Experiencing Frequent Delamination or Debonding in Sandwich Structures? A Guide to Selecting PVC Structural Foam Cores and Avoiding Common Process Pitfalls

Many composite material manufacturers face the same challenge: after the curing of sandwich core components, delamination between the face sheet and core material, local voids, and interfacial cracking occur, resulting in persistently high scrap rates. There are numerous causes for delamination defects—improper core material selection, inadequate surface treatment of panels, and unreasonable forming process parameters can all directly affect product quality. Today, drawing on practical cases of Swainor New Materials' PVC structural foam series, we will sort out the common causes and solutions for delamination in sandwich structures.

I. Four Core Material-Related Causes of Sandwich Structure Delamination

1. Uneven cell structure of core material leading to excessive resin penetration  Ordinary non-crosslinked foam has uneven cell sizes. During the forming process, large amounts of resin seep into the foam interior, forming a resin-rich layer on the surface. Inconsistent internal and external shrinkage generates interfacial stress after curing, inducing debonding. Swainor New Materials' PVC structural foam relies on a dry-wet composite foaming process, featuring fine, uniform, and stable closed cells. Its resin absorption rate is controllable, reducing interfacial defects caused by excessive resin penetration.

2. Insufficient temperature resistance of core material causing deformation during high-temperature curing  Some low-quality PVC foams have low temperature tolerance and may experience slight shrinkage and softening under the high-temperature curing conditions of epoxy systems. The inconsistent deformation between the face sheet and core material leads to gap delamination after cooling. Cross-linked PVC structural foam offers stable heat resistance, suitable for the curing temperature range of mainstream composite materials.

3. Mismatch between panel processing method and forming process  Blindly using perforated panels for flat components, or directly using flat panels for curved components, results in unreasonable resin flow paths. During vacuum infusion, air cannot be fully exhausted, forming bubbles inside the sandwich that turn into delamination hazards.

4. Insufficient compatibility between resin system and core material  The core material cannot adapt to the selected resin, resulting in insufficient interfacial bond strength. Ordinary foam is only compatible with a single resin, whereas the Cvinyl series PVC structural foam is compatible with mainstream systems such as epoxy, unsaturated polyester, vinyl ester, and bismaleimide resins, offering better interfacial bonding stability.

II. Practical Solutions to Reduce Delamination Risk

1. Select processed panels according to needs  For large vacuum-infused components, priority should be given to perforated panels or grooved and perforated panels to build resin flow channels and quickly exhaust air. For single-curved components, contoured panels should be selected; for double-curved surfaces, double-curved panels are preferred. For small, structurally flat parts, flat panels should be used.

2. Proper pre-treatment of core material  After panel processing, clean surface dust and debris to prevent dust from blocking the resin infiltration interface. In humid environments, pre-dry the panels to control moisture content.

Quality control of sandwich components begins with core material selection at the source. Stable cross-linked PVC structural foam, combined with reasonable panel processing solutions and forming processes, can effectively reduce delamination and void defects, helping enterprises control production costs. If you are troubled by composite material delamination defects, please follow us for more core material process matching solutions.