Carbonized hemp hurd powder for eco-friendly polybenzoxazine composite brake material: Excellent friction property and high mechanical performance

2.1 Materials

Benzoxazine resin (BA-35x) was based on bisphenol-A obtained from PTT Phenol Co., Ltd. (Rayong, Thailand), paraformaldehyde purchased from Merck Co., Ltd. (Darmstadt, Germany) and 3,5-xylidine purchased from Panreac Quimica SA. (Barcelona, Spain). Carbon fiber and glass fiber were obtained from SJ Sinthuphun Trading Co., Ltd. (Bangkok, Thailand) and Toho Beslon Co., Ltd. (Tokyo, Japan) respectively. Aramid pulp was supplied by Du Pont (Tokyo, Japan). Iron fibers, synthesis graphite (ρ = 2.18 g/cm³), zirconium silicate, barium sulfate, NBR and cashew dust were provided by Compact International Co., Ltd. (Phetchaburi, Thailand). Carbonized hemp hurd (ρ = 1.69 g/cm³) were supplied by Highland Research and Development Institute (Chiang Mai, Thailand). All the chemicals for the experiment were used without purification.

2.2 Preparation of BA-35x and CHH

BA-35x was synthesized by using bisphenol-A, paraformaldehyde and 3,5-xylidine at a molar ratio of 1:4:2 at a temperature of 110 °C for 40 min (Ishida, 1996). The light clear-yellowish solid resin was obtained at room temperature and the solid resin was then ground to fine powder and kept in a refrigerator for future-use.

Carbonized hemp hurd particles (CHH) were prepared by milling from carbonized hemp hurd. The fractions of the CHH sizes that pass through a sieve were similarly designed to commercial synthetic graphite particles (SG). The CHH were dried at a temperature of 105 °C for 24 h and kept in the desiccator before use. The elemental composition (wt %) was analyzed by ultimate analysis of CHH: C = 65.37, H = 3.48, N = 0.80, S = 0.16 and O = 19.57.

2.3 Preparation of SG/CHH-filled poly(BA-35x) composite samples

The SG/CHH-filled poly(BA-35x) composite samples are formulated from 10 to 11 ingredients in four categories as listed in Table 1. The various contents of SG and CHH, SG/CHH (wt%/wt%), are SG/CHH (10/0), SG/CHH (8/2), SG/CHH (6/4), SG/CHH (4/6), SG/CHH (2/8) and SG/CHH (0/10). The molding compounds from all ingredients were mechanically mixed at about 120 °C for 45 min. Then, the compounds were thermally cured at a temperature of 200 °C for 2 h by a compression-molder under a hydraulic pressure of 15 MPa. The fully cured composite samples was obtained after air-cooled in room temperature before their characterizations. Some examples of the composite samples are presented in Fig. 1.

Close

Fig. 1

Some examples of fully cured SG/CHH -filled poly(BA-35x) composite samples.

Export to PPT

2.4 Characterizations of the samples

Mechanical properties of the samples were measured on Universal Testing Machine, Instron 5567 (United State) using three-point bending mode. The dimensions of sample are 25 mm × 60 mm × 3 mm. The support span is 48 mm, and a crosshead speed is 2 mm/min according to ASTM D790. Five replicas were used for evaluation of mechanical properties.

Functional groups of the samples were studied using a spectrum GX FT-IR spectrometer from Perkin Elmer with an ATR accessory (Waltham, MA, USA). All spectra were taken as a function of time with 32 scans at resolution of 4 cm⁻¹ and wavenumber ranging from 4000 to 400 cm⁻¹. Three samples were repeated to confirm the findings.

Storage modulus (E′) and loss tangent (tan δ) of the samples were carried out using Dynamic Mechanical Analyzer, DMA1, Mettler Toledo (Switzerland). The dimensions of sample are 10 mm × 50 mm × 2.5 mm. The sample was measured by three-point bending mode at a frequency of 1 Hz with a heating rate of 2 °C/min from 30 °C to 300 °C under nitrogen atmosphere. Three samples were repeated to confirm the findings.

Thermal stabilities, i.e., degradation temperature at 5 % weight loss (T_d5) and residual weight of the samples were studied under dynamic conditions using a thermogravimetric analyzer TGA1, Mettler Toledo (Switzerland). The sample about 10 mg was operated at a heating rate of 20 °C/min from 30 °C to 1000 °C in nitrogen gas flow 50 ml/min. Each sample was repeated three times.

The worn surface of the sample was analyzed by scanning electron microscope (SEM), model JEOL JSM-6510 from JEOL Ltd. (Tokyo Japan) with an acceleration voltage of 5 kV. Each sample was given a thin layer of gold film using a sputter coater, model SCD 040 from Oerlikon Balzers Coating (Thailand) Co., Ltd. (Chonburi, Thailand).

Coefficient of friction (COF) of the sample at a room temperature of 25 °C was performed by a ball-on-disc tribometer (shown in Fig. 2(a)), CSM TRB-S-DE, Anton Paar (Australia) under dry sliding with a speed range of 0.366 m/s and a load of 10 N. The sliding distance of 1000 m was measured to obtain steady-state values of coefficient of friction (COF) of the samples. Material of testing balls is carbon steel. The COF of each sample was averaged of triplicate measurements.

Close

Fig. 2

(a) A ball-on-disc tribometer (b) The constant speed brake lining tester.

Export to PPT

Coefficient of friction (COF) and specific wear rate (V) of the sample as a function of temperature were determined from a constant speed brake lining tester, HP-8-LC (Tokyo, Japan) (shown in Fig. 2(b)) at test temperature levels of 100, 150, 200, 250, 300, and 350 °C according to TIS97-2557 which is similar to JIS-D4411 and GB5763-2008. The material of disc is grey cast iron. The sample size is 25 mm × 25 mm × 7 mm and the test conditions are listed in Table 2.

The V of the sample as a function of temperature was also calculated as follows equation (1).

2.5 Finite element analysis of disc brake system

The disc brake model (3D) consisted of disc and pad were designed in Design Modeller and their 3D solid model were analyzed by ANSYS Workbench 2022 R1 software, Ansys, Inc. Houston, USA. A 3D mesh was crated with tetrahedral 3D elements. The number of elements and nodes of the disc brake model are 39,208 and 20,351, respectively. Gray cast iron disc and pads (SG/CHH-filled poly(BA-35x) composite samples) were homogeneous and the pads were considered to be an isotropic elastic materials. The mechanical properties of the disc and the pads are listed in Table 3. Static structural simulation was chosen to analyze mechanical contact-brake disc pad. The total simulation time for braking was t = 673 s, the following initial time steps, and the structural boundary conditions applied to the pad are tabulated in Table 4. The calculation related to the contact pressure on the disc was determined.

2.6 Wear rate simulation

Wear predictions of the pad’s surface due to removal materials can be also solved by finite element analysis program, ANSYS. A generalized form of Archard’s wear law as given by equation (3) is proposed to predict wear in sliding contacts between disc and pad for disc brake system. It is assumed that the wear rate at any point on the contact surface is proportional to the normal contact pressure (p) and the relative sliding velocity (v). Moreover, the equation (3) can be reformulated as presented in equation (4).

A wear simulation procedure proposed by Põdra and Andersson, 1999 has been adopted in which the contact pressure distribution is computed by using the finite element analysis. With the obtained distribution, the wear of the brake pad is computed by numerical integration of equation (4) according to the explicit Euler integration scheme using the mathematical programming language MATLAB. The procedure is implemented in ANSYS and looped through a series of static structural analyses of the finite element model, each with an updated geometry of the pad surface. Each step starts with a static structural analysis that computes the nodal contact pressure at each of the surface nodes (Söderberg and Andersson, 2009). The wear depth at node number i after the jth simulation step is, $$h_{i,j}=h_{i,j-1}+{\mathrm{\Delta }h}_{i,j}$$ $$\mathrm{\Delta }{h}_{i,j}=k{p}_{i,j}\mathrm{\Delta }{s}_{i,j}$$ where h_i,j−1 is the wear depth after the (j − 1)th step, Δ h_i,j is the incremental nodal wear depth during the jth step, p_i,j is the nodal pressure, and Δ s_i,j is the incremental nodal sliding distance.

The incremental sliding distance of a node on the pad surface is proportional to its radial distance from the center of the rotor according to $\mathrm{\Delta }{s}_{i,j}=n_{j}2\pi r_i$ , where n_j is number of rotor revolutions during the jth step and r_i is number of rotor revolutions during the jth step.

3.1 Flexural properties of SG/CHH-filled poly(BA-35x) composite samples

The effect of CHH contents on flexural properties of poly(BA-35x) composites filled with SG/CHH of 10/0, 8/2, 6/4, 4/6, 2/8, and 0/10 (wt%/wt%) is depicted in Fig. 3. The flexural strength and modulus of the SG/CHH-filled poly(BA-35x) composites enhanced by an addition of the CHH content, i.e., from 43.2 MPa to 52.0 MPa and from 7.0 GPa to 9.0 GPa, respectively, for SG/CHH from 10/0 to 0/10. In general, the strength and modulus of reinforced composites mainly depends on the properties of their ingredients and interfacial adhesion between the filler and the matrix. Therefore, except the properties of their ingredients of the poly(BA-35x) composites, the improvement of strength of the composites suggested that the addition of the CHH could enhance the CHH-poly(BA-35x) interfacial adhesion because the poly(BA-35x) chains could go into the honeycomb-like pore structures of CHH (Fig. 4(b)), leading to better stress transfer efficiency from the poly(BA-35x) and CHH as can be seen the fractured surface in Fig. 4(c) which the good interfacial adhesion (green ambits) and the cohesive fracture surface developed in the poly(BA-35x) matrix region (red ambits) could be observed. While the SG-poly(BA-35x) interfacial adhesion showed at the outer surface of the SG only (white ambits) as presented in Fig. 4(f). Good CHH-poly(BA-35x) interfacial adhesion observed in Fig. 4(c) also resulted in the motion of the poly(BA-35x) chain restricted by CHH and the composites became increasing modulus. Moreover, it was remarked that the rather high flexural properties of the SG/CHH-filled poly (BA-35x) composite were obtained when compared with other polymer composites for friction materials, i.e., strength of 10.0–40.0 MPa and modulus of 3.0–8.0 GPa under flexure loading (Mathur et al., 2004).

Close

Fig. 3

Flexural properties of SG/CHH-filled poly(BA-35x) composite samples at various SG/CHH contents.

Export to PPT

Close

Fig. 4

SEM micrographs (a,b) CHH particles (c) 10 wt% CHH-filled poly(BA-35x) composite (d,e) SG particles (f) 10 wt% SG-filled poly(BA-35x) composite.

Export to PPT

3.2 Network formation of SG/CHH-filled poly(BA-35x) composite samples

To confirm the formation of an interfacial adhesion between CHH and poly(BA-35x) that resulted in an enhancement of mechanical property of the composite samples as above mentioned, FTIR spectroscopy was performed on the CHH, SG, poly(BA-35x), CHH-filled poly(BA-35x) composite sample and SG-filled poly(BA-35x) composite sample to determine the presence of the functional groups on them as can be seen in Fig. 5. Fig. 5(a), FTIR spectra of CHH shows the broad absorption band in a range of 3500–3000 cm⁻¹ attributed to free and associated hydroxyl groups and structural hydroxyl groups (–COOH and –COH). The absorption bands at 1587 cm⁻¹ (C = O stretching mode of conjugated ketones and quinones), 1380 cm⁻¹ (CH₂ units in biopolymers), 832–600 cm⁻¹ (C–H bond in aromatic and heteroatomic compounds) were detected (Sahoo et al., 2021; Srinivasan et al., 2015) In addition, the absorption band at 1300–1000 cm⁻¹ ascribed to the glycosidic bond was also observed (He et al., 2022). While, in Fig. 5(b), FTIR spectra of SG displays very less functional group as SG were characterized by a very well assembled layer of carbon. In case of poly(BA-35x), Fig. 5(c) indicates the absorption bands of the poly(BA-35x) after oxazine ring of BA-35x resin was opened by thermal polymerization, i.e., 3300 cm⁻¹ (hydroxy groups), 1488 cm⁻¹ (tetra-substituted aromatic ring) and 1240–1020 cm⁻¹ (asymmetric C-N-C stretching) (Jubsilp et al. (2018)).

Close

Fig. 5

FTIR spectra of (a) CHH (b) SG (c) poly(BA-35x) (d) CHH-filled poly(BA-35x) composite sample (e) SG-filled poly(BA-35x) composite sample.

Export to PPT

For the FTIR spectra of CHH-filled poly(BA-35x) composite sample as plotted in Fig. 5(d), it was observed that the intensity of an absorption band at 3300 cm⁻¹ of the poly(BA-35x) was quietly increased. This behavior may be the effect from hydroxyl groups of the CHH. In addition, it is possible that the OH groups of the poly(BA-35x) can be further interacted with the OH groups and C = O groups of the CHH to form hydrogen bonding (H-bonding) as can be seen the new absorption band at 1720 cm⁻¹ and the disappearance of the absorption band at 1587 cm⁻¹ of the CHH (Guo et al., 2010; Rimdusit et al., 2006, 2007). In case of SG-filled poly(BA-35x) composite sample as depicted in Fig. 5(e), it was observed that the intensity of an absorption band at 3300 cm⁻¹ of poly(BA-35x) was similar to that of the poly(BA-35x) due to no H-bonding formation as expected.

3.3 Thermomechanical properties of SG/CHH-filled poly(BA-35x) composite samples

Thermomechanical properties, i.e., storage modulus (E′) and loss tangent (tan δ) at a different of temperature of the poly(BA-35x) composite samples filled with SG/CHH of 10/0, 8/2, 6/4, 4/6, 2/8, and 0/10 (wt%/wt%) were determined by dynamic mechanical analysis as illustrated in Fig. 6. The E′ represents the energy stored in the samples following deformation under load at various temperature, and related to their stiffness which is one of the key parameters representing for COF and wear rate (Ahmadijokani et al., 2019; Wongpayakyotin et al., 2021; Wu et al., 2012).

Close

Fig. 6

(a) Storage modulus, (b) tan δ of SG/CHH-filled poly(BA-35x) composite samples at various SG/CHH contents.

Export to PPT

From Fig. 6(a), the E′ at glassy state (50 °C) of the poly(BA-35x) composites filled with SG/CHH from 10/0 to 0/10 (%wt/%wt) were found to be 4.93, 5.03, 5.18, 5.42, 5.51, and 5.64 GPa, respectively. In addition, their rubbery plateau modulus was also found improved with increasing CHH content. The increase in modulus could be also explained by the hydroxyl groups in the CHH that could react with the poly(BA-35x) to form significantly strong H-bonding, in consequence, the crosslink density increased. Moreover, the poly(BA-35x) composites filled with higher CHH contents showed more relative dimensional stability as it can be observed that the SG/CHH (10/0)-filled poly(BA-35x) composite sample showed stability of E′ at approximately 150 °C and then tended to significantly decrease as the thermal glass-rubber transition occurred. While, the E′ of the SG/CHH (0/10)-filled poly(BA-35x) composite sample was stable even when the temperature was up to 200 °C and the gradual decrease of the E′ of the composite sample was then observed.

Fig. 6(b) is a plot of tan δ at a different of temperature of the poly(BA-35x) composites filled with SG/CHH from 10/0 to 0/10 (wt%/wt%). The temperature at the tan δ peak was used to represent the glass transition temperature (T_g) of the composite samples. The T_g is described as a polymer change from a glassy state to a rubbery soft state related to 30–50 carbon chains start to move at the T_g. From the same figure, the tan δ peak of the SG/CHH-filled poly(BA-35x) composite samples was systematically shifted to higher temperature, i.e., 212, 215, 218, 222, 225, and 228 °C, respectively, with an increase of the CHH content from 0 wt% to 10 wt%. This performance indicates CHH filler-like effect to be more dominant with increase in the CHH to SG mass ratio, resulting in increased crosslinking density from the interfacial bonding formation between the hydroxyl groups in the CHH and the poly(BA-35x) which required more energy to transform from the glassy state to the rubbery state of the SG/CHH-filled poly(BA-35x) composite samples as similar characteristic discussed in high performance friction materials of aramid pulp/carbon fiber-reinforced polybenzoxazine composites (Lertwassana et al., 2019). It would be expected that the SG/CHH-filled poly(BA-35x) composite samples with higher T_g can provide wear performance better than those same type of composite samples with lower T_g as previously informed by Wu et al., 2012 and Wongpayakyotin et al., 2021.

3.4 Thermal stabilities of SG/CHH-filled poly(BA-35x) composite samples

As it is known that breaking may rise the temperature at the disc-pad interface up to 800 °C in severe conditions (Ahmadijokani et al., 2019; Hwang et al., 2010). Therefore, practical performances of polymer composite friction materials can be provided by one of crucial key parameters that is thermal stability. TGA thermograms of SG/CHH-filled poly(BA-35x) composite samples at SG/CHH contents from 10/0 to 0/10 (wt%/wt%) are depicted in Fig. 7(a). Three main degradation steps of the SG/CHH-filled poly(BA-35x) composite samples were observed. The first degradation step was found in the range of 250–500 °C corresponding to the degradation of cashew dust, NBR powder and poly(BA-35x) (Lertwassana et al., 2019). The second degradation step took place the onset temperature from 500 °C to 600 °C displaying the degradation of aramid pulp (Lertwassana et al., 2019; Liu and Yu, 2006) and CHH (Matykiewicz, 2020). The onset and offset temperatures of the third degradation step were observed at approximately 600 °C and 900 °C, respectively, related to degradation of barium sulphate zirconium silicate, synthetic graphite, carbon fiber and iron fiber (Ahmadijokani et al., 2019; Lertwassana et al., 2019).

Close

Fig. 7

(a) TGA thermograms of SG/CHH-filled poly(BA-35x) composite samples at various SG/CHH contents, CHH and SG (b) T_d5 and residual weight at 1000 °C of SG/CHH-filled poly(BA-35x) composite samples at various SG/CHH contents.

Export to PPT

In addition, the degradation temperature at 5 % weight loss (T_d5) and residual weight at 1000 °C of the SG/CHH-filled poly(BA-35x) composite samples was analyzed and depicted in Fig. 7(b). It was observed in the inserted figure that a decrease of CHH content was found to promote the T_d5 and residual weight of the SG/CHH-filled poly(BA-35x) composite samples. The T_d5 was 420, 418, 415, 411, 409, and 404 °C and the residual weight was 73.7, 73.5, 73.4, 73.1, 72.8, and 71.5 % for an addition of SG/CHH from 10/0 to 0/10 (wt%/wt%), respectively. This behavior is possible that T_d5 (>1000 °C) and residual weight (∼99.0 % at 1000 °C) of the SG was relatively higher than that T_d5 (330 °C) and residual weight (75.0 % at 1000 °C) of the CHH. However, under nitrogen atmosphere, the T_d5 and residual weight at 1000 °C of all SG/CHH-filled poly (BA-35x) composite samples exhibited higher values than T_d5 (∼350–400) and residual weight at 1000 °C (65–70 %) of the phenolic type samples which are widely used as commercial friction materials (Ahmadijokani et al., 2019; Bashir et al., 2021). Therefore, it is possible that higher residual weight of the SG/CHH-filled poly(BA-35x) composite samples than that of the phenolic type samples could limit the exothermicity of the pyrolysis reactions, decrease the production of volatile gases and inhibit the thermal conduction of composites.

3.5 Tribological properties of SG/CHH-filled poly(BA-35x) composite samples

Tribological responses and performances of friction materials could be measured through COF. Fig. 8 indicates COF at room temperature of 25 °C within the sliding distance of 1000 m of SG/CHH-filled poly(BA-35x) composite samples at SG/CHH contents from 10/0 to 0/10 (wt%/wt%). The COF of the SG/CHH-filled poly(BA-35x) composite samples were 0.30, 0.31, 0.32, 0.34, 0.36, and 0.38 for SG/CHH contents from 10/0 to 0/10 (wt%/wt%), respectively. The increment of the COF of the SG/CHH-filled poly(BA-35x) composite samples with increasing CHH content is possible that shear stresses may promote the disintegration of the CHH at the glycosidic bond and weaken the stress absorbing capacity of the composite with higher CHH content, resulting in the higher COF as similarly explained in the composite filled with cellulose fiber (Satapathy and Bijwe, 2004).

Close

Fig. 8

Coefficient of friction in a distance of 1000 m of SG/CHH-filled poly(BA-35x) composite samples at various SG/CHH contents.

Export to PPT

3.6 Tribological properties at 100 °C-350 °C of SG/CHH-filled poly(BA-35x) composite samples

From above-mentioned results, it was found that the addition of SG/CHH 2/8 (wt%/wt%) for poly(BA-35x) composite sample had a balance of properties, including COF, mechanical properties, and temperature resistance so that the composite sample can be considered to evaluate the COF and specific wear rate as a function of temperature.

The effect of temperature on COF and specific wear rate of the SG/CHH (2/8)-filled poly(BA-35x) composite sample was evaluated to compare with those of the SG/CHH (10/0)-filled poly(BA-35x) composite sample, NAO friction phenolic composite, and asbestos-based commercial brake pad as plotted in Fig. 9(a) and Fig. 9(b), respectively. The COF values at 100 °C-350 °C of the SG/CHH (2/8)-filled poly(BA-35) composite sample, i.e., 0.40–0.43 was relatively higher than that of the SG/CHH (10/0)-filled poly(BA-35x) composite sample, i.e., 0.35–0.38, the NAO friction phenolic composite, i.e., 0.37–0.45, and the asbestos-based commercial brake pad, i.e., 0.36–0.41. Such finding confirms that the addition of the CHH can help enhance COF of the SG/CHH-filled poly(BA-35x) composite sample. In addition, the obtained COF of the SG/CHH-filled poly(BA-35x) composite samples was in the range of 0.2–0.7 at temperature levels of 100 °C-350 °C according to TIS97-2557: Brake linings for vehicles. Furthermore, the SG/CHH (2/8)-filled poly(BA-35x) composite sample showed a more stable COF against the different temperatures compared with the NAO friction phenolic composite and the asbestos-based one. This behavior is possible that the thermal stability of the poly(BA-35x) matrix is higher than that phenolic which is a matrix for the NAO friction composite and the asbestos-based brake pad (Jubsilp et al., 2021).

Close

Fig. 9

(a) Coefficient of friction and (b) specific wear rate as a function of temperature of SG/CHH -filed poly(BA-35x) composite samples, NAO friction phenolic composite, and asbestos-based commercial brake pad.

Export to PPT

For specific wear rates, the addition of the CHH in the SG/CHH-filled poly(BA-35x) composite sample also showed an improvement of wear resistance when compared with the poly(BA-35x) composite sample unfilled CHH. It is possible that the higher T_g of the SG/CHH (2/8)-filled poly(BA-35x) composite sample can help it to retard softening (deformation). This in turn caused slower damage of the sample surface that eventually leads to generate small amount of wear debris. In comparison with the NAO and the asbestos ones, the SG/CHH (2/8)-filled poly(BA-35x) composite sample showed more wear resistance. This is may be due to significant interfacial adhesion between poly(BA-35x) and all ingredients, in consequence, a wear mechanism obtained from the development of friction force at the sliding surface of the SG/CHH (2/8)-filled poly(BA-35x) composite sample was different from that of the NAO and the asbestos ones.

3.7 Simulation of wear and contact pressure distribution of SG/CHH-filled poly(BA-35x) friction pads

Wear simulation and its effect on contact pressure distribution at the interface of SG/CHH-filled poly(BA-35x) friction pads and disc of disc brakes was studied by finite element analysis (FEA). In this work, the validity of the analyses in the FEA was evaluated by repetition following the previous work (Belhocine and Omar, 2016). In the FEA simulation, the initial parameters listed in Table 3 and Table 4 were used. From the simulation, the contours of the contact pressure distribution of the poly(BA-35x) friction pads filled with SG/CHH (2/8) and SG/CHH (10/0) at 100 °C-350 °C is presented in Fig. 10 and Fig. 11, respectively. In addition, experimental numerical data of COFs and simulated maximum contact pressure at 100 °C-350 °C of the poly(BA-35x) friction pads are displayed in Table 5 and Table 6. From Fig. 10 and Fig. 11, it was observed that the contours of the contact pressure distribution of both SG/CHH-filled poly(BA-35x) friction pads was quietly similar and tended toward the leading edge of the contact due to the induced frictional traction and the maximum contact pressure was at the edge of the friction pads. The maximum contact pressure at 100 °C-350 °C of the SG/CHH (2/8)- and SG/CHH (10/0)-filled poly(BA-35x) friction pads was in a range of 52.31–54.33 kPa and 54.13–54.95 kPa, respectively. It can be seen that the addition of the CHH to substitute the SG friction modifier was found to decrease the maximum contact pressure of the poly(BA-35x) friction pad. It is possible that the higher in the COF of the SG/CHH (2/8)-filled poly(BA-35x) friction pad is accompanied by a decrease in contact pressures of the friction pad (Belhocine and Omar, 2016).

Close

Fig. 10

Interface contact pressure distribution on SG/CHH (2/8)-filled poly(BA-35x) friction pad at 100 °C-350 °C.

Export to PPT

Close

Fig. 11

Interface contact pressure distributions on SG/CHH (10/0)-filled poly(BA-35x) friction pad at 100 °C-350 °C.

Export to PPT

In the case of specific wear rate (V) of the SG/CHH-filled poly(BA-35x) friction pads as also listed in Table 5 and Table 6, it was found as expected from simulation that the V of the SG/CHH (2/8)-filled poly(BA-35x) friction pad showed lower than that of the SG/CHH (10/0)-filled poly(BA-35x) friction pad. This behavior was related to their maximum contact pressures. The friction pad that showed lower maximum contact pressure would be worn harder than the friction pad having higher maximum contact pressure. In addition, the V from the wear simulation compared with that from the experimental of the poly(BA-35x) composite samples was in reasonable agreement as the difference V, i.e., lower than 3 % is within acceptable tolerance (Kim et al., 2005; Suresh et al., 2017).