![\"PET](\"https:\/\/www.raxpanel.com\/wp-content\/uploads\/PET-Foam-Sandwich-Panel.jpg\")
<\/figure>\nCore Material Preparation Stage<\/h2>\n\nCore preparation determines the structural ceiling of your sandwich panel. Inconsistent density or cell geometry in the core layer will propagate into bonding defects, regardless of how precisely you control lamination downstream.<\/p>\n<\/blockquote>\n
Foam Core Types and Processing<\/h3>\n
Foam cores represent the most widely specified category in industrial sandwich panel manufacturing. At Rax Panel, we process six primary foam types on our production line\u2014XPS, PET, PU, PVC, PMI, and EPP\u2014each selected based on the buyer’s performance requirements for thermal insulation<\/a>, compressive strength<\/a>, and weight targets. The critical factor during preparation is density consistency<\/a>. If a PET foam block varies from 80 kg\/m\u00b3 to 130 kg\/m\u00b3 across its width, the resulting panel will exhibit uneven shear transfer and localized delamination risk under load.<\/p>\nHere is a breakdown of the foam core materials we process, with their operational density ranges and thermal conductivity<\/a> benchmarks:<\/p>\n\n- XPS Foam Core:<\/strong> Density 25\u201345 kg\/m\u00b3, thermal conductivity 0.028\u20130.035 W\/mK. Cost-effective for RV wall panels and truck bodies where moderate insulation is sufficient.<\/li>\n
- PET Foam Core:<\/strong> Density 60\u2013200 kg\/m\u00b3, thermal conductivity 0.030\u20130.040 W\/mK. Recyclable thermoplastic structure with excellent chemical resistance, widely used in marine and cold room panels.<\/li>\n
- PU Foam Core:<\/strong> Density 30\u2013150 kg\/m\u00b3, thermal conductivity 0.022\u20130.028 W\/mK. Best-in-class insulation performance, making it the standard for refrigerated truck bodies and modular cold room panels.<\/li>\n
- PVC Foam Core:<\/strong> Density range overlaps with PET (60\u2013200 kg\/m\u00b3). Closed-cell structure provides superior water resistance for vessel and marine applications.<\/li>\n
- PMI Foam Core:<\/strong> Highest specific mechanical strength among structural foams<\/a>. Specified in aerospace, high-performance sports equipment, and applications demanding extreme stiffness-to-weight ratios.<\/li>\n
- EPP Foam Core:<\/strong> Exceptional energy absorption and impact recovery. Used in applications requiring repeated impact resistance rather than maximum stiffness.<\/li>\n<\/ul>\n
During processing, foam blocks are cut to target thickness using hot-wire or CNC rotary tools. Thickness tolerance must stay within \u00b10.3mm to ensure a uniform bond line during lamination. If the foam surface is scored, uneven, or contaminated with cutting debris, adhesive distribution becomes inconsistent\u2014directly increasing the risk of void formation and panel rejection.<\/p>\n
Our engineers verify incoming foam density with sample testing before any material enters the lamination stage, because catching a density deviation at receipt costs a fraction of what a field delamination claim costs downstream.<\/p>\n
Honeycomb Core Production<\/h3>\n
Honeycomb cores<\/a> trade the continuous insulation of foam for significantly higher compressive strength-to-weight ratios. Rax Panel manufactures PP honeycomb and fiberglass honeycomb cores, and we also supply aramid honeycomb and PC honeycomb for specialized applications. The defining quality parameter in honeycomb production is cell size consistency\u2014typically specified in the 3\u201312mm range\u2014because the cell geometry directly controls shear strength and compression behavior across the panel surface.<\/p>\n\n- PP Honeycomb Core:<\/strong> Density 50\u2013120 kg\/m\u00b3. Thermoplastic construction allows it to bond well with CFRT and GRP facings. When composited with fiberglass sheet, it delivers a structure that is both strong and light, ideal for RV floor panels and truck body sidewalls.<\/li>\n
- Fiberglass Honeycomb Core:<\/strong> Higher temperature resistance than PP, specified where fire ratings or elevated service temperatures are a factor\u2014such as clean room partition panels and architectural insulated panels.<\/li>\n
- Cell Size Consistency:<\/strong> Maintained within the 3\u201312mm specification window. Variation beyond this tolerance creates localized weak zones where shear stress concentrates under load, leading to premature core failure.<\/li>\n<\/ul>\n
The honeycomb expansion and bonding process requires precise control of node adhesive application. If the adhesive between cell nodes is insufficient, the honeycomb collapses under compression during panel lamination. If applied unevenly, weight increases without proportional strength gain\u2014undermining the entire engineering rationale for choosing a honeycomb core over foam.<\/p>\n
Our engineering team validates each honeycomb batch by testing node bond strength and cell uniformity before releasing material to the production floor. This is a step many commodity suppliers skip, and it is the reason panels from uncertified lines often fail under sustained thermal cycling or shear stress.<\/p>\n
\n\n\nCore Material<\/th>\n Density Range (kg\/m\u00b3)<\/th>\n Thermal Conductivity (W\/mK)<\/th>\n Key Properties<\/th>\n Preparation & QC Requirements<\/th>\n<\/tr>\n<\/thead>\n \n\nXPS Foam<\/td>\n 25\u201345<\/td>\n 0.028\u20130.035<\/td>\n Lightweight, moisture-resistant, cost-effective<\/td>\n Moisture content below 2%, surface grinding for bond adhesion, thickness tolerance \u00b10.3mm<\/td>\n<\/tr>\n \nPET Foam<\/td>\n 60\u2013200<\/td>\n 0.030\u20130.040<\/td>\n High compression strength, recyclable, thermoformable<\/td>\n Dimensional tolerance \u00b10.5mm, edge sealing required, density uniformity verification across full sheet<\/td>\n<\/tr>\n \nPU Foam<\/td>\n 30\u2013150<\/td>\n 0.022\u20130.028<\/td>\n Best insulation value, fire retardant grades available<\/td>\n Temperature-controlled storage at 15\u201325\u00b0C, surface cleaning before adhesive application, fire rating validation<\/td>\n<\/tr>\n \nPVC Foam<\/td>\n 30\u2013250<\/td>\n 0.030\u20130.045<\/td>\n Excellent chemical resistance, high strength-to-weight ratio<\/td>\n Fumed surface treatment for bonding, vacuum drying recommended, batch density testing per lot<\/td>\n<\/tr>\n \nPMI Foam<\/td>\n 32\u2013300<\/td>\n 0.020\u20130.035<\/td>\n Highest specific strength, aerospace-grade performance<\/td>\n Controlled environment processing, co-curing compatibility verification with facing resin systems<\/td>\n<\/tr>\n \nPP Honeycomb<\/td>\n 50\u2013120<\/td>\n 0.050\u20130.080<\/td>\n Exceptional shear transfer, impact-resistant, recyclable<\/td>\n Cell size consistency check, edge trimming to \u00b10.5mm, adhesive fill verification in honeycomb nodes<\/td>\n<\/tr>\n \nAramid Honeycomb<\/td>\n 29\u2013130<\/td>\n 0.040\u20130.070<\/td>\n Extreme fire resistance, high shear modulus<\/td>\n Moisture barrier storage required, specialized cutting tools, compression testing per batch for crush strength validation<\/td>\n<\/tr>\n \nPC Honeycomb<\/td>\n 60\u2013150<\/td>\n 0.045\u20130.075<\/td>\n Transparent options, good impact resistance, UV-stabilized grades<\/td>\n UV resistance certification for exterior applications, thermal expansion compatibility check with facing materials<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n![\"FRP](\"https:\/\/www.raxpanel.com\/wp-content\/uploads\/FRP-Facing-PU-Sandwich-Panel-Structure-Drawing-1200.webp\")
<\/figure>\nFacing Material Fabrication<\/h2>\n\nFacing fabrication is the first and most consequential stage of sandwich panel manufacturing. Surface defects, contamination, or thickness inconsistencies at this point propagate through every subsequent lamination step.<\/p>\n<\/blockquote>\n
GRP Sheet Manufacturing<\/h3>\n
Glass Reinforced Plastic (GRP) sheet production starts with continuous filament winding or pultrusion, where glass fibers are impregnated with a thermoset resin matrix\u2014typically polyester or vinyl ester. The fiber orientation and resin-to-glass ratio directly dictate the mechanical output of the final panel facing. At Rax Panel, we produce GRP sheets ranging from 0.5mm to 3.0mm in thickness, depending on the structural and application requirements of the buyer.<\/p>\n
The critical quality parameters during GRP fabrication are fiber wet-out uniformity and air void elimination. Incomplete resin saturation creates weak points that lead to facing delamination under thermal cycling or impact. Our production line maintains continuous tension control on the glass rovings, which prevents fiber waviness\u2014a defect that can reduce tensile strength by 15\u201325% in the finished sheet.<\/p>\n
We also manufacture FR4 fiberglass sheets for applications demanding higher electrical insulation and dimensional stability. These sheets undergo a higher-temperature cure cycle and use epoxy resin systems rather than polyester, which increases both cost and performance.<\/p>\n
CFRT Thermoplastic Facing Production<\/h3>\n
Continuous Fiber Reinforced Thermoplastic (CFRT) sheets represent a newer class of facing material that addresses several limitations of traditional thermoset GRP. Unlike thermoset resins, which undergo irreversible chemical cross-linking during curing, CFRT sheets<\/a> use a thermoplastic matrix\u2014typically polypropylene or PET\u2014that can be reheated and reformed. This makes the material fully recyclable and significantly faster to process during lamination, since no additional curing chemistry is required at the bonding stage.<\/p>\nCFRT sheets are produced through a continuous consolidation process where unidirectional (UD) glass fiber tapes are stacked in predetermined orientations\u2014commonly 0\u00b0\/90\u00b0 or quasi-isotropic layups\u2014and pressed through heated rollers. The result is a facing that is lighter and thinner than equivalent-strength GRP, typically ranging from 0.5mm to 2.0mm. Our thermoplastic UD tapes serve as both a standalone product and the feedstock for CFRT sheet lamination.<\/p>\n
\n\n\nFacing Material<\/th>\n Thickness Range<\/th>\n Surface Options<\/th>\n Key Properties & Applications<\/th>\n<\/tr>\n<\/thead>\n \n\nGRP\/FRP Sheets<\/td>\n 0.5 \u2013 3.0 mm<\/td>\n Gelcoat or non-gelcoat finish<\/td>\n Waterproof, insulating, flat, smooth surface; ideal for RV walls, truck bodies, marine vessels<\/td>\n<\/tr>\n \nCFRT Sheets<\/td>\n 0.5 \u2013 2.0 mm<\/td>\n Smooth thermoplastic finish<\/td>\n Lighter, thinner, resilient; continuous fiberglass reinforced thermoplastic for demanding structural applications<\/td>\n<\/tr>\n \nAluminum Sheets<\/td>\n 0.3 \u2013 2.0 mm<\/td>\n Mill finish, coated, or painted<\/td>\n Lightweight, corrosion-resistant; used in architectural insulated panels, cold room wall panels, exterior cladding<\/td>\n<\/tr>\n \nStainless Steel Sheets<\/td>\n 0.3 \u2013 1.5 mm<\/td>\n Brushed, polished, or matte<\/td>\n Superior corrosion resistance and hygiene; suitable for clean room panels, food-grade facilities, industrial environments<\/td>\n<\/tr>\n \nACP (Aluminum Composite Panel)<\/td>\n 0.3 \u2013 2.0 mm<\/td>\n PVDF, PE, or wooden grain coating<\/td>\n Aesthetic versatility with weather resistance; applied in exterior wall cladding, commercial building facades<\/td>\n<\/tr>\n \nPVC Facing<\/td>\n 0.5 \u2013 2.0 mm<\/td>\n Plain or textured surface<\/td>\n Cost-effective, moisture-resistant; commonly paired with foam cores for lightweight building panels<\/td>\n<\/tr>\n \nAluzinc Coated Steel<\/td>\n 0.3 \u2013 1.5 mm<\/td>\n Coated or pre-painted<\/td>\n Enhanced corrosion protection vs. galvanized steel; used in warehouse sandwich panels, agricultural insulated panels<\/td>\n<\/tr>\n \nPlywood Facing<\/td>\n 1.0 \u2013 5.0 mm<\/td>\n Film-faced or raw wood finish<\/td>\n Structural rigidity with screw-holding capability; suited for RV furniture panels, mobile home flooring<\/td>\n<\/tr>\n \nLWRT Sheets<\/td>\n 0.8 \u2013 2.5 mm<\/td>\n Textured or smooth thermoplastic<\/td>\n Lightweight random thermoplastic composite; reduces overall panel weight in vehicle and transit applications<\/td>\n<\/tr>\n \nFR4 Fiberglass Sheets<\/td>\n 0.5 \u2013 3.0 mm<\/td>\n Epoxy-based smooth finish<\/td>\n High electrical insulation and mechanical strength; used in industrial equipment and specialized sandwich panels<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n![\"PU](\"https:\/\/www.raxpanel.com\/wp-content\/uploads\/PU-Foam-Sandwich-Panel-1200.webp\")
<\/figure>\nAdhesive Application and Bonding Methods<\/h2>\n\nBond line thickness exceeding 0.5mm increases delamination risk by up to 40% under thermal cycling. Under-curing causes approximately 60% of field delamination claims. These two parameters define panel longevity.<\/p>\n<\/blockquote>\n
Thermoset vs. Thermoplastic Bonding<\/h3>\n
The adhesive system you select dictates not just bond strength, but the entire production workflow and recyclability of the finished panel. There are two dominant chemistries in composite sandwich panel manufacturing: thermoset polyurethane (PU) lamination and thermoplastic film bonding. They behave fundamentally differently on the factory floor.<\/p>\n
Thermoset polyurethane adhesives are the industry standard for bonding GRP\/FRP sheets to foam cores like PET, PU, XPS, and PVC. PU adhesives undergo an irreversible chemical cross-linking reaction during curing. Once cured, the polymer network cannot be remelted or reformed. This gives thermoset bonds excellent creep resistance and long-term durability under sustained static loads\u2014critical for RV wall panels and refrigerated truck bodies that experience constant vibration and thermal stress over years of service.<\/p>\n
Thermoplastic film bonding, by contrast, uses a heat-activated adhesive film that melts, flows, and solidifies through physical cooling rather than chemical reaction. This is the preferred method for CFRT sandwich panels where both the facing sheets and the core material are thermoplastic. The advantage: the entire panel\u2014facing, adhesive, and core\u2014becomes a mono-material system that is fully recyclable. European OEMs increasingly demand thermoplastic construction for regulatory compliance around end-of-life vehicle directives.<\/p>\n
The critical quality parameter shared by both systems is bond line thickness. This must be controlled to a range of 0.1\u20130.3mm. Why does this matter? A bond line below 0.1mm creates adhesive starvation\u2014there is insufficient resin to wet out the entire facing surface, leaving voids that become initiation points for delamination.<\/p>\n
A bond line above 0.3mm wastes adhesive and introduces a thick, weak layer between the core and facing. Exceeding 0.5mm is a serious defect: testing data shows delamination risk increases by up to 40% under thermal cycling because thicker adhesive layers exhibit greater differential expansion and lower shear transfer efficiency.<\/p>\n
At Rax Panel, we apply adhesive via precision metering rollers calibrated to the specific viscosity and open time of the adhesive system being used. For PU lamination on GRP foam core panels, two-component metering ensures the exact mix ratio is maintained. For thermoplastic CFRT panel production, pre-cut adhesive films with controlled thickness eliminate metering variability entirely.<\/p>\n
Pressing and Curing Parameters<\/h3>\n
Once adhesive is applied and the core-facing stack is assembled, the panel enters the pressing and curing stage. This is where the chemical cross-linking (thermoset) or physical consolidation (thermoplastic) occurs under controlled heat and pressure. The parameters here directly determine whether your panels will survive years of field service or fail prematurely.<\/p>\n
Curing temperature ranges from 80 to 140\u00b0C depending on the adhesive chemistry and core material sensitivity. PU adhesives typically cure at 80\u2013120\u00b0C. Going hotter accelerates cure time but risks deforming temperature-sensitive cores\u2014XPS foam begins to soften above 75\u00b0C if exposure is prolonged, so dwell time must be tightly managed.<\/p>\n
PET and PVC foams tolerate higher temperatures better, allowing cure temperatures at the upper end of the range. Thermoplastic films for CFRT panels generally activate between 120\u2013140\u00b0C to ensure complete melt flow and wetting.<\/p>\n
Pressure during pressing ranges from 0.2 to 0.8 MPa. Too little pressure fails to squeeze out trapped air and ensures inadequate contact between the adhesive and facing surface. Too much pressure compresses the foam core, reducing its thickness and compromising its insulation value. For low-density cores like XPS (25\u201345 kg\/m\u00b3), pressure must stay at the lower end. Higher-density cores like PET foam (60\u2013200 kg\/m\u00b3) can tolerate pressures toward 0.8 MPa without permanent deformation.<\/p>\n
The pressing method itself falls into two categories, each suited to different production requirements:<\/p>\n
\n- Continuous press lines:<\/strong> The panel stack passes through a heated roller press or double-belt press at a controlled speed. This is high-throughput production\u2014our line processes over 1,700 sqm daily. It maintains consistent pressure and temperature across the entire panel width. Continuous lines excel at producing standard-thickness panels with tight dimensional tolerance, but they limit maximum panel thickness based on the press gap opening.<\/li>\n
- Batch (discontinuous) press lines:<\/strong> Individual panel stacks are loaded into a hydraulic platen press, compressed, and held at temperature for the full cure cycle. Batch pressing accommodates custom thicknesses up to 200mm and allows multi-layer panel constructions. It is slower but provides greater flexibility for specialized orders like thick insulated cold room panels or marine-grade GRP balsa sandwich panels.<\/li>\n<\/ul>\n
Under-curing is the single largest cause of field delamination, responsible for approximately 60% of warranty claims in the composite panel industry. It occurs when panels are removed from the press before cross-linking reaches completion, or when temperature distribution across the platen is uneven, leaving cool spots where the adhesive remains partially uncured. At Rax Panel, we address this with multi-zone temperature control on our press platens and defined minimum dwell times verified through periodic cross-link density testing during production runs.<\/p>\n
If you are evaluating a sandwich panel supplier, ask them two specific questions: what bond line thickness they target and how they verify cure completion across the full panel surface. A manufacturer who cannot give you precise numbers or relies solely on visual inspection is gambling with your project’s long-term performance.<\/p>\n![\"PPGI](\"https:\/\/www.raxpanel.com\/wp-content\/uploads\/PPGI-Sandwich-Panel-Structure-Drawing-1200.webp\")
<\/figure>\nCutting, Machining, and Tolerances<\/h2>\n\nCutting and sealing composite panels is not a post-manufacturing afterthought; it is the final tolerance gate that determines if a panel survives field assembly without delamination.<\/p>\n<\/blockquote>\n
CNC Precision Cutting and Dimensional Tolerance<\/h3>\n
When you are fitting panels into an RV wall framework or a modular cold room, a 2mm gap turns into a thermal bridge and a structural liability. Standard industry practice often accepts dimensional variances that are simply unacceptable for specialized vehicle manufacturing and commercial construction. Holding a strict \u00b10.5mm dimensional tolerance is what separates a smooth assembly line from a logistical bottleneck filled with rework.<\/p>\n
Core preparation determines the structural ceiling of your sandwich panel. Inconsistent density or cell geometry in the core layer will propagate into bonding defects, regardless of how precisely you control lamination downstream.<\/p>\n<\/blockquote>\n
Foam Core Types and Processing<\/h3>\n
Foam cores represent the most widely specified category in industrial sandwich panel manufacturing. At Rax Panel, we process six primary foam types on our production line\u2014XPS, PET, PU, PVC, PMI, and EPP\u2014each selected based on the buyer’s performance requirements for thermal insulation<\/a>, compressive strength<\/a>, and weight targets. The critical factor during preparation is density consistency<\/a>. If a PET foam block varies from 80 kg\/m\u00b3 to 130 kg\/m\u00b3 across its width, the resulting panel will exhibit uneven shear transfer and localized delamination risk under load.<\/p>\n Here is a breakdown of the foam core materials we process, with their operational density ranges and thermal conductivity<\/a> benchmarks:<\/p>\n During processing, foam blocks are cut to target thickness using hot-wire or CNC rotary tools. Thickness tolerance must stay within \u00b10.3mm to ensure a uniform bond line during lamination. If the foam surface is scored, uneven, or contaminated with cutting debris, adhesive distribution becomes inconsistent\u2014directly increasing the risk of void formation and panel rejection.<\/p>\n Our engineers verify incoming foam density with sample testing before any material enters the lamination stage, because catching a density deviation at receipt costs a fraction of what a field delamination claim costs downstream.<\/p>\n Honeycomb cores<\/a> trade the continuous insulation of foam for significantly higher compressive strength-to-weight ratios. Rax Panel manufactures PP honeycomb and fiberglass honeycomb cores, and we also supply aramid honeycomb and PC honeycomb for specialized applications. The defining quality parameter in honeycomb production is cell size consistency\u2014typically specified in the 3\u201312mm range\u2014because the cell geometry directly controls shear strength and compression behavior across the panel surface.<\/p>\n The honeycomb expansion and bonding process requires precise control of node adhesive application. If the adhesive between cell nodes is insufficient, the honeycomb collapses under compression during panel lamination. If applied unevenly, weight increases without proportional strength gain\u2014undermining the entire engineering rationale for choosing a honeycomb core over foam.<\/p>\n Our engineering team validates each honeycomb batch by testing node bond strength and cell uniformity before releasing material to the production floor. This is a step many commodity suppliers skip, and it is the reason panels from uncertified lines often fail under sustained thermal cycling or shear stress.<\/p>\n Facing fabrication is the first and most consequential stage of sandwich panel manufacturing. Surface defects, contamination, or thickness inconsistencies at this point propagate through every subsequent lamination step.<\/p>\n<\/blockquote>\n Glass Reinforced Plastic (GRP) sheet production starts with continuous filament winding or pultrusion, where glass fibers are impregnated with a thermoset resin matrix\u2014typically polyester or vinyl ester. The fiber orientation and resin-to-glass ratio directly dictate the mechanical output of the final panel facing. At Rax Panel, we produce GRP sheets ranging from 0.5mm to 3.0mm in thickness, depending on the structural and application requirements of the buyer.<\/p>\n The critical quality parameters during GRP fabrication are fiber wet-out uniformity and air void elimination. Incomplete resin saturation creates weak points that lead to facing delamination under thermal cycling or impact. Our production line maintains continuous tension control on the glass rovings, which prevents fiber waviness\u2014a defect that can reduce tensile strength by 15\u201325% in the finished sheet.<\/p>\n We also manufacture FR4 fiberglass sheets for applications demanding higher electrical insulation and dimensional stability. These sheets undergo a higher-temperature cure cycle and use epoxy resin systems rather than polyester, which increases both cost and performance.<\/p>\n Continuous Fiber Reinforced Thermoplastic (CFRT) sheets represent a newer class of facing material that addresses several limitations of traditional thermoset GRP. Unlike thermoset resins, which undergo irreversible chemical cross-linking during curing, CFRT sheets<\/a> use a thermoplastic matrix\u2014typically polypropylene or PET\u2014that can be reheated and reformed. This makes the material fully recyclable and significantly faster to process during lamination, since no additional curing chemistry is required at the bonding stage.<\/p>\n CFRT sheets are produced through a continuous consolidation process where unidirectional (UD) glass fiber tapes are stacked in predetermined orientations\u2014commonly 0\u00b0\/90\u00b0 or quasi-isotropic layups\u2014and pressed through heated rollers. The result is a facing that is lighter and thinner than equivalent-strength GRP, typically ranging from 0.5mm to 2.0mm. Our thermoplastic UD tapes serve as both a standalone product and the feedstock for CFRT sheet lamination.<\/p>\n Bond line thickness exceeding 0.5mm increases delamination risk by up to 40% under thermal cycling. Under-curing causes approximately 60% of field delamination claims. These two parameters define panel longevity.<\/p>\n<\/blockquote>\n The adhesive system you select dictates not just bond strength, but the entire production workflow and recyclability of the finished panel. There are two dominant chemistries in composite sandwich panel manufacturing: thermoset polyurethane (PU) lamination and thermoplastic film bonding. They behave fundamentally differently on the factory floor.<\/p>\n Thermoset polyurethane adhesives are the industry standard for bonding GRP\/FRP sheets to foam cores like PET, PU, XPS, and PVC. PU adhesives undergo an irreversible chemical cross-linking reaction during curing. Once cured, the polymer network cannot be remelted or reformed. This gives thermoset bonds excellent creep resistance and long-term durability under sustained static loads\u2014critical for RV wall panels and refrigerated truck bodies that experience constant vibration and thermal stress over years of service.<\/p>\n Thermoplastic film bonding, by contrast, uses a heat-activated adhesive film that melts, flows, and solidifies through physical cooling rather than chemical reaction. This is the preferred method for CFRT sandwich panels where both the facing sheets and the core material are thermoplastic. The advantage: the entire panel\u2014facing, adhesive, and core\u2014becomes a mono-material system that is fully recyclable. European OEMs increasingly demand thermoplastic construction for regulatory compliance around end-of-life vehicle directives.<\/p>\n The critical quality parameter shared by both systems is bond line thickness. This must be controlled to a range of 0.1\u20130.3mm. Why does this matter? A bond line below 0.1mm creates adhesive starvation\u2014there is insufficient resin to wet out the entire facing surface, leaving voids that become initiation points for delamination.<\/p>\n A bond line above 0.3mm wastes adhesive and introduces a thick, weak layer between the core and facing. Exceeding 0.5mm is a serious defect: testing data shows delamination risk increases by up to 40% under thermal cycling because thicker adhesive layers exhibit greater differential expansion and lower shear transfer efficiency.<\/p>\n At Rax Panel, we apply adhesive via precision metering rollers calibrated to the specific viscosity and open time of the adhesive system being used. For PU lamination on GRP foam core panels, two-component metering ensures the exact mix ratio is maintained. For thermoplastic CFRT panel production, pre-cut adhesive films with controlled thickness eliminate metering variability entirely.<\/p>\n Once adhesive is applied and the core-facing stack is assembled, the panel enters the pressing and curing stage. This is where the chemical cross-linking (thermoset) or physical consolidation (thermoplastic) occurs under controlled heat and pressure. The parameters here directly determine whether your panels will survive years of field service or fail prematurely.<\/p>\n Curing temperature ranges from 80 to 140\u00b0C depending on the adhesive chemistry and core material sensitivity. PU adhesives typically cure at 80\u2013120\u00b0C. Going hotter accelerates cure time but risks deforming temperature-sensitive cores\u2014XPS foam begins to soften above 75\u00b0C if exposure is prolonged, so dwell time must be tightly managed.<\/p>\n PET and PVC foams tolerate higher temperatures better, allowing cure temperatures at the upper end of the range. Thermoplastic films for CFRT panels generally activate between 120\u2013140\u00b0C to ensure complete melt flow and wetting.<\/p>\n Pressure during pressing ranges from 0.2 to 0.8 MPa. Too little pressure fails to squeeze out trapped air and ensures inadequate contact between the adhesive and facing surface. Too much pressure compresses the foam core, reducing its thickness and compromising its insulation value. For low-density cores like XPS (25\u201345 kg\/m\u00b3), pressure must stay at the lower end. Higher-density cores like PET foam (60\u2013200 kg\/m\u00b3) can tolerate pressures toward 0.8 MPa without permanent deformation.<\/p>\n The pressing method itself falls into two categories, each suited to different production requirements:<\/p>\n Under-curing is the single largest cause of field delamination, responsible for approximately 60% of warranty claims in the composite panel industry. It occurs when panels are removed from the press before cross-linking reaches completion, or when temperature distribution across the platen is uneven, leaving cool spots where the adhesive remains partially uncured. At Rax Panel, we address this with multi-zone temperature control on our press platens and defined minimum dwell times verified through periodic cross-link density testing during production runs.<\/p>\n If you are evaluating a sandwich panel supplier, ask them two specific questions: what bond line thickness they target and how they verify cure completion across the full panel surface. A manufacturer who cannot give you precise numbers or relies solely on visual inspection is gambling with your project’s long-term performance.<\/p>\n Cutting and sealing composite panels is not a post-manufacturing afterthought; it is the final tolerance gate that determines if a panel survives field assembly without delamination.<\/p>\n<\/blockquote>\n When you are fitting panels into an RV wall framework or a modular cold room, a 2mm gap turns into a thermal bridge and a structural liability. Standard industry practice often accepts dimensional variances that are simply unacceptable for specialized vehicle manufacturing and commercial construction. Holding a strict \u00b10.5mm dimensional tolerance is what separates a smooth assembly line from a logistical bottleneck filled with rework.<\/p>\n\n
Honeycomb Core Production<\/h3>\n
\n
\n\n
\n \nCore Material<\/th>\n Density Range (kg\/m\u00b3)<\/th>\n Thermal Conductivity (W\/mK)<\/th>\n Key Properties<\/th>\n Preparation & QC Requirements<\/th>\n<\/tr>\n<\/thead>\n \n XPS Foam<\/td>\n 25\u201345<\/td>\n 0.028\u20130.035<\/td>\n Lightweight, moisture-resistant, cost-effective<\/td>\n Moisture content below 2%, surface grinding for bond adhesion, thickness tolerance \u00b10.3mm<\/td>\n<\/tr>\n \n PET Foam<\/td>\n 60\u2013200<\/td>\n 0.030\u20130.040<\/td>\n High compression strength, recyclable, thermoformable<\/td>\n Dimensional tolerance \u00b10.5mm, edge sealing required, density uniformity verification across full sheet<\/td>\n<\/tr>\n \n PU Foam<\/td>\n 30\u2013150<\/td>\n 0.022\u20130.028<\/td>\n Best insulation value, fire retardant grades available<\/td>\n Temperature-controlled storage at 15\u201325\u00b0C, surface cleaning before adhesive application, fire rating validation<\/td>\n<\/tr>\n \n PVC Foam<\/td>\n 30\u2013250<\/td>\n 0.030\u20130.045<\/td>\n Excellent chemical resistance, high strength-to-weight ratio<\/td>\n Fumed surface treatment for bonding, vacuum drying recommended, batch density testing per lot<\/td>\n<\/tr>\n \n PMI Foam<\/td>\n 32\u2013300<\/td>\n 0.020\u20130.035<\/td>\n Highest specific strength, aerospace-grade performance<\/td>\n Controlled environment processing, co-curing compatibility verification with facing resin systems<\/td>\n<\/tr>\n \n PP Honeycomb<\/td>\n 50\u2013120<\/td>\n 0.050\u20130.080<\/td>\n Exceptional shear transfer, impact-resistant, recyclable<\/td>\n Cell size consistency check, edge trimming to \u00b10.5mm, adhesive fill verification in honeycomb nodes<\/td>\n<\/tr>\n \n Aramid Honeycomb<\/td>\n 29\u2013130<\/td>\n 0.040\u20130.070<\/td>\n Extreme fire resistance, high shear modulus<\/td>\n Moisture barrier storage required, specialized cutting tools, compression testing per batch for crush strength validation<\/td>\n<\/tr>\n \n PC Honeycomb<\/td>\n 60\u2013150<\/td>\n 0.045\u20130.075<\/td>\n Transparent options, good impact resistance, UV-stabilized grades<\/td>\n UV resistance certification for exterior applications, thermal expansion compatibility check with facing materials<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n <\/figure>\nFacing Material Fabrication<\/h2>\n
\n
GRP Sheet Manufacturing<\/h3>\n
CFRT Thermoplastic Facing Production<\/h3>\n
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\n \nFacing Material<\/th>\n Thickness Range<\/th>\n Surface Options<\/th>\n Key Properties & Applications<\/th>\n<\/tr>\n<\/thead>\n \n GRP\/FRP Sheets<\/td>\n 0.5 \u2013 3.0 mm<\/td>\n Gelcoat or non-gelcoat finish<\/td>\n Waterproof, insulating, flat, smooth surface; ideal for RV walls, truck bodies, marine vessels<\/td>\n<\/tr>\n \n CFRT Sheets<\/td>\n 0.5 \u2013 2.0 mm<\/td>\n Smooth thermoplastic finish<\/td>\n Lighter, thinner, resilient; continuous fiberglass reinforced thermoplastic for demanding structural applications<\/td>\n<\/tr>\n \n Aluminum Sheets<\/td>\n 0.3 \u2013 2.0 mm<\/td>\n Mill finish, coated, or painted<\/td>\n Lightweight, corrosion-resistant; used in architectural insulated panels, cold room wall panels, exterior cladding<\/td>\n<\/tr>\n \n Stainless Steel Sheets<\/td>\n 0.3 \u2013 1.5 mm<\/td>\n Brushed, polished, or matte<\/td>\n Superior corrosion resistance and hygiene; suitable for clean room panels, food-grade facilities, industrial environments<\/td>\n<\/tr>\n \n ACP (Aluminum Composite Panel)<\/td>\n 0.3 \u2013 2.0 mm<\/td>\n PVDF, PE, or wooden grain coating<\/td>\n Aesthetic versatility with weather resistance; applied in exterior wall cladding, commercial building facades<\/td>\n<\/tr>\n \n PVC Facing<\/td>\n 0.5 \u2013 2.0 mm<\/td>\n Plain or textured surface<\/td>\n Cost-effective, moisture-resistant; commonly paired with foam cores for lightweight building panels<\/td>\n<\/tr>\n \n Aluzinc Coated Steel<\/td>\n 0.3 \u2013 1.5 mm<\/td>\n Coated or pre-painted<\/td>\n Enhanced corrosion protection vs. galvanized steel; used in warehouse sandwich panels, agricultural insulated panels<\/td>\n<\/tr>\n \n Plywood Facing<\/td>\n 1.0 \u2013 5.0 mm<\/td>\n Film-faced or raw wood finish<\/td>\n Structural rigidity with screw-holding capability; suited for RV furniture panels, mobile home flooring<\/td>\n<\/tr>\n \n LWRT Sheets<\/td>\n 0.8 \u2013 2.5 mm<\/td>\n Textured or smooth thermoplastic<\/td>\n Lightweight random thermoplastic composite; reduces overall panel weight in vehicle and transit applications<\/td>\n<\/tr>\n \n FR4 Fiberglass Sheets<\/td>\n 0.5 \u2013 3.0 mm<\/td>\n Epoxy-based smooth finish<\/td>\n High electrical insulation and mechanical strength; used in industrial equipment and specialized sandwich panels<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n <\/figure>\nAdhesive Application and Bonding Methods<\/h2>\n
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Thermoset vs. Thermoplastic Bonding<\/h3>\n
Pressing and Curing Parameters<\/h3>\n
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<\/figure>\nCutting, Machining, and Tolerances<\/h2>\n
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CNC Precision Cutting and Dimensional Tolerance<\/h3>\n
![\"CTA](\"https:\/\/www.raxpanel.com\/wp-content\/uploads\/hyperrealistic-photography-of-a-modern-agricultural-building-overview-scaled.jpg\")
<\/div>\n<\/div>\n![\"GRP](\"https:\/\/www.raxpanel.com\/wp-content\/uploads\/GRP-PU-Sandwich-Panel.jpg\")
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