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Abstract

The purpose of this work is to fabricate and analyse a light weight, recyclable, and non-toxic natural fiber reinforced industrial safety helmet. The fibers were extracted from agro-waste pseudostem of nendran variety banana plant. A facile needle punching technique was employed on banana fibers to produce a needle punched non-woven banana fiber fabric of enhanced mechanical properties without any chemical treatment. Subsequently, the needle punched banana fibers were impregnated with general purpose helmet grade polyester resin in an ISI (Indian standards Institute) endorsed mold to fabricate a needle punched banana fiber helmet (NPBFH). Similarly, 30 mm random banana fiber helmet (RBFH) and glass fiber reinforced helmets (RGFH) were fabricated. The fabricated helmets of 10–50 wt. % fiber content were tested as per ISI standards. The results show that the better properties were achieved at 40 wt. % of fiber content for all varieties of helmets. Significantly, the results revealed that the shock absorption, penetration resistance, and water absorption of NPBFH are 245 kgf, 4.75 mm, and 0.61%, respectively, which is much better than RBFH and comparable with RGFH. This study concluded that the NPBFH (40 wt. %) can be a potential replacement of synthetic fiber reinforced helmets for industrial applications.

Keywords

Banana fiber Industrial safety helmet Needle punching ISI standard Shock absorption test

Introduction

Materialists and technologists are on a rapid move to address the environmental and economic issues caused by ever depleting, non-biodegradable fossil fuels and its derived materials.¹ This has evoked persistent momentum in the usage of high performance natural sustainable fiber reinforced eco-friendly composites by mankind, as a prospective alternative for perilous synthetic fiber-based products.^2–5 Over 315,000 tons of plant fibers were utilized for composite fabrication in 2010, it is predicted to reach over 830,000 tons by 2020.^6,7 Sustainable technology gets impetus day by day due to copious accessibility and availability of plant fibers .^8,9 Moreover, plant fibers exhibit superior characteristics such as low density, non-abrasive, appropriate stiffness, dimensional stability, recyclability, low cost, and CO₂ sequestration.^10–13

Plant fibers derived from bamboo, oil palm, sugar palm, coir, sisal, flax, areca, banana, kenaf, jute, rice husk, etc. were endorsed by various researchers as a potential reinforcement in bio-composite materials.^14–20 However, intensive research work has been carried out on banana fiber as a potential reinforcement material due to its excellent strength and abundant availability.^21–24 There are more than 300 varieties of banana plants existing in this world.²⁵ This emphasizes the need for exploiting all these varieties for reinforcement purpose to make a greener world by materials researchers. Banana fiber is much lignified and coarser than other fibers, which are extracted from pseudostem (agro-waste) of banana plants. India and Brazil alone contribute 60% (29.16 million tonnes) of total banana harvested in the world.²⁶ Such a huge quantity of yield is accompanied with almost similar quantum of agro-waste pseudo stem. The reinforcement fibers for bio-composite fabrication are extracted from this agro-waste without any additional cost.

The fiber used for this experimentation was extracted from Musa Sapientum (nendran) variety banana plant which is extensively cultivated in the southern tropical region of India, especially in Tamilnadu. Although, ligno-cellulosic fibers play ascendant role in green composite field, researchers are facing enormous challenges while working with plant fiber reinforced composites (PFRC) due to its complex variation. They also have few more hassles such as high moisture absorption, aggregate formation during processing, poor compatibility between the fiber and matrix, and highly susceptible to microbial attack.²⁷ Moreover, thermo-physical properties of PFRC are greatly influenced by its processing method, aspect ratio; constituents phase structure, environmental condition, age of the plant, and cultivation soil.²⁸ Significantly, the interface of the composite constituents should be strong enough to have effective transfer of stress from matrix to fiber.^29,30 Various chemical treatments were preciously adopted to enhance the compatibility of the fiber matrix interface for superior mechanical properties.^31–35 However, they all have their own limitations due to time consumption, toxicity, high cost, and environment pollution. This work obviates the above-mentioned limitations by employing a facile needle punching technique for producing non-woven banana fiber fabric as a reinforcement material, which is first of its kind for banana fiber.

Products developed in multitude forms by using plant fibers are seamlessly making it by road in the industrial arena.^36–38 Based on the literature, it has been revealed, most of the developed NFRC are employed in automotive and aerospace field, where reduction in component weight plays predominant role.^39,40 However, to the best of the literature, none of the products evolved are pertinent to human safety aspects, especially industrial safety helmets. Out of the total human causality which occurs in industry, 15.3% is due to crashing, falling, and stumbling of huge objects on the head.^34,42 It is necessary to wear safety helmets while dealing with such hazardous work. However, majority of the fatal accidents were due to non-compliance of safety norms. Based on the views expressed by the industrial workers, it has been found that the feel of heaviness and inconvenience is the major reasons for non-wearing of helmets. The current pervasive helmets made up of Polypropylene (PP), Acrylonitrile Butadiene Styrene (ABS), Polycarbon (PC), Expanded Poly-styrene (EPS) is an encumbrance to the personnel at the industries. They are noticeably heavy, impeding the personnel’s activities, thereby resulting in non-compliance of safety norms leading to frequent accidents at work places.^43,44 Some of the industrial workers are even hesitant to wear helmets, due to the nexus between currently used fiber-glass and insalubrious diseases such as cancer, allergic reactions, and dermatitis, putting their own lives on the line.

Realizing the need for improvement and to eliminate the health hazards involved with the existing industrial safety helmets. This study aims to fabricate and synthesize a novel needle punched banana fiber (NPBF) reinforced polyester for industrial safety helmet which would provide the user with greater comfort and hazardous-free, while adhering to the current ISI industrial safety helmet standards. This study also elucidates and compares the synthesized NPBF helmet of 30 mm random banana fiber and commercially used glass fiber reinforced industrial safety helmet. The novelty of this work is the use of NPBFH without any toxic chemical treatment of fibers in the place of existing carcinogenic glass fiber reinforced industrial safety helmet. It is pertinent to punctuate once again the material’s light weight, recyclability, and non-toxic nature which translates to a congenial welcome by the work force, promoting a safer and unabated working.

Materials and methods

Banana fiber extraction

Banana plant is a perennial herb, in which the leaf sheaths are arranged almost spirally and in an overlapping manner making a compact mass called pseudostem. After removing the matured banana plant, the pseudo stem becomes a biological waste. Varieties of banana plants including nendran and its fibers were extensively studied by Kiruthika and Veluraja as a reinforcing material.⁴⁵ In this experimental findings, fibers of nendran banana variety purchased from KK natural fibers, Tuticorin, are used as reinforcement due to their excellent inherent strength (

\approx

450 MPa) and are economically viable than remaining varieties. The exterior layer of the pseudostem which is known as cortex region was peeled off after 9–12 days of harvesting of matured plant by a retting device. The moisture from the retted fibers was removed by sun drying for a period of 7–9 days. Subsequently, these sun-dried fibers were dried in an oven at a temperature of 50–60°C for a time span of 12–16 h to ensure entire moisture removal. Finally, the hurds (impurities) sticking at the exterior surface of the fibers were removed by employing mechanical scutching process. The processed raw banana fiber was tested for its physical and bio-chemical properties by employing standard procedure⁴⁶ at the South India Textile Research Association (SITRA), Coimbatore, Tamilnadu. Table 1 reported the evaluated test results. The process flow diagram of raw banana fiber from plant origin is shown in Figure 1.

Table 1.

Bio-chemical and physical properties of raw banana fiber.

Bio-chemical properties
Hemicellulose (%)	12.61
Cellulose (%)	71.08
Moisture (%)	6.73
Lignin (%)	7.67
Physical properties
Lumen size (μm)	6
Density (g/cm³)	1.28
Diameter (μm)	138 ± 0.0671
Microfibril angle (°)	11
Elongation at break (%)	27.89
Tensile strength (MPa)	412.5 ± 46.7

Figure 1.

Extraction of banana fiber (a) Various parts of banana plant, (b) Harvested pseudostem, (c) Peeled pseudostem, (d) Retting process (e) Sun-dried fibers and (f) Extracted raw banana fibers.

E-glass fiber

Continuous type glass fibers of electrical grade were purchased from Vruksha composites & services, Chennai, Tamilnadu. The fibers were cut into 30 mm length (approximately) short fibers and were used in helmet fabrication as reinforcement.

Matrix preparation

General purpose polyester resin (GP) of helmet grade, accelerator 3% Cobalt Octoate (CO), and catalyst Methyl-Ethyl-Ketone Peroxide (MEKP) purchased from Vruksha composites & services, Chennai, Tamilnadu, were preferred as matrix materials due to their high cross-linking tendency, better chemical and electrical resistivity, and dimensional stability. GP, CO, and MEKP were mixed in a measurable jar in a proportion of 97.5:1:1.5. The mixture was stirred at a constant rate of 100 rpm by a mechanical stirrer for 2–3 min to evolve a homogeneous mixture. Extreme care was taken to eliminate clumbing and tangling factors while mixing. The whole matrix preparation process was carried out under an ambient condition of 30^°C and a Relative Humidity (RH) of 65%. Though the specifications of chemical properties of polyester resin were provided by the seller, the procured resin was tested in Concord Testing Laboratory, Trichy, India for its validation. The specifications along with the validated results are indicated in Table 2.

Table 2.

Chemical properties of polyester resin.

SI.No	Property	Units	Specification	Results
1	Appearance	—	Clear liquid	Clear liquid
2	Brookfield Viscosity at 25^oC (Spindle no: 2 speed: 10 r/min	cps	600–800	800
3	Specific gravity at 25^oC	g/cc	1.14–1.15	1.142
4	Acid value	mg-KOH/g	23–27	24.05
5	Volatile content (2 g/150^oC/1h)	%	29–23	24.05
6	Gel time at 25^oC, Resin: 100 gms accelerator (3% Co.Octoate: 1.0 ml Catalyst (MEKP-505): 1.5 mL	min	15–25	15’20^″

Needle punching process

Needle punching technique

Banana fibers were needle punched using Dilo NFZ 22 needle punching machine made in Germany. This is a unique technique in which batts or webs of raw banana fibers (30 mm long) are entangled mechanically by thousands of reciprocating felting needles through the upward and downward movements to form a non-woven fabric. The produced non-woven fabric maintains its integrity by inter-fiber friction. Figure 2 shows the schematic representation of various processes involved in needle punching technique.

Figure 2.

Schematic representation of various processes involved in needle punching technique.

Selection of needling parameters

Needle Action

Properties of the produced needle punched banana fiber fabric depend greatly on the type of needle, its thickness, length, cross-section along with the number of projections, spacing, and dimensions of the barbs. A triangular barbed needle of double reduction type was employed for fabricating the needle punched banana fiber (NPBF) fabric due to the soft nature of the fiber.⁴⁷ Regular barb (RB) spacing was selected for this study, and hence, it implied an evenly spacing of 9 barbs on a blade of ≈ 30 mm in length. The number of fibers that could be collected in the barbs of a needle can be calculated by using the formula (1)

Number of fibers

n_{f} = (\frac{2 b_{d}}{d_{f}}) \times n_{b}

(1)

where, b_d – barb depth, d_f – fiber diameter, and n_b – number of acting barbs on the needle.

Penetration depth

It is the distance between the tip of the needle and the upper surface of the bed plate when the needles are located at the bottom dead center. The level of fiber entanglement, linear speed, and the advance per stroke can be evidenced by this parameter as it determines the number of barbs penetrating the batt or fabric on each stroke. In this study, an optimum value of 8 mm depth was employed. When tested for higher depths, visible damages to the fibers were observed due to severe action of barbs. On the other hand, a lower depth resulted in a poorly entangled puffy fabric.

Punch density

It is the number of needles penetrating per unit area (punch/cm²). Punch density affects the mechanical properties, volumetric density, and fabric thickness. It is calculated by employing the formula (2)

Punch density

P_{d} = \frac{n_{n}}{A} (\frac{punch}{{cm}^{2}})

(2)

where, n_n – number of needles per cm width of the needle-board and A – advance per stroke (cm), A can be calculated by

A = \frac{P}{S_{f}}

(3)

where, P – fabric production speed (cm/min) and S_f – punch frequency (punches/min).

In this study, punch density of 100 punches/cm² was found to be optimum and operating above the optimum level resulted in breakage of fibers leading to fabric of poor strength. In contrast, a lower punch density resulted in non-entanglement of fibers.

Industrial safety helmet fabrication

Needle punched banana fiber reinforced helmet (NPBFH), random banana fiber reinforced helmet (RBFH), and random glass fiber reinforced helmet (RGFH) of 10–50 wt. % of fiber were fabricated using ISI endorsed mold as shown in Figure 3. Prior to fabrication, the mold was cleaned with cloth and a releasing agent of silicon was applied inside the mold by a soft brush to ensure the easy removal of fabricated helmets. Needle punched banana fibers, were cut and preformed as per existing ISI standard helmet size. The preform was laid inside the mold with a minute preloading and the prepared matrix solution was gently poured over the preform. The mold was hydraulically pressed at 150^°C and 90 bar. After 2–3 min of pressing, the fabricated helmet was removed from the mold and kept under an ambient condition of 30^°C and RH of 65 % for 5–6 days before testing. To fabricate RBFH and RGFH, the preforms of respective fibers were used, followed by similar procedure as that of NPBFH. Figure 3 shows the flow process of fabrication of ISI standard industrial safety helmet.

Figure 3.

Fabrication of industrial safety helmet (a) Random banana fiber preform, (b) Needle punched banana fabric, (c) Random glass fiber preform, (d) Preform process, (e) ISI endorsed compression mold, and (f) Fabricated helmet.

Testing of industrial safety helmet

The following tests were carried out on each fabricated helmet as per IS 2925 standard. In each case, five specimens were tested and standard deviation values were considered for the analysis.

Shock absorption test

Prior to testing, helmets of each fiber wt. % (10–50) of all varieties were treated in hot, cold, and wet condition. In hot condition, the helmets were kept in a hot oven with a prevailing temperature of 49^°C–50^°C for 4 h. In cold condition, the helmets were placed in a cold freezer at −10^°C $\pm$ 2^°C for 4 h. In wet condition, water was allowed to flow over the entire helmet shell continuously at the rate of 1 L/min for 4 h. After conditioning, each helmet was wiped off by a clean cloth for shock absorption test.

Shock absorption test equipment has a strong monolithic base (height 1 m, length 1 m, width 0.6 m, and mass 1 ton) on which the entire mechanical stand is located. It consists of wooden head foam, 3 kg rectangular striker (horizontal striking face of 180 mm × 180 mm), lifting handle, release lever, load cell, and a digital indicator system as shown in Figure 4. The conditioned helmet was placed over the head foam in accordance with the IS 2925 standard. The test helmet was maintained with required tension by adjusting the chin strap of the helmet. The striker was raised to the height of 1.5 m by rotating the striker lifting handle. Care has been taken to keep the striker in a stable position (without any oscillation). Finally, the striker was released with the help of release lever. As soon as the striker hits the helmet, a load cell was used to compute the shock absorption which was displayed in the digital indicator. Table 3 indicates the BIS standard for shock absorption test.

Figure 4.

Shock absorption test rig.

Table 3.

BIS standard for shock absorption test.

BIS No	Description	Striker weight (kg)	Drop height (M)	Max permissible shock absorption (kgf)
IS 2925	Industrial helmet	3	1.5	500

Penetration test

The conditioned helmets which produced worst results in the shock absorption test were selected for penetration test as per IS 2925 standard. The helmet was mounted on an appropriate head foam. A plumb bob of conical shape weighing 0.5 kg made up of steel having an included angle of 36° with a spherical pointed radius of 0.5 mm was used. With the help of a nylon cord, the bob was positioned at an appropriate height of 3 m in accordance to IS 2925 standard. The position of the plumb bob was aligned such that it hits the center of the crown of the helmet. The plumb bob was released to fall freely, as soon as the bob hits the helmet, it penetrates on the crown of the helmet as shown in Figure 5. The penetration depth was measured with a digital depth gauge. A careful visual investigation was done on the tested helmet for separation of material, denting, and damage of any other part of the helmet due to the plumb bob hit. Table 4 indicates the BIS standard for penetration test.

Figure 5.

Penetration at the crown of the helmet.

Table 4.

BIS standard for penetration test.

BIS No	Description	Plumb bob weight (kg)	Drop height(M)	Max permissible penetration (mm)
IS 2925	Industrial helmet	0.5	3	10

Flammability resistance test

The helmets were placed on a steel table for inducing flame by a burner at the top of the helmet crown at an angle of 45^o vertically. The experimental set up is shown in Figure 6. The end of flame distance was maintained between 50 and 100 mm from the crown. The flame was induced for a period of 10 s. After removal of the flame, burning with emission of the helmet shell was monitored. Table 5 indicates the BIS standard for flammability resistance.

Figure 6.

Flammability test set up.

Table 5.

BIS standard for flammability test.

BIS No	Description	Flame inducing Period (sec)	Requirements
IS 2925	Industrial helmet	10	No burning for 5 s

Electrical resistance test

After removing all the fittings, the test helmet was inverted and placed on a frame in a plastic tub. A solution of 6 gm sodium chloride dissolved in 1 L of water was prepared. Since the fabricated helmet was provided with holes, the solution was filled upto 12 mm depth below the holes as per ISI standards. The helmet was allowed to remain in the solution for 18–24 h with a prevailing temperature of 25°C–35°C. After 18 h, an alternating voltage of 2000 V at 50 Hz in a sine wave form was applied between two electrodes for 1 min, one electrode was placed inside the solution and the other one outside of the helmet. An ammeter was attached at both the sides of electrode circuit for noticing the current leakage. Table 6 indicates the BIS standard for electrical resistance test.

Table 6.

BIS standard for electrical resistance test.

BIS No	Description	Maximum voltage (V)	Permissible current leakage (mA)
IS 2925	Industrial helmet	2000	3

Water absorption and corrosion resistance test

The helmet shell was weighed prior to testing. After weighing, the shell was immersed in water at a temperature of 25°C–35°C for a period of 24 h. After removing from the water, the shell was weighed again. Average gain in mass was reported by using the equation (4)

% of mass gain = \frac{M_{1} - M_{2}}{M_{1}} * 100

(4)

where M₁ and M₂ are the weights of the helmet shell before and after immersing in water. The removed helmets were tested for corrosion resistance by visual inspection. This test was conducted as per ISI regulation, to check the corrosion resistance of the aluminium strap of the helmet. Table 7 indicates the BIS standard for water absorption test.

Table 7.

BIS standard for water absorption test.

BIS No	Description	Period of immersion in water (hours)	Permissible mass gain
IS 2925	Industrial helmet	24	5 % of maximum weight

Heat resistance test

The helmet shells were placed inside an oven at a temperature of 93^oC ± 5°C for a time period of 15 min. Extreme care was taken to shield the shell from direct radiation. The helmet shells were removed from the oven and examined for softening, distortion, and separation. Table 8 indicates the BIS standard for heat resistance test.

Table 8.

BIS standard for heat resistance test.

BIS No	Description	Time period and temperature in hot oven	Requirements
IS 2925	Industrial helmet	93^oC ± 5°C for 15 min	No Distortion, separation, and softening

Chin strap strength test

The helmet to be tested was placed on an appropriate head foam with the chin strap fastened. A load of 10 kg was applied to the chinstrap by using an “S” hook. The load was applied for 5 min. After 5 min, the chinstrap was examined for any damage such as pull out and elongation. Table 9 indicates the BIS standard for chin strap strength test.

Table 9.

BIS standard for chin strap strength test.

BIS No	Description	Time period and weight of the load applied	Observation
IS 2925	Industrial helmet	10 kg for 5 min	No damage

Results and discussion

Evaluation of shock absorption energy

The magnitude of shock absorption of fabricated RBFH, NPBFH, and RGFH under shock load is shown in Figure 7. The obtained result inferred that as the fiber wt. % of the helmet is increased from 10 to 40 wt. %, the shock absorption keeps on decreasing. However, beyond 40 wt. % (i.e., at 50 wt. %), a sudden rise in shock absorption was noticed. Also, it was observed that 10 and 20 wt. % of fiber content of RBFH were completely failed. Similar case was noticed in 10 wt. % of fiber content of NPBFH. Hence, their quantity of shock absorption is not indicated in the Figure 7. The best properties of all varieties of helmets were achieved at 40 wt. % of fiber content.

Figure 7.

Shock absorption of RBFH, NPBFH, and RGFH.

Shock absorption is an indication of extent of damages of a material.⁴⁸ Higher the shock absorption, higher is the extent of damage and vice versa. For 10–20 wt. %, fiber content of RBFH was completely failed due to predominant brittle nature of resin material. A similar phenomenon occurred in NPBFH of 10 wt. % fiber content. However, when the fiber content is increased to 30 wt. % due to minimal increase in the interfacial bonding between the composite constituents, the helmets exhibit enhanced resistance to applied shock load. Thus, the shock absorption of 30 wt. % helmets was lower than 20 wt. % as shown in Figure 7. Significantly, when the fiber content is increased to 40 wt. % due to better interfacial bonding,²⁸ a maximum resistance to shock^42,43 was obtained for RBFH, NPBFH, and RGFH. Hence, the lowest shock absorption among all other wt. % was experienced. Interestingly, beyond 40 wt. % fiber loading, a sudden rise in shock absorption was noticed due to agglomeration factor in which fiber-to-fiber contact becomes more dominant due to inadequate resin.³³ This phenomenon resulted in poor interfacial bonding and stress transfer among the composite constituents.

The better properties of NPBFH over RBFH and almost on par with RGFH are due to the effect of needle punching. Initially, the glassy layer of wax which was adhering with the fiber’s exterior surface might have been removed due to the felting action of needles. As a result, the fibers outer surface has been roughened to have enhanced micro mechanical interlocking between composite constituents.⁴⁹ Secondly, the homogeneous way of laying the fibers during the needle punching process led to a constant mass per unit area (GSM) at all wt. % imparts smooth transfer of stress from matrix to fiber over the entire helmet. Hence, the load bearing capacity of the NPBFH is increased drastically than RBFH and comparable with RGFH. Finally, the best punch density of 100 punches/cm²and 8 mm penetration depth produces the fabric of better peg formation due to which higher resin uptake was noticed.⁵⁰ This phenomenon enhanced the strength of the NPBFH than RBFH and almost equivalent with RGFH. However, when the fiber content is increased beyond 40 wt. % due to highly cramped packing factor, the penetration of matrix into the fiber was hindered, resulting in poor resin uptake and poor interfacial bonding.⁵¹ Hence, at 50 wt. %, the helmet strength got reduced drastically.

Analysis of Penetration depth

The penetration depth of RBFH, NPBFH, and RGFH is shown in Figure 8. Since the RBFH of 10–20 wt. % and NPBFH of 10 wt. % fiber content were completely broken during the shock absorption test, their penetration test results are not indicated in the Figure 8. It can be observed that when the fiber content of the helmet is increased from 10 to 40 wt. %, the penetration depth keeps on reducing. The lowest penetration depth was obtained at 40 wt. % for all varieties of helmets. However, beyond 40 wt. %, the penetration depth abruptly increased. The penetration resistance of NPBFH is much better than RGFH and almost equivalent with RGFH.

Figure 8.

Penetration depth of RBFH, NPBFH, and RGFH.

The lower wt. % (10–20) fiber content of RBFH, NPBFH, and RGFH consists of a higher amount of resin material which produced low toughness due to brittle nature of the matrix. When the fiber content is increased, the toughness also increases. Hence, the penetration resistance also increases. At 40 wt. %, due to better interfacial bonding between the composite constituents, the helmets exhibited maximum toughness resulting in a very meagre penetration depth.⁴⁹ However, beyond 40 wt. %, the toughness of the helmets decreases suddenly due to the agglomeration factor. Hence, the penetration depth increases. Significantly, the toughness of NPBFH is much higher than RBFH and comparable with RGFH. This is attributed due to the homogenous laying pattern of fibers, enhanced wettability, increase in resin uptake, and better peg formation as an effect of suitable punch density and penetration depth of needles. The increase in the penetration depth of helmets beyond 40 wt. % is the result of inadequate resin for better bonding, cramped packing factor, and poor wettability.

Flammability Analysis

Flammability test results of RBFH, NPBFH, and RGFH are indicated in Table 10. It can be revealed that except 50 wt. % of RBFH and NPBFH, all other fiber wt. % of helmets comply with the ISI standard. The flammability tendency of E-glass fibers is very low. Hence, even after the addition of fibers, they are non-flammable. On the other hand, the burning tendency of banana fibers is high. Therefore, adding of banana fibers beyond 40 wt. % (i.e., 50 wt. %) in RBFH and NPBFH were exposed to flammable due to insufficient resin. This resulted in burning of banana fiber reinforced helmet as shown in Figure 9a. However, less than 40 wt. % fiber content of the helmet are inflammable as shown in Figure 9b.

Table 10.

Flammability test results of RBFH, NPBFH, and RGFH.

Fiber wt. %	RGFH	NPBFH	RBFH
10	No burning	No burning	No burning
20	No burning	No burning	No burning
30	No burning	No burning	No burning
40	No burning	No burning	No burning
50	No burning	Burning	Burning

Figure 9.

Helmet of (a) Burning and (b) No burning tendency.

Electrical resistance test

Electrical resistance test results of RBFH, NPBFH, and RGFH are indicated in Table 11. At 10–40 wt. %, fiber content of all varieties of helmets shows no leakage of current. However, all varieties of helmets exhibit leakage at 50 wt. % fiber content. The leakage occurred at 50 wt. % fiber content of RGFH helmets is 5–6 mA. This might be due to the higher conductivity of glass fiber compared with resin. Moreover, at 50 wt. %, RBFH and NPBFH produced less leakage owing to lower conductivity of banana fiber as compared with glass fiber.⁵¹ The occurrence of leakage at 50 wt. % fiber content is due to agglomeration factor in which the fiber-to-fiber interaction becomes more dominant as shown in Figure 10. Hence, during the immersion, the fiber was slightly exposed to sodium chloride solution to have a closed circuit.

Table 11.

Electrical resistance test results of RBFH, NPBFH, and RGFH.

Fiber wt. %	RGFH	NPBFH	RBFH
10	No leakage	No leakage	No leakage
20	No leakage	No leakage	No leakage
30	No leakage	No leakage	No leakage
40	No leakage	No leakage	No leakage
50	5–6 mA	1–2 mA	3–4 mA

Figure 10.

Helmet of 50 wt. % fiber content.

Water absorption and corrosion characteristics

Water absorption characteristics of RBFH, NPBFH, and RGFH are shown in Figure 11. It can be observed that the water absorption % of RGFH is very meagre in comparison to RBFH and NPBFH. As the fiber wt. % is increased, the water absorption capacity of RBFH and NPBFH keeps on increasing due to hydrophilic tendency of banana fiber. However, the rate of water absorption is very less in RGFH due to hydrophobic tendency of glass fibers. The water absorption in banana fiber-based helmets is due to the presence of OH group in the ligno-cellulosic fiber. As the fiber wt. % is increased, the amount of OH group also increases which makes the composite more hydrophilic to have higher percentage of water absorption.^24,31 Since the glass fiber has high resistance to water absorption (hydrophobic) even after the addition of fibers from 10 to 40 wt. %. The glass fiber-based helmets have very less percentage of water absorption than banana fiber reinforced helmets. Interestingly, the percentage of water absorption of all varieties of helmets is well within the permissible limit. The corrosion test results are listed in Table 12. Significantly, no sign of corrosion was found in all varieties of helmets. Since the corrosion test is particularly conducted for the aluminium buckle of the helmet, the buckles were keenly examined. After careful examination, it is was found all the buckles were free from corrosion.

Figure 11.

Water absorption of RBFH, NPBFH, and RGFH.

Table 12.

Corrosion test results of RBFH, NPBFH, and RGFH.

Fiber wt. %	RGFH	NPBFH	RBFH
10	No sign of corrosion	No sign of corrosion	No sign of corrosion
20	No sign of corrosion	No sign of corrosion	No sign of corrosion
30	No sign of corrosion	No sign of corrosion	No sign of corrosion
40	No sign of corrosion	No sign of corrosion	No sign of corrosion
50	No sign of corrosion	No sign of corrosion	No sign of corrosion

Heat resistance test

Heat resistance properties of RBFH, NPBFH, and RGFH are shown in Table 13. It can be noted that very minute softening was observed at 10 wt. % fiber content of RBFH and NPBFH. At 20–40 wt. %, no distortion was found in all varieties of helmets. At 50 wt. %, RBFH and NPBFH exhibit very minute crispy distortion, whereas RGFH shows very minute softening. The softening of RBFH and NPBFH at 10 wt. % is due to high mobility of resin materials.⁵² When the fiber content is increased from 10 to 40 wt. %, owing to better interfacial bonding, the mobility of the matrix material becomes compact, hence no distortion was observed. However, the fibers were well exposed to heat in the oven due to inadequate resin at 50 wt. % of all varieties of helmets. This phenomenon, makes at 50 wt. % all varieties of helmets, exhibited some kind of distortion and softening. In addition, the poor interfacial bonding also led to little crispening in RBFH and NPBFH and minute softening in RGFH.

Table 13.

Heat resistance test results of RBFH, NPBFH, and RGFH.

Fiber wt. %	RGFH	NPBFH	RBFH
10	No sign of damage	Minute softening	Minute softening
20	No sign of damage	No sign of damage	No sign of damage
30	No sign of damage	No sign of damage	No sign of damage
40	No sign of damage	No sign of damage	No sign of damage
50	Very minute softening	Minute crispy distortion	Minute crispy distortion

Chin strap strength test

Test results of RBFH, NPBFH, and RGFH are indicated in Table 14. Remarkably, no damage was found in the chin strap of all varieties of helmets except a small pull out experienced in the RBFH at 50 wt. % fiber content. The helmets of fiber content varying from 10 to 40 wt. % were having adequate interfacial bonding with the resin material to hold the prescribed load as per IS 2925 standard. However, beyond 40 wt. %, owing to poor interfacial bonding led to slight elongation of fiber materials.

Table 14.

Chin strap test results of RBFH, NPBFH, and RGFH.

Fiber wt. %	RGFH	NPBFH	RBFH
10	No elongation	No elongation	No elongation
20	No elongation	No elongation	No elongation
30	No elongation	No elongation	No elongation
40	No elongation	No elongation	No elongation
50	No elongation	No elongation	Minute pull out

Conclusion

In this work, three varieties of helmets, namely, NPBFH, RBFH, and RGFH were fabricated and tested as per ISI standards using needle punched banana fiber and 30 mm random banana and glass fiber, respectively. Scientifically, it proves, needle punched banana fiber imparts better mechanical properties when reinforced with matrix material. All the fabricated varieties of helmets exhibited optimal properties at 40 wt. % of fiber content. However, the dynamic response of NPBFH is much better to RBFH and almost comparable with commercially used RGFH. The results revealed that the shock absorption, penetration resistance, and water absorption of NPBFH are 245 kgf, 4.75 mm and 0.61%, respectively, which is much better than RBFH and comparable with RGFH. The synthesized NPBFH is light in weight, recyclable, and non-toxic and comply with all the test standards and well within the permissible limit of ISI norms. Hence, this work endorses, NPBFH of 40 wt. % fiber content can be used by industrial workers as an ISI compliant industrial safety helmet. To accentuate the use of this alternative superior helmet in industries would be the inceptive step for our country’s prized industries taking a turn for the better.

Footnotes

Declaration of conflicting interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author(s) received no financial support for the research, authorship, and/or publication of this article.

ORCID iDs

Jack J Kenned

C. Suresh Kumar

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Evaluation of structural integrity of needle punched banana fiber reinforced industrial safety helmets

Abstract

Keywords

Introduction

Materials and methods

Banana fiber extraction

E-glass fiber

Matrix preparation

Needle punching process

Needle punching technique

Selection of needling parameters

Needle Action

Penetration depth

Punch density

Punch density

Industrial safety helmet fabrication

Testing of industrial safety helmet

Shock absorption test

Penetration test

Flammability resistance test

Electrical resistance test

Water absorption and corrosion resistance test

Heat resistance test

Chin strap strength test

Results and discussion

Evaluation of shock absorption energy

Analysis of Penetration depth

Flammability Analysis

Electrical resistance test

Water absorption and corrosion characteristics

Heat resistance test

Chin strap strength test

Conclusion

Footnotes

Declaration of conflicting interests

Funding

ORCID iDs

References