Progressive Damage and Failure Prediction of Open Hole Tension and Open Hole Compression Specimens

Abstract

Progressive damage and failure in open hole composite laminate coupons under tensile and compressive loading conditions is modeled using Enhanced Schapery Theory (EST). The input parameters required for EST are obtained using standard coupon level test data and are interpreted in conjunction with finite element (FE) based simulations. The capability of EST to perform the open hole strength prediction accurately is demonstrated using three different layups of IM7/8552 carbon fiber composite. A homogenized approach uses a single composite shell element to represent the entire laminate in the thickness direction and this requires the fiber direction fracture toughness to be modeled as a laminate property. The results obtained using the EST method agree quite well with experimental results.

The EST Model for Predicting Progressive Damage and Failure of Open Hole Bending Specimens

“…While axial failure is independent of the matrix failure modes, matrix mode I and mode II failure are related to each other and their interaction is defined by a mixed-mode failure initiation and propagation laws. 1,2 All three failure mechanisms are modeled using crack band theory. The fundamental principle behind the crack band theory is expressed by the equation below (equation 1).…”

“…Since EST uses a single composite shell element, it is required to scale the fracture toughness with the layup according to the approach suggested by Camanho and Catalatonni. 8 More discussions on the failure parameters can be found in Joseph et al 2 All the input parameter used in this open hole bending study are the same as the input parameters used in the previous open hole tension/compression study. 2 The reader is advised to refer to Pineda and Waas 1 and Joseph et al 2 for more details on the EST model.…”

“…8 More discussions on the failure parameters can be found in Joseph et al 2 All the input parameter used in this open hole bending study are the same as the input parameters used in the previous open hole tension/compression study. 2 The reader is advised to refer to Pineda and Waas 1 and Joseph et al 2 for more details on the EST model. A discussion on the mesh-objectivity of the EST model can be found in Pineda and Waas.…”

“…Consequently, the inputs to EST that reflect the effects of damage and failure at scales below this scale (those that can be modeled using micromechanics, for example the kink band angle in fiber compression) must also be obtained in a manner that preserves the length scale of interest. Previous studies carried out by Davidson et al 6 and Joseph et al 2 presented a unified model for the open hole tension (OHT) and open hole compression (OHC) strength predictions using Enhanced Schapery Theory (EST). The EST model is extended in the present study to address the failure events when the open hole coupon is subjected to flexural loading.…”

Comparison of Test Methods to Determine Failure Parameters for MAT162 Calibration

“…The technical maturity of these methods is related to the capability of the codes to predict damage for the loading case and is tied to the understanding of the relevant physics for that case. PDFA methods have been shown to be technically mature for a number of static applications including open-hole tension and compression [1] [2] and low velocity impact [3] [4]. Fatigue capable PDFA tools currently require additional analysis and development as intralaminar fatigue becomes better understood.…”