Self-reinforced Composites Research Articles

Dually self-reinforced Poly(ε-caprolactone) composites based on unidirectionally arranged fibers

Dually self-reinforced Poly(ε-caprolactone) (PCL) composites were prepared to broaden its load-bearing applications as tissue engineering scaffolds. The composites were prepared from bi-component PCL yarns composed of self-nucleated PCL drawn fibers and PCL matrix by a combined process of yarns winding and hot pressing. Differential Scanning Calorimetry (DSC) results showed that incorporating of self-nucleating agents can improve the melting points of the fibers, creating a process temperature window for hot pressing. The orientation parameters of the fibers were accurately measured by Confocal Raman microscopy (CRM) and the results showed that the orientation parameter of the fibers could be up to 0.9 after drawn. Tensile tests showed that the self-nucleated drawn fibers had stronger mechanical properties than the control fibers with the same draw ratios. The hot pressing parameters (temperature and pressure) were also optimized during hot-pressing. The Young's modulus and break strength of the dually self-reinforced composites in longitudinal direction could be up to 118% and 400% higher than that of pristine PCL although their elongation at break decreased. Decline of mechanical properties of the composites in transverse direction was not observed, indicating good adhesion between the fibers and the matrix, which was confirmed by scanning electron microscope analysis.

High-Performance Polyimide Filaments and Composites Improved by O₂ Plasma Treatment.

Interface issues urgently need to be addressed in high-performance fiber reinforced composites. In this study, different periods of O2 plasma treatment are proposed to modify twist-free polyimide (PI) filaments to improve hydrophilicity and mechanical and interfacial properties. Feeding O2 produces chemically active particles to modify the filament surface via chemical reactions and physical etching. According to the X-ray photoelectron spectroscopy (XPS) results, the PI filaments exhibit an 87.16% increase in O/C atomic ratio and a 135.71% increase in the C–O functional group after 180 s O2 plasma treatment. The atomic force microscope (AFM) results show that the root mean square roughness (Rq) of the treated PI filaments increases by 105.34%, from 38.41 to 78.87 nm. Owing to the increased surface oxygenic functional groups and roughness after O2 plasma treatment, the contact angle between treated PI filaments and water reduces drastically from the pristine state of 105.08° to 56.15°. The O2 plasma treated PI filaments also demonstrate better mechanical properties than the pristine PI filaments. Moreover, after O2 plasma treatment, the adhesion between PI filaments and poly(amic acid) (PAA) is enhanced, and the tensile strength of the polyimide/poly(amic acid) (PI/PAA) self-reinforced composites increases from 136 to 234 MPa, even causing the failure mode of the composite changes from adhesive failure to partly cohesive failure.

Development and characterization of poly(ethylene terephthalate) based injection molded self-reinforced composites. Direct reinforcement by overmolding the composite inserts

This work presents the concept of using the self-reinforced inserts, suitable for overmolding during the standard injection molding procedure. The reinforcing inserts made from self-reinforced poly(ethylene terephtahalte) sheets (srPET) were overmolded by the matrix polymer. Two types of poly(ethylene terephthalate) were used as the matrix material, PET (pure bottle grade resin) and G-PET (amorphous PET based copolymer). Samples prepared under different conditions of the injection molding process were tested in terms of mechanical properties, DMA and DSC analysis. The results of mechanical tests confirmed the different fracture behavior, more favorable for G-PET samples, where the increase of tensile strength and E modulus reached 60% and 32% respectively. The most significant increase was observed for impact resistance values, for both types of polyesters the impact strength reach around 50 kJ/m2, from the initial value below 5 kJ/m2. The SEM microscopy was used to investigate the morphology of matrix-reinforcement interface. The observations of the bonding interface indicate the lack of delamination process and high level of adhesion between the matrix materials and reinforcing srPET insert. The presented results confirm that the proposed concept of using the overmolding technology for preparation of self-reinforced composites has the potential for industrial implementation.

Polymers and Related Composites via Anionic Ring-Opening Polymerization of Lactams: Recent Developments and Future Trends.

This paper presents a comprehensive overview of polymers and related (nano)composites produced via anionic ring opening polymerization (AROP) of lactams. It was aimed at surveying and showing the important research and development results achieved in this field mostly over the last two decades. This review covers the chemical background of the AROP of lactams, their homopolymers, copolymers, and in situ produced blends. The composites produced by AROP were grouped into nanocomposites, discontinuous fiber, continuous fiber, textile fabric, and self-reinforced composites. The manufacturing techniques were introduced and the most recent developments highlighted. Based on this state-of-art survey some future trends were deduced and as their “driving forces” novel and improved manufacturing techniques identified.

Development of multifunctional self-reinforced composites

Nanocomposites based on Polypropylene and carbon nanotubes were used as the matrix in self-reinforced composites. Morphological, thermal and mechanical characterization was performed. Electrical behavior was investigated to analyze the materials ability to monitor damage from strain-induced electrical changes. Nanocomposites obtained at high extrusion speed presented better filler dispersion and hence, improved tensile and electrical response. Processing conditions mainly affected the composites consolidation quality and thus, their failure mode. While poorer consolidated materials presented delamination, those better consolidated mostly failed by fiber fracture. Composites with an open PP fabric exhibited electrical resistivity values adequate for strain sensing but worse tensile properties.

Fabrication of self-reinforced polyester composites and their mechanical and flame retardant properties

Fabrication of self-reinforced polyester composites and their mechanical and flame retardant properties

Machining and characterization of self-reinforced polymers

This Paper focuses on obtaining the mechanical properties and the effect of the different machining techniques on self-reinforced composites sample and to derive the best machining method with remarkable properties. Each sample was tested by the Tensile and Flexural tests, fabricated using hot compaction test and those loads were calculated. These composites are machined using conventional methods because of lack of advanced machinery in most of the industries. The advanced non-conventional methods like Abrasive water jet machining were used. These machining techniques are used to get the better output for the composite materials with good mechanical properties compared to conventional methods. But the use of non-conventional methods causes the changes in the work piece, tool properties and more economical compared to the conventional methods. Finding out the best method ideal for the designing of these Self Reinforced Composites with and without defects and the use of Scanning Electron Microscope (SEM) analysis for the comparing the microstructure of the PP and PE samples concludes our process.

Preparation and characterization of biodegradable poly(ϵ-caprolactone) self-reinforced composites and their crystallization behavior

Preparation and characterization of biodegradable poly(ϵ-caprolactone) self-reinforced composites and their crystallization behavior

Effect of Fiber Orientation on the Wrinkling Behavior of Thermoplastic Composite

In this work, experiments were conducted to examine the impact of fiber orientation of self-reinforced polypropylene on wrinkling phenomenon. Defects due to wrinkling are major quality issues in rapid forming of sheet materials. This article examines the influence of two fiber orientations [0°/90° and 45°/-45°] on wrinkling initiation of a self-reinforced polypropylene composite (Curv®) material system. It was found that 45°/-45° specimen wrinkles at smaller axial displacement compared to 0°/90° specimen. In both specimens, there was an abrupt change in strain increment ratio that corresponded to the onset of wrinkling. This phenomenon validates the robustness of the wrinkling indictor based on strain increment ratio concept.

Multivariable dependency of thermal shrinkage in highly aligned polypropylene tapes for self-reinforced polymer composites

Self-reinforced composites offer a unique combination of properties such as high specific strength, high impact resistance, and recyclability by incorporating highly aligned fibers within a random matrix of the same polymer. However, high temperatures will shrink the system to recover randomness in the aligned segments, compromising the composite thermal stability during processing as self-reinforced tapes are consolidated into the final composite through heating and pressure. Hence, the dynamic nonlinear multivariable (i.e., time, temperature, stress) shrinkage exhibited by self-reinforced polypropylene (SRPP) tapes was measured and modeled at the maximum shrinkage limit achieved in the proximity of the composite processing temperature [∼140 to160°C]. At high stress (∼7.5MPa) the thermal shrinkage of the SRPP tapes was reduced and a parallel creep mechanism was activated. The modeling, and prediction of the main factors governing the thermal shrinkage expand and diversify the dynamic design window for new SRPP composites.

The influence of processing conditions on the mechanical properties and structure of poly(ethylene terephthalate) self-reinforced composites

The self-reinforced composites based on poly(ethylene terephthalate) (PET) are relatively new materials, competitive to composites based on polymers from the group of polyolefins. The use of PET as a base material should be another step forward for this technology, taking into account the properties, price, and the recycling possibility of proposed composites. In this research work, the main subject was to assess the impact of processing conditions on the final properties of the PET self-reinforced composites (srPET). The examined samples were prepared by hot-compaction technique under variable thermal conditions. The input material was composed of PET resin and low-melting copolymer (LPET). The high tenacity PET fibers were used as reinforcement for PET copolymer matrix. Initially both materials were in the form of continuous fiber; they were woven into a hybrid yarn wherein the proportion of PET and LPET fibers was 50/50. The properties of this hybrid yarn were investigated by differential scanning calorimetry (DSC) analysis, where the hot-compaction process conditions were simulated. Composite samples were investigated using the dynamic mechanical analysis (DMA) and static tension tests. The structure of the composite was observed using the optical microscope. The obtained mechanical properties of such a composite are not comparable to commercially made composite sheets, in which overall properties are mostly higher.

Nonlinear creep response of oriented polypropylene tapes

The creep response of a highly oriented polypropylene tape used for the manufacture of self-reinforced polypropylene or all-polypropylene composites was studied over a range of stresses and temperatures. Similar to oriented polyethylene, the creep compliance is linear viscoelastic at short loading times, whereas pronounced stress dependence is observed at longer loading times. A mathematical model is proposed, where the total deformation of the fibre is regarded as being composed of a stress-linear delayed elastic component and a nonlinear plastic flow contribution. Model predictions are in good agreement with the experimental data.

Environmental performance of self-reinforced composites in automotive applications — Case study on a heavy truck component

A screening environmental life cycle analysis (LCA) of the novel self-reinforced poly(ethylene therephthalate) (SrPET) is presented in this paper. A truck exterior panel is used as case study where a concept design made by SrPET is assessed and compared to a glass fibre reinforced composite and a thermoplastic blend that are currently used for the selected component. The results showed that the SrPET panel has 25% lower environmental impact compared to the current design, with no significant life cycle trade-offs. SrPET offers possibilities for weight reduction while maintaining good mechanical properties. As the impact during use phase is expected to decrease in the future the relative importance of manufacturing and end-of-life (EOL) will increase. Thus SrPET can be considered a competitive material for replacing existing energy intense non-recyclable composites.

Self-reinforced composites based on commercial PP woven fabrics and a random PP copolymer modified with quartz

Self-reinforced composites based on commercial polypropylene (PP) woven fabrics and a random PP copolymer modified with quartz were obtained by film stacking. The effect of the incorporation of quartz on the materials fracture and failure behavior was studied through uniaxial tensile tests and quasi-static fracture experiments. Acoustic emission analysis was also performed in situ in the tensile tests. A higher consolidation quality was obtained for the composites containing quartz. In the composite with random PP modified with 5 wt% quartz, the higher consolidation and the better dispersion of quartz particles positively impacted on the materials tensile and fracture behavior. From the results of acoustic emission analysis, fiber fracture appears as the dominant failure mechanism in the investigated composites. Copyright © 2016 John Wiley & Sons, Ltd.

Effect of temperature and blank holder force on non-isothermal stamp forming of a self-reinforced composite

Effect of temperature and blank holder force on non-isothermal stamp forming of a self-reinforced composite

Preparation and characterization of uniaxial poly(lactic acid)-based self-reinforced composites

Abstract Uniaxial poly(lactic acid)-based self-reinforced composites have been developed by bonding poly ( l -lactic acid) (PLLA) fibers by depositing poly(D, l -lactic acid) (PDLLA) which was dissolved in ethyl acetate. The microstructure and the thermal and mechanical properties of this self-reinforced composite have been characterized using scanning electron microscopy, dynamic mechanical analysis, and tensile testing. The results revealed that after ethyl acetate treatment, the PLLA fibers maintained their geometry and orientation well, had an increased crystallinity, and showed a slightly damaged surface. Electron microscopy and thermal analysis showed that the interface between the PLA fiber and the PLA matrix had good compatibility, which was expected since they possess the same chemical structure. The modulus, tensile strength, and elongation, as well as the thermal stability of uniaxial poly(lactic acid) self-reinforced composites, were all significantly greater than those of the PDLLA film. The results showed that we have developed a method to prepare PLA composites with enhanced mechanical properties, without the problem of narrow processing temperature window normally required when using traditional thermal processing techniques.

Cost-Effective Microfibrillar Reinforced Composites for Lightweight Applications

Microfibrillar reinforced composites (MFC) are self-reinforced polymer-polymer composites, consisting of a cold drawn (fibrillized) phase in an isotropic matrix. They are manufactured via melt blending of two immiscible polymers with different melting temperatures, followed by a subsequent cold drawing and thermal annealing step. The present study examines the manufacturing of composite material out of melt-spun microfibrillar reinforced filaments. Polypropylene (PP) and Polyethylene terephthalate (PET) were chosen as the low-melting matrix and the high-melting reinforcement phase, respectively.The filaments were woven to flat textile structures and processed to composites via hot pressing. They represent a bidirectional reinforced composite, comparable to other fiber reinforced polymers. To ensure optimized processing the influence of relevant parameters has been investigated with respect to mechanical properties of the MFC‑filaments and the derived composites. In addition, the morphology was visualized by SEM imaging after all manufacturing steps. An important observation was that the reinforcing fibrils are still intact after thermal processing, leading to a significant increase in mechanical properties of the resulting composites. Quasistatic tensile tests show more than 100 % higher modulus and more than 50 % higher strength of the only 20 wt-% reinforced PET‑PP composites compared to neat PP. The influence of the amount of PET reinforcement, the variation in processing conditions and composite layup were investigated. Additionally, an outlook on the melt-spinning of blends with Polyamide (PA) is given. In future work it is meant to show that a broad spectrum of tailored properties can easily be achieved by such polymer blends and composites outperforming existing homopolymers as well as thermoplastic composites like short glass‑fiber‑reinforced Polypropylene.The material cost reduction thanks to adding cheaper mass‑production polymers and the transfer onto conventional manufacturing lines is meant to ensure the feasibility of industrial production. The low density and excellent recycling options of these composites underline their potential for automotive and aircraft applications.

Mechanical and Tribological Properties of Self-Reinforced Polyphenylene Sulfide Composites

25%, 50%, and 75% polyphenylene sulfide (PPS) long fiber reinforced PPS resin were prepared by a hot pressing method. Neat resin PPS and PPS fiber samples were also prepared to compare with the self-reinforced PPS composites. The reinforcing fibers were preheat treated at 240°C for 24 h. The tribological properties of the self-reinforced PPS composites against an AISI 1045 steel ring were determined by a block on ring type friction tester. Differential scanning calorimetry (DSC) results indicated that a higher degree of crystallinity was retained in the self-reinforced PPS composites than in neat PPS resin after hot pressing. Therefore, the addition of PPS fiber improved both the mechanical and tribological properties of PPS resin significantly. Dynamic mechanical analysis (DMA) demonstrated that the PPS fibers increased the glass transition temperature (Tg) of the PPS resin. SEM images of the fracture surfaces indicated that the toughness of the samples increased with increasing PPS fiber content. Additionally, PPS fibers improved the tribological properties of PPS resin by significantly reducing the friction coefficient and wear rate.

Is the use of correct terms and definitions important in creation of new materials?

and widely applied term is a case in composite community, where the thermodynamic term ‘phase’ is used instead of the term ‘component’. Obviously, the misuse of the term ‘phase’ is a remnant from the time when the colloid chemistry was formulated (second half of 19th century, i.e. long before the polymer science was defined). The confusion of this misuse can be easily demonstrated by poly(vinylidene fluoride) (PVDF) exhibiting five crystalline polymorphic modifications (phases!) and one amorphous phase but PVDF is still a one-component system. While this example does not have a direct effect on the creation of new materials, the next one, the definition of the relatively new type of polymer composites, the single polymer composites (SPCs), does. SPCs have also been called: one polymer composites (R. Porter), homocomposites, self-reinforced composites, one-phase composites, homogeneous composites, or all-polymer composites. The concept of SPCs has been formulated by R. Porter some 40 years ago (DOI: 10.1007/BF00554928) as attempt to solve the basic problem in polymer science and technology, namely, the low adhesion quality between matrix and reinforcement due to their different chemical composition. The approach is quite simple – the matrix and the reinforcement have to be of the same polymer, i.e. to be chemically identical. The idea attracted the attention of academia and industry during the last decade when patents were registered and products were commercialized; nanofibrillar SPCs with superior mechanical properties were also created (DOI: 10.1002/mame.201200226). What is more, similar products were prepared and called also SPCs (DOIs: 10.1007/s10853-009-3792-1, and 10.1016/j.compscitech.2013.12.006) using highly oriented poly propylene (PP) (as reinforcement) and the random copolymer of PP (usually with polyethylene) as a matrix thus neglecting the basic requirement (R. Porter) for identical chemical composition of matrix and reinforcement. Strictly speaking, such composites belong to the category of polymer–polymer composites. The same holds for thermoplastic copolyesters reinforced with ‘homo’-poly(ethylene terephthalate). The argument that the two chemically different components belong to the same polymer family (DOI: 10.1016/j.compscitech.2013.12.006) could hardly be seriously considered – it only smears the boundary between the two types of composites, the polymer-polymer ones and the SPCs and makes the clear definition of single polymer composites hardly possible affecting in this way negatively their further development! In order to make use of the unique properties of SPCs we should not forget that they could be multi-phase but always remain one-component systems!

Development and Characterization of the Injection-Molded Polymer Composites Made from Bicomponent Fibers

The results of this study are related to the implementation of the concept of self-reinforced composites. The input materials in preparation process were the bicomponent fibers. The studies were carried out on three types of fibers, HDPE/PP, cPP/PP, LPET/PET. In each case, the matrix material was a low melting polymer, and the core was made of a higher melting point polymer. The research was conducted for the materials shaped by an injection-molding technique. The analyses confirmed the two-component structure. Properties of the resulting composites confirmed the applicability of bicomponent fibers in the preparation of self-reinforced composites.