Abstract:

Printout, a common issue in Fiber-Reinforced Polymer (FRP) laminates, primarily stems from resin shrinkage during the curing process. While polyester resin with glass reinforcement offers durability, its inherent shrinkage poses challenges for surface appearance.

Introducing a surfacing veil into lamination significantly reduces resin shrinkage, resulting in a smooth, consistent resin-rich surface. This surface acts as a corrosion and UV barrier, enhancing finish quality and reducing porosity. Moreover, surfacing veils enhance operational efficiency by facilitating resin flow, shortening demold time, and bolstering gel coat strength and adhesion.

Introduction:

Resin shrinkage represents a pervasive challenge in the composites industry, often managed rather than eliminated. Understanding its mechanisms is crucial for effective mitigation. Polyester resin, a common thermoset composite material, undergoes polymerization during curing, resulting in cross-linked polymer chains and subsequent shrinkage upon hardening. While resin shrinkage remains inherent, its impact on surface quality necessitates strategic interventions.

Detailed Description:

Resin shrinkage, a fundamental characteristic of thermoset composites, poses multifaceted challenges in the production of FRP laminates. During the curing stage, polyester resin undergoes polymerization, transforming from a liquid state to a solid cross-linked polymer structure. This transformation, while essential for laminate integrity, introduces the risk of shrinkage, particularly at the surface where the resin encounters minimal resistance to contraction.

The consequences of resin shrinkage manifest as printout, wherein the surface of the laminate exhibits irregularities, such as depressions or waves, caused by differential contraction of the resin matrix. These imperfections compromise the aesthetic appeal and functional integrity of the composite part, necessitating corrective measures to achieve desired surface quality.

Surfacing veils offer a strategic solution to mitigate printout and enhance surface finish in FRP laminates. By incorporating a surfacing veil into the lamination process, resin shrinkage at the surface is effectively minimized. The veil acts as a barrier, facilitating the formation of a resin-rich surface layer that not only addresses printout but also provides additional benefits, including corrosion resistance, UV protection, and improved surface smoothness.

Furthermore, the presence of a surfacing veil streamlines manufacturing operations by promoting faster resin flow during closed-mold processes, reducing demold time, and enhancing the bond between the gel coat and reinforcement layers. These efficiency gains translate into tangible benefits for manufacturers, including increased productivity, reduced labor costs, and improved overall product quality.

In summary, the strategic integration of surfacing veils represents a proactive approach to managing resin shrinkage and optimizing surface quality in FRP laminates. By leveraging the unique properties of surfacing veils, manufacturers can achieve consistent, high-quality composite parts that meet the stringent requirements of diverse industries and applications.

Resin shrinkage poses a significant challenge in composite manufacturing, particularly in the context of printout on the surface of Fiber Reinforced Polymer (FRP) laminates. This phenomenon, rooted in the inherent properties of polyester resin with glass reinforcement, underscores a fundamental contradiction: the very strength and durability of this composite material can inadvertently lead to surface irregularities during the curing process.

During polymerization, as the resin hardens, it undergoes a contraction or shrinkage, while the glass fibers remain unchanged. This creates a visual effect where the glass fibers seem to protrude through the surface, commonly referred to as printout. However, it’s crucial to recognize that what appears as glass fibers poking through is, in fact, the resin retracting from the surface, leaving behind an uneven finish.

Further complicating matters is the evaporation of styrene during polymerization, which contributes to resin shrinkage. Interestingly, the rate of styrene evaporation is influenced more by the surface area than the volume of resin or gel coat. In open mold situations, where there’s a path for styrene to escape, the surface against the mold experiences less shrinkage compared to the backside of the laminate. Conversely, closed molding restricts the escape of styrene, resulting in more uniform shrinkage across the laminate surface.

Addressing resin shrinkage requires a nuanced approach. While options like low-profile additives and barrier coats offer some improvement, they may not fully resolve the issue. This is where surfacing veils come into play. By incorporating a surfacing veil into the lamination process, manufacturers can significantly enhance surface quality and consistency.

Surfacing veils play a multifaceted role. Firstly, they promote a resin-rich surface, effectively mitigating printout and creating a smooth, uniform finish. Additionally, surfacing veils offer a range of benefits, including corrosion and UV resistance, reduced porosity, and improved mechanical properties.

Moreover, the use of surfacing veils enhances operational efficiency. They facilitate faster resin flow, leading to shorter cycle times in closed-mold scenarios. Demolding times can also be reduced, improving overall production throughput. Additionally, surfacing veils provide protection for pultrusion dies and aid in equalizing mold temperatures, contributing to more consistent and reliable manufacturing processes.

In summary, surfacing veils serve as a comprehensive solution to the challenges posed by resin shrinkage in composite laminates. By addressing surface imperfections and enhancing performance, they play a vital role in ensuring the quality, durability, and efficiency of composite manufacturing processes.

How does a surfacing veil promote a resin-rich surface?

Surfacing veils serve as indispensable components in composite manufacturing processes, particularly in ensuring the formation of resin-rich surfaces that are vital for achieving superior product quality and durability. Understanding the intricate mechanisms by which surfacing veils facilitate this outcome sheds light on their significance in composite fabrication.

What is a surfacing veil?

At the core of surfacing veils‘ functionality lies their ability to facilitate the uniform distribution of resin across the composite structure’s surface. Unlike traditional reinforcement materials that may lead to uneven resin distribution and the formation of resin-rich pockets, surfacing veils ensure a more consistent resin dispersion, resulting in a smoother and more resilient surface finish.

In particular, continuous-strand glass surfacing veils exemplify this principle, offering a versatile solution across a wide range of applications. These veils are engineered with evenly dispersed independent glass fibers, held together by a light resin binder. This meticulous arrangement of 25-micron filaments strikes a delicate balance between loft and density, enabling efficient resin flow without compromising the structural integrity of the reinforcement.

In contrast, conventional reinforcement materials, such as chop-strand mats or woven rovings, often feature densely packed filaments that impede resin penetration, leading to irregular surface textures and compromised finish quality.

During the lamination process, surfacing veils play a strategic role by being positioned between the gel coat and the reinforcement mat. This positioning acts as a barrier to resin shrinkage, allowing for the creation of a smooth and resin-rich surface layer that enhances the overall appearance and performance of the composite component.

The versatility of surfacing veils extends beyond their role in surface enhancement, encompassing various industries and manufacturing processes. Whether utilized in compression molding, continuous lamination, electrical flat sheet production, or filament winding, surfacing veils consistently deliver exceptional results, ensuring the production of high-quality composite products with impeccable surface characteristics.

By delving into the intricate mechanisms and applications of surfacing veils, manufacturers gain valuable insights into optimizing their composite fabrication processes, ultimately elevating the quality and durability of their end products to new heights.

How does the surfacing veil work?

Surfacing veils stand as a linchpin in composite fabrication processes, offering intricate functionalities designed to optimize resin distribution and bolster surface integrity. To grasp the nuanced workings of surfacing veils, it’s imperative to dissect their composition and operational mechanisms, elucidating how they facilitate resin flow and counteract the detrimental effects of shrinkage.

Facilitating Resin Flow:

At the heart of surfacing veils lies their ability to act as conduits for resin flow, a function intricately linked to their unique fiber dispersion and structure. Unlike traditional reinforcement materials characterized by dense configurations that impede resin penetration, surfacing veils exhibit a finely dispersed fiber network that fosters rapid resin wet-out. This phenomenon arises from the independent nature of the veil’s fibers, which collectively create a smooth pathway for resin migration. In contrast to woven-roving mats or chop-strand mats, where resin infiltration is hindered by dense fiber clusters, surfacing veils offer unparalleled efficiency in resin distribution. The swift wet-out achieved by surfacing veils underscores their pivotal role in expediting composite lamination processes, enhancing productivity, and ensuring consistent resin impregnation across the laminate surface.

Limiting Resin Shrinkage:

Beyond facilitating resin flow, surfacing veils play a crucial role in mitigating resin shrinkage, a ubiquitous challenge in composite manufacturing that jeopardizes surface quality and structural integrity. The key to their shrinkage-mitigating prowess lies in the meticulously engineered fiber dispersion that creates a uniform density profile at the surface. Unlike conventional reinforcement materials prone to forming resin-rich pockets susceptible to shrinkage, surfacing veils maintain a smooth and homogeneous surface topology, minimizing the occurrence of shrinkage-induced defects. By virtue of their compact and evenly distributed fiber arrangement, surfacing veils effectively counteract the forces of resin shrinkage, ensuring that the final composite product boasts impeccable surface finish and dimensional stability.

By unraveling the intricate interplay between fiber dispersion, resin flow dynamics, and shrinkage mitigation, manufacturers can harness the full potential of surfacing veils to elevate the quality, performance, and aesthetics of composite materials. The seamless integration of these veils into lamination processes not only streamlines resin distribution but also fortifies the structural integrity of composite products, paving the way for unparalleled advancements in the realm of composite fabrication.

Why a resin-rich surface?

In the realm of composite materials, the longevity of laminate hinges upon the presence of a resilient resin-rich surface, acting as a formidable shield against external assailants. Whether facing surface erosion or deeper infiltration, a laminate’s endurance is contingent upon robust protection, a mantle seamlessly provided by a resin-rich surface.

Confronting the Peril of Porosity:

Porosity emerges as a dire threat to laminate integrity, heralding potential deterioration and compromised performance. The absence of a resin-rich surface lays the groundwork for porosity to proliferate, spelling doom for the structural integrity of the laminate. Much like a porous highway succumbing to annual thaws, water infiltration into microscopic crevices and fissures triggers structural degradation, manifesting as potholes. While advancements in highway technology strive to mitigate such vulnerabilities, the inevitability of potholes persists.

Empowering Solutions through Surfacing Veils:

In the arena of composite manufacturing, technological innovations offer a beacon of hope in combating porosity and fortifying laminate resilience. Surfacing veils emerge as a game-changing solution, facilitating uniform resin flow at the surface and curbing resin shrinkage, thereby bolstering surface integrity. Even amidst meticulous control of environmental factors and material ratios, porosity remains an inescapable menace, particularly evident in open molds.

In a seminal study conducted by the National Composites Center, the efficacy of surfacing veils in mitigating porosity was unequivocally demonstrated. Identical specimens, one outfitted with a surfacing veil and the other devoid of such reinforcement, underwent rigorous testing, revealing stark differentials in surface roughness. While the naked eye discerned no perceptible disparities, precise measurements unveiled a staggering contrast. The veil-equipped specimen boasted a negligible roughness average of 28, starkly juxtaposed against the non-veiled counterpart’s roughness average of 4500.

By serving as a bulwark against porosity, surfacing veils emerge as indispensable assets in safeguarding laminate longevity and preserving structural integrity, heralding a new era of durability and reliability in composite fabrication.

In the meticulous realm of composite fabrication, precision measurements wield immense significance, offering profound insights into surface integrity.

The stylus profilometer, a stalwart tool in this pursuit, meticulously gauges the roughness average (RA) of a vertical profile, unraveling crucial details about surface quality.

Although it does not discern a class “A” finish, its discernments, denoted in 1/10,000 of an inch increments, offer invaluable clarity. The monumental disparity between specimen A, bereft of a veil, boasting an RA of 45/10,000 of an inch, and specimen B, with a veil, flaunting a minuscule RA of 28/1,000,000 of an inch, paints a vivid picture of the transformative power of surfacing veils.

The staggering 160-fold reduction in roughness epitomizes the profound refinement achieved with the inclusion of a veil, underscoring its pivotal role in elevating surface smoothness to unprecedented levels.

It’s imperative to underscore that this illuminating profilometer test was conducted on a laminate featuring a 20-mil gel coat. In scenarios where gel coat application is foregone, exacerbating porosity, the protective shield conferred by a veil assumes even greater significance. Without the veil’s fortification, porosity poses a formidable challenge, particularly when subsequent painting is envisaged. Even with a coat of paint, porosity remains a lurking concern, underscoring the indispensable role of a resin-rich surface in fortifying laminate resilience.

Shielding Against Corrosion:

A resin-rich surface emerges as a formidable bulwark against corrosive onslaughts, safeguarding laminate integrity against insidious attacks. In the automotive domain, where corrosion poses a perennial threat, the protective prowess of surfacing veils finds profound resonance. While road salt historically haunted automotive longevity, contemporary advancements in paint systems and materials herald a new era of rust-free resilience, epitomized by iconic brands like Saturn. Beyond mere aesthetics, composite components like pultruded drive shafts epitomize the fusion of durability and performance, fortified by the inclusion of a corrosion-resistant veil. Shielded from corrosive assailants like road salt and transmission fluid, these components epitomize the pinnacle of automotive engineering prowess.

Mitigating UV Degradation:

In the relentless battle against UV degradation, surfacing veils emerge as steadfast guardians, fortifying laminates against the ravages of time and weather. The deleterious effects of UV exposure, from color degradation to surface delamination, imperil composite longevity, underscoring the imperative of UV-inhibited veils. With every passing day, as novel composite innovations emerge from research and development laboratories, the need for UV protection becomes increasingly paramount. From heat shields to battery trays, composite components traverse a perilous landscape of chemical exposure, necessitating robust UV defenses to ensure enduring performance.

Embracing the Class “A” Finish:

Elevating surface aesthetics to unprecedented heights, surfacing veils epitomize the quintessence of a class “A” finish, a hallmark of automotive excellence. By eradicating printout and enhancing surface smoothness, veils lay the foundation for impeccable paint application, cementing their status as indispensable ingredients in the pursuit of automotive perfection. Through their unwavering weatherability and durability, veils imbue laminates with enduring resilience, embodying the epitome of class “A” finish requirements.

In essence, the inclusion of a surfacing veil transcends mere surface refinement; it heralds a new era of composite excellence, where resilience, aesthetics, and longevity converge to redefine automotive ingenuity.

Where else can I improve surface?

Beyond the realms of traditional corrosion defense, the quest for surface perfection extends its reach to diverse manufacturing processes, ushering in a new era of composite excellence.

Pultrusion Precision:

In the realm of pultrusion, where functionality often supersedes aesthetics, the inclusion of a surfacing veil emerges as a strategic imperative, fortifying critical components against insidious corrosion threats. Take, for instance, the pultruded drive shaft, a linchpin of automotive engineering. While visual allure may not be a primary concern, the surface integrity conferred by a veil assumes paramount importance, shielding against corrosive assailants and ensuring enduring performance in the face of adversity.

Unveiling the Potential of SMC:

In the realm of Sheet Molding Compound (SMC), where surface perfection is traditionally achieved sans veil, occasional imperfections necessitate innovative solutions. When color degradation rears its head in cured SMC parts, often attributed to disparate mold temperatures, the transformative power of a glass surfacing veil comes to the fore. By harmonizing mold temperatures and bestowing a uniform appearance upon cured SMC components, veils offer a respite from cosmetic inconsistencies, ensuring a flawless finish that embodies the pinnacle of composite craftsmanship.

In essence, the inclusion of surfacing veils transcends traditional paradigms, empowering manufacturers across diverse processes to achieve unparalleled surface integrity and imbue their products with enduring resilience. Whether fortifying pultruded components against corrosion or harmonizing mold temperatures in SMC applications, veils herald a new era of composite excellence, where surface perfection knows no bounds.

How does surfacing veil increase efficiency?

While the spotlight often shines on the cosmetic enhancements brought forth by surfacing veils, their transformative impact extends far beyond aesthetics. Indeed, veils serve as unsung heroes in the realm of efficiency enhancement, ushering in a new era of streamlined operations and resource optimization.

Time and Effort Savings:

At the forefront of efficiency gains lies the realm of resource savings, where time and effort emerge as prized commodities. By seamlessly integrating surfacing veils into the manufacturing process, industries unlock a treasure trove of temporal efficiencies. The rapid wet-out properties of veils facilitate expedited resin flow, accelerating production timelines and curtailing labor-intensive processes. With veils at the helm, the laborious task of surface refinement is streamlined, freeing up valuable time and manpower for other critical tasks.

Hidden Benefits Unveiled:

Beneath the veneer of cosmetic enhancement lies a tapestry of hidden benefits, each contributing to the overarching goal of operational efficiency. Veils act as silent sentinels, safeguarding against the scourge of resin shrinkage and printout, thereby minimizing the need for corrective interventions and rework. Moreover, their corrosion-resistant properties bolster the longevity of composite components, mitigating the risk of premature degradation and obviating the need for frequent repairs or replacements.

In essence, the integration of surfacing veils heralds a paradigm shift in manufacturing efficiency, where resource savings and hidden benefits converge to propel industries towards unprecedented heights of productivity and performance. By harnessing the multifaceted advantages of veils, enterprises unlock a gateway to streamlined operations, fortified surfaces, and sustainable success.

Quicker resin flow in a closed mold 

In the intricate dance of resin infusion within closed molds, such as those employed in vacuum-assisted RTM processes, the challenge of efficient resin flow looms large. Within these tightly packed fiberglass enclosures, resin encounters impediments to its seamless dissemination, prolonging production cycles and exacerbating surface imperfections. Yet, amidst this labyrinth of obstacles, surfacing veils emerge as unsung facilitators, orchestrating a symphony of efficiency and precision.

Surfacing Veils: Unveiling Hidden Conduits

At the heart of closed molding processes lies the imperative for swift and uniform resin flow, a feat made possible by the strategic integration of surfacing veils. As resin permeates the mold, veils unfurl their hidden prowess, morphing into conduits that guide resin along the surface with unparalleled celerity. In essence, these veils act as invisible pathways, channeling resin from one end of the mold to the other with effortless grace. This accelerated journey not only expedites production timelines but also empowers resin to swiftly infiltrate the fiberglass matrix, catalyzing the curing process and hastening demolding procedures.

Unveiling Hidden Benefits

Beyond the realm of resin flow optimization lies a tapestry of hidden benefits, each contributing to the overarching goal of operational excellence. As resin traverses the mold’s surface guided by veils, it encounters a transformative experience. By infiltrating the fiberglass with unprecedented swiftness, resin saturates the substrate, minimizing the dwell time within the mold and expediting the curing process. This dual-action synergy not only enhances production efficiency but also imbues the final laminate with superior structural integrity and surface finish.

In essence, the strategic deployment of surfacing veils within closed molding processes heralds a new era of efficiency and precision. By unraveling hidden conduits and amplifying resin flow dynamics, veils pave the way for streamlined production cycles, fortified surfaces, and unparalleled manufacturing prowess. As industries navigate the complexities of modern manufacturing, veils stand as beacons of innovation, illuminating the path towards sustainable success and operational excellence.

Earlier de-mold time for closed and open mold   

The duration a laminate remains within a mold is pivotal and varies depending on the molding process. Whether it entails meticulously filling the mold with resin until the glass reinforcement reaches saturation or proceeding to the curing phase post-saturation, each step significantly impacts the final product.

In an open mold setup, resin flow dynamics are not a concern. However, regardless of the molding method, once the glass is adequately saturated, the laminate must undergo curing.

The incorporation of a surfacing veil proves invaluable in both scenarios. By diminishing resin shrinkage at the surface, the surfacing veil enhances the quality of demolded parts. Even as the exothermic curing process causes further resin contraction, the presence of the veil continues to minimize this shrinkage, even if a part is prematurely removed from the mold.

However, it’s crucial to approach this concept with meticulous care due to the multitude of variables involved. Testing becomes imperative to fine-tune timing parameters, considering factors such as resin content variations over time, which can affect curing times even within open mold hand spray-up processes.

Protects pultrusion dies 保护拉挤模具

In the pultrusion process, glass rovings are tightly pulled through a mold under high pressure, packing a significant amount of glass into a confined space. This intense operation can accelerate wear and tear on the mold, leading to costly damage over time. However, by integrating a surfacing veil into the process, this issue is mitigated. The veil acts as a protective barrier, reducing the friction and abrasion caused by the rovings, thus preserving the integrity of the expensive dies and extending their lifespan.

Strengthens the gel coat 

The application of a surfacing veil not only enhances the surface quality of laminates but also strengthens the gel coat, a critical component in composite structures.

Similar to how reinforcement mat fortifies resin, the surfacing veil bolsters the gel coat, offering protection against chipping and cracking.

Without a veil, gel coat remains vulnerable due to its lack of reinforcement. However, by incorporating a continuous-strand glass surfacing veil onto the gel coat while it is still tacky or incompletely cured, the veil’s loft ensures that each glass fiber remains independent, allowing them to embed into the gel coat.

Once cured, the surfacing veil reinforces the gel coat, providing added durability and resilience against wear and tear.

This hidden benefit applies regardless of whether the process involves an open mold or closed mold technique, making it a valuable addition to composite manufacturing processes.

Bonds gel coat to reinforcement 

Applying a surfacing veil to a tacky gel coat serves another crucial purpose:

it facilitates the bonding of the gel coat to the reinforcement material. As with the strengthening of the gel coat, the veil partially embeds into the gel coat while the remaining portion combines with the resin that interacts with the reinforcement mat.

This process creates a cohesive bond between the gel coat and the underlying reinforcement. In essence, the surfacing veil functions as a bridge, linking the gel coat with the reinforcement material.

This interlocking effect is akin to preparing a smooth surface with an abrasive texture before applying paint, ensuring strong adhesion between layers and enhancing the overall structural integrity of the composite laminate.

CONCLUSION

In conclusion, achieving a class “A” surface is paramount in industries like automotive manufacturing, where surface perfection is a prerequisite.

Printout, resulting in an uneven surface profile, poses a significant challenge to attaining this standard.

However, the integration of a surfacing veil into the lamination process offers a solution by generating a consistent resin-rich surface.

This resin-rich surface not only eliminates printout but also serves as a protective barrier against corrosive chemicals and harmful UV radiation.

Furthermore, the surfacing veil contributes to a substantial reduction in porosity, enhancing the durability and longevity of the laminate.

The symbiotic relationship between the surfacing veil and gel coat is equally crucial. Beyond strengthening the gel coat, the veil plays a pivotal role in bonding the gel coat to the reinforcement material, ensuring structural integrity and longevity of the composite.

Moreover, the addition of a surfacing veil to the lamination process is a cost-effective measure, with minimal expenses involved.

Its affordability makes it an attractive option, especially considering its multifaceted benefits, including improved surface quality, enhanced efficiency in production processes, earlier demolding times, and expedited resin flow in closed molds.

Ultimately, the incorporation of a surfacing veil translates to increased productivity and superior quality in composite manufacturing operations.