Compressive Strength of Production Parts Without Compression Testing

Abstract

The purpose of this paper is to present a methodology to estimate the compressive strength of fiber-reinforced composite prototype and production parts. The procedure is based on test data that incorporates the effects of sample size and sample preparation but simpler to obtain than compression test data. A simple formula is derived to relate the compressive strength to the shear stiffness, shear strength, and standard deviation of fiber misalignment. The formula is completely defined in terms of these three parameters, all of which can be measured by standard experimental procedures. It is proposed to use the shear stiffness and shear strength from coupon tests, usually available from the material supplier or from the characterization phase of the design/build project. Since these two parameters are relatively insensitive to part size and sample preparation, the coupon data are reliable and representative of the actual production part. Since fiber misalignment depends on the processing conditions, the third parameter used is the standard deviation of fiber misalignment, measured on samples from actual production parts. These three values characterize the compressive strength of the carbon/epoxy layups for which experimental data are found in the literature and those evaluated in this investigation. The predictions are then validated against data from a variety of specimens tested at high and low temperatures, as well as data from production prototype parts.

Statistical modelling of compression and fatigue damage of unidirectional fiber reinforced composites

“…Making the correction on the volume content of fibers (65%/ 50%), we obtain the estimation of the compressive strength in this case as 1040 MPa. Similar results have been obtained in [31] (1000-1200 MPa). Comparing this value with Fig.…”

A Constitutive Model for Elastic Damage in Fiber-Reinforced PMC Laminae

“…This is a consequence of the assumption that the principal directions of the second-order damage tensor D remains aligned with the material principal directions over the entire life of the material. Under these conditions, shear damage is interpreted as a combination of longitudinal and transverse matrix cracks, which is supported by experimental observations [4,22]. However, as experimentally observed, most of the damage is in the form of longitudinal cracks, so that the following must be satisfied.…”

“…Using the experimental data of Reference [4] for unidirectional Cytec-Fiberite M30/949 carbon/epoxy, Equation (34) Next, the constitutive model is solved incrementally with an applied inplane shear strain and the parameters γ 0 , c 1 and c 2 are adjusted to match the experimental shear stress-strain data, as shown in Figure 1. Material properties as well as damage parameters are provided in Table 1.…”

“…The parameters γ o , c 1 and c 2 are determined by fitting the experimental shear stress-strain plot. When this plot is not available, but only the undamaged inplane shear modulus G 12 and failure inplane shear strength F 6 are known, the curve can be reconstructed using (40) which is known to represent shear experimental data very well [1,3,4]. Since experimental values of F 6 and G 12 are available in the literature, all the parameters of the proposed damage evolution model can be completely identified from available data.…”

Characterization of self -healing composite materials

“…The constitutive relationships and evolution equations that define CDM and CDHM models, define a non-linear differential problem, which is solved through the use of a numerical algorithm. The CDM model has been validated with numerous comparisons of predicted damage and experimental damage [14,16,17,18,20] [18] has not been validated with experimental data and does not describe the type of experimental produce that is necessary to determine the material parameters.…”