Palm fiber composites for aircraft interiors

Over the last decades, aircraft manufacturers have produced synthetic fiber thermoset composites to be used for interior components of aircraft. However, the ever increasing dependence on synthetic fibers and thermosetting resin has set the aerospace industry under considerable pressure to reduce its carbon footprint and enhance its sustainable credentials. The unrelenting passion of sustainability has led to an expanding search for eco-friendly fiber reinforced composite from renewable sources. However, there remains a significant challenge to produce palm fiber composite fit for aircraft interiors owing to its ease of combustibility. Various flame retardants and expandable graphite (EG) at different concentrations were introduced into the epoxy composites reinforced with approximately 18 to 20% fiber (mass fraction). Amongst the flame retardant filled composites fabricated by resin infusion technique, two formulations with incorporation of (i) 10% ammonium phosphate (APP) and 5% alumina trihydrate (ATH) hybrid and (ii) 10% ammonium phosphate (APP) and 5% zinc borate (ZB) hybrid into EFB fiber reinforced epoxy composites demonstrated promising capability to meet the vertical Bunsen burner requirements for aircraft interiors, where zero molten drip time and zero flame time were observed, along with the lowest recorded gross heat of combustion being less than 27.4 MJ/kg from bomb calorimeter instrument. It was found that the lab-scale mechanical performances enhanced with inclusion of alkaline treated fibre compared with those of untreated fibre composites. For expandable graphite filled composites fabricated by compression molding technique, all the composites containing EG was observed to possess the capability to meet the vertical Bunsen burner test requirements of aircraft interior parts. Palm fibre composites with inclusion of 5 %wt and 7 %wt EG fillers showed zero flame time, drip flame time and negligible burned length. From Bomb calorimetry and TGA tests, formulation with 7% EG filler (CEG7) recorded a gross heat of combustion of 27.91 MJ/kg and mass residue of 28.31 wt% at 700 °C. In a separate approach where 3 wt% and 5 wt% EG were coated onto the exterior surface of neat EFB fiber reinforced epoxy composite without any additional fillers, it was observed that composite coated with 5 wt% EG met the requirements of vertical Bunsen burner test. With regards to mechanical properties, the incorporation of EG fillers into EFB fiber composite dropped the mechanical behaviors. The mechanical performances of EG filled composite was found to improve with the alkali treatment of EFB fibers. Lab scale measured mechanical behaviors were observed to be in the acceptable range for the required application. Finally, an aerospace grade Nomex honeycomb was used to fabricate laminate with the natural fibre composite skins, which could be a structure of an aircraft interior component for a sidewall, ceiling or partition. Two different types of composite face sheets were used, one with the optimum formulation from flame retardant filled composite (hybrid 10 wt% APP with 5 wt% ATH) and the other with 7 wt% expandable graphite. The requirements of 12 s vertical Bunsen burner testing were fully met for the panels. Three of the optimum formulations (APP/ATH hybrid, APP/ZB hybrid and EG7) were tested against 60 s vertical Bunsen burner experiment and found capable of meeting the test specifications of flame time, drip flame time and burn length

Elastomer Characterization Method for Trapped Rubber Processing

The increasing high-volume demand for polymer matrix composites (PMCs) brings into focus the need for autoclave alternative processing. Trapped rubber processing (TRP) of PMCs is a method capable of achieving high pressures during polymer matrix composite processing by utilizing thermally induced volume change of a nearly incompressible material inside a closed cavity mold. Recent advances in rubber materials and computational technology have made this processing technique more attractive. Elastomers can be doped with nanoparticles to increase thermal conductivity and this can be further tailored for local variations in thermal conductivity for TRP. In addition, recent advances in computer processing allow for simulation of coupled thermomechanical processes for full part modeling. This study presents a method of experimentally characterizing prospective rubber materials. The experiments are designed to characterize the dynamic in situ change in temperature, the dynamic change in volume, and the resulting real-time change in surface pressure. The material characterization is specifically designed to minimize the number and difficulty of experimental tests while fully capturing the rubber behavior for the TRP scenario. The experimental characterization was developed to provide the necessary data for accurate thermomechanical material models of nearly incompressible elastomeric polymers for use in TRP virtual design and optimization

Fabrication: Mechanical testing and structural simulation of regenerated cellulose fabric elium\uae thermoplastic composite system

Regenerated cellulose fibres are an important part of the forest industry, and they can be used in the form of fabrics as reinforcement materials. Similar to the natural fibres (NFs), such as flax, hemp and jute, that are widely used in the automotive industry, these fibres possess good potential to be used for semi-structural applications. In this work, the mechanical properties of regenerated cellulose fabric-reinforced poly methyl methacrylate (PMMA) (Elium\uae) composite were investigated and compared with those of its natural fibre composite counterparts. The developed composite demonstrated higher tensile strength and ductility, as well as comparable flexural properties with those of NF-reinforced epoxy and Elium\uae composite systems, whereas the Young’s modulus was lower. The glass transition temperature demonstrated a value competitive (107.7 \ub0C) with that of other NF composites. Then, the behavior of the bio-composite under bending and loading was simulated, and a materials model was used to simulate the behavior of a car door panel in a flexural scenario. Modelling can contribute to predicting the structural behavior of the bio-based thermoplastic composite for secondary applications, which is the aim of this work. Finite element simulations were performed to assess the deflection and force transfer mechanism for the car door interior

Flammability, Smoke, Mechanical Behaviours and Morphology of Flame Retarded Natural Fibre/Elium\uae Composite

The work involves fabrication of natural fibre/Elium\uae composites using resin infusion technique. The jute fabrics were treated using phosphorus-carbon based flame retardant (FR) agent, a phosphonate solution and graphene nano-platelet (GnP), followed by resin infusion, to produce FR and graphene-based composites. The properties of these composites were compared with those of the Control (jute fabric/Elium\uae). As obtained from the cone calorimeter and Fourier transform infrared spectroscopy, the peak heat release rate reduced significantly after the FR and GnP treatments of fabrics whereas total smoke release and quantity of carbon monoxide increased with the incorporation of FR. The addition of GnP had almost no effect on carbon monoxide and carbon dioxide yield. Dynamic mechanical analysis demonstrated that coating jute fabrics with GnP particles led to an enhanced glass transition temperature by 14%. Scanning electron microscopy showed fibre pull-out locations in the tensile fracture surface of the laminates after incorporation of both fillers, which resulted in reduced tensile properties

Investigation of fire protection performance and mechanical properties of thin-ply bio-epoxy composites

Hybrid composites composed of bio-based thin-ply carbon fibre prepreg and flameretardant mats (E20MI) have been produced to investigate the effects of laminate design on their fire protection performance and mechanical properties. These flame-retardant mats rely primarily on expandable graphite, mineral wool and glass fibre to generate a thermal barrier that releases incombustible gasses and protects the underlying material. A flame retardant (FR) mat is incorporated into the carbon fibre bio-based polymeric laminate and the relationship between the fire protection properties and mechanical properties is investigated. Hybrid composite laminates containing FR mats either at the exterior surfaces or embedded 2-plies deep have been tested by the limited oxygen index (LOI), vertical burning test and cone calorimetry. The addition of the surface or embedded E20MI flame retardant mats resulted in an improvement from a base line of 33.1% to 47.5% and 45.8%, respectively. All laminates passed the vertical burning test standard of FAR 25.853. Cone calorimeter data revealed an increase in the time to ignition (TTI) for the hybrid composites containing the FR mat, while the peak of heat release rate (PHRR) and total heat release (TTR) were greatly reduced. Furthermore, the maximum average rate of heat emission (MARHE) values indicated that both composites with flame retardant mats had achieved the requirements of EN 45545-2. However, the tensile strengths of laminates with surface or embedded flame-retardant mats were reduced from 1215.94 MPa to 885.92 MPa and 975.48 MPa, respectively. Similarly, the bending strength was reduced from 836.41 MPa to 767.03 MPa and 811.36 MPa, respectively

Flammability, Smoke, Mechanical Behaviours and Morphology of Flame Retarded Natural Fibre/Elium® Composite

The work involves fabrication of natural fibre/Elium® composites using resin infusion technique. The jute fabrics were treated using phosphorus-carbon based flame retardant (FR) agent, a phosphonate solution and graphene nano-platelet (GnP), followed by resin infusion, to produce FR and graphene-based composites. The properties of these composites were compared with those of the Control (jute fabric/Elium®). As obtained from the cone calorimeter and Fourier transform infrared spectroscopy, the peak heat release rate reduced significantly after the FR and GnP treatments of fabrics whereas total smoke release and quantity of carbon monoxide increased with the incorporation of FR. The addition of GnP had almost no effect on carbon monoxide and carbon dioxide yield. Dynamic mechanical analysis demonstrated that coating jute fabrics with GnP particles led to an enhanced glass transition temperature by 14%. Scanning electron microscopy showed fibre pull-out locations in the tensile fracture surface of the laminates after incorporation of both fillers, which resulted in reduced tensile properties

Palm fiber composites for aircraft interiors

Over the last decades, aircraft manufacturers have produced synthetic fiber thermoset composites to be used for interior components of aircraft. However, the ever increasing dependence on synthetic fibers and thermosetting resin has set the aerospace industry under considerable pressure to reduce its carbon footprint and enhance its sustainable credentials. The unrelenting passion of sustainability has led to an expanding search for eco-friendly fiber reinforced composite from renewable sources. However, there remains a significant challenge to produce palm fiber composite fit for aircraft interiors owing to its ease of combustibility. Various flame retardants and expandable graphite (EG) at different concentrations were introduced into the epoxy composites reinforced with approximately 18 to 20% fiber (mass fraction). Amongst the flame retardant filled composites fabricated by resin infusion technique, two formulations with incorporation of (i) 10% ammonium phosphate (APP) and 5% alumina trihydrate (ATH) hybrid and (ii) 10% ammonium phosphate (APP) and 5% zinc borate (ZB) hybrid into EFB fiber reinforced epoxy composites demonstrated promising capability to meet the vertical Bunsen burner requirements for aircraft interiors, where zero molten drip time and zero flame time were observed, along with the lowest recorded gross heat of combustion being less than 27.4 MJ/kg from bomb calorimeter instrument. It was found that the lab-scale mechanical performances enhanced with inclusion of alkaline treated fibre compared with those of untreated fibre composites. For expandable graphite filled composites fabricated by compression molding technique, all the composites containing EG was observed to possess the capability to meet the vertical Bunsen burner test requirements of aircraft interior parts. Palm fibre composites with inclusion of 5 %wt and 7 %wt EG fillers showed zero flame time, drip flame time and negligible burned length. From Bomb calorimetry and TGA tests, formulation with 7% EG filler (CEG7) recorded a gross heat of combustion of 27.91 MJ/kg and mass residue of 28.31 wt% at 700 °C. In a separate approach where 3 wt% and 5 wt% EG were coated onto the exterior surface of neat EFB fiber reinforced epoxy composite without any additional fillers, it was observed that composite coated with 5 wt% EG met the requirements of vertical Bunsen burner test. With regards to mechanical properties, the incorporation of EG fillers into EFB fiber composite dropped the mechanical behaviors. The mechanical performances of EG filled composite was found to improve with the alkali treatment of EFB fibers. Lab scale measured mechanical behaviors were observed to be in the acceptable range for the required application. Finally, an aerospace grade Nomex honeycomb was used to fabricate laminate with the natural fibre composite skins, which could be a structure of an aircraft interior component for a sidewall, ceiling or partition. Two different types of composite face sheets were used, one with the optimum formulation from flame retardant filled composite (hybrid 10 wt% APP with 5 wt% ATH) and the other with 7 wt% expandable graphite. The requirements of 12 s vertical Bunsen burner testing were fully met for the panels. Three of the optimum formulations (APP/ATH hybrid, APP/ZB hybrid and EG7) were tested against 60 s vertical Bunsen burner experiment and found capable of meeting the test specifications of flame time, drip flame time and burn length

TRAPPED RUBBER PROCESSING SIMULATION FOR HIGH PERFORMANCE / HIGH RATE PROCESSING

Trapped rubber processing (TRP) is an autoclave alternative to achieving high pressures during processing, utilizing temperature induced change in volume of a hyperelastic material. Recent advances in material and computational technology have made this processing technique more attractive. Through detailed experimental characterization, a design tool has been developed. In addition, a method has been developed for this characterization process that can be used for other TRP materials. TRP allows more design freedom with more advanced shapes and less risk of processing failure while maintaining the possibility for custom distributions of pressures and temperatures, therefore, high-quality consolidation during curing is achieved

High performance/high rate composite processing with trapped rubber

Trapped rubber processing (TRP) is an autoclave alternative to achieving high pressures during polymer matrix composite processing, utilizing thermally induced volume change of a nearly incompressible material inside a closed cavity mould. Recent advances in material and computational technology have made this processing technique more attractive. Computer electronics research has led to the development of elastomers with relatively high thermal conductivity. In addition, recent advances in computer processing have opened the possibility to simulate complex thermomechanical processes with finite element analysis. In this study, the volumetric change and resulting pressure is captured via a series of experiments. These experiments are used to characterize the dynamic in situ change in temperature, the dynamic change in volume and the resulting real-time change in surface pressure at multiple locations throughout the sample. The material characterization includes an iterative testing and computational modelling framework where the design of experiments is fed by initial material models based on the linear coefficient of thermal expansion and then the characterization is improved by the experimental tests. The silicone rubber elastomer used in this initial study was chosen to be compatible with the cure cycle for Hexcel M21 epoxy prepreg system, due to the large amount of material and processing data available. The development of an accurate thermomechanical material model of nearly incompressible elastomeric polymers for use in advanced trapped rubber processing modelling will allow more design freedom with more advanced shapes and less risk of processing failure while maintaining the possibility for custom distributions of pressures and temperatures, therefore, high-quality consolidation during curing