## 1 Introduction
[PERSON] et al. [16], on the other hand, compared the behavior of the natural fibers of jute and sisal, compared to the polypropylene fiber in cement, cement-line and cement-APA (air entraining plasticizer admixture) mortars. Finding that, at higher percentages of natural fiber up to 2%, the resistance is affected, this was attributed to an increase in the porosity of the material compared to the reference material. Concrete beams strengthened with an ultra-rapid-hardening fiber-reinforced mortar were investigated by [17] and increases of 11% in the flexural strength and 15% in the toughness were found. Meanwhile, [PERSON] et al. [18] report the use of natural fibers as pineapple leaf, sisal, linen, and others, as aggregates of ordinary concrete, highlighting their benefits. These materials have a potential application as masonry structures, and previous works [19; 20; 21] used sisal fibers as sustainable materials for construction, as well as structural health monitoring applications [22] and electrical insulation [23]. All this speaks about the several applications and uses of natural and synthetic fibers in structures, considering not only their benefits in mechanical properties, but also their characteristics of thermal and acoustic insulation and biodegradability. Despite this, the design of composite structures is quite conservative in engineering practice as it is expensive and time-consuming, and many tests must be performed to ensure the safety of the structures [24]. Therefore, the mechanics of continuous damage play an important role in the design, production, and health control of composite structures, through the study of the criteria of discontinuity, accumulation of damage, softening of properties, etc. [25]. The damage of a material is caused by a reduction in the area, due to the generation of cracks or discontinuities, which implies a decrease in the ability to resist efforts as the stresses increase [26]. A continuous damage model does not attempt to describe what happens at the point where such discontinuity is caused, but rather is governed by the basic hypothesis of obtaining a global response from the structure affected by the phenomenon of the fracture, through constitutive equations and damage evolution based on irreversible thermodynamic processes, together with the theory of internal state variables [26]. Moreover, a hybrid model was proposed by [PERSON] et al. to analyze the resin-rich uncertainty in the composite material. The discretization window size was mitigated using microstructure images and point-to-point mapping for the estimation of the mechanical properties [27]. [PERSON] et al. investigated the ability of continuous damage models to accurately predict the matrix failure and layer splitting. He used two approaches, one based on incremental small strain increments and Cauchy stress, and another approach that takes strain kinematics into account by using Green-Lagrange strain and Piola-Kirchhoff second stress [28]. In this paper, we aim to establish a failure criterion for continuous damage for a thermostable polymer matrix verifying the influence of the mass of heenquen fibers, as the reinforcement, on the mechanical properties, considering that the propagation of aggregation and nucleation does not produce an instantaneous collapse of the matrix or rapid structural collapse, since the transverse microcracks of the matrix produce an intralaminar failure, which degrades the mechanical properties of the material gradually and gradually until its total collapse is presented.