NUMERICAL SIMULATION STUDIES OF TRANSVERSE CRACK ON COMPOSITES STRUCTURES

• Main Author: Mae Merida Catalya M, Rebecca
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/49972
• Institution: Institut Teknologi Bandung

Composite weakness to transverse loading makes it susceptible to interlaminar transverse crack and delamination. Composite material’s strength is on fiber direction but when they are subjected to transverse loading, the strength of the structure is on the matrix (which is not actually the main load-bearing part). This could start matrix cracking, or interlaminar cracking. If the loading continues, the crack will propagate on the transverse direction until it reaches the interface of laminates and then convert into longitudinal crack along the laminates interface and hence delamination happens. Apart from making the structure lost its ability to carry loads, delamination is also quite invincible, making it hard to be detected. Numerical study to simulate transverse crack and its transision to delamination on composite structures is performed using finite element method. Transverse crack and delamination are modeled using cohesive element. The numerical model is based on the writer’s experimental specimen of the same purpose. Bamboo is used as natural composite specimen due to its unidirectional fiber. The specimens are cut into unidirectional laminae and then glued with PVAc as such it forms a [0/90] laminate. The specimens are then put into three-point bending test. The bending subjected to the specimen will give transverse load to the 90o ply. As the impactor displaced, the bending load on the specimen grows until the stress reaches a damage initiation criterion (in this case, the bamboo tensile transverse strength). Transversal cohesive elements will then fail under Traction Separation Law. As the loading continues, more cohesive elements will fail representing transverse crack propagation before it halts when reaching the [0/90] laminate interface. The loading continues but now only the 0o ply bears the load. At a point of loading, longitudinal crack along the [0/90] interface develop representing delamination. The structural response to three-point bending, transverse crack initiation and propagation, and delamination is recorded in Load-Displacement graph and will be analyzed.