Mechanical strength, tribological performance, and waste control in filler-modified glass fiber–reinforced epoxy composites

Adhikesavan, Madhanagopal; Bunpheng, Wasurat; Wang, Xianpeng; Dhairiyasamy, Ratchagaraja

doi:10.1590/1517-7076-RMAT-2026-0208

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Articles • Matéria (Rio J.) 31 • 2026 • https://doi.org/10.1590/1517-7076-RMAT-2026-0208 linkcopy

Mechanical strength, tribological performance, and waste control in filler-modified glass fiber–reinforced epoxy composites

Authorship SCIMAGO INSTITUTIONS RANKINGS

Glass fiber–reinforced epoxy composites are used in lightweight structural and sliding components, yet dry-contact damage can shorten service life and generate wear debris. Filler engineering offers a practical route to strengthen the matrix-rich surface while controlling friction and material loss. A coordinated comparison of lubricating, ceramic, and lamellar fillers within a single glass fiber–epoxy platform is still needed. This study aims to assess the mechanical, tribological, and waste-control response of graphite-, SiC-, and MoS₂-filled glass fiber–epoxy laminates. Laminates containing 0, 2, 3, and 5 wt.% filler were fabricated by hand lay-up and compression molding, then tested by tensile, flexural, Shore D hardness, notched Izod impact, ASTM G99 pin-on-disc wear, profilometry, SEM, and response surface modelling. S5 recorded 328 MPa tensile strength, 438 MPa flexural strength, 90 Shore D hardness, and 1.70 × 10⁻⁴ mm³ N^-1 m^-1 specific wear rate, representing 13.1%, 15.3%, 9.8%, and 39.5% gains over C1. M3 recorded 65 kJ m⁻² impact strength, 0.374 coefficient of friction, and 1.510 µm roughness, giving 12.1%, 40.4%, and 19.8% gains. The results support application-specific filler selection: SiC is suitable for load-bearing wear components, while MoS₂ is suitable for low-friction sliding interfaces. Future innovation should extend validation to high loads, ageing, filler mapping, and multi-criteria ranking.

Keywords:
Glass fiber–reinforced epoxy composites; Pin-on-disc tribology; Response surface methodology; Solid lubricant fillers; Waste recycling

STUDY OBJECTIVE	METHODOLOGY	MATERIALS/PARAMETERS	KEY FINDINGS	RELEVANCE TO CURRENT STUDY
Waste tribology review	Literature synthesis	Agricultural, industrial, post-consumer fillers	Waste fillers improved wear utility	Supports waste-control framing [¹²]
Dry-sliding CFRP lubrication	Hydrothermal hybrid filler	FGr@MoS₂, carbon fabric, epoxy	Friction and wear decreased substantially	Supports lamellar transfer-film logic [¹³]
Resin comparison under wear	Dry wear testing	GFRE, GFRP, sliding load	Epoxy composites retained tribological potential	Supports GF/epoxy material selection [¹⁴]
GFRC drilling-wear analysis	Mechanical, wear, SEM tests	B₄C, graphite, GFRC	Graphite improved wear resistance	Supports graphite comparison [¹⁵]
Predict GFRE tribology	Taguchi, ANN, FESEM	GNP, load, dry sliding	SWR and COF optimized	Supports DOE-based tribology analysis [¹⁶]
Hybrid epoxy bearing design	Steel/self-contact tribology	UHMWPE, MoS₂, base oil	COF reached 0.08–0.10	Supports MoS₂ lubricant selection [¹⁷]
PTFE particle-size effect	Reciprocating wear tests	PTFE size, GF/epoxy	Large PTFE reduced wear order	Supports filler-size concern [¹⁸]
Powder epoxy tribology	Graphite-filled epoxy tests	Powder epoxy, graphite content	Abrasive tendency became lower	Supports graphite dosage control [¹⁹]
2D hybrid coating design	Hydrothermal synthesis, coating wear	h-BN/MoS₂, epoxy coating	COF and wear rate decreased	Supports MoS₂ film mechanism [²⁰]
Dual hard/lubricant coating	Electrocodeposition wear tests	Nano-SiC, graphite, Ni coating	Mixed particles protected surfaces	Supports hard-soft filler logic [²¹]

COMPOSITE ID	COMPOSITE DESCRIPTION	FILLER TYPE	FILLER LOADING, WT.%
C1	GF/Epoxy	None	0
G2	GF/Epoxy + graphite	Graphite	2
G3	GF/Epoxy + graphite	Graphite	3
G5	GF/Epoxy + graphite	Graphite	5
S2	GF/Epoxy + SiC	SiC	2
S3	GF/Epoxy + SiC	SiC	3
S5	GF/Epoxy + SiC	SiC	5
M2	GF/Epoxy + MoS₂	MoS₂	2
M3	GF/Epoxy + MoS₂	MoS₂	3
M5	GF/Epoxy + MoS₂	MoS₂	5

MATERIAL	SPECIFICATION	SUPPLIER GRADE/PURITY	MEAN SIZE/FORM
E-glass fabric	Bidirectional woven fabric	Structural reinforcement grade	220 g m⁻²
Epoxy resin	Araldite LY556	Laminating grade	Liquid resin
Hardener	HY951	Amine curing agent	Liquid hardener
Graphite	Nano-graphite powder	99.5%	1–2 µm
Silicon carbide	SiC powder	>99.9%	60 µm
Molybdenum disulfide	MoS₂ nanopowder	99.9%	80–100 nm

PARAMETER	VALUE
Fabrication route	Hand lay-up followed by compression moulding
Mould size	300 mm × 300 mm × 3 mm
Number of glass-fabric layers	10
Resin:hardener ratio	10:1 by mass
Filler loading basis	Relative to epoxy matrix mass
Filler drying condition	60 °C for 2 h
Mechanical stirring	1000 min^-1 for 20 min
Ultrasonication	30 min
Vacuum degassing	−0.08 MPa for 10 min
Compression pressure	5 MPa
Curing condition	24 h at 27 ± 2 °C
Final laminate thickness	3.0 ± 0.2 mm

TEST/CHARACTERIZATION	STANDARD/METHOD	SPECIMEN GEOMETRY	NUMBER OF SPECIMENS OR MEASUREMENTS
Tensile strength	ASTM D3039	250 mm × 25 mm × 3 mm	5 specimens per composite
Flexural strength	ASTM D790	127 mm × 12.7 mm × 3.2 mm	5 specimens per composite
Shore D hardness	ASTM D2240	Flat laminate coupon	5 readings per composite
Notched Izod impact strength	ASTM D256	63.5 mm × 12.7 mm × 3.2 mm	5 specimens per composite
Pin-on-disc wear	ASTM G99	10 mm × 10 mm × 3 mm rectangular pin	3 repeats per load–speed condition
Surface roughness	Contact profilometry	Worn wear-test surface	3 traces per worn surface
SEM morphology	Secondary electron imaging	Worn wear-test surface	Representative worn specimens

TEST	STANDARD	SPECIMEN SIZE	FIXTURE/GEOMETRY	INSTRUMENT/SETTING	REPLICATES
Tensile strength	ASTM D3039	250 mm × 25 mm × 3 mm	Axial tensile grips; longitudinal axis parallel to 0° fabric direction	Tinius Olsen HK50L; 2 mm min^-1	5
Flexural strength	ASTM D790	127 mm × 12.7 mm × 3.2 mm	Three-point bending; 52 mm span; span-to-thickness ratio 16.25:1; 5 mm loading-nose radius; 5 mm support-nose radius	Tinius Olsen HK50L; 2 mm min^-1	5
Hardness	ASTM D2240	Flat laminate coupon	Shore D indentation; 15 s dwell	Shore D durometer	5 readings
Impact strength	ASTM D256	63.5 mm × 12.7 mm × 3.2 mm	Notched Izod; 45° V-notch; 0.25 mm notch-tip radius; notch toward striker	Izod impact tester; 5.5 J pendulum	5

PARAMETER	VALUE
Standard	ASTM G99
Instrument	DUCOM TR-20 pin-on-disc tribometer
Specimen geometry	Rectangular laminate pin
Wear specimen size	10 mm × 10 mm × 3 mm
Nominal contact area	100 mm²
Counterface material	EN31 steel disc
Counterface hardness	60 HRC
Initial counterface roughness	Ra 0.2 µm
Applied loads	10, 20, 30 N
Nominal contact pressures	0.10, 0.20, 0.30 MPa
Sliding speeds	1, 2, 3 m s^-1
Sliding distance	1000 m
Track diameter	60 mm
Track radius	30 mm
Environment	Dry sliding, 27 ± 2 °C, 65 ± 5% RH
Repeats per condition	3
Total wear runs	270
Cleaning solvent	Acetone
Balance readability	0.1 mg

PARAMETER	SYMBOL	UNIT	METHOD/SOURCE
Initial specimen mass	m₀	g	Analytical balance
Final specimen mass	m₁	g	Analytical balance
Mass loss	Δm	g	Equation (10)
Dry mass in air	m_α	g	Archimedes measurement
Apparent immersed mass	m_i	g	Archimedes measurement
Immersion-medium density	ρ_i	g cm⁻³	Standard density value at test temperature
Composite density	ρ	g cm⁻³	Equation (9)
Wear volume loss	ΔV	mm³	Equation (11)
Applied normal load	F_N	N	Pin-on-disc setting
Sliding distance	D	m	Test condition
Specific wear rate	K_s	mm³ N^-1 m^-1	Equation (12)
Coefficient of friction	μ	Dimensionless	Equation (13)

CHARACTERIZATION METHOD	PARAMETER	VALUE
Profilometry	Instrument	Mahr Surf GD120
Profilometry	Roughness parameter	R_α
Profilometry	Cut-off length	0.8 mm
Profilometry	Evaluation length	4 mm
Profilometry	Traces per worn surface	3
SEM	Instrument	Carl Zeiss EVO 18 Research
SEM	Accelerating voltage	20 kV
SEM	Magnification range	100× to 5000×
SEM	Imaging mode	Secondary electron imaging
SEM	Sample cleaning	Ultrasonic cleaning in ethanol for 10 min
SEM	Coating method	Gold sputter coating

INSTRUMENT / PROCESS	CALIBRATION OR VERIFICATION PROCEDURE	FREQUENCY
Universal testing machine	Load-cell zero check; crosshead-displacement check; grip alignment check	Before tensile and flexural testing
Shore D durometer	Reference-block verification	Before hardness testing
Izod impact tester	Pendulum zero check; free-swing verification	Before impact testing
Pin-on-disc tribometer	Load application, spindle rotation, alignment, and track-radius verification	Before each test series
Analytical balance	Verification using standard weights	Before mass-loss measurement
Contact profilometer	Zero setting and stylus-response verification	Before each measurement batch
SEM preparation	Fixed cleaning, drying, and gold-coating procedure	Before SEM imaging

ITEM	CRITERION
Mechanical test replicates	5 specimens per composite group
Tribology replicates	3 runs per load–speed condition
Roughness measurements	3 traces per worn surface
Reported summary	Mean ± standard deviation
Statistical method	One-way ANOVA
Multiple-comparison method	Tukey post hoc test
Significance threshold	Equation (15)

FACTOR	SYMBOL	UNIT	LOW LEVEL	CENTRE LEVEL	HIGH LEVEL	CODED FORM
Applied normal load	F_N	N	10	20	30	Equation (16)
Sliding speed	V	m s^-1	1	2	3	Equation (17)

RESPONSE	SYMBOL	UNIT	DATA SOURCE
Specific wear rate	K_S	mm³ N^-1 m^-1	Equations (9)–(12)
Coefficient of friction	μ	Dimensionless	Equation (13)
Surface roughness	R_α	µm	Equation (14)

QUANTITY	SYMBOL	INSTRUMENT/SOURCE	RESOLUTION OR CONTROL TOLERANCE
Specimen mass	m	Analytical balance	0.1 mg
Specimen length/width / thickness	l, b, t	Vernier caliper/micrometer	0.01 mm
Applied normal load	F_N	Pin-on-disc loading system	±0.1 N
Sliding distance	D	Tribometer setting	±1 m
Sliding speed	V	Tribometer setting	±0.01 m s^-1
Surface roughness	R_α	Contact profilometer	0.001 µm
Test temperature	T	Laboratory thermometer	±2 °C
Relative humidity	RH	Hygrometer	±5% RH

COMPOSITE	AVERAGE SPECIFIC WEAR RATE, ×10⁻⁴ mm³ N^-1 m^-1	RELATIVE WASTE K_S ×10–4 INDEX, W_i	WEAR-CONTROL EFFICIENCY, ηW, %	RELATIVE SERVICE-LIFE FACTOR, L_f
C1	2.81	1.000	0.0	1.00
G2	2.31	0.822	17.8	1.22
G3	1.96	0.698	30.2	1.43
G5	2.13	0.758	24.2	1.32
S2	2.20	0.783	21.7	1.28
S3	1.91	0.680	32.0	1.47
S5	1.70	0.605	39.5	1.65
M2	2.09	0.744	25.6	1.34
M3	1.75	0.623	37.7	1.61
M5	1.94

COMPOSITE	LOAD, N	SLIDING SPEED, m s^-1	SPECIFIC WEAR RATE, ×10⁻⁴ mm³ N^-1 m^-1	COEFFICIENT OF FRICTION, μ
C1	10	1	2.35	0.600
C1	10	2	2.48	0.588
C1	10	3	2.62	0.576
C1	20	1	2.68	0.635
C1	20	2	2.81	0.623
C1	20	3	2.95	0.612
C1	30	1	3.05	0.670
C1	30	2	3.17	0.657
C1	30	3	3.22	0.641
Mean used in Figure 8 / Figure 9	—	—	2.81	0.628

MEASURED PROPERTY	DOMINANT PHYSICAL MEANING	RELEVANT FILLER EFFECT	TRIBOLOGICAL IMPLICATION	SUPPORTING MECHANISM
Tensile strength	Fibre–matrix load transfer	Improved matrix constraint	Delayed fibre exposure	Stronger interfacial stress transfer
Flexural strength	Bending stiffness and matrix support	Rigid particle reinforcement	Reduced surface deformation	Lower subsurface cracking
Shore D hardness	Resistance to indentation	SiC surface stiffening	Lower abrasive penetration	Archard-type hardness control
Impact strength	Dynamic fracture-energy absorption	MoS₂ lamellar sliding	Less brittle surface damage	Crack deflection and frictional sliding
Coefficient of friction	Interfacial shear resistance	MoS₂/graphite tribofilm	Lower tangential force	Low-shear transfer layer
Surface roughness	Worn-surface stability	Hard or lubricating filler action	Lower topographic damage	Reduced ploughing and debris adhesion
Specific wear rate	Material loss per load–distance	Hardness and tribofilm effects	Lower wear volume	Combined and control

COMPOSITE	RESPONSE		MODEL p-VALUE	SIGNIFICANT TERMS
G3	Specific wear rate	0.976	2.85 × 10^-16	A, B
G3	Coefficient of friction	0.896	1.28 × 10^-9	A, B
G3	Surface roughness	0.989	6.13 × 10^-20	A, B
S5	Specific wear rate	0.976	2.67 × 10^-16	A, B, AB
S5	Coefficient of friction	0.904	5.57 × 10^-10	A, B
S5	Surface roughness	0.987	3.17 × 10^-19	A, B
M3	Specific wear rate	0.978	1.23 × 10^-16	A, B, AB
M3	Coefficient of friction	0.836	1.38 × 10^-7	A, B
M3	Surface roughness	0.994	8.63 × 10^-23	A, B, AB

COMPOSITE	OPTIMUM LOAD (N)	OPTIMUM SPEED (m/s)	PREDICTED SPECIFIC WEAR RATE (mm³/N·m)	PREDICTED COF	PREDICTED ROUGHNESS, R_α (µm)	DOMINANT ADVANTAGE
G3	10	1	1.491 × 10^–4	0.428	1.133	Balanced graphite response
S5	10	1	1.318 × 10^–4	0.513	1.090	Highest wear resistance
M3	10	1	1.367 × 10^–4	0.370	1.064	Lowest friction and smoothest surface

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