Compressive intralaminar fracture toughness and residual strength of 2D woven carbon fibre reinforced composites: New developments on using the size effect method

Abstract

This paper presents new developments in the use of the size effect method for obtaining the compressive fracture toughness of 2D woven carbon fibre composites. A modification of the Double Edge Notch Compression (DENC) specimen geometry is proposed, to fit the Combined Loading Compression (CLC) standard fixture, and shown to reduce peak load dispersion. The notch tip diameter sensitivity on the peak load is also investigated, experimentally and numerically, and shown not to have a significant influence on fracture toughness. The use of the CLC fixture also allows for the residual compressive strength of the material to be calculated from post-peak crushing.

Computational modelling of the crushing of carbon fibre-reinforced polymer composites

“…Compact tension (CT) and compact compression (CC) tests, adapted from tests designed for metals [101,102], have been developed [103,104] with various modifications proposed to mitigate known problems of damage occurring at the loading points and areas of high stresses away from the crack tip [105,106]. An alternative approach which does not require the tracking of a propagating crack tip, as is required for CT/CC testing, is to exploit the size-effect law, originally proposed by Bazant & Planas [107], where a series of selfsimilar double-notched specimens of different sizes are tested in tension or compression and the results used to generate resistance (R-) curves [108][109][110]. Provided that CT/CC/size effect tests are conducted carefully, there is a high level of consistency in the results obtained under quasi-static loading conditions.…”

A case for Tsai’s Modulus, an invariant-based approach to stiffness

“…Many studies have already benefited from the use of trace in the mechanics of composite materials, including new laminate concepts [3,4] and structures [5], preliminary design [6][7][8] and optimization [9,10], fast notched strength prediction tools [11], generation of statistical virtual allowables [12] and fracture mechanics [13,14].…”

“…Dalli et al [13,14] used trace-normalized moduli to simplify the expressions of the geometric correction factors used in fracture mechanics of orthotropic Using Tsai's modulus as a normalizing factor, Dalli et al [13,14] proposed a general formulation for the energy release rate, G, that can be used with the majority of standard balanced woven CFRPs:…”

Assessing the current modelling approach for predicting the crashworthiness of Formula One composite structures

“…woven CFRP which was characterised in previous work [32,33]. There are actually two SIS design variants on each side of an F1 car, referred to as upper and lower [34], each composed of a different number of plies.…”

“…For the dynamic simulation, half the mass of the sled impactor was assigned to the crushing plate (390 kg), together with the same initial velocity condition as that observed experimentally ( 10.1 m/s). The material properties used to simulate the structural response of the SIS are reported in Table 5, and were obtained from in-house experimental characterisation, reported in [32,33].…”