Screw strength

For screw connections in Compacfoam we recommend screws with wooden threads and thick screw cores and sharp threads, e.g., typical window frame anchors with diameter starting from 6mm. Screws can be screwed directly into Compacfoam without pre-drilling. The material displaced by the core is compressed sideways in the screw hole, and hence it considerably increases the pull-out resistance. When making screw connection with small diameters (<5mm) in small thicknesses (CF100, CF150) the tightening torque must be limited in order to prevent over winding.

Recommended screw types or similar, e.g.:

EJOT frame anchor RA-P 7.5xL VBH greenteQ window frame screw T30 7.5xL flat head

schraubenfestigkeit_ejot_rahmenanker.pdf

Due to manifold stresses and installation situations, we recommend a use-specific test of the fastening. We are pleased to offer you support with advising and tests in our laboratory.

axial pull-out resistance – tenacity:

when using commercially available wood screws, the axial pull-out strength is essentially linearly dependent on screw diameter and anchoring depth.

Load-bearing capacity perpendicular to screw axis – shearing resistance

the load-bearing capacity of screw connection in Compacfoam normal to the screw axis depends on screw diameter, Compacfoam density class and thread depth. Differences also occur depending on whether the force is applied directly in front of the insulation element, or whether a separation fitting is located in front.

Photo: Laboratory test shearing force resistance screw with flush fitting and separation fitting

Test values frame anchor diameter: 7.5mm thread depth: 60mm, direct fitting:

average deformation	1 mm	2 mm	5 mm
CF100	215 N	310 N	350 N
CF150	370 N	575 N	770 N
CF200	525 N	840 N	1195 N
CF300	605 N	1100 N	1780 N
CF400	780 N	1450 N	2450 N

the necessary component reliability must be coordinated with respect to the application, and the average test values must be reduced by this amount.

Load-bearing capacity perpendicular to screw axis with separation fitting

In all materials, a significant influence on the load-bearing capacity with shear stress is whether the load is applied directly near the component surface or whether a separation fitting is placed in front. Increasing screw bending and higher compression of the hole edge significantly decrease the bearable capacity of the screw connection. In specific, with relatively small loads, the screw already bends in the hole.

Test values frame anchor diameter: 7.5mm thread depth: 60mm, separation fitting 23 mm: