Mechanical Performance/Cost Ratio Analysis of Carbon/Glass Interlayer and Intralayer Hybrid Composites

Abstract

Hybrid composites combining carbon and glass fibers are increasingly studied for their potential to enhance mechanical properties and cost efficiency. Understanding how different hybrid structures influence these properties is critical for optimizing material design and application. In this paper, the mechanical properties of carbon/glass (C/G) interlayer and intralayer hybrid composites, including tensile, compressive, and flexural properties, were tested, and the cost performances of hybrid composites were analyzed to assess the economic feasibility of different stacking configurations. It was revealed that the specific tensile, compressive, and flexural modulus/cost and strength/cost ratios of interlayer and intralayer hybrid composites decreased with increasing carbon fiber content, indicating that adding carbon fiber reduced cost performance. With the combined hybrid ratio and the interlayer structure with glass fiber sandwiching carbon fiber, the tensile and compressive properties were the most cost-effective. When the dispersion degree of the intralayer hybrid structure was 0, the tensile and compressive properties were the most cost-effective. Specifically, for intralayer hybrid composites with a dispersion degree of 0 and C:G = 1:4, the specific tensile strength/cost ratio was 6.7 × 10⁴ N·m/USD, and the specific compressive modulus and strength/cost ratio was 3.8 × 10⁶ N·m/USD and 4.7 × 10³ N·m/USD, respectively. However, the flexural performance/cost ratio was found to be opposite to the tensile and compressive results. When carbon fiber was distributed in the bottom layer or used to sandwich the glass fiber, the flexural performance/cost ratio of interlayer hybrid composites was nearly as good as that of glass fiber. Moreover, by considering the working condition of composites, the cost performance of mechanical properties can be optimized and improved through careful design of hybrid ratios and stacking structures.

1. Introduction

Fiber-reinforced composites are widely utilized across various fields, including aerospace, transportation, infrastructure, and energy saving, due to their numerous benefits such as low weight and high strength [1,2,3]. However, factors such as their manufacturing process, the high cost of raw materials, and low production efficiency have led to the high cost of composites, which is the most critical factor limiting the widespread application of carbon fiber composites [4].

Cost accounting for composites is relatively complex, typically consisting of manufacturing and material cost. In recent years, manufacturing cost accounted for the majority of composites costs, comprising around 60%–70% of the total. Most research on composites cost analysis has focused on optimizing the molding process [5]; with improvements in this area, manufacturing costs of composites have steadily decreased. For instance, Boeing and the United Kingdom’s Advanced Manufacturing Research Center (AMRC) have developed a low-cost manufacturing technology that reduced energy consumption by over 50%, costs by over 45%, and manufacturing time by 70% [6]. Additionally, Choi [7,8] developed a suite of cost evaluation software based on the composites manufacturing process, calculating the cost of aircraft aileron structures. Similarly, Ye [9] used parameter estimation methods to create cost calculation models for composites manufacturing. Ye [10] developed a theoretical model for manufacturing process time, referencing the cost models from advanced composites manufacturing. Lu [11] optimized the manufacturing process of wind turbine blades using the manufacturing process cost model (MPCM), demonstrating the model’s effectiveness in identifying inefficient parts of the production process for further optimization. Grant et al. [12] explored a low-cost composites technology for automobiles according to their applications.

Material cost is a significant component of the overall cost of composites, influenced by factors such as market price, raw material cost, material supply, and demand. To reduce composites cost, existing research has primarily focused on several key areas [13,14,15]: hybrid composites, large tow carbon fiber, and low-cost resin.

Hybrid composites offer numerous advantages over single-fiber composites, including significant performance and reduced material cost [13,16]. Carbon fiber and glass fiber are the most common raw materials for hybrid composites. Carbon fiber is characterized by light weight, high strength, and higher cost compared to glass fiber. Adding carbon fiber into glass fiber enhances the mechanical properties of hybrid composites and reduces density, but it also raises the cost. Therefore, it is crucial to optimize the mechanical properties, weight, and cost of carbon/glass (C/G) hybrid composites and to develop high-performance, low-cost, and low-density composites structures.

To reduce the material cost of composites, this study comprehensively designed C/G interlayer and intralayer hybrid structures and tested the tensile, compressive, and flexural properties of hybrid composites. Focusing solely on the cost of raw materials, we explored the relationship between the mechanical properties, weight, and cost of these hybrid composites. To ensure the fairness and scientific validity of our experiments, we maintained consistency in other factors, such as resin cost and manufacturing process, thereby avoiding any influence from these variables on the results. This work provides a valuable reference for practical applications of C/G interlayer and intralayer composites.

2. Materials and Methods

2.1. Materials

In this work, carbon fiber was provided by TORAY Inc., E-glass fiber was sourced from CPIC glass fiber Inc. (Chongqing, China), and epoxy resin was obtained from SWANCOR Inc. (Shanghai, China).

Table 1. Material parameters.

Material	Source	Density (kg/m3)	Weight Cost (USD/kg)	Volume Cost (USD/cm3)
Glass fiber	CPIC ECT469L-2400	2560	4.4	0.011
Carbon Fiber	TORAY 620SC-24K-50C	1770	44.1	0.078
Epoxy Resin	SWANCOR 2511-1A/BS	1100	5.8	0.006

reports specific parameters and cost of the raw materials. Five unidirectional warp-knitted fabrics are detailed in

Table 2. Fiber fabrics specifications.

Fabric Type	Area Density (g/m2)		Ratio of Carbon/Glass
	Carbon Fiber	Glass Fiber
Carbon fiber fabric	728.3	0	1:0
Glass fiber fabric	0	944.9	0:1
C-C-G-G	364.2	472.4	1:1
C-G-G	242.8	629.9	1:2
C-G-G-G-G	145.7	755.9	1:4

and Figure 1, including a pure carbon fiber fabric, a glass fiber fabric, and three hybrid fabrics with varying C/G ratios. The cost data were obtained directly from the suppliers. As revealed from the cost comparison, the cost of carbon fiber is 10 times higher than that of glass fiber, while the density of carbon fiber is 46% lower than glass fiber.

2.2. Interlayer Hybrid Structures

In this study, C/G interlayer and intralayer hybrid structures were developed, with the interlayer hybrid structures comprising carbon fiber fabric and glass fiber fabric. Four hybrid ratios were utilized in the experiment: 1:1, 1:2, 1:3, and 1:4. For each hybrid ratio, different structures were created by varying the sequences of carbon fiber fabric and glass fiber fabric. The interlayer hybrid structure scheme is detailed in

Table 3. Interlayer hybrid structures configurations.

C/G Hybrid Ratio	Stacking Sequences
1:1
	[G/G/C/C]	[G/C/C/G]	[C/G/G/C]	[G/C/G/C]
1:2
	[G/G/C]	[G/C/G]
1:3
	[G/G/G/C]	[G/G/C/G]
1:4
	[G/G/G/G/C]	[G/G/G/C/G]	[G/G/C/G/G]

Note: the black color in the laminates indicates carbon fiber, while the white color represents glass fiber. This color scheme is consistent throughout.

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2.3. Intralayer Hybrid Scheme

Three C/G hybrid fabrics (Figure 1c–e) were used to form intralayer composites structures. In these hybrid fabrics, carbon fiber bundles and glass fiber bundles were alternately arranged in-plane based on various ratios. To create the intralayer hybrid composites, three hybrid ratios (C/G = 1:1, 1:2, and 1:4) were designed. For each hybrid ratio, in-plane hybrid fabrics were arranged differently to achieve various dispersion degrees and structures. The intralayer hybrid scheme is detailed in

Table 4. Intralayer hybrid structures configurations.

Hybrid Fabrics	Stacking Sequences
C-C-G-G (C:G = 1:1)
	[C-C-G-G-0]			[C-C-G-G-1]			[C-C-G-G-2]
	[C-C-G-G-0.5]			[C-C-G-G-1.5]
C-G-G (C:G = 1:2)
	[C-G-G-0]	[C-G-G-1]			[C-G-G-0.5]			[C-G-G-1.5]
C-G-G-G-G (C:G = 1:4)
	[C-G-G-G-G-0]		[C-G-G-G-G-1]			[C-G-G-G-G-2]
	[C-G-G-G-G-0.5]		[C-G-G-G-G-1.5]			[C-G-G-G-G-2.5]

Note: The numbers in the table indicate the degree of hybrid dispersion, reflecting the dislocation degree between the upper and lower layers. A higher dispersion degree signifies more noticeable fabric dislocation.

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2.4. Manufacturing and Mechanical Properties Testing

The modified vacuum-assisted resin transfer molding (VARTM) process was used to prepare composite specimens with a controlled fiber volume fraction of around 50%. This method ensures uniform resin distribution and high-quality composite fabrication, which are essential for the mechanical performance of the final products. The mold cavity was elevated using gaskets and sealed with a vacuum bag, and clamps were applied to maintain pressure and prevent the preforms from springing up. A vacuum pump evacuated the air, allowing resin infusion into the fabric. The curing process was conducted at 120 °C for 8 h.

Laminates were subjected to mechanical testing, including tensile, compressive, and flexural properties, referring to the testing standards ASTM D3039 [17], ASTM D6641 [18], and ASTM D7264M [19], respectively. The test samples and equipment are shown in Figure 2, and the specific parameters of each sample are listed in

Table 5. Specific size parameters of hybrid composites.

Composite Structures	C/G Hybrid Ratios	Layers	Laminate Thickness/mm	Width/mm			Span /mm
				Tensile Testing	Compressive Testing	Flexural Testing
Pure carbon composites	1:0	4	3.2	15	12	13	64
Pure glass composites	0:1	4	3.2	15	12	13	64
Interlayer laminates	1:1	4	3.2	15	12	13	64
	1:2	3	2.4	15	12	13	48
	1:3	4	3.2	15	12	13	64
	1:4	5	4	15	12	13	80
Intralayer laminates	1:1	4	3.2	20			64
	1:2	4	3.2	15			64
	1:4	4	3.2	25			64

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The calculation formulas for tensile and compressive strength as well as modulus are as follows:

$${\sigma }_t={\sigma }_c=\frac{P}{b·h}; E_t=E_c=\frac{\sigma }{\epsilon }$$

(1)

The calculations of flexural properties are as below:

$${\sigma }_f=\frac{3P·l}{2b·h^2}; E_f=\frac{l^3·∆P}{4b·h^3·∆S}$$

(2)

where ${\sigma }_t{,\sigma }_c$, and ${\sigma }_f$ represent tensile, compressive, and flexural strength (MPa), respectively; P is the failure load (N); l is the span (mm); h is the thickness of the specimen (mm); b is the width of specimen (mm); $E_t$, $E_c$, and $E_f$ are the tensile, compressive, and flexural modulus (GPa), respectively; $∆P$ and $∆S$ is the load increment and deflection increment of the initial load–deflection curve; $\epsilon$ is strain.

2.5. Representation of Mechanical Performance/Cost

The relationship between C/G hybrid composites mechanical properties and the material cost and weight was analyzed. Given the differences in density and cost of raw materials, the density and cost of hybrid composites could be determined based on the proportion of carbon fiber, glass fiber, and resin in the composites and their respective costs. The formulas are as follows:

Density:

$${\mathsf{\rho }}_{Hybird}={\rho }_C{V}_C+{\rho }_G{V}_G{+\rho }_R{V}_R$$

(3)

Cost:

$${\mathsf{\theta }}_{Hybrid}={\theta }_C{V}_C+{\theta }_G{V}_G{+\theta }_R{V}_R$$

(4)

where ${\mathsf{\rho }}_{Hybird}$ refers to the density of hybrid composites (kg/m³); ${\rho }_C$, ${\rho }_G$, and ${\rho }_R$ are the density of carbon fiber, glass fiber, and resin (kg/m³), respectively; $V_C$, $V_G$, and $V_R$ denote the volume fraction of carbon fiber, glass fiber, and resin, respectively; ${\mathsf{\theta }}_{Hybrid}$ indicates the cost of the hybrid composites (USD/m³); ${\theta }_C$, ${\theta }_G$, AND ${\theta }_R$ are the cost of carbon fiber, glass fiber, and resin, respectively.

Under various hybrid ratios, the density and cost of hybrid composites are different, as presented in

Table 6. Density and cost of hybrid composites.

Hybrid Ratio	Volume Content (%)			Density (kg/m3)	Weight Cost (USD/kg)
	Carbon Fiber	Glass Fiber	Resin
Carbon	51.4	0	48.60	1440	216.96
Glass	0	46.1	53.90	1770	35.13
C:G = 1:1	25.7	23.05	51.25	1610	116.76
C:G = 1:2	17.13	30.73	52.14	1660	87.75
C:G = 1:3	12.85	34.58	52.57	1690	73.96
C:G = 1:4	10.28	36.88	52.84	1710	65.90

, for which the data were provided by the material suppliers.

It can be observed from Table 6 that as the material density increased, the carbon fiber content decreased. Therefore, reducing carbon fiber content could significantly lower the cost of C/G hybrid composites.

The parameters included the following: Specific strength and specific modulus were introduced to represent the tensile strength and the modulus of composites per unit weight; the formulas are presented as Formulas (5) and (6). Higher values indicate that the hybrid composites are lightweight with better mechanical properties. To determine the relationship between the performance, weight, and cost of hybrid composites, the specific strength and specific modulus were divided by the material cost, as shown in Formulas (7) and (8). These metrics evaluate the specific modulus and specific strength of hybrid composites per unit cost and density, indicating cost performance; a higher value signifies that the composites take on good mechanical properties for the same weight and cost.

Specific modulus:

$$E_{\rho }=\frac{E_{hybrid}}{{\rho }_{hybrid}}$$

(5)

Specific strength:

$${\sigma }_{\rho }=\frac{{\sigma }_{hybrid}}{{\rho }_{hybrid}}$$

(6)

Specific modulus/cost:

$$R_{E:C}=\frac{E_{\rho }}{{Cost}_{hybrid}}$$

(7)

Specific strength/cost:

$$R_{\sigma :C}=\frac{{\sigma }_{\rho }}{{Cost}_{hybrid}}$$

(8)

where $E_{\rho }$ indicates the specific modulus of hybrid composites (N·m/kg); $E_{hybrid}$ represents the modulus (GPa); ${\sigma }_{\rho }$ refers to the specific strength (N·m/kg); ${\sigma }_{hybrid}$ is the strength of hybrid composites (MPa); ${Cost}_{hybrid}$ represents the weight cost of hybrid composites (USD/kg); $R_{E:C}$ is the ratio of specific modulus to cost (N·m/USD); $R_{\sigma :C}$ is the ratio of specific strength to cost (N·m/USD).

3. Results and Discussion

3.1. Tensile Performance/Cost Analysis

Tensile properties are among the most critical mechanical aspects of composites. This section analyzes the tensile performance/cost ratio of interlayer and intralayer hybrid composites, and Figure 3 illustrates the tensile modulus of C/G interlayer and intralayer hybrid composites.

As revealed from Figure 3, the tensile modulus of interlayer and intralayer hybrid composites increased with the rising C/G hybrid ratio; however, the tensile modulus varied little at the same C/G hybrid ratio. Figure 4a summarizes the tensile modulus of interlayer and intralayer hybrid composites with various C/G ratios, confirming that the tensile modulus of hybrid composites exhibited an almost linear upward trend with increasing C/G ratio.

Comparisons of the tensile-specific modulus/cost ratio of composites with various hybrid ratios are presented in Figure 4b. The data indicate that with increasing carbon fiber content, the specific modulus/cost of hybrid composites progressively decreased, following an exponential law. This means that the tensile modulus of hybrid composites decreased at the same cost and density. Therefore, increasing the specific modulus by adding more carbon fiber was not cost-effective, as it increased the overall cost and reduced the specific modulus/cost ratio.

Figure 5 shows the tensile strength of hybrid composites. The tensile strength of interlayer hybrid composites was determined by the hybrid ratio and stacking structure. As the carbon fiber content increased, the tensile strength also increased, falling between that of carbon and glass fiber composites. At the same hybrid ratio, the structure with glass fiber sandwiching carbon fiber had comparatively high tensile strength. Conversely, when carbon fiber and glass fiber were distributed in asymmetric layers, the tensile strength tended to be lower. This is because the glass fiber on one side only provides support for the carbon fiber at the C/G bonding zone, resulting in a weak synergistic effect for the carbon fiber and causing early failure of the carbon fiber, thus reducing tensile strength [20]. For the intralayer structures, as the carbon fiber content increased, the tensile strength took on an upward trend. At the same C/G ratio, higher dispersion degrees in intralayer composites led to lower tensile strength, with some hybrid structures even having tensile strength below that of glass fiber.

Figure 6 presents the correlation between the specific strength/cost ratio of hybrid composites and the carbon fiber content. The results indicate that the specific tensile strength/cost decreased with increasing carbon fiber content, with little variation across various hybrid ratios. At the same hybrid ratio, the stacking structure with glass fiber sandwiching carbon fiber had the highest specific strength/cost, indicating the most excellent strength at the same cost and density. For the [G-C-G-G] structure with C:G = 1:4, the specific tensile strength/cost ratio was 6.6 × 10⁴ N·m/USD.

In terms of intralayer hybrid structures, a larger dispersion degree, where adjacent layers are evidently dislocated, resulted in a lower specific strength/cost. Conversely, when the dispersion degree was low, the tensile strength/cost ratio was the highest. Specifically, the [C-G-G-G-G-0] structure, with a dispersion degree of 0 and C:G = 1:4, had a specific tensile strength/cost ratio of 6.7 × 10⁴ N·m/USD. As a result, interlayer hybrid structures with glass fiber sandwiching carbon fiber or intralayer structures with a low dispersion degree are suitable for applications where composites are subjected to tensile forces.

3.2. Compressive Performance/Cost Ratio Analysis

Figure 7 shows the compressive modulus of hybrid composites, which mirrors the trend seen with the tensile modulus, increasing with higher carbon fiber content. At the same C/G ratio, the interlayer structure with glass fiber sandwiching carbon fiber exhibited the maximum modulus. In this structure, the glass fiber exerted an inward compressive force on the carbon fiber, creating a synergistic effect that made the inner carbon fiber less prone to compressive deformation. Additionally, since the compressive fracture strain of glass fiber is greater than that of carbon fiber, the outer glass fiber continued to provide interlaminar normal stress to the inner carbon fiber before failing, preventing buckling under compression [21]. For the intralayer structure, the modulus of the composites with a 0 dispersion degree tended to be large.

Figure 8 shows the compressive specific modulus/cost ratio of hybrid composites. The data reveal that, similar to the tensile modulus, the compressive-specific modulus/cost of hybrid composites exhibited a downward trend as the content of carbon fiber increased. While maintaining a consistent hybrid ratio, generally, the interlayer hybrid structure with glass fiber sandwiching carbon fiber had a higher compressive modulus at the same cost and density. The compressive modulus was the most cost-effective when the dispersion degree of intralayer structures was 0. For instance, the intralayer hybrid composites with a dispersion degree of 0 and C:G = 1:4 had the highest specific compressive modulus/cost ratio at 3.8 × 10⁶ N·m/USD.

Figure 9 exhibits the compressive strength of interlayer and intralayer hybrid composites. It can be observed that the impact of the hybrid structures on the compressive strength of interlayer hybrid composites was greater than that of the hybrid ratio. For the stacking structure [G-C-C-G] with glass fiber sandwiching carbon fiber, the compressive strength reached a high level, even higher than that of carbon fiber by 11%. Conversely, with carbon fiber sandwiching glass fiber, the compressive strength was below that of glass fiber composites. The reason is that the fibers in the specimen are aligned in the 0° direction, and the compressive performance is mainly determined by the compressive properties of the resin and the bonding performance between the resin and fibers. The compressive strength of intralayer hybrid composites was lower than that of carbon and glass fiber composites and was minimally affected by the hybrid ratio. Moreover, the compressive strength was the highest while the dispersion degree of intralayer hybrid structures was 0 at the same hybrid ratio.

Figure 10 presents the compressive-specific strength/cost ratio of interlayer and intralayer hybrid composites. The findings indicate that as the carbon fiber content increased, the specific strength/cost presented a downward trend. For the interlayer hybrid structures, with glass fiber sandwiching carbon fiber, the composites demonstrated the highest specific strength/cost, achieving superior cost performance in compressive strength compared to the intralayer structures through the laminate design. For the intralayer structures, with variations in stacking structures, the compressive strength was the most cost-effective when the dispersion degree was 0. Specifically, the intralayer hybrid structure [C-G-G-G-G-0] with a dispersion degree of 0 and C:G = 1:4 had the highest specific compressive strength/cost ratio at 3.8 × 10⁶ N·m/USD.

3.3. Flexural Performance Cost Analysis

Figure 11 presents the flexural performances of C/G hybrid composites.

From the results of Figure 11, it can be concluded there is no evident indication that the flexural properties of interlayer hybrid composites correlate with the C/G ratio. Instead, they were primarily determined by the stacking structure, which was opposite to the tensile and compressive results. The flexural modulus of the structure with glass fiber sandwiching carbon fiber tended to be the lowest. However, with carbon fiber sandwiching glass fiber or carbon fiber distributing at the bottom layer, the flexural modulus achieved the highest value. For intralayer hybrid composites, both the C/G ratio and structure were key factors influencing flexural properties. The flexural modulus was higher when the carbon fiber content was lower or when the dispersion degree was greater.

As found from Figure 12, the stacking structure was considered the key factor for the cost performance of the flexural-specific modulus of interlayer and intralayer hybrid composites. As the carbon fiber content increased, the overall cost performance tended to decrease slightly. Interlayer hybrid structures [G/G/G/G/C] and [C/G/G/C] exhibited an outstanding flexural-specific modulus/cost, which was close to that of glass fiber. Alterations in hybrid structures of intralayer composites exerted no evident impact on the cost performances. For the structures with a high dispersion degree, the flexural modulus tended to be more cost-effective. Generally, the interlayer structures could achieve a higher flexural modulus/cost performance than intralayer composites through the optimization of laminate structures.

Figure 13 shows the result of flexural strength for hybrid composites. It can be seen that the flexural strength of the interlayer hybrid composite was mainly determined by the stacking structure, with minimal effect from the hybrid ratio. With carbon fiber located at the lower layer and glass fiber distributed at the upper layer, the flexural strength of composites tended to be high, primarily due to the lower compression fracture strain of carbon fiber. For example, in the [C-G-C-G] structure, the flexural strength reached 1083 MPa, which is 32% and 38% higher than that of glass and carbon fiber composites, respectively. In contrast, the flexural strength was relatively lower when carbon fiber was in the upper layer and glass fiber in the lower layer. The flexural strength of intralayer hybrid composites was affected by the stacking structure rather than the C/G hybrid ratio. Generally, the flexural strength of the structure with a high dispersion degree was outstanding.

Figure 14 presents the flexural-specific strength/cost ratio of hybrid composites. Generally, with increasing carbon fiber content, the cost performance of flexural-specific strength for hybrid composites took on a downward trend, similar to the specific modulus/cost. The structure had a certain amount of influence on the cost performance of flexural strength. For the interlayer hybrid structures, the flexural strength of asymmetric structures or those with carbon fiber at the bottom layer tended to be high. The interlayer structure [C-G-G-G-G] exhibited the maximum flexural specific strength/cost ratio at 6 × 10⁴ N·m/USD. For the intralayer hybrid composites, the cost performance of specific strength was affected by both the hybrid ratio and hybrid structures As the carbon fiber content and the dispersion degree decreased, the cost performance tended to be higher. The C/G interlayer hybrid structures with asymmetric laminates or carbon fiber at the bottom layer as well as the intralayer structures with a 0 dispersion degree are recommended for applications where flexural load is assumed.

4. Conclusions

This study adopted a cost-effective method to analyze the tensile, compressive, and flexural properties of carbon/glass interlayer and intralayer hybrid composites, introducing specific modulus/cost and specific strength/cost metrics to evaluate mechanical properties. The main conclusions are as follows:

The tensile-, compressive-, and flexural-specific modulus/cost and strength/cost ratios of interlayer and intralayer hybrid composites decreased with increasing carbon fiber content, indicating that adding carbon fiber into composites generally reduced cost performance. The specific flexural modulus/cost and strength/cost ratios were still influenced by the stacking structure, with the latter having a greater impact. For interlayer hybrid structure with glass fiber sandwiching carbon fiber, the tensile and compressive specific strength/costs were higher, while the flexural strength/cost ratio showed an opposite trend. The intralayer hybrid structure with a 0 dispersion degree exhibited higher specific tensile and compressive strength/cost ratios but a lower flexural strength/cost ratio. Specifically, for intralayer hybrid composites with a dispersion degree of 0 and C:G = 1:4, the specific tensile strength/cost ratio was 6.7 × 10⁴ N·m/USD, and this structure had the highest specific compressive modulus and strength/cost ratios at 4.7 × 10³ N·m/USD and 3.8 × 10⁶ N·m/USD, respectively. The modulus/cost ratio of interlayer hybrid composites, especially for structures with carbon fiber at the bottom, approached that of glass fiber, reaching up to 3.6 × 10⁶ N·m/USD. Therefore, interlayer structures can achieve superior specific flexural modulus/cost and strength/cost ratios through optimized laminate design.

For applications where cost performance is critical, reducing carbon fiber content may enhance the specific tensile, compressive, and flexural modulus/cost and strength/cost ratios. For applications requiring high specific tensile and compressive performance/cost ratios, intralayer hybrid composites with a 0 dispersion degree and C:G = 1:4 are recommended. Interlayer hybrid composites with glass fiber sandwiching carbon fiber should be considered for designs requiring higher specific tensile and compressive performance/cost ratios. To achieve superior flexural specific modulus/cost ratios, interlayer structures with optimized laminate designs, particularly with carbon fiber positioned at the bottom, are suggested.

However, the cost analysis was based on current market prices, and future price fluctuations or regional cost differences could impact the generalizability of the cost-performance conclusion. This work enables the optimization of the cost performance of mechanical properties in the design of carbon/glass hybrid composites by adopting reasonable hybrid ratios and laminate structures tailored to real working conditions.