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Article

Fabrication of Mechanically Robust Water-Soluble Core Molds and Experimental Validation to Manufacture a Composite Part

by
Tianbo Yang
1,
Lei Tan
1,
Yuntao Fu
1,
Ziwen Sun
1,
Yang Chen
1,
Wei Luo
2,
Shengtai Zhou
1,*,
Mei Liang
1,* and
Huawei Zou
1
1
State Key Laboratory of Advanced Polymer Materials, Polymer Research Institute, Sichuan University, Chengdu 610065, China
2
AVIC Chengdu Aircraft Industry Group Co., Ltd., Chengdu 610092, China
*
Authors to whom correspondence should be addressed.
Appl. Sci. 2025, 15(18), 10039; https://doi.org/10.3390/app151810039
Submission received: 29 July 2025 / Revised: 6 September 2025 / Accepted: 12 September 2025 / Published: 14 September 2025
(This article belongs to the Section Materials Science and Engineering)
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Versions Notes

Abstract

In this work, a core mold which combines excellent high-temperature compressive properties and rapid water solubility was successfully fabricated by using polyvinyl alcohol (PVA) as the adhesive and quartz sands as reinforcing particles. The influence of the molecular weight and alcoholysis degree of PVA, the concentration of PVA and the size of the quartz sands on the compressive performance and water penetration rate of core molds was studied in detail. The results revealed that core molds which were prepared using PVA-4 (i.e., a degree of polymerization of 2400 and an alcoholysis degree of PVA of 88%) and 160–200 mesh quartz sands with a mass ratio of 1.2:10 possessed a 160 °C compressive strength of 7.4 MPa, a 160 °C compressive modulus of 179.3 MPa and 50 °C water penetration rate of 0.94 mm/s. Furthermore, a validation experiment was conducted to verify the efficacy of using the as-prepared core mold to fabricate a hollow composite part, which shows a promising application in industrial sectors.

1. Introduction

Nowadays, carbon fiber reinforced composites (CFRCs) play a significant role in manufacturing structural components which have characteristics such as light weight, high strength and high modulus, as well as ease of fabrication [1,2,3,4]. The rapid development in the industrial sectors, especially in automotive, aerospace and aviation industries, has encountered great challenges in fabricating high-precision composite parts that cannot be readily prepared due to the intricate structural design and complexity in component assembly (e.g., hollow parts with changing diameters or cross-sectional area) [5,6].
Conventionally, CFRCs are prepared using metal core molds [7], airbag-assisted core molds [8] and water-soluble core molds [9]. Among them, water-soluble core molds demonstrate promising application due to their easy design and preparation, as well as fast removal after the fabrication of composite parts. They are typically prepared by utilizing water-soluble polymers as the bonding adhesive to glue inorganic sand particles together, which exhibits dimensional accuracy and mechanical robustness when preparing composite parts using autoclaves. Water-soluble core molds received widespread attention from the 1970s to the 1990s [10]. In recent years, a trend has begun for developing water-soluble core molds to suit the increasing need to prepare complex composite parts in industrial sectors. For example, Lombardi et al. [11] prepared water-soluble tooling materials by mixing a thermally resistant polymer with ceramic microspheres and plaster, which was used for manufacturing complex composite parts. Li et al. [12] prepared water-soluble core molds by casting a mixture of alumina, quartz sand, kaolinite, and plaster as the aggregate and a combination of polyethylene glycol (PEG) and sodium silicate as the adhesive. They found that the core molds which were prepared using 30 wt% sodium silicate exhibited a compressive strength and water solubility of 1.023 MPa and 0.24 g/s, respectively, making them suitable for the resin transfer molding process. Mu et al. [13] adopted the direct ink writing (DIW) method to prepare water-soluble cores by using calcium carbonate as the matrix, polyethylene glycol aqueous solution as the binder, and nano-ZrO2 as the modifier, followed by sintering at 1400 °C. When the nano-ZrO2 content was 10 wt%, the water solubility of the above core mold was 4.21 g/(s·m2), and it exhibited optimal mechanical properties, which could be applied in industrial sectors.
Water-soluble polymers are key elements that significantly determine the performance of core-molds, and they should satisfy the characteristics of non-toxicity and non-pollution, high bonding strength, ease of fabrication, and most importantly, ease of dissolution in water [14,15]. Conventionally, PEG, polyacrylic acid (PAA), polyvinyl pyrrolidone (PVP), and polyvinyl alcohol (PVA) are widely adopted as the water-soluble adhesives [16,17,18,19]. Among them, PEG is hygroscopic and it has a low mechanical strength that restricts its application in advanced composite manufacturing sectors [19]; PAA has a low initial thermal decomposition temperature (about 170 °C) [20], and PVP has a melting point of about 130 °C [21]. Neither polymer is suitable for making parts at high temperatures. Although PVA starts to degrade above 200 °C, the mechanical properties and adhesion performance of PVA are acceptable and there is potential for improving the temperature resistance [22,23,24]. As a result, PVA becomes a good candidate to prepare polymer-based water-soluble core molds. In comparison with alumina, kaolin, and plaster, quartz sand is a better choice as a reinforcement filler due to its multi-hydroxyl surface, stable physicochemical properties, and resistance to abrasion [25,26]. In addition, PVA and quartz sand are easy to access and they pose an insignificant burden to environment. During the water dissolution process, quartz sands can be reclaimed for reuse purposes. Furthermore, the recyclability of PVA has been demonstrated in the literature, where the reclaimed PVA was employed for the fabrication of recyclable hydrogels and self-healing gels [27,28].
Recently, Bai et al. [29] prepared water-soluble core molds using alumina powder, potassium sulfate (K2SO4), plasticizers, and calcined corundum powder through cold compaction and injection molding. They reported that when the K2SO4 content was 30 wt%, the core mold exhibited a lower porosity and a flexural strength of 2.63 MPa, demonstrating the best overall performance. Zhang et al. [10] prepared water-soluble core molds which possessed a tensile strength exceeding 2 MPa at room temperature by using binder jetting technology and sintering. After soaking in water for 1 h, the residual tensile strength was approximately 0.12 MPa, making them promising for use in producing aluminum alloy castings. Xiao et al. [6] prepared water-soluble core molds by using 3D direct printing (3DP) technology. The core molds were able to completely dissolve in water and exhibited a flexural strength of 53.90 MPa. Zhang et al. [30] prepared water-soluble core molds with high porosity and low shrinkage through vat photopolymerization (VPP), and they rapidly dissolved in water at room temperature. However, the cost of preparing core molds using such methods is high, the process conditions are stringent, and they are not suitable for fabricating large-sized components.
In this present work, water-soluble core molds were prepared using a traditional hot-pressing process. The preparation procedure is straightforward, with no complicated post-treatment steps, and offers low cost. The water-soluble core molds can be used for preparing composite parts using the autoclave method, which is suitable for the production of large-size components. A PVA-based water-soluble core mold which combines excellent high temperature compressive properties and rapid water solubility was prepared using PVA as the adhesive and quartz sands as reinforcing fillers. The influence of the molecular weight and alcoholysis degree of PVA, the concentration of PVA and the size of quartz sands on the density, mechanical performance and water solubility of core molds was studied. Additionally, the efficacy of using the core molds which were prepared using 10 wt% PVA-4 (i.e., with a degree of polymerization of 2400 and an alcoholysis rate of PVA of 88%) and 160–200 mesh quartz sands was experimentally validated to manufacture a hollow composite part. The results revealed that the composite part which was prepared with the aid of the water-soluble core mold exhibited high dimensional accuracy and stability, demonstrating promising application in the fabrication of intricate composite parts in automotive, aerospace and aviation industries, among others.

2. Materials and Methods

2.1. Materials

PVA-1 to PVA-5 were purchased from Tianjin Xindema Suspension Co., Ltd., Tianjin, China. PVA-6 and PVA-7 were provided by Chongqing SVW Chemical Co., Ltd., Chongqing, China. The quartz sands of different sizes (18–35 mesh, 70–110 mesh, 110–160 mesh and 160–200 mesh) were purchased from Henan Minghai Environmental Protection Quartz Sand Factory, Zhengzhou, China. Deionized water (DW) was obtained from Chengdu Pincheng Science and Technology Ltd., Chengdu, China. The molecular weight and degree of alcoholysis of different PVAs are tabulated in Table 1. Carbon fiber fabric (twill, T300-3K, areal density: 70 g/slice, 150 × 150 mm2/slice) was purchased from Yixing Fuyou Composite Materials Co., Ltd., Yixing, China. PTFE (Polytetrafluoroethylene)-coated release fabric (thickness: 0.13 mm) was purchased from Jiangsu Yuxin Composite Materials Co., Ltd. (Jingjiang, China).

2.2. Preparation of Water-Soluble Core Mold and Its Application

The preparation of water-soluble core molds is depicted in Figure 1, and can be briefly described as follows: (1) The 10 wt% PVA aqueous solution was achieved by mixing 10 g PVA and 90 g RO at 75 °C for 3 h. (2) The PVA solution was extensively mixed with the quartz sands through mechanical mixing. The mass ratio of PVA matrix to the quartz sands was kept at 1.2:10. This mass ratio was determined through the optimization of preliminary work. (3) Afterwards, the above pre-mixed mixture was transferred to a metal mold, which was compacted and solidified to prepare PVA-based water-soluble core molds. The curing conditions were 100 °C for 1 h and 130 °C for 2 h, under a pressure of 8 MPa.
In order to verify the efficacy of using water-soluble core molds to prepare carbon fiber reinforced composite parts, a validation experiment was conducted. Briefly, the core mold material was first wrapped with PTFE-coated release fabric, followed by wrapping with 8 layers of carbon fiber fabric, and the wrapped core mold was sent to a hot press tank for curing. The curing conditions were 75 °C for 45 min and 125 °C for 2 h, under a pressure of 0.3 MPa. The core mold was cooled down to room temperature and a hollow composite structure was obtained by dissolving the core mold using a customized water gun. A patent was filed for the design of the water gun (patent no. CN202310523247.0).

2.3. Characterization

High-temperature compression measurements (UTM5105S, SUNS, Zhangzhou, China) were conducted to test the mechanical performance of water-soluble core molds. According to ISO 679:1989 [31], the size of the samples was 40 × 40 × 40 mm3 and the compression rate was 2400 ± 200 N/s. The water solubility of core molds was assessed using a self-designed testing device. The size of core molds is 40 × 40 × 40 mm3, the temperature and pressure of water are 50 °C and 0.3 MPa, and the distance between the nozzle of the testing device and the core mold is 45 mm. The water solubility was calculated by the water penetration time divided by sample thickness, i.e., 40 mm. The pore structure of the inner cut surface of the water-soluble core mold was characterized using an Eclipse E400 polarized light microscope (Nikon, Tokyo, Japan). The cross-sectional morphology of PVA-based core molds was observed using an Aztec X-Max20 field-emission scanning electron microscope (SEM, Oxford Instruments, Abingdon, UK). The sample surface was coated with a thin layer of gold to enhance image resolution. The thermal stability of PVA was characterized using a high-performance simultaneous thermal analyzer (STA 449, NETZSCH, Waldkraiburg, Germany). The hydrogen bonding structures of thin films were tested using FTIR with ATR mode (Nicolet 570, test range: 4000–400 cm−1, resolution: 32 cm−1, Green Bay, WI, USA). The porosity of core molds was tested using a fully automated mercuric piezometer (Model 9520, Mack, Greensboro, NC, USA). The pores and fiber damage of carbon fiber components were characterized using an X-ray 3D CT scanning device (Micro CT, Phoenix V|tome|x S240, Waygate Technologies, Skaneateles, NY, USA).

3. Results and Discussion

3.1. Compressive Properties of Core Molds

The influence of the molecular weight and alcoholysis degree of PVA on the mechanical properties of water-soluble core molds is presented in Figure 2. Figure 2a showed that the high temperature (160 °C) compressive strength and compressive modulus of core molds increased with an increase in molecular weight, i.e., the degree of polymerization when the hydrolysis degree was 88%. For example, the compressive strength and modulus of core molds which were prepared using PVA-1 were only 2.6 and 48.2 MPa, respectively. The compressive strength and modulus of core molds which were prepared using PVA-4 reached as high as 7.4 and 179.3 MPa, representing an increase of 184.6% and 272.0% when compared with those of PVA-1. However, the 160 °C compressive strength and modulus were slightly decreased with further increases in the degree of polymerization of PVA when compared with PVA-4, which was likely related to the entanglement of molecular chains. An excessively high molecular weight of the adhesive could lead to severe chain entanglement, resulting in excessive viscosity and thicker adhesive layers [32,33]. This impaired the adhesion among quartz sands, thereby leading to a decrease in compressive properties.
Figure 2a,b revealed that given the same molecular weight, the 160 °C compressive strength and compressive modulus of core molds increased with an increase in the alcoholysis degree of PVA. For example, the 160 °C compressive strength and compressive modulus of core molds which were prepared using PVA-5 were the highest among the studied samples, and were 5.4% and 7.0% higher than PVA-4. In this scenario, the higher alcoholysis degree of PVA was able to render a greater number of hydrogen bonds among the molecular chains, thereby causing an increase in the mechanical properties.

3.2. Water Penetration Rate of Core Molds

The water solubility of different types of core molds was evaluated by measuring the water penetration rate using the self-designed apparatus. As shown in Figure 3a, when the hydrolysis rate of PVA was kept the same, the water penetration rate of PVA-based water-soluble core molds decreased significantly with increasing molecular weight. The water penetration rate of PVA-1 was 5.46 mm/s, whereas it was reduced to 0.94, 0.69 and 0.56 mm/s for PVA-4, PVA-6 and PVA-7, respectively. The above results suggested that the water solubility of core molds decreased significantly, which was due to the fact that an increase in the chain entanglements greatly reduced the chain mobility of PVA. However, for a given molecular weight, the water solubility of core molds was also decreased with an increase in the alcoholysis degree of PVA. For example, PVA-5 core molds were not able to be dissolved after being flushed using water for 5 min, as displayed in Figure 3c. In this scenario, an excessively high alcoholysis degree of high-molecular-weight PVA (i.e., PVA-5) formed sufficient hydrogen bonds that severely impeded the dissolution of PVA. Figure 3d showed that 10 wt% PVA-4 revealed a distinct peak at 3300 cm−1, corresponding to the lower wavenumber band (3570–3200 cm−1) that was associated with hydroxyl groups. Figure 3e showed that the 10 wt% PVA-4 film had a T5% above 200 °C, indicating excellent thermal stability. In addition, Figure 3f showed that only one endothermic peak which corresponded to water evaporation was observed between room temperature and 160 °C [34]. Consequently, the core mold which was fabricated using PVA-4 was able to maintain its mechanical integrity during the actual manufacturing of composite components.
Figure 3a reveals that the water solubility of PVA-1 was the highest among the studied systems, followed by PVA-2, PVA-3 and PVA-4. The water penetration rate of PVA-4 was 0.94 mm/s, meeting the criteria for practical applications. The possible mechanism behind the significant difference in water penetration rate of core molds is depicted in Figure 4. Taking PVA-1, PVA-4 and PVA-5 as examples, PVA-4 with longer molecular chains likely formed heavy entanglements that restricted the mobility of molecular chains. Moreover, PVA-5, which had both higher molecular weight and higher hydrolysis degree, formed a significantly higher amount of hydrogen bonding interactions that severely reduced the mobility of chain segments. As a result, the water penetration capacity of PVA-5 became very poor, and it was even unable to be penetrated after being water-flushed for 5 min. Considering the above results, PVA-4 was chosen as the suitable core mold for subsequent characterizations.

3.3. Effect of PVA Concentration on the Performance of Core Molds

Based on the above analysis, PVA-4 was selected as a model system to further study the performance of core molds. Herein, the influence of the concentration of PVA (i.e., 10, 15 and 20 wt%) on the 160 °C compressive performance and water solubility of core molds was detailed. The size of quartz sand was 160–200 mesh, and the core molds which were prepared using different concentrations of PVAs were prepared with a hot press.
The 160 °C compressive properties of core molds are presented in Figure 5. The results show that the compressive strength of core molds increased with an increase in PVA concentration, whereas the compressive modulus showed an initial increasing and then decreasing trend. The content of PVA adhesive among the quartz sands increased with increasing PVA concentration, which resulted in the formation of a larger amount of hydrogen bonding interactions. Under conditions of similar density (PVA20 = 1.556 g/cm3, PVA15 = 1.534 g/cm3, PVA10 = 1.527 g/cm3), increased PVA concentration results in tighter bonding between quartz sand particles, thereby enhancing the compressive strength of the core mold.
The PVA chains not only glued the quartz sands, but also played a critical role in determining the water dissolubility of core molds. Figure 6a showed that the water penetration rate of core molds decreased with increasing PVA concentration, which suggested that a higher content of PVA adhesive led to lower water dissolubility. When the concentration of PVA was increased from 10 to 20 wt%, the water penetration rate of core molds was reduced from 0.94 to 0.35 mm/s, which significantly affected the performance of core molds in terms of water dissolubility.
Both the optical and SEM images of core molds which were prepared using 20 wt% PVA (i.e., PVA20) after water penetration tests are provided in Figure 6b. The results revealed a significant amount of PVA adhesive residue surrounding the penetrated area, as highlighted in the SEM image, which suggested that more water was required to disintegrate the core molds that were bonded by PVA molecules. Therefore, the concentration of PVA should not be too high, as this would significantly deteriorate the water solubility of core molds that are not suitable for practical applications.

3.4. Effect of Quartz Sand Size on the Performance of Core Molds

The influence of quartz sand size on the compressive properties and density of core molds is presented in Figure 7. Herein, the concentration of PVA was 10 wt% and the matrix was PVA-4. Figure 7a showed that the 160 °C compressive strength decreased with an increase in the particle size of quartz sands. For example, the 160 °C compressive strength of core molds with 200–300 mesh quartz sands reached as high as 8.0 MPa, which was 900% higher than that of the core mold with 18–35 mesh quartz sands. In this scenario, the improvement in compressive strength was attributed to the increased packing density of small size quartz sands, as revealed by the highest density of core molds with 200–300 mesh quartz sands (see Figure 7c). As a result, the bonding area of smaller-sized quartz sands was higher, which reduced the internal voids or defects and significantly improved the mechanical properties.
The compressive modulus of core molds is displayed in Figure 7b. The results indicated that samples with 160–200 mesh quartz sands exhibited the highest compressive modulus among the studied systems, whereas the compressive modulus of samples with 200–300 mesh quartz sands was 14.6 MPa lower than that of samples with 160–200 mesh quartz sands. This was related to the fact that the number of quartz sands per unit volume of core molds increased significantly, and they were unable to be fully bonded by PVA adhesive, making them prone to slide or detach under external mechanical influence.
The water penetration rate of core molds which were prepared using different sizes of quartz sands is presented in Figure 8. Figure 8a reveals that the water penetration rate of core molds with 18–35 mesh quartz sand was 4.40 mm/s, and it reduced to 0.57 mm/s for core molds with 200–300 mesh quartz sands. In this scenario, the larger particle sizes of quartz sands led to looser packing of inorganic particles, which provided more channels for the penetration of water molecules, facilitating sufficient contact between PVA adhesive and water molecules as well as improving the water penetration rate of the core molds.
The porosity of a representative core mold which was prepared using PVA-4 (10 wt%) and 160–200 mesh quartz sand was quantified via the mercury intrusion porosimetry (MIP) method, as shown in Figure 8b. The results revealed that in the region below 1 μm, the curve was nearly flat, confirming the absence of submicron pores. The narrow peaks observed in the 8–15 μm range indicated a uniform pore size distribution, which is beneficial for maintaining the mechanical properties of the core mold. Furthermore, the core mold exhibited a pore size range of approximately 8–15 μm, indicating that the porosity primarily stemmed from the interparticle voids, which in turn contributed to its favorable water solubility. The observed water penetration trend can be rationalized using the capillary flow model. According to the Lucas–Washburn framework, the effective pore radius and wetting properties control capillary pressure, while the overall water infiltration velocity is limited by the permeability between the sand and PVA matrix. The use of coarser sands leads to the formation of larger pores and higher permeability, resulting in faster water infiltration rates despite lower capillary pressure [35,36]. The above observation aligns with the water flow through rate measurements in Figure 8. As shown in Figure 9, larger sized quartz sands result in the formation of larger sized pores within the core mold. Under the influence of the initial hydraulic pressure of the water flow, these larger pores are rapidly wetted. In this case, the capillary effect becomes less significant, and the pore size between sand particles emerges as the dominant factor that governs the water infiltration.
The optical appearance and microstructure of core molds with different sizes of quartz sands are exhibited in Figure 9. As shown in Figure 9, both the optical (Figure 9a–c) and SEM images (Figure 9d–f) revealed that reducing the size of quartz sands resulted in the formation of a denser core mold with fewer internal pores and defects, thereby enhancing compressive strength and density.

3.5. Experimental Validation of Core Molds

A validation experiment was conducted to prepare a carbon-fiber-reinforced part with the aid of the as-prepared core molds. A rectangular core mold with dimensions of 265.48 cm3 (approximately 40 mm wide and 150 mm long) was prepared with a hot press. Then, the carbon fiber fabric along with resin matrix was wrapped around the core mold, and it was cured in an autoclave. The curing conditions were 100 °C for 1 h and 130 °C for 2 h, under a pressure of 8 MPa. Afterwards, the sample was placed in a water tank with 50 °C water. As shown in Figure 10, the core mold gradually collapsed in the water, which was related to the dissolution of PVA. After the complete collapse of the core mold, the composite part was taken out of the water tank. Figure 10d revealed that a hollow composite part which demonstrated good dimensional accuracy was prepared with the aid of the core mold, indicating that PVA-based water-soluble core molds can be used to fabricate advanced carbon-fiber-reinforced composite parts for engineering applications.
Additionally, the fabricated composite part was subject to micro-CT scanning, as shown in Figure 11. Figure 11a provides the optical image of the composite part which was used for micro-CT analysis. Figure 11b–k indicate that the component exhibited neither delamination nor fiber damage. Only a very small amount of voids was observed, and this fell within the acceptable range for an autoclave-processed composite structure. The above findings further demonstrate that the removal of the PVA-based water-soluble core did not compromise the structural integrity of the composite part. The above validation experiment served as a proof-of-concept to demonstrate the feasibility of employing PVA-based water-soluble core molds to prepare composite structures using a standard autoclave process.

4. Conclusions

In this study, PVA-based water-soluble core molds were successfully prepared by using PVA as an adhesive and quartz sands as reinforced particles. The density, 160 °C compressive properties and water penetration performance of water-soluble core molds was affected by the molecular weight and alcoholysis degree of PVA, the concentration of PVA and the particle size of the quartz sands. Based on the findings, the following conclusions could be drawn:
(1)
The density of the core molds was increased by reducing the particle size of quartz sands, and it reached 1.617 g/cm3 for samples containing 200–300 mesh quartz sands. The 160 °C compressive strength of the core molds reached as high as 8.0 MPa, representing a seven-fold increase when compared with those with 18–35 mesh quartz sands.
(2)
The water penetration rate decreased with the increasing molecular weight and alcoholysis degree of PVA, the concentration of PVA and the packing density of quartz sands. Samples which were prepared using 10 wt% PVA-4 and 160–200 mesh quartz sands yielded optimal mechanical performance and water solubility that met the criteria for practical application in industrial sectors.
(3)
A validation experiment was conducted to verify the efficacy of using the as-prepared core molds to prepare carbon-fiber-reinforced composite parts, and this provided a satisfactory outcome.
This work provided an easy strategy for fabricating water-soluble core molds that exhibit promising applications in advanced manufacturing sectors. Despite these advancements, a key limitation lies in the trade-off between the water solubility and mechanical strength of core molds. The higher concentration of PVA improved the compressive properties, but the water dissolubility was, to a certain degree, impaired. Future work can be directed to explore biopolymer alternatives to PVA to address environmental concerns and integrate with modern additive manufacturing techniques to enable the fabrication of composite parts with intricate geometries.

Author Contributions

Conceptualization, L.T. and S.Z.; Data curation, L.T. and W.L.; Formal analysis, T.Y., L.T. and S.Z.; Investigation, T.Y. and W.L.; Methodology, T.Y., L.T. and Y.F.; Resources, H.Z.; Software, L.T.; Supervision, S.Z., M.L. and H.Z.; Validation, L.T., Y.C. and W.L.; Writing—original draft, T.Y. and Z.S.; Writing—review and editing, S.Z. and W.L. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no funding.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

The original contributions presented in this study are included in the article. Further inquiries can be directed to the corresponding authors.

Conflicts of Interest

Author Wei Luo was employed by the company AVIC Chengdu Aircraft Industry Group Co., Ltd. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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Applsci 15 10039 g001
Figure 1. The schematic illustration of the preparation of PVA-based water-soluble core molds.
Figure 1. The schematic illustration of the preparation of PVA-based water-soluble core molds.
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Figure 2. The 160 °C (a) compressive strength and (b) compressive modulus of core molds which were prepared using different types of PVA.
Figure 2. The 160 °C (a) compressive strength and (b) compressive modulus of core molds which were prepared using different types of PVA.
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Figure 3. (a) The water penetration rate of different core molds; (b) the setup for measuring the water penetration rate; (c) the optical images of PVA-5 before and after water flushing for 5 min; (d) FTIR spectra; and (e) TG and DTG and (f) DSC curves of 10 wt% PVA-4 film.
Figure 3. (a) The water penetration rate of different core molds; (b) the setup for measuring the water penetration rate; (c) the optical images of PVA-5 before and after water flushing for 5 min; (d) FTIR spectra; and (e) TG and DTG and (f) DSC curves of 10 wt% PVA-4 film.
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Figure 4. The schematic illustration of the interactions between different types of quartz sand.
Figure 4. The schematic illustration of the interactions between different types of quartz sand.
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Figure 5. (a) The 160 °C compressive strength and (b) compressive modulus of core molds which were prepared with different concentrations of PVA-4.
Figure 5. (a) The 160 °C compressive strength and (b) compressive modulus of core molds which were prepared with different concentrations of PVA-4.
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Figure 6. (a) The influence of PVA concentration on the water penetration rate of core molds; (b) the optical and SEM images of the PVA20 core mold after the water penetration test.
Figure 6. (a) The influence of PVA concentration on the water penetration rate of core molds; (b) the optical and SEM images of the PVA20 core mold after the water penetration test.
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Figure 7. (a) The 160 °C compressive strength, (b) compressive modulus and (c) density of core molds which were prepared using different sizes of quartz sands.
Figure 7. (a) The 160 °C compressive strength, (b) compressive modulus and (c) density of core molds which were prepared using different sizes of quartz sands.
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Figure 8. (a) The water penetration rate of core molds which were prepared using different sizes of quartz sands; (b) porosity distribution within the core mold.
Figure 8. (a) The water penetration rate of core molds which were prepared using different sizes of quartz sands; (b) porosity distribution within the core mold.
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Figure 9. (a–c) The optical and (d–f) SEM images of core molds with different size of quartz sands.
Figure 9. (a–c) The optical and (d–f) SEM images of core molds with different size of quartz sands.
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Figure 10. (a) The size of the composite part with the core mold; the core mold, which was placed in a water tank for (b) 5 min and (c) 10 min; and (d) the size of the composite part after completely dissolving the core molds.
Figure 10. (a) The size of the composite part with the core mold; the core mold, which was placed in a water tank for (b) 5 min and (c) 10 min; and (d) the size of the composite part after completely dissolving the core molds.
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Figure 11. (a) Optical image of the composite part, (b) 3D image of the sample, (c) defect analysis, (d–g) cross-sectional images across thickness direction, and (h–k) cross-sectional images from the micro-CT analysis.
Figure 11. (a) Optical image of the composite part, (b) 3D image of the sample, (c) defect analysis, (d–g) cross-sectional images across thickness direction, and (h–k) cross-sectional images from the micro-CT analysis.
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Table 1. The molecular weight and degree of alcoholysis of different PVAs.
Table 1. The molecular weight and degree of alcoholysis of different PVAs.
Sample ID (Tradename)Degree of PolymerizationDegree of Alcoholysis (%)
PVA-1 (PVA 5088)50088
PVA-2 (PVA 0872)80072
PVA-3 (PVA 1780)170080
PVA-4 (PVA 2488)240088
PVA-5 (PVA 2499)240099
PVA-6 (PVA 2688)260088
PVA-7 (PVA 3688)360088
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MDPI and ACS Style

Yang, T.; Tan, L.; Fu, Y.; Sun, Z.; Chen, Y.; Luo, W.; Zhou, S.; Liang, M.; Zou, H. Fabrication of Mechanically Robust Water-Soluble Core Molds and Experimental Validation to Manufacture a Composite Part. Appl. Sci. 2025, 15, 10039. https://doi.org/10.3390/app151810039

AMA Style

Yang T, Tan L, Fu Y, Sun Z, Chen Y, Luo W, Zhou S, Liang M, Zou H. Fabrication of Mechanically Robust Water-Soluble Core Molds and Experimental Validation to Manufacture a Composite Part. Applied Sciences. 2025; 15(18):10039. https://doi.org/10.3390/app151810039

Chicago/Turabian Style

Yang, Tianbo, Lei Tan, Yuntao Fu, Ziwen Sun, Yang Chen, Wei Luo, Shengtai Zhou, Mei Liang, and Huawei Zou. 2025. "Fabrication of Mechanically Robust Water-Soluble Core Molds and Experimental Validation to Manufacture a Composite Part" Applied Sciences 15, no. 18: 10039. https://doi.org/10.3390/app151810039

APA Style

Yang, T., Tan, L., Fu, Y., Sun, Z., Chen, Y., Luo, W., Zhou, S., Liang, M., & Zou, H. (2025). Fabrication of Mechanically Robust Water-Soluble Core Molds and Experimental Validation to Manufacture a Composite Part. Applied Sciences, 15(18), 10039. https://doi.org/10.3390/app151810039

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