Film Stacking Method Research Articles

Tensile Fracture and Failure Behavior of Thermoplastic Starch with Unidirectional and Cross‐Ply Flax Fiber Reinforcements

AbstractThermoplastic starch (MaterBi®) based composites containing flax fibers in unidirectional and crossed‐ply arrangements were produced by hot pressing using the film stacking method. The flax content was varied in three steps, viz. 20, 40 and 60 wt.‐%. Static tensile mechanical properties (stiffness and strength) of the composites were determined on dumbbell specimens. During their loading the acoustic emission (AE) was recorded. Burst type AE signal characteristics (amplitude, width) were traced to the failure mechanisms and supported by fractographic inspection. The mechanical response and failure mode of the composites strongly depended on the flax content and the flax fiber lay‐up. It was established that the tensile strength increases until 40 wt.‐% flax fiber content but stays almost constant above this value. In the case of 40 wt.‐% unidirectional fiber reinforcement, the tensile strength of the composite was 3 times greater than that of the pure starch matrix. The flax fiber reinforcement increased the tensile modulus of the pure starch by several orders of amplitude.SEM picture of the fracture surface of a composite with UD flax reinforcement.magnified imageSEM picture of the fracture surface of a composite with UD flax reinforcement.

Natural fibres: can they replace glass in fibre reinforced plastics?

In this work, natural fibres (sisal, kenaf, hemp, jute and coir) reinforced polypropylene composites were processed by compression moulding using a film stacking method. The mechanical properties of the different natural fibre composites were tested and compared. A further comparison was made with the corresponding properties of glass mat reinforced polypropylene composites from the open literature. Kenaf, hemp and sisal composites showed comparable tensile strength and modulus results but in impact properties hemp appears to out-perform kenaf. The tensile modulus, impact strength and the ultimate tensile stress of kenaf reinforced polypropylene composites were found to increase with increasing fibre weight fraction. Coir fibre composites displayed the lowest mechanical properties, but their impact strength was higher than that of jute and kenaf composites. In most cases the specific properties of the natural fibre composites were found to compare favourably with those of glass.

Effect of the microstructure of GMT on its mechanical properties

AbstractThe effect of microstructure of GMT on its mechanical properties was investigated. The studied microstructure includes the fiber mat structure, the through‐thickness glass fiber content‐distribution of GMT sheets and the void content. The fiber bundle GMT (FB‐GMT) and the single fiber GMT (SF‐GMT) were prepared by the impregnation process using continuous fiber bundle mats and continuous single fiber mats as reinforcement, respectively. The mechanical properties of the two GMTs were compared to reveal the difference in reinforcing effect between the fiber bundle and the single fiber. The effect of needle density of the fiber mat on the mechanical properties of GMT was also studied, which indicated that needle‐punching improves the mechanical properties of GMT, and that the optimal needle density is 40∼60 needles/cm2. The through‐thickness glass fiber content‐distribution, which is inhomogeneous and can be modified by the film‐stacking method, significantly affects the mechanical properties of GMT. Finally, the study of the effect of void content indicated that with increasing void content, the strength and modulus of GMT decrease, but the impact property increases slightly.

A Study on Biodegradable Composite Prepared from Jute Felt and Polyesteramide (BAK)

Jute-polyesteramide(BAK) composite specimens having 45, 50, 55, 60 and 65% of jute by mass were prepared following film stacking method by compression molding technique. It was found that with increase in jute content, the flexural strength and modulus increased from 25.89 and 4709 MPa (45% jute) to 41.75 and 8613 MPa (60% jute) respectively and thereafter decreased with higher loading of fiber. For tensile strength and modulus, the same trend was observed. At 45% jute content, the values were 33.61 and 2599 MPa respectively, whereas at 60% jute content the values were 41.23 and 3346 MPa respectively. The thermogravimetric analysis of jute felt, BAK film and jute-BAK composites (60% jute) were made. The biodegradability of the composite specimens were studied by soil burial test, IR and SEM analyses.

Fabrication and Mechanical Properties of PE/PE Knitted Fabric Composites

Combinations of inorganic fibers and organic matrices can produce high performance composites such as CFRP and GFRP. Normally, the adhesion between these two material types is not good due to their Completely different nature. Composites that consist of a matrix reinforced with fibers of the same material however, may have excellent interfacial strength. Often, the melting temperature of thermoplastic fibers is higher than that of the corresponding bulk material due to molecular orientation in the fibers. Therefore, a processing window between the two melting temperatures of the fibers and the bulk materials may enable fabrication of composites with a high strength interface and fiber reinforcement. We call this class of composites “Interface-less Composites”. In this paper, UHMWPE fibers and PE film were selected as the first step in the validation of this concept. Knitted PE fabric with good drapeability was also used as a reinforcement. The effects of processing temperature and time in film stacking method on mechanical properties were investigated. Even at a low fiber volume fraction (12%) PE/PE composites showed two times higher tensile strength than the neat PE matrix. On the other hand, the tensile strength of PE/Epoxy composites was lower than that of Epoxy resin. This concept can be extended to any thermoplastic material. The use of these composites could greatly improve the recycle ability since matrix and reinforcement are the same materials.

Mechanical properties of natural-fibre-mat-reinforced thermoplastics based on flax fibres and polypropylene.

Thermoplastic composites based on flax fibres and a polypropylene (PP) matrix were manufactured using (i) a film-stacking method based on random fibre mats and (ii) a paper making process based on chopped fibres. The influence of fibre length and fibre content on stiffness, strength and impact strength of these so-called natural-fibre-mat-reinforced thermoplastics (NMTs) is reported and compared with data for glass-mat-reinforced thermoplastics (GMTs), including the influence of the use of maleic-anhydride grafted PP for improved interfacial adhesion. In addition some preliminary data on the influence of fibre diameter on composite stiffness and strength is reported. The data is compared with the existing micro-mechanical models for strength and stiffness. A good agreement was found between theory and experiment in case of stiffness whereas in the case of strength the experimental values fall well below the theoretical predictions. Results indicated that NMTs are of interest for low-cost engineering applications and can compete with commercial GMTs when a high stiffness per unit weight is desirable. Results also indicated that future research towards significant improvements in tensile and impact strength of these types of composites should focus on the optimisation of fibre strength rather than interfacial bond strength.

Stress Characteristics of Multilayered Polysilicon Film for the Fabrication of Microresonators

Micro-polysilicon actuators, which are widely used in the field of microelectromechanical system (MEMS) technology, were fabricated using a novel stacking method. Polysilicon film was deposited to have a symmetrical layer structure using a low-pressure chemical vapor deposition (LPCVD) system. We have also measured the physical characteristics using micromachined test patterns to verify the minimal stress and stress gradient in the polysilicon layers, according to the film stacking, doping, and thermal treatment methods. Finally, the fabricated planar polysilicon resonators, symmetrically stacked to 6.5 µm thickness, showed Q of 1270 and oscillation amplitude of 5 µm under 1000 mTorr. The developed micro-polysilicon resonator can be utilized in the fabrication of both microgyroscopes and accelerometer sensors.

Natural-Fibre-Mat-Reinforced Thermoplastic Composites based on Flax Fibres and Polypropylene

Natural-fibre-mat-reinforced thermoplastics (NMTs) based on flax fibres and a polypropylene (PP) matrix were manufactured using a film-stacking method. The influence of fibre content on stiffness and strength is reported and compared with data for glass-matreinforced-thermoplastics (GMTs), including the influence of improved fibre/matrix adhesion as a result of the use of maleic-anhydride grafted PP. Additionally, unidirectional and random-flax-mat composites based on epoxy resin were manufactured as reference materials. Results indicated that NMTs are of interest for low cost engineering applications, especially when a high stiffness per unit weight is desirable.

Fabrication of Knitted Glass Fibre Fabric Reinforced Thermoplastic Composite Laminates

It has been shown that knitted fabric reinforced thermoplastic composites can be fabricated by compression moulding in two ways namely, film stacking method and co-knitted fabric method. The processability of co-knitted fabric method was better than the film stacking method. Tensile properties in the wale direction of the knitted fabric were higher than those of the course direction.

Strength of fibre composites at an angle to fibre axis

In the present study the properties of carbon fiber reinforced poly ether ketone (PEK) is compared with carbon fiber reinforced epoxy (EP) composite fabricated by compression moulding technique. PEK carbon fiber (PK-CF) composites are prepared by film stacking method whereas the epoxy carbon fiber (EP-CF) composites are prepared by conventional compression moulding route maintaining a constant 60wt% carbon fiber. The tensile properties analysis indicated that PK-CF composite possesses a tensile strength of 425MPa which was much higher than 311MPa recorded by EP-CF. The stress intensity factor (KIC) values of PK-CF composites are found to be 10% higher than EP-CF counterparts. It is seen that the PK-CF composites possess higher glass transition temperature enabling them to be used at elevated temperatures. The investigation of flame retardant behaviour of the composite is conducted by Limiting Oxygen Index (LOI) test, and highest value is obtained for PK-CF composite.