Initial Tests of CCLT – A timber sandwich structure with COMBOO core
Topic(s) : Material and Structural Behavior - Simulation & Testing
Co-authors :
Jean-Marc WITZMANN (GERMANY), Ralf FÖRSTER , Andreas LOTH (GERMANY)Abstract :
Introduction
CLT (cross laminated timber) is a massive timber plywood usually made of pine boards in several layers aligned under an angle of 90 degrees (fibre orientation). A total thickness of up to 450 mm is available at a length of up to 13 meters and width of up to 7 meters. It is widely used in civil engineering and architecture to build even high rise wooden buildings. The consumption of large amounts of timber and its density of 0.45 g/cm3 can somehow be a disadvantage.
COMBOO is a honeycomb pattern of cut bamboo rings with many interesting technical properties and a density of 0.2 g/cm3 [1, 2]. The combination of both provides the properties of a sandwich structure and could be an alternative material for CO2 friendly construction. An initial compression test of the new approach called CCLT– “COMBOO cross laminated timber” is the subject of this abstract.
Material / Manufacturing
Bamboo rods (Moso bamboo) cut into rings of the same length of 20 mm and arranged in a honeycomb pattern form the core layer for the new CCLT material. The top and bottom layers consist of two sheets of pine wood with a thickness of 20 mm, each of which were glued together with a single component PU glue (Otto Coll P84, Otto Chemie, Germany), which is a standard glue for CLT production. The COMBOO core layer was added on top of the two boards of the bottom layer, also glued with the P84. After 12 hours of hardening the upper shell was added and fixed with the glue too. Finally specimens of the desired sizes (L x W x H) 80 x 80 x 100 mm and 200 x 200 x 100 mm were cut out of the prepared CCLT boards. For comparison of compression test results, a 5 layer CLT board was manufactured in a similar manner, using the same type of pine wood with the same geometry as above as well as the same glue. The CLT board was then cut into specimens of the size 76 x 76 x 100 mm and 200 x 200 x 100 mm.
Investigations / results
The universal testing machine used for the compression tests on all the samples was a TESTING Bluhm & Feuerherdt GmbH with a maximal load of 300 kN. The CCLT samples with the dimensions 80 x 80 x 100 mm showed compressive stress of 3.1 - 3.97 MPa at 10% compressive deformation perpendicular to the fibre, an average value of 3.5 MPa, and a standard deviation of 0.36 MPa. The CCLT samples with the dimensions 200 x 200 x 100 mm, showed stresses of 3.39 - 3.42 MPa, an average value of 3.40 MPa with a standard deviation of 0.01 MPa. The conventional CLT samples’ measured stress ranged between 3.49 and 4.14 MPa, with an average of 3.76 MPa and a standard deviation of 0,24 MPa.
CLT (cross laminated timber) is a massive timber plywood usually made of pine boards in several layers aligned under an angle of 90 degrees (fibre orientation). A total thickness of up to 450 mm is available at a length of up to 13 meters and width of up to 7 meters. It is widely used in civil engineering and architecture to build even high rise wooden buildings. The consumption of large amounts of timber and its density of 0.45 g/cm3 can somehow be a disadvantage.
COMBOO is a honeycomb pattern of cut bamboo rings with many interesting technical properties and a density of 0.2 g/cm3 [1, 2]. The combination of both provides the properties of a sandwich structure and could be an alternative material for CO2 friendly construction. An initial compression test of the new approach called CCLT– “COMBOO cross laminated timber” is the subject of this abstract.
Material / Manufacturing
Bamboo rods (Moso bamboo) cut into rings of the same length of 20 mm and arranged in a honeycomb pattern form the core layer for the new CCLT material. The top and bottom layers consist of two sheets of pine wood with a thickness of 20 mm, each of which were glued together with a single component PU glue (Otto Coll P84, Otto Chemie, Germany), which is a standard glue for CLT production. The COMBOO core layer was added on top of the two boards of the bottom layer, also glued with the P84. After 12 hours of hardening the upper shell was added and fixed with the glue too. Finally specimens of the desired sizes (L x W x H) 80 x 80 x 100 mm and 200 x 200 x 100 mm were cut out of the prepared CCLT boards. For comparison of compression test results, a 5 layer CLT board was manufactured in a similar manner, using the same type of pine wood with the same geometry as above as well as the same glue. The CLT board was then cut into specimens of the size 76 x 76 x 100 mm and 200 x 200 x 100 mm.
Investigations / results
The universal testing machine used for the compression tests on all the samples was a TESTING Bluhm & Feuerherdt GmbH with a maximal load of 300 kN. The CCLT samples with the dimensions 80 x 80 x 100 mm showed compressive stress of 3.1 - 3.97 MPa at 10% compressive deformation perpendicular to the fibre, an average value of 3.5 MPa, and a standard deviation of 0.36 MPa. The CCLT samples with the dimensions 200 x 200 x 100 mm, showed stresses of 3.39 - 3.42 MPa, an average value of 3.40 MPa with a standard deviation of 0.01 MPa. The conventional CLT samples’ measured stress ranged between 3.49 and 4.14 MPa, with an average of 3.76 MPa and a standard deviation of 0,24 MPa.