INTRODUCTION
Soric is a bulker material that is designed to be placed in a sandwich with fibre reinforced skins. In this capacity, Soric allows impact behavior of a sandwich close to that of a full glass laminate.
Soric TF is typically used to improve the surface of a composite laminate.
The other Soric grades build thickness and act as a flow medium in infusion and RTM. Historical impact tests have proven that a laminate with Soric has comparable resistance to impact as a full fibre laminate. In order to assess whether the failure mechanism is also comparable, a series of comparative impact tests is performed. For impact testing a drop weight tower is used.
In order to assess the total damage in the laminate, ultrasonic C-scan is used.
From each considered laminate a panel will be selected which will be cut along a damaged area in order to compare the failure mode. Main mode of failure is breaking (fracturing) of the resin. No inter-laminar failures occur. In light of the test results it is recommendable to add a layer of CSM between the barrier coat and the Soric.
ADOPTING LANTOR SORIC
This document is originally a part of the campaign to adopt Lantor Soric into a yacht infusion process.
In particular, the Soric TF is assessed as a surface enhancer. Soric TF is a bulker material that is designed to be placed in a sandwich with fibre reinforced skins. In this capacity, Soric TF allows impact behavior of a sandwich close to that of a full glass laminate.
GOAL
To analyze the failure mode after impact in a laminate with Soric
RESULTS
FAILURE MODE
Below the cross sections of a selected hole (impacted with 27 Joule) for each laminate is given.
The cross-section in panel 1A location 3, which is impacted at 61 Joule, is presented first.
This location is the one with the clearest damage and will be used to analyze the failure mechanics involved.
breakline
Possible fibre
No fibre between Soric and barrier coat
Perpendicular
Fibre bundle
The first layer of CSM seems to be interrupted next to the centre of the impacted area.
The absence of any dark spots between the fibre layers and the Soric
indicates the absence of interlaminar (delamination) failures.
A break line can be seen running through the Soric XF, indicating a break in the core.
The laminate cross-section becomes ‘whiter’ to the center below the impacted area.
This is because of the damage to the resin, or the breaking of the resin,
making the otherwise transparent polyester resin opaque.
Because the opacity of the damaged resin ‘masks’ the fibres of the top EQX layer, fibre breaking cannot be established.
The absence of indicators for delamination and the shift in resin opacity nearer to the impacted area, shows that the observed damage areas from the c-scan indicate the area where the resin in the core is broken and does not indicate delamination as it would do for full fibre laminates. The darker areas in the fibre layers are the fibre bundles perpendicular to the cross-section surface.
Of the failure symptoms only the impact location and matrix cracks can be observed.
CONCLUSIONS
Under impact, a laminate without any CSM between the barrier coat and the Soric TF will suffer a damaged area almost two times as large as a laminate with CSM 600gsm between the barriercoat and Soric TF.
Applying CSM 450gsm results in a 30% larger damaged area.
Main mode of failure is breaking (fracturing) of the resin, which can be observed visually as the resin becoming less transparent (opaque, whiter) near the impact area.
No delamination, separation of fibre layer and core, is observed. Fibre breaking of the EQX cannot be seen. Impact deformation is fully absorbed by the Soric TF and XF.
RECOMMENDATIONS
Consider using Soric as a bulker material when delamination after impact is a design concern.
In light of the test results it is recommendable to add a layer of CSM between the barriercoat and the Soric TF. This will significantly reduce the damaged area after impact and therefore the area that should be repaired.
Applying a greater mass of CSM reduces the damaged area even further. Because the TF is applied mainly for cosmetic purposes it is recommended to apply a fine fibre CSM (200-450gsm). The fibres in CSM of 450 gsm and below have fibres with a smaller diameter, leading to better surface finish and less obvious print-through. To obtain the impact behavior of adding a CSM 600gsm, two layers of CSM 300gsm may be considered.
