Core Materials – Lightweight Structures, High Performance


Core materials are an essential part of sandwich-structured composites, where the goal is to combine light weight with excellent mechanical durability. The core is placed between two reinforced laminates, significantly increasing the stiffness of the structure without adding much weight. This makes them an ideal choice for applications such as boat building, transportation, construction panels, and wind turbine components.

Gurit® – Ydinaineet

Core materials are an essential part of sandwich-structured composites, where the goal is to combine light weight with excellent mechanical durability. The core is placed between two reinforced laminates, significantly increasing the stiffness of the structure without adding much weight. This makes them an ideal choice for applications such as boat building, transportation, construction panels, and wind turbine components.

Recommended storage temperature: 10 – 30 °C and relative humidity below 70%. Avoid direct sunlight.


                                       PH-PLAIN                                   PH-PLAIN / perforated                   VIC CUT- Vacuum Infusion Version



Cuts

Composite structures are typically not flat, so core materials must conform to the shape of the structure. This can be achieved through thermoforming or longitudinal cuts. Additionally, cuts help air movement and resin flow in vacuum infusion processes.


                            SC- Single CUT                                    DC- Double CUT                                 CS- Grid Scored




Typical Properties of Core Materials


Density

kg/m³

Compressive Strength

MPa

Compressive Modulus

MPa

Tensile Strength

MPa

Elongation at Break

%  

Shear Strength

MPa 

Shear Modulus

MPa

Thermal Resistance

°C

Polystyrene

28–48

0,2–0,4




0,2–0,4

0,006–0,011


Polyurethane

32–320

0,2–5,9




0,1–3,1

1–103

135–150

PVC

40–250

0,52–6,88

29–296

0,71–7,19

6–35

0,47–4,37

15–98


Corecell M (SAN)

60–200

0,55–4,4

12–317


20–53

0,68–2,95

20–98


PMI

32–200

0,4–15,8


1,9–3,5


0,4–2,4

13–50

180–250



Thermoforming

In thermoforming, the panel is shaped using heat. Gurit’s Corecell and PVC cores are thermoformable. Recommended temperatures for each material are shown in the table below. Exceeding the maximum temperature may soften the core material.

Process:

1.       Heating

2.       Forming

3.       Post-forming

Tyyppi Tuote Lämpötila lämpömuovauksessa (°C)
Suositeltu Maksimilämpötila
Gurit® Corecell™ SAN
(styreeni akryylinitriili)		 M 110 120
Gurit® PVC
(polyvinyylikloridi)		 PVC 120 135
PVC HT 140 155
Kerdyn™ Green PET 140 160

Hand Lamination & Infusion

All core materials are porous. The lower the density and the larger the cell structure, the more resin will be consumed. Excess resin consumption also depends on the manufacturing technique.

 

Prepreg/Sprint

Each core material has a maximum temperature limit, after which mechanical properties begin to degrade.

Type

Product

Typical Process Temperature Limit

Gurit® Corecell™ SAN

(styrene acrylonitrile)

M

120ºC for 1 h

Gurit® PVC

(polyvinyl chloride)

PVC

Not recommended for prepreg processing


PVC HT

120ºC for 1 h


Main Core Material Types​

PVC Foam Sheets

PVC core material is now one of the standard raw materials in boat building and repair. The sheets are ideal for applications requiring low weight and high strength – particularly in boats where excellent fatigue strength and minimal water absorption are important. PVC foam is compatible with all common resin systems.

Properties:

  • Excellent chemical resistance
  • Self-extinguishing
  • Suitable for all sandwich structures

 

PET Foam Sheets

  • Gurit® Kerdyn™ Green Core Material: Made from 100% recycled material
  • High processing temperature
  • Excellent chemical resistance
  • Good adhesion and mechanical properties
  • Recyclable
  • Low resin uptake

 

SphereCel Core Mat

A filled core mat for sandwich constructions.

SphereCel core mats are made from fiberglass fabric and microspheres. They are used when thickness and stiffness need to be quickly added to a composite structure. Typically used in a few millimeter thicknesses, SphereCel can be applied to flat or contoured laminates. Its use can reduce laminate weight by up to 40–60% compared to chopped strand mat.


Balsa Wood

A natural and extremely strong core material with high compressive and shear strength. Particularly suitable for demanding load conditions and moist environments.

 

We stock a wide range of panel sizes. If you're interested, please contact us directly at kevra@kevra.fi or 09 6126820 and we’ll be happy to assist you.

More Information

Core Brochure  

Structural Core Processing Guide