Novel progressive failure model for quasi-orthotropic pultruded FRP structures: Formulation and calibration of parameters (Part I)

This paper presents a novel progressive failure model for the 3D simulations of pultruded FRP structures which allows the modelling of the laminates as a homogeneous material. The failure initiation model proposed requires only the strength in each direction as input, combining them to retrieve in-plane and out-of-plane failure indexes. The damage propagation model can be divided in two main stages: (i) damage progression and (ii) constant stress beyond a limit strain. The former stage uses the in-plane and out-of-plane failure indexes to determine the damage progression, using different parameters in each direction to account for the different damage responses, while the latter is characterized by a constant stress after a limit strain is reached, also different for each direction. FE models were developed with the proposed damage propagation model, requiring as input the strengths obtained from standardize experimental material coupon testing, the results of which, namely the load/stress vs. displacement/strain curves, are used to calibrate all the parameters needed to established the model. The results show that the proposed damage propagation model, using a homogenized material, is well able to predict the experimental behaviour even for very complex cases such as interlaminar shear tests. Furthermore, in a companion paper the accuracy and limitations of the model are further assessed in the simulation of transverse compact tension and web-crippling tests.