Scaling Effects in Sublaminate-Level Scaled Composite Laminates

Abstract

A series of tensile tests has been performed to determine the effect of specimen size on the mechanical response of composite laminates that were scaled at the sublaminate level. The two material systems studied were AS4/3502 and APC-2. In the case of AS4/3502, three generic layups were considered: [±30/90 2 L,, [±45/0/90]™, and [90/0/90/0]™ deg, where n = 1, 2, 3, or 4. For the APC-2 system, only the [±45/0/90],,.? deg layup was studied with n = 1 and 4. The effect of specimen size was examined with respect to first-ply failure strain, delamination onset strain, and ultimate stress and strain. In general, the strength of scaled specimens increased with increasing specimen size. Models from the literature were applied to attempt to explain the variations observed. It was found that the effect of ply constraint is not addressed properly in existing theories.

A Review of Similitude Methods for Structural Engineering

“…Many articles [33,[68][69][70][71][72][73][74][75][76][77][78][79][80][81][82][83][84][85][86][87] showed that stacking sequence is a key parameter in scaling composite materials. There are three scaling approaches, namely ply level scaling ( Fig.…”

“…The choice of the scaling strategy has significant consequences on the response of the composite specimen. This choice is studied in many works [68][69][70][71][72] in which it is demonstrated that ply level scaling applied only to the thickness or to all the geometric dimensions (also known as one-and three-dimensional scaling, respectively) leads to a decreasing tensile strength with increasing size. Such behavior is due to the increased severity of edge delamination and debonding, creating stress concentrations that lower the strength of hybrid materials.…”

Scaling effects in the manufacture and testing of grid-stiffened composite structures

“…Johnson et al. 8 undertook a series of tensile tests on scaled carbon fiber reinforced samples based on both epoxy and PEEK matrices. The authors noted that the strength of the composite samples increased with increasing specimen size.…”

Unification of strength scaling between unidirectional, quasi-isotropic, and notched carbon/epoxy laminates

“…A size effect can be defined as a change in strength with specimen dimensions [1]. Unnotched specimens of continuous fibre reinforced laminates have been extensively tested [2][3][4][5][6], emphasizing the volume-scaling effects.…”

“…Unnotched quasi-isotropic specimens [3,6] have also been tested to study the size effects, and free edge delaminations were identified to be one of the potential failure modes [6]. These free edge effects have been previously studied [7][8][9].…”