower specific modulus and specific strength for both solid and microcellular specimens. In addition, increasing the PBAT content increased the average cell size, but decreased the cell density of the microcellular samples. Finally, the crystallinity of PHBV in the PHBV/PBAT blends decreased significantly with increasing PBAT content for both solid and microcellular specimens. POLYM. ENG. SCI., 50:1440-1448, 2010. © 2010 Society of Plastics Engineers.

The effects of addition of hyperbranched polyesters (HBPs) and nanoclay on the material properties of both solid and microcellular polylactide (PLA) produced via a conventional and microcellular injection-molding process, respectively, were investigated. The effects of two different types of HBPs (i.e., Boltorn H2004® and Boltorn H20®) at the same loading level (i.e., 12%), and the same type of HBP at different loading levels (i.e., Boltorn H2004® at 6 and 12%), as well as the simultaneous addition of 12% Boltorn H2004® and 2% Cloisite®30B nanoclay (i.e., HBP–nanoclay) on the thermal and mechanical properties (both static and dynamic), and the cell morphology of the microcellular components were noted. The addition of HBPs and/or HBP with nanoclay decreased the average cell size, and increased the cell density. The stress–strain plots of all the solid and microcellular PLA-H2004 blends showed considerable strain softening and cold drawing, indicating a ductile fracture mode. Among the two HBPs, samples with Boltorn H2004® showed higher strain-at-break and specific toughness compared to Boltorn H20®. Moreover, the sample with Boltorn H2004® and nanoclay exhibited the highest strain-at-break (626% for solid and 406% for microcellular) and specific toughness (405% for solid and 334% for microcellular). Finally, the specific toughness, strain-at-break, and specific strength of microcellular samples were found to be lower than their solid counterparts.

The effects of adding epoxy-functionalized chain-extender (CE) and processing conditions such as die temperature on the cell morphology, volume expansion ratio (VER), open cell content (OCC), and crystallization of microcellular extruded polylactide (PLA) were investigated. When compared with pure PLA, the addition of talc decreased the average cell size and increased the cell density. Moreover, the simultaneous addition of talc and CE led to denser and more uniform cell structure up until 1.0% CE content. In general, the volume expansion ratio and open cell content of all the formulations decreased with the die temperature. The addition of talc decreased both VER and OCC, whereas the addition of CE increased both. The die temperature did not affect the degree of crystallinity significantly. The addition of talc increased the crystallinity, but the addition of CE decreased it. Finally, the molecular weight of PLA increased significantly with the addition of CE. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers

The effects of adding an epoxy-based chain-extender (CE) on the properties of injection-molded solid and microcellular polylactide (PLA) were studied. PLA and PLA with 8 wt.% CE (PLA-CE) were melt-compounded using a twin-screw extruder. Solid and microcellular specimens were produced via a conventional and microcellular injection-molding process, respectively. Various characterization techniques including gel permeation chromatography, tensile testing and dynamic mechanical analysis, scanning electron microscopy and differential scanning calorimetry were applied to study the molecular weight, static and dynamic mechanical properties, cell morphology, and crystallization behavior, respectively. The addition of CE enhanced the molecular weight but decreased the crystallinity of PLA. The addition of CE also reduced the cell size and increased the cell density. Furthermore, the decomposition temperatures and several tensile properties, including specific strength, specific toughness, and strain-at-break of both solid and microcellular PLA specimens, increased with the addition of CE.

Polylactide (PLA)-recycled wood fiber (RWF) composites with a small amount of silane were compounded using a kinetic-mixer and molded using an injection molding machine. The molded PLA-RWF compo- sites were characterized using gel permeation chromatog- raphy, scanning electron microscope, X-ray diffraction, differential scanning calorimeter, tensile testing machine, and a dynamic mechanical analyzer. As observed in the stress-strain plots, the amount of necking before fracture decreased with an increasing RWF content. Similarly, the strain-at-break also decreased with the RWF content. The tensile strength remained the same irrespective of the RWF content. Both the tensile modulus and the storage modulus of the PLA-RWF composites increased with the RWF content. The degree of crystallinity of the PLA increased with the addition of RWF. No reduction in the number-average molecular weight (Mn) was observed for pure PLA and PLA-10%RWF-0.5%Silane composites af- ter injection molding; however, substantial reduction in Mn was found in PLA-20%RWF-0.5%Silane composites. Finally, a theoretical model based on Halpin-Tsai empiri- cal relations is presented to compare the theoretical results with that of the experimental results. V C 2008 Wiley Periodi

Polylactide–flax fiber composites with 1, 10 and 20 wt% fiber were melt-compounded and subsequently molded via the conventional and microcellular injection-molding processes. Silane was used as a coupling agent. The effects of fiber and silane content on cell morphology, static and dynamic mechanical properties, and crystallization properties have been studied. The average cell size decreased while the cell density increased with the fiber content. The degree of crystallinity increased with the fiber content. Silane treatment of fibers affected neither the cell morphology nor the degree of crystallinity. The toughness and strain-at-break of solid samples decreased with the fiber content while silane treatment increased both properties; however, neither fiber content nor silane treatment had much influence on the toughness and strain-at-break of microcellular samples. The specific modulus of both solid and microcellular samples increased with the fiber content. The specific strength of the solid and microc...

Biobased and biodegradable polylactide (PLA)-pine wood flour (PWF) composites were investigated as a means to reduce the overall material cost and tailor the material properties. The composites were prepared using a kinetic-mixer and an injection molding machine. The tensile modulus of the PLA-PWF composites increased with the PWF content whereas the toughness and strain-at-break decreased. The tensile strength remained the same irrespective of the PWF content (up to 40%). The storage modulus also increased with the PWF content. Additionally, composites containing PWF treated with silane showed higher storage modulus than those without the silane treatment. The area integration underneath the tan δ peaks decreased with increasing PWF, indicating that the PLA-PWF composites exhibited more elastic behavior with increasing PWF. The degree of crystallinity of the PLA-PWF composites increased significantly with the PWF content. Furthermore, the treatment of PWF with silane had a positive effect on its nucleating ability, as treated PLA-PWF composites showed higher crystallinity compared with their untreated counterparts. The morphology of the fracture surfaces were studied using a scanning electron microscope. Finally, a Halpin-Tsai analytical model to predict Young's modulus of PLA-PWF composites was presented to compare the theoretical results with that of experimental results. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers

Recycled paper shopping bag fibers were melt-compounded using a batch mixer with biobased/biodegradable polylactide (PLA) at 10 and 30 wt.% using silane as a coupling agent. These PLA/fiber composites were then injection molded to produce both solid and microcellular tensile bars. The mechanical properties (specific modulus, specific tensile strength, specific toughness, and strain at break) of the neat PLA and PLA composites were tested and the cell morphology of the microcellular samples was examined using scanning electron microscopy. It was observed that the addition of the recycled paper shopping bag fibers resulted in an increase in cell density and decrease in average cell size for the microcellular components when compared with the neat PLA. The addition of the fibers increased the specific modulus of both solid and microcellular components, and high fiber contents (30 wt.%) resulted in an increase in specific tensile strength, yet yielded a decrease in the strain at break and specific toughness. The storage modulus was also improved with the addition of 10 and 30 wt.% fibers for both solid and microcellular components.

In this study, polylactide (PLA)-multi-walled carbon nanotube (MWCNT) nanocomposites were melt-compounded using a twin-screw extruder. Solid and microcellular tensile bar specimens were produced via conventional and microcellular injection molding, respectively. Various characterization techniques were applied to study the static and dynamic mechanical properties, degree of MWCNT dispersion, cell morphology, and crystallization behavior. The addition of a small amount of MWCNTs led to a decrease in the cell size and an increase in the cell density of the microcellular PLA specimens. A transmission electron microscopy analysis of the PLA-MWCNT specimens revealed a higher degree of MWCNT dispersion in the microcellular PLA-MWCNT composite compared with its solid counterpart, indicating that the microcellular injection molding process further dispersed the MWCNTs. For both solid and microcellular specimens, the addition of 1.5 wt% MWCNTs reduced the specific strength, specific toughness and strain-at-break while exerting less impact on the specific modulus. The storage modulus was not affected significantly with the addition of MWCNTs, but was found to be higher for the microcellular specimens compared with their solid counterparts. Finally, the crystallinity of PLA increased with the addition of MWCNTs.

Over the past few years, the field of renewable polymers has attracted wide interest across the scientific community especially owing to their bionature properties such as biobased, biodegradable, biocompatible, and biorenewable. In fact, biopolymers help to reduce the global dependence on petroleum-based polymers, reduce the accumulation of persistent plastic waste, and balance greenhouse gases by sequestrating or better controlling the emission of CO2 in the environment. Among the many different biopolymers available, polyalkylene carbonates (PAC) occupy a special place as they are synthesized from CO2, thereby leveraging enhanced sustainability compared to other biopolymers that are usually made from sugar resources. Polypropylene carbonate (PPC) is one such PAC that is synthesized from CO2 and propylene oxide in the presence of a metal catalyst. Compared to other PACs, the primary advantage of PPC is its wide range of tunable mechanical properties obtained by controlling the amount of ether linkage. This chapter provides a general overview of PACs and their synthesis mechanisms especially focusing on PPC, its blends (with bio- and synthetic polymers) and composites (with macro-, micro-, and nanoreinforcements) with special emphasis on the mechanical properties of PPC-based blends and composites. Finally, a summary of the static mechanical performance of PPC-based blends and composites is presented with criteria for designing these materials with enhanced properties.

Bio-based laminate composites, consisting of alternatively stacked poly(lactic acid) (PLA) sheet and randomly oriented areca fiber mat, were processed via film stacking technique (FST). FST was chosen as it is a commercially viable, low energy-intensive process for fabricating fiber-reinforced composite, thereby advocating environmental sustainability. Laminate composites exhibited mechanical strength of 6.5 MPa at 16 wt % fiber loading. Crystallinity of as-received PLA sheets was found to be 26% due to the presence of ∼30 wt % inorganic filler, and showed further enhancement to 50% upon the addition of 22 wt % areca fiber. Dynamic mechanical analysis showed higher glass transition temperature (83 °C) for PLA sheets, mainly due to the presence of higher filler content. This work demonstrates the use of bio-based laminate composite processed at the lowest possible temperatures as viable alternatives to thermoplastic polyolefins in automobiles. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 135, 45795.

Bio-based polymer foams have been gaining immense attention in recent years due to their positive contribution towards reducing the global carbon footprint, lightweighting, and enhancing sustainability. Currently, polylactic acid (PLA) remains the most abundant commercially consumed biopolymer, but suffers from major drawbacks such as slow crystallization rate and poor melt processability. However, blending of PLA with a secondary polymer would enhance the crystallization rate and the thermal properties based on their compatibility. This study investigates the physical and compatibilized blends of PLA/poly (butylene succinate-co-adipate) (PBSA) processed via supercritical fluid-assisted (ScF) injection molding technology using nitrogen (N2) as a facile physical blowing agent. Furthermore, this study aims at understanding the effect of blending and ScF foaming of PLA/PBSA on crystallinity, melting, and viscoelastic behavior. Results show that compatibilization, upon addition of triphenyl phosphite (TPP), led to an increase in molecular weight and a shift in melting temperature. Additionally, the glass transition temperature (Tg) obtained from the tanδ curve was observed to be in agreement with the Tg value predicted by the Gordon–Taylor equation, further confirming the compatibility of PLA and PBSA. The compatibilization of ScF-foamed PLA–PBSA was found to have an increased crystallinity and storage modulus compared to their physically foamed counterparts.

Composites are now extensively used in applications where outstanding mechanical properties are necessary in combination with weight savings, due to their highly tunable microstructure and mechanical properties. These properties present great potential for part integration, which results in lower manufacturing costs and faster time to market. Composites also have a high level of styling flexibility in terms of deep drawn panel, which goes beyond what can be achieved with metal stampings. The so-called multifunctional or smart composites provide significant benefits to the vehicles as compared to the traditional materials that only have monotonic properties. CAE Design and Failure Analysis of Automotive Composites focuses on the latest use of CAE (Computer-Aided Engineering) methods in design and failure analysis of composite materials and structures, beginning with a brief introduction to the design and failure analysis of composite materials, and then presenting some recent, innovative CAE design examples of composite structures by engineers from major CAE developers and automobile OEMs and suppliers. This title brings together 12 SAE technical papers, carefully selected by the editors covering three main areas of expertise: • Design and Failure Analysis of Composites: Static Loading • Design and Failure Analysis of Composites: Dynamic and Impact Loading • Design and Failure Analysis of Composites: Blast Loading

A battery pack case of an electric vehicle was developed with a fibrous thermoplastic composite material. Due to cost effectiveness, long fiber reinforced thermoplastics by direct process (D-LFT) were adopted. PA6 (Polyamide 6) based composites were processed using a D-LFT pilot machine at the temperature range between 250°C and 290°C. Glass and carbon fibers were added in the matrix varying the mixture ratio of the fibers while keeping the weight fraction 40%. The increase of carbon fibers in the mixture increased tensile modulus and strength, however, decreased Izod impacts strength. The fatigue life of developed composites was evaluated by fatigue tests in tension, which were over one million cycles at the maximum fatigue loading less than 60% of the composite strength. Associated with fiber orientation, anisotropic mechanical behavior was investigated in terms of flexural properties and mold shrinkage. A shape of strand placement was suggested minimizing the anisotropic behavior for in-plane mechanical properties and mold shrinkage. A design for the lower case of a battery pack case with the composite material was developed. CAE (Computeraided Engineering) simulations were conducted to optimize the structural performance with respect to impact performance and structural durability. Non-destructive evaluation using X-ray showed no defects in the prototype. It satisfied the requirement of sled and vibration tests. The weight reduction of 31% was achieved.

In this study, poly(e-caprolactone) (PCL)/sodium chloride (NaCl), PCL/poly(ethylene oxide) (PEO)/NaCl and PCL/PEO/NaCl/hydroxyapatite (HA) composites were injection molded and characterized. The water soluble and sacrificial polymer, PEO, and NaCl particulates in the composites were leached by deionized water to produce porous and interconnected microstructures. The effect of leaching time on porosity, and residual contents of NaCl and NaCl/HA, as well as the effect of HA addition on mechanical properties was investigated. In addition, the biocompatibility was observed via seeding human mesenchymal stem cells (hMSCs) on PCL and PCL/HA scaffolds. The results showed that the leaching time depends on the spatial distribution of sacrificial PEO phase and NaCl particulates. The addition of HA has significantly improved the elastic (E') and loss moduli (E″) of PCL/HA scaffolds. Human MSCs were observed to have attached and proliferated on both PCL and PCL/HA scaffolds. Taken together, the molded PCL and PCL/HA scaffolds could be good candidates as tissue engineering scaffolds. Additionally, injection molding would be a potential and high throughput technology to fabricate tissue scaffolds.

Foamed poly(lactide) (PLA)/poly(butylene adipate-co-terephthalate) (PBAT) blends were processed via the microcellular extrusion process using CO2 as a blowing agent. Talc has been added to promote heterogeneous nucleation. Two types of PLA/PBAT blend systems were investigated: Ecovio, which is a commercially available compatibilized PLA/PBAT blend; and a non-compatibilized PLA/PBAT blend at the same PLA/PBAT ratio (i.e., 45:55 by weight percent). Six different formulations were investigated: pure PLA, PLA-talc, Ecovio, Ecovio-talc, non-compatibilized PLA/PBAT blend, and non-compatibilized PLA/PBAT-talc. The effects of various processing parameters such as die temperature, talc and compatibilization on various foaming properties such as cell morphology, volume expansion ratio (VER), open cell content (OCC) and crystallinity were investigated. As per the DSC thermograms, it was observed that compatibilization has merged the two distinctive melting peaks of PLA and PBAT into a single peak while lowering the peak temperature. In general, the addition of talc has decreased the average cell size and VER and increased the cell density and crystallinity; however, it has varying effects on the open cell content. Compatibilization has reduced the average cell size and volume expansion but increased the cell density and had varying and no effects on the OCC and crystallinity, respectively. Similar to compatibilization, the die temperature was found to have varying and no effects on the OCC and crystallinity, respectively. Except for PLA and non-compatibilized PLA/PBAT blend, the cell size and VER of all other formulations did not vary much throughout the entire temperature range (130-150°C). The cell density was found to be insensitive to die temperatures except for Ecovio and Ecovio-talc.

A methodology for predicting the non-linear static response and reliability of plates made of conventional composite and nanocomposite materials is presented. The methodology was developed by integrating micromechanics models for both conventional composites and nanocomposites with tools for strength and reliability analysis of plates. Inputs to the model for strength analysis are the material properties of the composite obtained from the micromechanics model and the plate geometry and boundary conditions. Output of the model for strength analysis includes the load-deflection data for a plate under axial or transverse loading. The reliability analysis approach yields the probabilities of the failure modes and the sensitivities of these probabilities to the random variables. The methodology is demonstrated on a rectangular plate subjected to an in-plane compressive load with initial imperfections.